Tetravinylpyrazine compound, method for preparing same and electroluminescent element and non-linear optical material using same

Herein disclosed are a tetravinylpyrazine compound which has high light-emitting efficiency and thermal stability and which is represented by the following general formula (1): ##STR1## wherein R represents an aromatic ring or a heterocyclic ring; X represents a hydrogen atom, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, a halogen atom, a hydroxyl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, an acylamino group, a dialkylamino group, a nitro group, an acyloxy group or an acyloxycarbonyl group; a method for preparing the tetravinylpyrazine; and electroluminescent elements and non-linear optical materials using the pyrazine compound.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a tetravinylpyrazine compound having a 
vinyl bond at the 2-, 3-, 5- and 6-positions of the pyrazine ring 
respectively, a method for preparing the pyrazine compound and an 
electroluminescent element and nonlinear optical material obtained using 
the pyrazine compound. 
2. Description of the Prior Art 
Due to the recent marked progress in the information industry and 
information-oriented society, there has been increasing requirements for 
members capable of displaying information which exhibit higher quality. 
Among elements for such members, electroluminescent elements (EL elements) 
which make use of an electroluminescence (EL) phenomenon have become of 
major interest lately because of their excellent properties such as good 
visibility. 
There have been developed and already put on the market so-called intrinsic 
type EL elements such .as those in which inorganic fine particles are 
dispersed in a matrix of an organic substance and those obtained by 
sandwiching inorganic thin films of, for instance, znS between insulating 
thin films. However, these elements require high driving voltages and it 
is difficult to obtain elements which emit lights having wavelengths 
falling within, for instance, the blue range. 
There have been known injection-type EL elements in addition to the 
intrinsic-type ones. These injection-type elements emit light through 
recombination of electrons and positive holes which have been injected 
into p-n junctions of, for instance, semiconductors. These elements are, 
for instance, characterized in that they can be operated at a low DC 
voltage and that they have high efficiencies of converting electric energy 
into light. Inorganic crystalline semiconductors such as GaP have 
principally been used to produce these injection-type EL elements. 
However, they suffer from the problems that they are limited in the colors 
of emitted lights and that it is difficult to enlarge the area of the 
elements. 
For this reason, there have been recent been requirements for the 
development of techniques for producing EL elements which operate at a low 
driving voltage, can emit lights of any desired colors and have a large 
surface area. 
Recently, there have been proposed novel injection-type EL elements which 
make use of thin films of organic compounds (see C. T. Tang, Appl. Phys. 
Lett., 1987, 51(12), p. 193) and have attracted much attention. This is 
because the colors of emitted lights can arbitrarily be selected due to 
the use of organic substances, the elements can be operated at a low DC 
voltage and an element having a large area can be obtained by a thin 
film-forming method such as a deposition or coating method. However, there 
still remains some problems. For example, the EL elements comprising the 
thin films of these organic compounds suffer from a problem of reduction 
in the brightness of the emitted lights when they are operated over an 
extended time, i.e., the problem of so-called deterioration. 
One of the sources of such deterioration may be the degeneration of the 
organic compounds due to generation of heat. This is because, the 
efficiency of converting an electric energy into light is presently on the 
order of several percentages and most of the energy is converted into 
heat. Therefore, it is necessary to develop an element which makes use of 
an organic compound having good heat resistance and light-emitting 
efficiency in order to eliminate the problem of deterioration. 
Incidentally, there have been proposed, as materials for organic thin layer 
EL elements, 2,5-distyryl pyrazine derivatives (see M. Nohara, Chem. 
Lett., 1990, p. 189), but the EL elements obtained from these materials 
suffer from the problem of low stability. 
Further, non-linear optical devices which make use of tertiary non-linear 
optical effects such as optical bistable elements and optical gate 
switches have been anticipated as key devices for future ultrahigh speed 
electronic data processing systems. In order to improve the quality of 
these devices, it is necessary to develop non-linear optical materials 
which have a high non-linear susceptibility (hereinafter referred to as 
".chi..sup.(3) ") and high speed responsibility. 
Inorganic materials have conventionally been employed, but organic 
materials having E electron conjugated systems have attracted much 
attention recently because of their high responsibility and high 
non-linear susceptibility due to the presence of .pi. electrons. There 
have been known, for instance, polymer systems such as polyacetylene and 
polydiacetylene; and low molecular systems such as azomethines. All of 
these compounds have one-dimensional .pi. electron conjugation and the 
maximum .chi..sup.(3) thereof is 10.sup.-8 esu due to the response of 
these electron systems. However, this value is substantially determined on 
the basis of the presence or absence of the one-dimensional .pi. electron 
conjugation and is not dependent upon the chemical structure of a specific 
compound selected. Thus, there has not yet been discovered any organic 
materials having .chi..sup.(3) substantially greater than 10.sup.-8 esu. 
Moreover, the quality indices of non-linear optical devices are given by 
.chi..sup.(3) /(.alpha..tau.) (wherein .tau. is a response speed and 
.alpha. is the coefficient of light absorption) and, therefore, the 
indices must be increased as high as possible. However, there is a limit 
in the quality of these organic materials having one-dimensional .pi. 
electron conjugation. For this reason, it has been required for the 
discovery of other materials different from the foregoing materials. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the present invention is to provide specific 
tetravinylpyrazine compounds which are preferably used as organic 
optoelectric functional materials for electroluminescent elements and 
non-linear optical elements and are excellent in thermal stability. 
Another object of the present invention is to provide an EL element which 
makes use of a thin film comprising a specific tetravinylpyrazine compound 
as a light-emitting layer and has a high light-emitting efficiency and 
excellent thermal stability. 
A still further object of the present invention is to provide a non-linear 
optical material which comprises a specific tetravinylpyrazine compound 
and exhibits high non-linear optical properties. 
The inventors of this invention have conducted various studies to 
accomplish the foregoing objects, have found that specific 
tetravinylpyrazine compounds show excellent properties favorable for use 
as organic optoelectric functional materials and thus have completed the 
present invention. 
According to an aspect of the present invention, there is provided a 
tetravinylpyrazine compound represented by the following general formula 
(1): 
##STR2## 
wherein R represents an aromatic ring or a heterocyclic ring; X represents 
a hydrogen atom, an aliphatic hydrocarbon group, an alicyclic hydrocarbon 
group, an aromatic hydrocarbon group, a halogen atom, a hydroxyl group, an 
alkoxy group, a carboxyl group, an alkoxycarbonyl group, an acylamino 
group, a dialkylamino group, a nitro group, an acyloxy group or an 
acyloxycarbonyl group. 
According to a second aspect of the present invention, there is provided a 
method for preparing a tetravinylpyrazine compound represented by the 
foregoing general formula (1) which comprises the step of reacting 
2,3,5,6-tetramethyl pyrazine represented by the following formula (2): 
##STR3## 
with an aldehyde compound represented by the following general formula 
(3): 
EQU X-R-CHO (3) 
(wherein R represents an aromatic ring or a heterocyclic ring; X represents 
a hydrogen atom, an aliphatic hydrocarbon group, an alicyclic hydrocarbon 
group, an aromatic hydrocarbon group, a halogen atom, a hydroxyl group, an 
alkoxy group, a carboxyl group, an alkoxycarbonyl group, an acylamino 
group, a dialkylamino group or a nitro group) in the presence of an acid 
anhydride. 
According to a third aspect of the present invention, there is provided an 
electroluminescent element having a monolayer or multilayer thin film 
structure comprising at least one light-emitting layer; a positive 
hole-transporting layer and a light-emitting layer which are laminated in 
this order; or a positive hole-transporting layer, a light-emitting layer 
and an electron-transporting layer which are laminated in this order, the 
mono- or multi-layer thin film structure being positioned between two 
electrodes, wherein the light-emitting layer is a thin film comprising a 
tetravinylpyrazine compound represented by the foregoing general formula 
(1). 
According to a fourth aspect of the present invention, there is provided a 
non-linear optical material used for producing a non-linear optical 
device, which comprises a tetravinylpyrazine compound represented by the 
foregoing general formula (1).

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the compounds of the present invention represented by the foregoing 
general formula (1), the aromatic ring represented by the substituent R 
is, for example, a benzene, naphthalene, anthracene or pyrene ring. The 
heterocyclic ring comprises, as hetero atoms, oxygen, nitrogen and/or 
sulfur and if the ring comprises at least two hetero atoms, these hetero 
atoms may be the same or different. Examples of the heterocyclic rings are 
pyridine, quinoline, furan, thiophene, benzoxazole and benzothiazole. 
In the compounds of the present invention represented by the foregoing 
general formula (1), the substituent X represents a hydrogen atom, an 
aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic 
hydrocarbon group, a halogen atom, a hydroxyl group, an alkoxy group, a 
carboxyl group, an alkoxycarbonyl group, an acylamino group, a 
dialkylamino group, a nitro group, an acyloxy group or an acyloxycarbonyl 
group. Examples of these substituents are methyl and ethyl groups for the 
aliphatic hydrocarbon group; cyclopentyl and cyclohexyl groups for the 
alicyclic hydrocarbon group; phenyl and naphthyl groups for the aromatic 
hydrocarbon group; chlorine and fluorine atoms for the halogen atom; 
methoxy and ethoxy groups for the alkoxy group; methoxycarbonyl and 
ethoxycarbonyl groups for the alkoxycarbonyl group; acetylamino group for 
the acylamino group; and dimethylamino and diethylamino groups for the 
dialkylamino group. Moreover, it is also possible to prepare compounds of 
Formula (1) wherein at least two X's are linked to R in addition to those 
in which only one X is bonded to R. 
Typical examples of the compounds of the present invention will be given 
below. 
Examples of the compounds of Formula (1) wherein x is a hydrogen atom 
include those in which R is an aromatic ring such as 
2,3,5,6-tetrakis[2-(phenyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(1-naphthyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(2-naphthyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(1-anthryl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(2-anthryl)vinyl]pyrazine and 
2,3,5,6-tetrakis[2-(9-anthryl)vinyl]pyrazine and those in which R is a 
heterocyclic ring such as 2,3,5,6-tetrakis[2-(2-pyridyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(4-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(2-quinolyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(3-quinolyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(4-quinolyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(5-quinolyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(6-quinolyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(7-quinolyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(8-quinolyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(2-furyl) vinyl]pyrazine, 2,3,5,6-tetrakis[2-( 
3-furyl)vinyl]pyrazine, 2,3,5,6-tetrakis[2-(2-thienyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(3-thienyl)vinyl]pyrazine, 2,3,5,6-tetrakis[ 
2-(benzoxazyl)vinyl]pyrazine and 2,3,5,6-tetrakis[2- (benzothiazyl) 
vinyl]pyrazine. 
Examples of the compounds of Formula (1) wherein X is a substituent other 
than hydrogen atom and R is an aromatic ring include those in which X is 
an aliphatic hydrocarbon group such as 
2,3,5,6-tetrakis[2-(p-tolyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(o-tolyl)vinyl]pyrazine, 2,3,5,6-tetrakis[2-(m-tolyl) 
vinyl]pyrazine, 2,3,5,6-tetrakis [2-(p-ethylphenyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(o-ethylphenyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(m-ethylphenyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(p-propylphenyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(o-propylphenyl) vinyl]pyrazine and 
2,3,5,6-tetrakis[2-(m-propylphenyl) vinyl]pyrazine; those in which X is an 
alicyclic hydrocarbon group such as 
2,3,5,6-tetrakis[2-(2-cyclohexylphenyl) vinyl]pyrazine and 
2,3,5,6-tetrakis[2-(3-cyclohexylphenyl) vinyl]pyrazine; those in which X 
is an aromatic hydrocarbon group such as 
2,3,5,6-tetrakis[2-(2-biphenyl)vinyl]pyrazine, 2,3,5,6-tetrakis 
[2-(3-biphenyl)vinyl]pyrazine and 
2,3,5,6-tetrakis[2-(4-biphenyl)vinyl]pyrazine; those in which X is a 
halogen atom such as 2,3,5,6-tetrakis[2-(4-chlorophenyl) vinyl] pyrazine, 
2,3,5,6-tetrakis [2-(3-chlorophenyl) vinyl]pyrazine and 2,3,5,6-tetrakis 
[2-(2-chlorophenyl) vinyl]pyrazine; those in which X is a hydroxyl group 
such as 2,3,5,6-tetrakis[2-(4-hydroxyphenyl)vinyl]pyrazine, 
2,3,5,6-tetrakis [2-(3-hydroxyphenyl)vinyl]pyrazine and 
2,3,5,6-tetrakis[2-(2-hydroxyphenyl)vinyl]pyrazine; those in which X is an 
alkoxy group such as 2,3,5,6-tetrakis[2-(4-methoxyphenyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(3-methoxyphenyl) vinyl]pyrazine and 
2,3,5,6-tetrakis[2-(2-methoxyphenyl) vinyl]pyrazine; those in which X is a 
carboxyl group such as 2,3,5,6-tetrakis[2-(2-carboxyphenyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(3-carboxyphenyl)vinyl]pyrazine and 
2,3,5,6-tetrakis[2-(4-carboxyphenyl)vinyl]pyrazine; those in which X is an 
alkoxycarbonyl group such as 
2,3,5,6-tetrakis[2-(2-methoxycarbonylphenyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(3-methoxycarbonylphenyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(4-methoxycarbonylphenyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(2-ethoxycarbonylphenyl)vinyl]pyrazine, 
2,3,5,6-tetrakis [2-(3-ethoxycarbonylphenyl)vinyl]pyrazine and 
2,3,5,6-tetrakis[2-(4-ethoxycarbonylphenyl)vinyl]pyrazine; those in which 
X is an acylamino group such as 2,3,5,6-tetrakis[2-(2-a 
cetylaminophenyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(3-acetylaminophenyl)vinyl]pyrazine and 
2,3,5,6-tetrakis[2-(4-acetylaminophenyl)vinyl]pyrazine; those in which X 
is a dialkylamino group such as 
2,3,5,6-tetrakis[2-(2-dimethylaminophenyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(3-dimethylaminophenyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2 -(4-dimethylaminophenyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(2-diethylaminophenyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(3-diethylaminophenyl)vinyl]pyrazine and 
2,3,5,6-tetrakis[2-(4-diethylaminophenyl)vinyl]pyrazine; and those in 
which X is a nitro group such as 2,3,5,6-tetrakis[2-(2-nitrophenyl) 
vinyl]pyrazine, 2,3,5,6-tetrakis[2-(3-nitrophenyl) vinyl]pyrazine and 
2,3,5,6-tetrakis[2-(4-nitrophenyl) vinyl]pyrazine. 
Examples of compounds of Formula (1) wherein R is a heterocyclic ring 
include those in which X is an aliphatic hydrocarbon group such as 
2,3,5,6-tetrakis[2-((3-methyl)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-(((4-methyl)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-methyl)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-methyl)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-methyl)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-methyl)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-methyl)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-methyl)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-methyl)-4-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((3-methyl)-4-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((3-ethyl)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-ethyl)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-ethyl)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-ethyl)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-ethyl)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4 -ethyl)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-ethyl)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-ethyl)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-ethyl)-4-pyridyl) vinyl]pyrazine and 
2,3,5,6-tetrakis[2-((3-ethyl)-4-pyridyl) vinyl]pyrazine; those in which X 
is an alicyclic hydrocarbon group such as 
2,3,5,6-tetrakis[2-((3-cyclohexyl)-2-pyridyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-cyclohexyl)-2-pyridyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-cyclohexyl)-2-pyridyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-cyclohexyl)-2-pyridyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-cyclohexyl)-3-pyridyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-cyclohexyl)-3-pyridyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-cyclohexyl)-3-pyridyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-cyclohexyl)-3-pyridyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-cyclohexyl)-4-pyridyl) vinyl]pyrazine and 
2,3,5,6-tetrakis[2-((3-cyclohexyl)-4-pyridyl)vinyl]pyrazine; those in 
which X is an aromatic hydrocarbon group such as 
2,3,5,6-tetrakis[2-((3-phenyl)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-phenyl)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-phenyl)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-phenyl)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-phenyl)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-phenyl)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-phenyl)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-phenyl)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-phenyl)-4-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((3-phenyl)-4-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((3-(1-naphthyl))-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[ 2-((4-(1-naphthyl))-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-(1-naphthyl))-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-(1-naphthyl))-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-(1-naphthyl))-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-(1-naphthyl))-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-(1-naphthyl))-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-(1-naphthyl))-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-(1-naphthyl))-4-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((3-(2-naphthyl))-4-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((3-(2-naphthyl))-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-(2-naphthyl))- 2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-(2-naphthyl))-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-(2-naphthyl))-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-(2-naphthyl))-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-(2-naphthyl))-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-(2-naphthyl))-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-(2-naphthyl))-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-(2-naphthyl))-4-pyridyl)vinyl]pyrazine and 
2,3,5,6-tetrakis[2-((3-(2-naphthyl))-4-pyridyl)vinyl]pyrazine; th6Se in 
which X is a halogen atom such as 
2,3,5,6-tetrakis[2-((3-chloro)-2-pyridyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-chloro)-2-pyridyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-chloro)-2-pyridyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-chloro)-2-pyridyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-chloro)-3-pyridyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-chloro)-3-pyridyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5 -chloro)-3-pyridyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-chloro)-3-pyridyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-chloro)-4-pyridyl) vinyl]pyrazine and 
2,3,5,6-tetrakis[2-((3-chloro)-4-pyridyl) vinyl]pyrazine; those in which X 
is a hydroxyl group such as 
2,3,5,6-tetrakis[2-((3-hydroxy)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-hydroxy)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-hydroxy)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-hydroxy)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-hydroxy)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-hydroxy)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-hydroxy)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-hydroxy)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-hydroxy)-4-pyridyl)vinyl]pyrazine and 
2,3,5,6-tetrakis[2-((3-hydroxy)-4-pyridyl)vinyl]pyrazine; those in which X 
is an alkoxy group such as 
2,3,5,6-tetrakis[2-((3-methoxy)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-methoxy)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-methoxy)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-methoxy)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-methoxy)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-methoxy)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-methoxy)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-methoxy)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-methoxy)-4-pyridyl)vinyl]pyrazine and 
2,3,5,6-tetrakis[2-((3-methoxy)-4-pyridyl)vinyl]pyrazine; those in which X 
is a carboxyl group such as 
2,3,5,6-tetrakis[2-((3-carboxy)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-carboxy)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-carboxy)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-carboxy)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-carboxy)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-carboxy)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-carboxy)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-carboxy)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-carboxy)-4-pyridyl)vinyl]pyrazine and 
2,3,5,6-tetrakis[2-((3-carboxy)-4-pyridyl)vinyl]pyrazine; those in which X 
is an alkoxycarbonyl group such as 
2,3,5,6-tetrakis[2-((3-methoxycarbonyl)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-methoxycarbonyl) -2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-methoxycarbonyl)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[ 2-((6-methoxycarbonyl)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-methoxycarbonyl)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-methoxycarbonyl)-3-pyridyl) vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-methoxycarbonyl)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-methoxycarbonyl) -3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-methoxycarbonyl)-4-pyridyl)vinyl]pyrazine and 
2,3,5,6-tetrakis[2-((3-methoxycarbonyl)-4-pyridyl)vinyl]pyrazine; those in 
which X is an acylamino group such as 
2,3,5,6-tetrakis[2-((3-acetylamino)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-acetylamino)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-acetylamino)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-acetylamino)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-acetylamino)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-acetylamino)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-acetylamino)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-acetylamino)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-acetylamino)-4-pyridyl)vinyl]pyrazine and 
2,3,5,6-tetrakis[2((3-acerylamino)-4-pyridyl)vinyl]pyrazine; those in 
which X is a dialkylamino group such as 
2,3,5,6-tetrakis[2-((3-dimethylamino)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-dimethylamino)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-dimethylamino)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-dimethylamino)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-dimethylamino)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-dimethylamino)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-dimethylamino)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-dimethylamino)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-dimethylamino)-4-pyridyl)vinyl]pyrazine and 
2,3,5,6-tetrakis[2-((3-dimethylamino)-4-pyridyl)vinyl]pyrazine; those in 
which X is a nitro group such as 
2,3,5,6-tetrakis[2-((3-nitro)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-nitro)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-nitro)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-nitro)-2-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-nitro)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((4-nitro)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((5-nitro)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((6-nitro)-3-pyridyl)vinyl]pyrazine, 
2,3,5,6-tetrakis[2-((2-nitro)-4-pyridyl)vinyl]pyrazine and 
2,3,5,6-tetrakis[2-((3-nitro)-4-pyridyl)vinyl]pyrazine; those in which X 
is an acyloxy group such as 2,3,5,6-tetrakis 
[2-(4-benzoyloxyphenyl)vinyl]pyrazine; and those in which X is an 
acyloxycarbonyl group such as 
2,3,5,6-tetrakis[2-(4-benzoyloxycarbonylphenyl)vinyl]pyrazine. 
The tetravinylpyrazine compounds listed above can be prepared by reacting 
2,3,5,6-tetramethyl pyrazine represented by the following chemical formula 
(2): 
##STR4## 
with aldehyde compounds represented by the following general formula (3): 
EQU X--R--CHO (3) 
in the presence of an acid anhydride. 
The acid anhydrides which may be used in the present invention include, for 
instance, benzoic anhydride, acetic anhydride and butyric anhydride, with 
benzoic anhydride being preferred. In addition, inorganic dehydrating 
agents such as zinc chloride may be used, but the use thereof is limited 
in the reaction rate or the like. Thus, the use of acid anhydrides is more 
preferred. 
The reaction temperature ranges from 50.degree. to 300.degree. C., 
preferably 150.degree. to 250.degree. C. On the other hand, the reaction 
time varies depending on the reaction temperature selected, but in general 
ranges from several hours to 20 hours. 
Regarding the atmosphere during the reaction, the reaction is preferably 
carried out while passing an inert gas such as nitrogen gas through the 
reaction system or having the reaction system filled with an inert gas in 
order to inhibit side reactions such as oxidation of starting compounds. 
The reaction of tetramethyl pyrazine with the aldehyde compounds is 
preferably carried out in the presence of an excess of the aldehyde 
compounds and thus the molar ratio of the tetramethyl pyrazine to the 
aldehyde compound ranges from 1:1 to 1:20, preferably 1:5 to 1:15. In this 
respect, the relative ratio of the aldehyde compound to the acid anhydride 
is preferably approximately 1:1 expressed in terms of molar ratio. 
The foregoing tetravinylpyrazine compounds of the present invention listed 
above are symmetrical compounds in which all of the four substituents 
represented by X-R- in Formula (1) are identical to one another, but it is 
also possible to prepare asymmetrical tetravinylpyrazine compounds in 
which a part or all of the four substituents are replaced with different 
substituents in the same manner discussed above. In this case, these four 
substituents can be introduced simultaneously or stepwise. If they are 
simultaneously introduced, the reaction rate of each aldehyde compound 
with tetravinylpyrazine is determined in advance and the charge rate of 
the aldehyde compounds is accordingly determined on the basis of the 
results. On the other hand, if they are stepwise introduced, these 
aldehyde compounds are reacted with tetramethyl pyrazine in such a manner 
that the aldehydes are introduced into the pyrazine in the order of 
increasing reaction rate to control the reaction time and hence the number 
of each substituent to be introduced. Thus, the asymmetrical 
tetravinylpyrazine compounds can be prepared. 
The asymmetrical tetravinylpyrazine compounds obtained according to the 
foregoing method may be a mixture of different pyrazine compounds, but 
each component of the mixture can be isolated from other components by a 
variety of separation methods such as solvent separation, 
recrystallization and column separation. 
A part or most of the compounds of Formula (1) in which the substituent X 
is a hydroxyl or carboxyl group prepared by the foregoing method in the 
presence of the acid anhydride are present in the form of esters or acid 
anhydrides, but they can easily be hydrolyzed to give the desired pyrazine 
compounds in which the substituent X is a hydroxyl or carboxyl group. 
The tetravinylpyrazine compounds defined by Formula (1) are useful as 
materials for producing thin film light-emitting elements and non-linear 
optical elements. 
An important embodiment of the EL element according to the present 
invention has a structure which comprises, as a light-emitting source, at 
least one thin film comprising the tetravinylpyrazine compounds sandwiched 
between an electrode for injecting positive holes (hereinafter referred to 
as "first electrode") and an electrode for injecting electrons 
(hereinafter referred to as "second electrode"). More specifically, 
preferred embodiments have a monolayer or multilayer thin film structure 
comprising at least one light-emitting layer; a positive hole-transporting 
layer and light-emitting layer which are laminated in this order; or a 
positive hole-transporting layer, a light-emitting layer and an 
electron-transporting layer which are laminated in this order, the mono-or 
multi-layer thin film structure being positioned between these two 
electrodes. These preferred embodiments are shown in FIGS. 1 to 4. FIG. 1 
shows an element comprising one layer of an organic thin film (1) 
comprising the tetravinylpyrazine compound. The organic thin film 
comprising the tetravinylpyrazine compound may comprise the 
tetravinylpyrazine compound alone or in combination with a positive 
hole-transporting material, an electron-transporting material or mixture 
thereof. FIG. 2 shows an element having a two-layer structure comprising a 
layer of an organic thin film (1) comprising the tetravinylpyrazine 
compound and a layer (5) of a positive hole-transporting material and FIG. 
3 shows an element having a two-layer structure comprising a layer of an 
organic thin film (1) comprising the tetravinylpyrazine compound and a 
layer (6) of an electron-transporting material. In any case, the organic 
thin film layer may comprise the tetravinylpyrazine compound alone or in 
combination with a positive hole-transporting material, an 
electron-transporting material or mixture thereof. 
FIG. 4 shows an element having a three-layer structure which comprises a 
layer (5) of a positive hole-transporting material, a layer (1) of an 
organic thin film comprising the tetravinylpyrazine compound and a thin 
film layer (6) of an electron-transporting material. In this embodiment, 
the organic thin film layer may likewise comprise the tetravinylpyrazine 
compound alone or in combination with a positive-hole transporting 
material, an electron-transporting material or mixture thereof. 
In FIGS. 1 to 4, the reference numeral (2) represents a first electrode of, 
for instance, a transparent conductive film; the reference numeral (3) is 
a second electrode such as a metal electrode and the reference numeral (4) 
is a substrate such as a glass substrate. The electrodes (2) and (3) are 
connected, respectively, to positive and negative terminals of a power 
supply. 
The structure of these elements is not restricted to a specific one and is 
appropriately selected depending on the properties of the thin film 
comprising the tetravinylpyrazine compound. 
The thin film comprising the tetravinylpyrazine compound can be formed from 
at least one compound represented by Formula (1). In short, it is 
important, in the present invention, to use a thin film comprising the 
tetravinylpyrazine compound. 
These thin films can be formed according to a variety of methods such as 
vacuum deposition, sublimation and coating methods which are properly 
selected. 
The thin film may have any structure such as an amorphous structure, a 
microcrystalline structure, a microcrystal-containing amorphous structure, 
a polycrystalline structure and a single crystal structure which are 
likewise appropriately selected. The preferred film-forming method is one 
which can provide a thin film free of pinholes and having a uniform 
thickness. 
The thickness of the thin film is not restricted to a specific range, but 
is in general in the order of from 50 to 5000 .ANG.. It is a matter of 
course that the thickness thereof may be beyond the range defined above. 
The positive hole-transporting thin film will now be detailed below. 
The positive hole-transporting film is a thin film of an organic or 
inorganic substance having an ability of transporting positive holes. 
In the case of organic thin films, materials therefor are by no means 
limited to any specific ones and any known organic material having an 
ability of transporting positive holes may be used. Preferred examples 
thereof are diamine compounds such as 
N,N'-diphenyl-N,N'-bis-(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine; 
phthalocyanine compounds such as copper phthalocyanine; polymeric 
compounds such as polyvinyl carbazole and polymethylphenyl silane. 
The organic thin films may be formed by, for instance, vacuum deposition, 
sublimation and coating methods which are properly selected. In addition, 
it is also possible to use organic thin films prepared from a mixture of 
at least two such organic materials or by laminating at least two layers 
of one or more organic materials. 
The thickness thereof is not restricted to a particular range, but usually 
ranges from 10 to 3000 .ANG.. The thickness thereof may of course be 
beyond the range defined above. 
The inorganic film may be a thin film of an amorphous or microcrystalline 
semiconductor. Preferred are, for instance, Si- and SiC-based materials, 
more preferably hydrogenated amorphous SiC, hydrogenated microcrystalline 
Si and hydrogenated microcrystalline SiC. The thin films of this type are 
made positive hole-conductive by modulation of the composition and doping 
and by laminating a plurality of thin films. 
The thickness thereof is not likewise limited to a specific range, but in 
general ranges from 10 to 3000 .ANG.. The thickness thereof may of course 
be beyond the range defined above. 
These inorganic thin films can be prepared by a variety of thin film-foming 
techniques such as photo assisted CVD (chemical vapor deposition), plasma 
CVD, thermal CVD, MBE (molecular beam epitaxy), vapor deposition and 
sputtering methods. 
Referring now to the electron-transporting thin films, these thin films 
are, for instance, organic and inorganic thin films having an ability of 
transporting electrons. 
Materials for the organic thin films are not restricted to specific ones 
and may be any known organic materials having an ability of transporting 
electrons. Preferred examples thereof are metal complexes such as 
tris-(8-hydroxyquinolinol) aluminum; and oxadiazole compounds such as 
2,5-bis-(4'-diethylamino-phenyl)-1,2,4-oxadiazole. 
The electron-transporting organic thin films may be formed by, for 
instance, vacuum deposition, sublimation and coating methods which are 
properly selected. In addition, it is also possible to use organic thin 
films prepared from a mixture of at least two such organic materials or by 
laminating at least two layers of one or more organic materials. 
The thickness thereof is not restricted to a particular range, but usually 
ranges from 10 to 3000 .ANG.. The thickness thereof may of course be 
beyond the range defined above. 
The electron-transporting inorganic thin films may be thin films of 
amorphous or microcrystalline semiconductors. Preferred are, for instance, 
Si- and SiC-based materials, more preferably hydrogenated amorphous SiC, 
hydrogenated microcrystalline Si and hydrogenated microcrystalline SiC. 
The thin films of this type are made electron-conductive by modulation of 
the composition thereof and doping and by laminating a plurality of thin 
films. 
The thickness thereof is not likewise limited to a specific range, but in 
general ranges from 10 to 3000 .ANG.. The thickness thereof may of course 
be beyond the range defined above. 
These inorganic thin films can be prepared by a variety of thin film-foming 
techniques such as photo assisted CVD, plasma CVD, thermal CVD, MBE, vapor 
deposition and sputtering methods. 
The first electrode will now be explained in detail below. 
The first electrode can be formed from thin films of, for instance, metals, 
alloys, metal oxides and metal silisides; thin films of, for instance, 
conductive polymers; and laminated thin films of these materials. 
Preferred examples thereof include transparent conductive films of; for 
instance, tin oxide (SnO.sub.2), indium tin oxide (ITO) and zinc oxide 
(ZnO); metal films such as gold (Au); and conductive polymers such as 
polyarylene vinylene and polythiophene. 
The second electrode will now be explained in detail below. 
The second electrode can be formed from thin films of, for instance, 
metals, alloys, metal oxides and metal silisides and laminated thin films 
of these materials. Preferred are metal thin films of Group II of the 
Periodic Table such as Mg and Group III such as Al; metal alloy thin films 
of Groups II and I such as Mg-Ag; and metal alloy thin films of Groups II 
and III such as Mg-In. 
The thickness of the foregoing electrodes are not restricted to a specific 
range, but in general range from 10 to 5000 .ANG.. The thickness thereof 
may of course be beyond the range defined above. 
The foregoing electrodes can be prepared according to a variety of thin 
film-forming methods such as vapor deposition, sputtering, electrolytic 
polymerization and coating methods which are properly selected. 
The method for producing the EL element of the present invention and for 
evaluating the resulting element will hereinafter be explained in detail. 
A transparent conductive film is first applied onto the surface of a glass 
substrate through the electron beam vacuum deposition technique. A 
positive hole-transporting material, a light-emitting material and an 
electron-transporting material (several mg each) are charged into a 
plurality of quartz boats (1 cc volume) which are wound with-heating wires 
(1 .phi.; 5 turns). These quartz boats are heated by passing an electric 
current (8 .ANG.) through the heating wires under vacuum to deposit the 
materials. In this respect, however, if thin films having different 
properties are laminated, an electric current is in order-passed through 
each corresponding boat to deposit the material. In addition, if a mixed 
film of the materials having different properties is deposited, the 
materials are co-deposited by simultaneously passing an electric current 
through a desired number of quartz boats while monitoring the deposition 
rate to determine the mixing ratio of the materials. 
The deposition is performed at a degree of vacuum in the order of 5E-5 
(Torr). The film thickness is monitored using a quartz oscillator. The 
film thickness is determined by the correlative data prepared in advance 
between the number of vibration and the film thickness. The substrate 
carrying a deposited film is taken out of the vacuum chamber and placed on 
a metal mask of another vacuum deposition system so that a part thereof is 
not covered with a metal layer. Then metal particles are placed on a 
coiled tungsten wire (0.5 .phi.; 4 turns), the vaccum chamber is evacuated 
to a degree of vacuum of about 2E-6 (Torr) and then an electric current of 
about 12 .ANG. is passed through the tungsten wire to deposit the metal. 
The deposited substrate is taken out of the vacuum chamber and the 
transparent electrode and the metal electrode are connected, respectively, 
to the positive and negative voltage terminals of a DC power supply. The 
volume of the DC power supply is gradually increased while observing the 
voltage, electric current and brightness of the emitted light by measuring 
apparatuses. 
The present invention also relates to a non-linear optical material which 
makes use of the tetravinylpyrazine compound of the invention. 
The non-linear optical devices make use of the tertiary non-linear optical 
effect and examples thereof include optical bistable elements and optical 
gate switches. Therefore, the non-linear optical materials used for 
producing these devices must be those exhibiting tertiary non-linear 
optical effects. 
The inventors of this invention have conducted intensive studies, have 
found that specific tetravinylpyrazine compounds show high tertiary 
non-linear optical effects and thus have completed the present invention. 
The tetravinylpyrazine compounds have molecular structures having 
two-dimensional .pi. electron conjugated systems which are effective for 
obtaining high non-linear optical effects. 
The non-linear optical materials according to the present invention 
comprise a tetravinylpyrazine compound represented by Formula (1). In this 
case, the tetravinylpyrazine compound can be used alone or in combination 
with other organic or inorganic materials. The compounds may be in 
amorphous states, microcrystalline states, microcrystal-containing 
amorphous states or polycrystalline states which may be appropriately 
selected. Preferred are those comprising regularly arranged molecules from 
the optical standpoint. 
The non-linear optical material is preferably in the form which comprises a 
substrate provided thereon with a thin film of the tetravinylpyrazine 
compound; or a thin layer or a film of the compound dispersed in another 
organic material such as a polymer; or such a layer or film deposited on a 
substrate. The thickness of the optical material is on the order of 10 
.ANG. to 100 .mu.. The non-linear optical material can be formed by a 
variety of methods such as vapor deposition, sublimation and coating 
methods which are appropriately selected. 
If the compounds of the present invention are used for the production of 
electroluminescent elements and non-linear optical material, the 
substituent X in Formula (1) is preferably a hydrogen atom, an alkyl 
group, a halogen atom, a phenyl group, a dialkylamino group or an alkoxy 
group. 
The present invention will hereinafter be described in more detail with 
reference to the following non-limitative working Examples. 
Example 1 
To a 200 ml volume egg-plant type flask equipped with a reflux condenser 
and a tube for introducing nitrogen gas, there were added 3.00 g (0.022 
mole) of 2,3,5,6-tetramethyl pyrazine, 28.05 g (0.264 mole) of 
benzaldehyde and 59.72 g (0.264 mole) of benzoic anhydride and the 
contents of the flask were reacted for 10 hours with heating at 
230.degree. C. in a silicone oil bath while gradually passing nitrogen 
gas. After the reaction, the heating was interrupted, 100 ml of ethanol 
was added when the temperature of the reaction system reached 60.degree. 
to 65.degree. and the system was allowed to stand overnight. Crystals 
precipitated were recovered through filtration under reduced pressure. The 
crystals recovered on a filters paper were washed several times with 
ethanol and dried under reduced pressure. After drying, the crystals were 
recrystallized from toluene to give 
2,3,5,6-tetrakis[2-(phenyl)vinyl]pyrazine as needles of pale yellowish 
brown. The yield thereof was 5.19 g (48.3%). 
The melting point of the resulting 
2,3,5,6-tetrakis[2-(phenyl)vinyl]pyrazine was 261.5.degree.-263.5.degree. 
C. The mass spectrogram and NMR spectrogram of the product are shown in 
FIGS. 5 and 6 respectively. 
Example 2 
To a 200 ml volume egg-plant type flask equipped with a reflux condenser 
and a tube for introducing nitrogen gas, there were added 2.00 g (0.0147 
mole) of 2,3,5,6-tetramethyl pyrazine, 21.17 g (0.176 mole) of 
4-methylbenzaldehyde and 39.88 g (0.176 mole) of benzoic anhydride and the 
contents of the flask were reacted for 10 hours with heating at 
240.degree. C. in a silicone oil bath while gradually passing nitrogen 
gas. After completion of the reaction, the heating was interrupted, 100 ml 
of ethanol was added when the temperature of the reaction system reached 
60.degree. to 65.degree. C. and the system was allowed to stand overnight. 
Crystals precipitated were recovered through filtration under reduced 
pressure. The crystals recovered on a filter paper were washed several 
times with ethanol and dried under reduced pressure. After drying, the 
crystals were recrystallized from toluene to give 
2,3,5,6-tetrakis[2-(4-methylphenyl) vinyl]pyrazine as needles of golden 
yellow. The yield thereof was 5.19 g (48.3%). 
The melting point of the resulting 
2,3,5,6-tetrakis[2-(4-methylphenyl)vinyl]pyrazine was 
283.degree.-286.degree. C. The mass spectrogram and NMR spectrogram 
thereof are shown in FIGS. 7 and 8 respectively. 
Example 3 
To a 200 ml volume egg-plant type flask equipped with a reflux condenser 
and a tube for introducing nitrogen gas, there were added 2.00 g (0.0147 
mole) of 2,3,5,6-tetramethyl pyrazine, 24.74 g (0,176 mole) of 
4-chlorobenzaldehyde and 39.88 g (0.176 mole) of benzoic anhydride and the 
contents of the flask were reacted for 10 hours with heating at 
240.degree. C. in a silicone oil bath while gradually passing nitrogen 
gas. After completion of the reaction, the heating was interrupted, 100 ml 
of ethanol was added when the temperature of the reaction system reached 
60.degree. to 65.degree. C. and the system was allowed to stand overnight. 
Crystals precipitated were recovered through filtration under reduced 
pressure. The crystals recovered on a filter paper were washed several 
times with ethanol and dried under reduced pressure. After drying, the 
crystals were recrystallized from toluene to give 
2,3,5,6-tetrakis[2-(4-chlorophenyl) vinyl]pyrazine as needles of orange 
color. The yield thereof was 5.83 g (63.3%). 
The melting point of the resulting 
2,3,5,6-tetrakis[2-(4chlorophenyl)vinyl]pyrazine was 
317.degree.-318.degree. C. The mass spectrogram and NMR spectrogram 
thereof are shown in FIGS. 9 and 10 respectively. 
Example 4 
To a 200 ml volume egg-plant type flask equipped with a reflux condenser 
and a tube for introducing nitrogen gas, there were added 2.00 g (0.0147 
mole) of 2,3,5,6-tetramethyl pyrazine, 27.53 g (0.176 mole) of 
1-naphthylaldehyde and 39.88 g (0.176 mole) of benzoic anhydride and the 
contents of the flask were reacted for 9 hours with heating at 230.degree. 
C. in a silicone oil bath while gradually passing nitrogen gas. After 
completion of the reaction, the heating was interrupted, 100 ml of ethanol 
was added when the temperature of the reaction system reached 60.degree. 
to 65.degree. C. and the system was allowed to stand overnight. 
Crystals precipitated were recovered through filtration under reduced 
pressure. The crystals recovered on a filter paper were washed several 
times with ethanol and dried under reduced pressure. After drying, the 
crystals were recrystallized from toluene to give 
2,3,5,6-tetrakis[2-(1-naphthyl)vinyl]pyrazine as red needles. The yield 
thereof was 0.21 g (2.1% ). 
The melting point of the resulting 2,3,5,6-tetrakis [2- 
(1-naphthyl)vinyl]pyrazine was 311.degree.-315.degree. C. The mass 
spectrogram and NMR spectrogram thereof are shown in FIGS. 11 and 12 
respectively. 
Example 5 
To a 300 ml volume flask equipped with a reflux condenser and a tube for 
introducing nitrogen gas, there were added 3.00 g (0,022 mole) of 
2,3,5,6-tetramethyl pyrazine, 28.31 g (0.264 mole) of pyridine-3-aldehyde 
and 41.76 g (0.264 mole) of butyric anhydride and the contents of the 
flask were heated for 7 hours at 230.degree. C. while passing nitrogen 
gas. After completion of the reaction and cooling down to about room 
temperature, an aqueous solution of sodium hydroxide (25.34 g NaOH/100 ml 
H.sub.2 O) was added and the mixture was stirred. To the mixture, there 
was added 130 ml of methylene chloride, followed by stirring and allowing 
to stand overnight. Since solids were precipitated out in the methylene 
chloride phase, the solids were filtered after removing the water phase. 
The solids were dried and then recrystallized from dimethylformamide (DMF) 
to give 4.34 g (yield 40.11%) of 
2,3,5,6-tetrakis[2-(3-pyridyl)vinyl]pyrazine as needles of orange color. 
The melting point of the resulting 
2,3,5,6-tetrakis[2-(3-pyridyl)vinyl]pyrazine was 300.degree.-302.degree. 
C. The resulting crystal was confirmed to be the desired compound by mass 
spectroscopic and NMR spectroscopic measurements. 
Example 6 
To a 500 ml volume flask equipped with a reflux condenser and a tube for 
introducing nitrogen gas, there were added 3.00 g (0.022 mole) of 
2,3,5,6-tetramethyl pyrazine, 32.24 g (0.264 mole) of 
p-hydroxybenzaldehyde, 59.80 g (0.264 mole) of benzoic anhydride and 100 
ml of decalin and the contents of the flask were refluxed for 7 hours 
while passing nitrogen gas. After completion of the reaction and cooling 
down to about 50 .degree. C., 200 ml of ethanol was added and the mixture 
was allowed to stand overnight. 
The solids precipitated were dried and then recrystallized from DMF-ethanol 
mixed solvent to give 11.28 g (yield 52.96%) of 
2,3,5,6-tetrakis[2-(4-benzoyloxyphenyl)vinyl]pyrazine as yellow needles. 
The melting point of the resulting 
2,3,5,6-tetrakis[2-(4-benzoyloxyphenyl)vinyl]pyrazine was 
249.degree.-251.degree. C. The resulting crystal was confirmed to be the 
intended compound by mass spectroscopic and NMR spectroscopic 
measurements. 
Example 7 
To a 200 ml volume flask equipped with a reflux condenser, there was added 
2.13 g (0.022 mole) of 
2,3,5,6-tetrakis[2-(4-benzoyloxyphenyl)vinyl]pyrazine and then 30 ml of 
DMF was added to dissolve the compound. A 3% sodium hydroxide solution 
(141 ml) was added to the flask and the contents of the flask were reacted 
by heating at 90.degree. C. for one hour. After completion of the reaction 
and cooling down to about room temperature, 100 ml of acetone was added 
and the mixture was sufficiently stirred. 
The solids formed were filtered off and the filtrate was concentrated. 
Methanol was added to the concentrate to give solids . The solids were 
dissolved under heating and recrystallized from the methanol to give 
2,3,5,6-tetrakis[2-(4-hydroxyphenyl)vinyl]pyrazine as yellow crystals. 
The resulting crystal was confirmed to be the intended compound by mass 
spectroscopic and NMR spectroscopic measurements. 
Example 8 
To a 500 ml volume flask equipped with a reflux condenser and a tube for 
introducing nitrogen gas, there were added 3.00 g (0,022 mole) of 
2,3,5,6-tetramethyl pyrazine, 39.63 g (0.264 mole) of p-formylbenzoic 
acid, 59.80 g (0,264 mole) of benzoic anhydride and 150 ml of decalin and 
the contents of the flask were refluxed for 5 hours while passing nitrogen 
gas. After completion of the reaction, the reaction system was allowed to 
stand overnight to give yellow solids. An amount of 200 ml of ethanol was 
added and the mixture was stirred for 2 hours. 
The solids precipitated were filtered and then dried to give 30.63 g of 
2,3,5,6-tetrakis[2-(4-benzoyloxycarbonylphenyl) vinyl]pyrazine as yellow 
solids. 
The resulting solids were confirmed to be the intended compound by mass 
spectroscopic and NMR spectroscopic measurements. 
Example 9 
An ITO film of 1000 A thickness serving as a first electrode was formed on 
a glass substrate. As a positive hole-transporting thin film, a film of 
N,N'-diphenyl-N,N'-bis-(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine was 
formed to a thickness of 600 .ANG. by the resistance heating evaporation 
method. As a light-emitting layer, an organic thin film of 
2,3,5,6-tetrakis[2-(phenyl)vinyl]pyrazine was formed to a thickness of 600 
.ANG. by the resistance heating evaporation method. Further an Mg metal 
layer was deposited by the resistance heating evaporation method to give a 
second electrode and to thus complete an EL element having a structure as 
shown in FIG. 2. In this respect, the area of the deposited film of Mg 
metal was 1 cm square. The ITO electrode and the Mg electrode were, 
respectively, connected to positive and negative voltage terminals of a 
power supply and an electric voltage was applied to the element. As a 
result, a bright yellow light which could be recognized under the 
irradiation with light rays from an indoor fluorescent lamp was emitted 
from the element at a voltage of not less than ten-odd volts. More 
specifically, the brightness observed was 1100 (cd/m.sup.2) at an applied 
DC voltage of 13 V and a current density of 56 mA/cm.sup.2. Moreover, the 
EL element emitted a light at high brightness and showed stable 
properties. More specifically, it was confirmed that the element could 
withstand continuous operation over several thousand hours at a brightness 
of several hundreds (cd/m.sup.2). 
Example 10 
An ITO film of 1000 .ANG. thickness serving as a first electrode was formed 
on a glass substrate. As a positive hole-transporting thin film, a film of 
N,N'-diphenyl-N,N'-bis-(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine was 
formed to a thickness of 600 .ANG. by the resistance heating evaporation 
method. As a light-emitting layer, an organic thin film of 
2,3,5,6-tetrakis[2-(phenyl)vinyl]pyrazine was formed to a thickness of 300 
.ANG. by the resistance heating evaporation method. Then a thin film of 
tris-(8-hydroxyquinolinol)aluminum serving as an electron-transporting 
thin film was formed on the light-emitting film to a thickness of 300 
.ANG. by the resistance heating evaporation method. Further an Mg metal 
thin film was deposited by the resistance heating evaporation method to 
give a second electrode and to thus complete an EL element having a 
structure as shown in FIG. 4. In this respect, the area of the deposited 
film of Mg metal was 1 cm square. The ITO electrode and the Mg electrode 
were, respectively, connected to positive and negative voltage terminals 
of a power supply and an electric voltage was applied to the element. As a 
result, a bright yellow light which could be recognized under the 
irradiation with light rays from an indoor fluorescent lamp was emitted 
from the element at a voltage of not less than ten-odd volts. More 
specifically, the brightness observed was 3357 (cd/m.sup.2) at an applied 
DC voltage of 28 V and a current density of 156 mA/cm.sup.2. Moreover, the 
EL element emitted a light at high brightness and showed stable 
properties. More specifically, it was confirmed that the element could 
withstand continuous operation over several thousand hours at a brightness 
of several hundreds (cd/m.sup.2). 
Example 11 
An ITO film of 1000 .ANG. thickness serving as a first electrode was formed 
on a glass substrate. As a positive hole-transporting thin film, a film of 
N,N'-diphenyl-N,N'-bis-(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine was 
formed to a thickness of 600 .ANG. by the resistance heating evaporation 
method. As a light-emitting layer, an organic thin film of 
2,3,5,6-tetrakis[2-(4-methylphenyl)vinyl]pyrazine was formed to a 
thickness of 300 .ANG. by the resistance heating evaporation method. Then 
a thin film of tris-(8-hydroxyquinolinol)aluminum serving as an 
electron-transporting thin film was formed on the light-emitting film to a 
thickness of 300 .ANG. by the resistance heating evaporation method. 
Further an Mg metal thin film was deposited by the resistance heating 
evaporation method to give a second electrode and to thus complete an EL 
element having a structure as shown in FIG. 4. In this respect, the area 
of the deposited film of Mg metal was 1 cm square. The ITO electrode and 
the Mg electrode were, respectively, connected to positive and negative 
voltage terminals of a power supply and an electric voltage was applied to 
the element. As a result, a bright yellow light which could be recognized 
under the irradiation with light rays from an indoor fluorescent lamp was 
emitted from the element at a voltage of not less than ten-odd volts. More 
specifically, the brightness observed was 4069 (cd/m.sup.2) at an applied 
DC voltage of 32 V and a current density of 151 mA/cm.sup.2. Moreover, the 
EL element emitted a light at high brightness and showed stable 
properties. More specifically, it was confirmed that the element could 
withstand continuous operation over several thousand hours at a brightness 
several hundreds (cd/m.sup.2). 
Example 12 
An ITO film of 1000 .ANG. thickness serving as a first electrode was formed 
on a glass substrate. As a positive hole-transporting thin film, a film of 
N,N'-diphenyl-N,N'-bis-(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine was 
formed to a thickness of 600 .ANG. by the resistance heating evaporation 
method. As a light-emitting layer, an organic thin film of 
2,3,5,6-tetrakis[2-(4-chlorophenyl)vinyl]pyrazine was formed to a 
thickness of 300 .ANG. by the resistance heating evaporation method. Then 
a thin film of tris-(8-hydroxyquinolinol)aluminum serving as an 
electron-transporting thin film was formed on the light-emitting film to a 
thickness of 300 .ANG. by the resistance heating evaporation method. 
Further an Mg metal thin film was deposited by the resistance heating 
evaporation method to give a second electrode and to thus complete an EL 
element having a structure as shown in FIG. 4. In this respect, the area 
of the deposited film of Mg metal was 1 cm square. The ITO electrode and 
the Mg electrode were, respectively, connected to positive and negative 
voltage terminals of a power supply and an electric voltage was applied to 
the element. As a result, a bright yellow light which could be recognized 
under the irradiation with light rays from an indoor fluorescent lamp was 
emitted from the element at a voltage of not less than ten-odd volts. More 
specifically, the brightness observed was 1513 (cd/m.sup.2) at an applied 
DC voltage of 35 V and a current density of 75 mA/cm.sup.2. Moreover, the 
EL element emitted a light at high brightness and showed stable 
properties. More specifically, it was confirmed that the element could 
withstand continuous operation over several thousand hours at a brightness 
of several hundreds (cd/m.sup.2). 
Example 13 
An ITO film of 1000 .ANG. thickness serving as a first electrode was formed 
on a glass substrate. As a positive hole-transporting thin film, a film of 
N,N'-diphenyl-N,N'-bis-(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine was 
formed to a thickness of 600 .ANG. by the resistance heating evaporation 
method. As a light-emitting layer, an organic thin film of 
2,3,5,6-tetrakis[2-(1-naphthyl)vinyl]pyrazine was formed to a thickness of 
300.ANG. by the resistance heating evaporation method. Then a thin film of 
tris-(8-hydroxyquinolinol)aluminum serving as an electron-transporting 
thin film was formed on the light-emitting film to a thickness of 300 
.ANG. by the resistance heating evaporation method. Further an Mg metal 
thin film was deposited by the resistance heating evaporation method to 
give a second electrode and to thus complete an EL element having a 
structure as shown in FIG. 4. In this respect, the area of the deposited 
film of Mg metal was 1 cm square. The ITO electrode and the Mg electrode 
were, respectively, connected to positive and negative voltage terminals 
of a power supply and an electric voltage was applied to the element. As a 
result, a bright yellow light which could be recognized under the 
irradiation with light rays from an indoor fluorescent lamp was emitted 
from the element at a voltage of not less than ten-odd volts. More 
specifically, the brightness observed was 752 (cd/m.sup.2) at an applied 
DC voltage of 29 V and a current density of 80 mA/cm.sup.2. Moreover, the 
EL element emitted a light at high brightness and showed stable 
properties. More specifically, it was confirmed that the element could 
withstand continuous operation over several thousand hours at a brightness 
of several hundreds (cd/m.sup.2). 
Example 14 
An ITO film of 1000 .ANG. thickness serving as a first electrode was formed 
on a glass substrate. As a positive hole-transporting thin film, a film of 
N,N'-diphenyl-N,N'-bis-(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine was 
formed to a thickness of 600 .ANG. by the resistance heating evaporation 
method. As a light-emitting layer, an organic thin ,film of 
2,3,5,6-tetrakis[2-(3-pyridyl)vinyl]pyrazine was formed to a thickness of 
600 .ANG. by the resistance heating evaporation method. Further an Mg 
metal thin film was deposited by the resistance heating evaporation method 
to give a second electrode and to thus complete an EL element having a 
structure as shown in FIG. 2. In this respect, the area of the deposited 
film of Mg metal was 1 cm square. The ITO electrode and the Mg electrode 
were, respectively, connected to positive and negative voltage terminals 
of a power supply and an electric voltage was applied to the element. As a 
result, a bright orange light which could be recognized under the 
irradiation with light rays from an indoor fluorescent lamp was emitted 
from the element at a voltage of not less than ten-odd volts. More 
specifically, the brightness observed was 250 (cd/m.sup.2) at an applied 
DC voltage of 24 V and a current density of 77 mA/cm.sup.2. Moreover, the 
EL element emitted a light at high brightness and showed stable 
properties. More specifically, it was confirmed that the element could 
withstand continuous operation over several thousand hours at a brightness 
of several hundreds (cd/m.sup.2). 
Example 15 
An ITO film of 1000 .ANG. thickness serving as a first electrode was formed 
on a glass substrate. As a positive hole-transporting thin film, a film of 
N,N'-diphenyl-N,N'-bis-(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine was 
formed to a thickness of 600 .ANG. by the resistance heating evaporation 
method. As a light-emitting layer, an organic thin film of 
2,3,5,6-tetrakis[2-(3-pyridyl)vinyl]pyrazine was formed to a thickness of 
300 .ANG. by the resistance heating evaporation method. Then a thin film 
of tris-(8-hydroxyquinolinol)aluminum serving as an electron-transporting 
thin film was formed on the light-emitting film to a thickness of 300 
.ANG. by the resistance heating evaporation method. Further an Mg metal 
thin film was deposited by the resistance heating evaporation method to 
give a second electrode and to thus complete an EL element having a 
structure as shown in FIG. 4. In this respect, the area of the deposited 
film of Mg metal was 1 cm square. The ITO electrode and the Mg electrode 
were, respectively, connected to positive and negative voltage terminals 
of a power supply and an electric voltage was applied to the element. As a 
result, a bright orange light which could be recognized under the 
irradiation with light rays from an indoor fluorescent lamp was emitted 
from the element at a voltage of not less than ten-odd volts. More 
specifically, the brightness observed was 120 (cd/m.sup.2) at an applied 
DC voltage of 23 V and a current density of 21 mA/cm.sup.2. Moreover, the 
EL element emitted a light at high brightness and showed stable 
properties. More specifically, it was confirmed that the element could 
withstand continuous operation over several thousand hours at a brightness 
of several hundreds (cd/m.sup.2). 
The present invention can provide electroluminescent elements which 
comprise thin films of uniform thickness, have excellent light-emitting 
properties and thermal stability and can withstand the operation over a 
long time, as seen from the results obtained in Examples 9 to 15. 
Example 16 
An organic thin film of 2,3,5,6-tetrakis[2-(phenyl) vinyl]pyrazine was 
deposited onto a quartz substrate to a thickness of 500 .ANG. by the 
resistance heating evaporation method. The value of .chi. .sup.(3) of the 
organic thin film was determined by the four-light wave mixing method and 
found to be 1.39.times.10.sup.-6 esu at 460 nm. This value is two digits 
higher than those of the conventionally known organic non-linear optical 
materials. 
Example 17 
An organic thin film of 2,3,5,6-tetrakis[2-(4-methylphenyl)vinyl]pyrazine 
was deposited onto a quartz substrate to a thickness of 500 .ANG. by the 
resistance heating evaporation method. The value of .chi. .sup.(3) of the 
organic thin film was determined by the four-light wave mixing method and 
found to be 2.65.times.10.sup.31 6 esu at 460 nm. This value is two digits 
higher than those of the conventionally known organic nonlinear optical 
materials. 
Example 18 
An organic thin film of 2,3,5,6-tetrakis[2-(4-chlorophenyl)vinyl]pyrazine 
was deposited onto a quartz substrate to a thickness of 500 .ANG. by the 
resistance heating evaporation method. The value of .chi..sup.(3) of the 
organic thin film was determined by the four-light wave mixing method and 
found to be 1.03.times.10.sup.-6 esu at 460 nm. This value is two digits 
higher than those of the conventionally known organic nonlinear optical 
materials. 
Example 19 
An organic thin film of 2,3,5,6-tetrakis[2-(1-naphthyl)vinyl]pyrazine was 
deposited onto a quartz substrate to a thickness of 500 .ANG. by the 
resistance heating evaporation method. The value of .chi..sup.(3) of the 
organic thin film was determined by the four-light wave mixing method and 
found to be 1.25.times.10.sup.6 esu at 460 nm. This value is two digits 
higher than those of the conventionally known organic non-linear optical 
materials. 
Example 20 
An optical bistable element was produced as an example of a tertiary 
non-linear optical device. The structure of the resulting optical bistable 
element and an apparatus for evaluating properties thereof are shown in 
FIG. 13. As shown in FIG. 13, a film of 
2,3,5,6-tetrakis[2-(phenyl)vinyl]pyrazine vapor-deposited on a glass plate 
13 through an anti-reflection coating and a glass plate 11 provided with 
an anti-reflection coating were held by a metal holder through spacers 14 
of PZT to give a Fabry-Perot type element. The light rays from a 
variable-wavelength laser source 15 was divided into two portions through 
a half mirror 16 and one of these was guided towards a Fabry-Perot type 
element. The light rays passed through the etalon were detected by a 
photodetector 18. The laser rays used had a wavelength of 460 nm and were 
focused on the etalon at an intensity of 100 mW to give a spot of 10 
.mu.m. The resulting data were displayed and plotted on an oscilloscope 
with the intensity of light incident upon the etalon on the X-axis and 
that of light passing through the etalon on the Y-axis, while changing the 
intensity of the light incident upon the etalon. As a result, when the 
intensity of the incident light was first increased and then decreased, 
the intensity of the output light followed two different traces as shown 
in FIG. 14, i.e., exhibited the bistable characteristic. The device 
exhibited this characteristic even at a light intensity of not more than 
10 mW. Thus the non-linear optical material according to the present 
invention shows excellent quality. 
The results obtained in the foregoing Examples 16 to 20 clearly indicate 
that the non-linear optical material which makes use of the 
tetravinylpyrazine compound exhibits the nonlinear optical effect 
substantially greater than that achieved by the conventional materials.