Methine and azamethine dyes based on naphthoquinones in nonlinear optics

Naphthalene derivatives of the formula ##STR1## where the rings A and B may be benzofused, PA1 X is nitrogen or a radical of the formula CH or CH.dbd.CH--CH, PA1 Z is a heterocyclic radical or additionally, when x is CH.dbd.CH--CH, a 5- or 6-membered aromatic carbocyclic radical, and PA1 R.sup.1, R.sup.2 and R.sup.3 are hydrogen, C.sub.1 -C.sub.4 -alkyl or C.sub.5 -C.sub.7 -cycloalkyl, are useful in nonlinear optics.

This application is a 371 of PCT/EP95/02328 filed Jun. 16, 1995. 
The present invention relates to the use of methine or azamethine dyes 
based on naphthoquinones in nonlinear optics and to novel methine dyes. 
The nonlinear optical properties of organic compounds find application in 
many areas of optoelectronics. Examples are applications in frequency 
doubling, phase modulators, optical amplifiers, interferometers, optical 
switches or communications technology. 
It is common knowledge that organic materials, in particular polymers with 
specific chromophores, can have nonlinear optical properties which in some 
instances are more considerable than those of comparable inorganic 
materials. 
The materials currently most frequently used are inorganic crystals, for 
example of potassium dihydrogenphosphate or lithium niobate. These 
crystals are complicated and costly to produce and, owing to their rigid 
structure, difficult to use in optical apparatus. A further disadvantage 
are their small nonlinear effects. 
A particular advantage of suitable organic chromophores and their use in 
polymeric materials is their simple preparation and processing. 
The chromophores used in nonlinear optics are generally used either in 
crystalline form or in polymer-bound form. 
DE-A-3 904 797, EP-A-312 856 and EP-A-572 898 disclose the use of dyes in 
polymeric nonlinear optical systems. 
It is an object of the present invention to provide suitable methine or 
azamethine dyes based on naphthoquinones which shall be advantageously 
used in polymeric nonlinear optical systems. More particularly, such dyes 
shall have large hyperpolarizability values, good thermal stability, good 
compatibility with the polymers used in nonlinear optical systems, and 
good film-forming properties with copolymers. 
We have found that this object is achieved by naphthalene derivatives of 
the formula I 
##STR2## 
where the rings A and B may each be benzofused, 
X is nitrogen or a radical of the formula CH or CH.dbd.CH--CH, 
Z is a 5- or 6-membered aromatic heterocyclic radical or additionally, when 
X is CH.dbd.CH--CH, a 5- or 6-membered aromatic carbocyclic radical, and 
R.sup.1, R.sup.2 and R.sup.3 are independently of one other hydrogen, 
C.sub.1 -C.sub.4 -alkyl or C.sub.5 -C.sub.7 -cycloalkyl, in nonlinear 
optics. 
Z in the formula I can be derived for example from components of the 
benzene, thiophene, thiazole, oxadiazole or thiadiazole series. 
Particularly suitable radicals Z include for example those of the formulae 
IIIa to IIIf 
##STR3## 
where the ring K may be benzofused, 
L.sup.1 and L.sup.2 are independently of each other hydrogen, C.sub.1 
-C.sub.10 -alkyl which may be phenyl-, hydroxyl-, acryloyloxy- or 
methacryloyloxy-substituted, or phenyl, or L.sup.1 and L.sup.2 are 
together with the nitrogen atom joining them together pyrrolidinyl, 
piperidinyl, morpholinyl, piperazinyl or N-(C.sub.1 -C.sub.4 
-alkyl)piperazinyl, 
L.sup.3 and L.sup.4 are independently of each other hydrogen, C.sub.1 
-C.sub.10 -alkyl, C.sub.5-C.sub.7 -cycloalkyl, C.sub.1 -C.sub.10 -alkoxy, 
cyano or halogen, and 
L.sup.5 is hydrogen, C.sub.1 -C.sub.10 -alkyl which may be phenyl-, 
hydroxyl-, acryloyloxy- or methacryloyloxy-substituted, C.sub.5 -C.sub.7 
-cycloalkyl, phenyl, C.sub.1 -C.sub.10 -alkoxy, cyano, nitrogen or 
halogen. 
Any alkyl appearing in the abovementioned formulae may be straight-chain or 
branched. 
In any substituted alkyl appearing in the abovementioned formulae the 
number of substituents is generally 1 or 2. 
L.sup.1, L.sup.2, L.sup.3, L.sup.4, L.sup.5, R.sup.1, R.sup.2 and R.sup.3 
are each for example methyl, ethyl, propyl, isopropyl, butyl, isobutyl, 
sec-butyl or tert-butyl. 
L.sup.1, L.sup.2, L.sup.3, L.sup.4 and L.sup.5 may each also be for example 
pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, 2-methylpentyl, heptyl, 
octyl, 2-ethylhexyl, isooctyl, nonyl, isononyl, decyl or isodecyl (the 
above designations isooctyl, isononyl and isodecyl are trivial names 
derived from the oxo process alcohols--cf. Ullmann's Encyclopedia of 
Industrial Chemistry, 5th Edition, Vol. A1, pages 240 to 293, and Vol. 
A10, pages 284 to 285). 
L.sup.3, L.sup.4, L.sup.5, R.sup.1, R.sup.2 and R.sup.3 may each also be 
for example cyclopentyl, cyclohexyl or cycloheptyl. 
L.sup.3, L.sup.4 and L.sup.5 may each also be for example methoxy, ethoxy, 
propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, pentyloxy, 
isopentyloxy, neopentyloxy, tert-pentyloxy, hexyloxy, 2-methylpentyloxy, 
heptyloxy, octyloxy, 2-ethylhexyloxy, isooctyloxy, nonyloxy, isononyloxy, 
decyloxy, isodecyloxy, fluorine, chlorine, bromine or iodine. 
L.sup.1 and L.sup.2 L.sup.5 may each also be for example benzyl, 1- or 
2-phenylethyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 
2-hydroxybutyl, 4-hydroxybutyl, 5-hydroxypentyl, 6-hydroxyhexyl, 
7-hydroxyheptyl, 8-hydroxyoctyl, 9-hydroxynonyl, 10-hydroxydecyl, 
2-acryloyloxyethyl, 2-methacryloyloxyethyl, 2- or 3-acryloyloxypropyl, 2- 
or 3-methacryloyloxypropyl, 2- or 4-acryloyloxybutyl, 2- or 
4-methacryloyloxybutyl, 5-acryloyloxypentyl, 5-methacryloyloxypentyl, 
6-acryloyloxyhexyl, 6-methacryloyloxyhexyl, 7-acryloyloxyheptyl, 
7-methacryloyloxyheptyl, 8-acryloyloxyoctyl, 8-methacryloyloxyoctyl, 
9-acryloyloxynonyl, 9-methacryloyloxynonyl, 10-acryloyloxydecyl or 
10-methacryloyloxydecyl. 
Preference is given to the use of naphthalene derivatives of the formula I 
where the rings A and B are not benzofused. 
Preference is further given to the use of naphthalene derivatives of the 
formula I where R.sup.1, R.sup.2 and R.sup.3 are each hydrogen. 
Preference is further given to the use of naphthalene derivatives of the 
formula I where Z is derived from a component of the thiophene, thiazole, 
oxadiazole or thiadiazole series or additionally, when X is CH.dbd.CH--CH, 
from a component of the benzene series. 
Particular preference is given to the use of naphthalene derivatives of the 
formula I where Z is derived from a component of the thiophene or thiazole 
series, especially from radicals of the formula IIIb, IIIc or IIId or 
additionally, when X is CH.dbd.CH--CH, from a component of the benzene 
series, especially from the radicals of the formula IIIa. 
The naphthalene derivatives of the formula I are partly known and described 
for example in J. Chem. Soc. Perk. Trans. I, pages 2434 to 2442, 1988. 
The present invention further provides naphthalene derivatives of the 
formula II 
##STR4## 
where the rings A and B may each be benzofused, 
w is a radical of the formula CH or CH.dbd.CH--CH, 
Z is a 5- or 6-membered aromatic heterocyclic radical or additionally, when 
W is CH.dbd.CH--CH, a 5- or 6-membered aromatic carbocyclic radical, and 
R.sup.1, R.sup.2 and R.sup.3 are independently of one other hydrogen, 
C.sub.1 -C.sub.4 -alkyl or C.sub.5 -C.sub.7 -cycloalkyl. 
Preference is given to naphthalene derivatives of the formula II where the 
rings A and B are not benzofused. 
Preference is further given to naphthalene derivatives of the formula II 
where R.sup.1, R.sup.2 and R.sup.3 are each hydrogen. 
Preference is further given to naphthalene derivatives of the formula II 
where Z is derived from a component of the thiophene, thiazole, oxadiazole 
or thiadiazole series or additionally, when W is CH.dbd.CH--CH, from a 
component of the benzene series. 
Particular preference is given to naphthalene derivatives of the formula II 
where Z is derived from a component of the thiophene or thiazole series, 
especially from radicals of the formula IIIb, IIIc or IIId or 
additionally, when W is CH.dbd.CH--CH, from a component of the benzene 
series, especially from the radicals of the formula IIIa. 
The naphthalene derivatives of the formula II can be prepared by methods 
known per se. 
For example, a dicyanomethylnaphthalene of the formula IV 
##STR5## 
where R.sup.1, R.sup.2 and R.sup.3 and the rings A and B are each as 
defined above, can be condensed with an aldehyde of the formula V 
EQU Z--(CH.dbd.CH).sub.n --CHO (V), 
where Z is as defined above and n is 0 or 1. 
The aldehydes of the formula V are generally described in the literature. 
The preparation of heterocyclic aldehydes of this kind is described for 
example in German Patent Application P 44 01 912.2. 
The naphthalene derivatives of the formula I are thermally stable above 
200.degree. C. and have particularly large molecular hyperpolarizability 
values (.beta.). The dyes also possess good compatibility with the 
polymers used in nonlinear optical systems and also good film-forming 
properties in copolymers. 
The molecular hyperpolarizability can be determined for example by 
measuring the solvatochromism (see for example Z. Naturforschung, 20a 
(1965), 1441-1471, or J. Org. Chem., 54 (1989), 3775-3778). This method of 
measurement involves determining the position of the absorption band of a 
compound in different solvents, for example in dioxane or dimethyl 
sulfoxide. The shift of the absorption band is then directly proportional 
to the .beta. value, i.e. compounds having a large solvatochromic shift 
have a large molecular hyperpolarizability and are therefore highly 
suitable for use in nonlinear optical systems (see for 45 example 
Chemistry and Industry, 1 Oct. 1990, pages 600 to 608). 
Attention may be drawn in particular to the suitability of the novel 
compounds for use in communications technology, electro-optical modulators 
(e.g. Mach-Zehnder interferometers), optical switches, frequency mixing or 
waveguides.

THE EXAMPLES WHICH FOLLOW ILLUSTRATE THE INVENTION 
EXAMPLE 1 
3.50 g (0.02 mol) of 4-(dimethylamino)cinnemaldehyde and 3.84 g (0.02 mol) 
of 1-dicyanomethylnaphthalene were heated in 40 ml of acetic anhydride at 
80.degree. C. for 3 h. After cooling down, the batch was stirred at 
20.degree. C. for a further 6 h. The residue was filtered off with 
suction, washed with isopropanol and dried at 50.degree. C. under reduced 
pressure, yielding 2.95 g of the compound of the formula 
##STR6## 
C.sub.24 H.sub.19 N.sub.3 (349) Calculated: C 82.49 H 5.48 N 12.03 Found: C 
82.10 H 5.38 N 12.05 
EXAMPLE 2 
1.7 g (0.005 mol) of the compound of the formula 
##STR7## 
and 0.96 g (0.005 mol) of 1-dicyanomethylnaphthalene were heated in 15 ml 
of acetic anhydride at 75.degree. C. for 2 h. After cooling down, the 
batch was stirred at 20.degree. C. for 12 h. The resulting precipitate was 
filtered off with suction, washed with a little methanol and dried at 
50.degree. C. under reduced pressure, yielding 0.5 g of the compound of 
the formula 
##STR8## 
C.sub.33 H.sub.30 N.sub.4 S (515) Calculated: C 77.01 H 5.88 N 10.89 S 6.23 
Found: C 76.84 H 5.68 N 10.81 S 6.10 
EXAMPLE 3 
3.9 g (0.01 mol) of the compound 
##STR9## 
and 1.9 g (0.01 mol) of 1-dicyanomethylnaphthalene were heated in 20 ml of 
acetic anhydride at 80.degree. C. for 2 h in the presence of 0.35 g of 
sodium acetate. After cooling down, the batch was stirred at 20.degree. C. 
for 12 h. The resulting precipitate was filtered off with suction, washed 
with isopropanol and dried at 50.degree. C. under reduced pressure, 
yielding 2.59 g of the compound of the formula 
##STR10## 
C.sub.33 H.sub.32 N.sub.4 S (517) Calculated: C 76.71 H 6.24 N 10.84 S 6.21 
Found: C 75.70 H 6.11 N 10.82 S 6.26 
EXAMPLE 4 
3.16 g (0.01 mol) of the compound of the formula 
##STR11## 
and 1.9 g (0.01 mol) of 1-dicyanomethylnaphthalene were heated at the boil 
in 30 ml of acetic anhydride for 1 h. The resulting dye was filtered off 
with suction, washed with isopropanol and dried at 50.degree. C. under 
reduced pressure, yielding 3.81 g of the compound of the formula 
##STR12## 
C.sub.31 H.sub.30 N.sub.4 S (491) Calculated: C 75.88 H 6.16 N 11.42 S 6.53 
Found: C 75.69 H 6.02 N 11.66 S 6.48 
EXAMPLE 5 
1.12 g (0.01 mol) of 2-formylthiophene and 1.9 g (0.01 mol) of 
1-dicyanomethylnaphthalene were heated at the boil in 30 ml of acetic 
anhydride for 1 h. After cooling down, the batch was stirred at 20.degree. 
C. for 12 h. The resulting product was filtered off with suction, washed 
with isopropanol and dried at 50.degree. C. under reduced pressure, 
yielding 2.2 g of the compound of the formula 
##STR13## 
C.sub.18 H.sub.10 N.sub.2 S (286) Calculated: C 75.50 H 3.52 N 9.78 S 11.20 
Found: C 75.48 H 3.68 N 10.50 S 10.20 
EXAMPLE 6 
1.23 g (0.01 mol) of 2-formyl-5-methylthiophene and 1.9 g (0.01 mol) of 
1-dicyanomethylnaphthalene were heated at the boil in 30 ml of acetic 
anhydride for 1 h. After cooling down, the precipitate was filtered off 
with suction, washed with isopropanol and dried at 50.degree. C. under 
reduced pressure, yielding 2.0 g of the compound of the formula 
##STR14## 
C.sub.19 H.sub.12 N.sub.2 S (300) Calculated: C 75.97 H 4.03 N 9.33 S 10.67 
Found: C 75.80 H 4.10 N 9.15 S 10.42 
EXAMPLE 7 
2.87 g (0.01 mol) of the compound of the formula 
##STR15## 
and 1.9 g (0.01 mol) of 1-dicyanomethylnaphthalene were heated at the boil 
in 40 ml of acetic anhydride for 1 h. After cooling down, the batch was 
stirred at 20.degree. C. for a further 12 h, the resulting dye was 
filtered off with suction and washed with isopropanol, and the product was 
dried at 50.degree. C. under reduced pressure, yielding 2.8 g of the 
compound of the formula 
##STR16## 
C.sub.30 H.sub.27 N.sub.2 O.sub.2 (447) Calculated: C 83.14 H 6.24 N 6.25 
Found: C 82.88 H 6.10 N 6.18 
EXAMPLE 8 
3.38 g (0.01 mol) of the compound of the formula 
##STR17## 
and 1.9 g (0.01 mol) of 1-dicyanomethylnaphthalene were reacted by heating 
in acetic anhydride for 1 h. Thereafter Example 7 was repeated, affording 
3.42 g of the compound of the formula 
##STR18## 
C.sub.33 H.sub.38 N.sub.4 O.sub.2 (512) Calculated: C 77.34 H 5.47 N 10.94 
Found: C 76.68 H 5.21 N 10.33 
EXAMPLE 9 
3.43 g (0.01 mol) of the compound of the formula 
##STR19## 
and 1.9 g (0.01 mol) of 1-dicyanomethylnaphthalene were reacted by heating 
in acetic anhydride for 1 h. Thereafter Example 7 was repeated, affording 
3.6 g of the compound of the formula 
##STR20## 
C.sub.34 H.sub.35 N.sub.2 O.sub.2 (503) Calculated: C 81.11 H 6.96 N 5.56 
Found: C 81.01 H 6.82 N 5.70 
The method described in Z. Naturforschung, 20 a (1965), 1441-1471, was 
followed to measure the absorption maximum of the individual dyes in both 
dioxane and dimethyl sulfoxide (DMSO) to determine the solvatochromic 
shift .DELTA..nu. cm.sup.-1 !. 
The respective measurements are listed below in Table 1. 
TABLE 1 
______________________________________ 
Ex. .lambda..sub.max 
.lambda..sub.max 
.DELTA..nu. 
No. (dioxane) nm! (DMSO) nm! 
cm.sup.-1 ! 
______________________________________ 
1 599 691 2223 
2 614 663 1204 
3 625 712 1755 
7 599 690 2202 
8 623 710 
9 593 690 
______________________________________ 
The suitability of the dyes of the present invention for use in nonlinear 
optics may in addition be illustrated by determining the 
hyperpolarizability (.beta..sub.0) of the dye described in Example 1. The 
hyperpolarizability was determined by an electro-optical measurement of 
absorption. The complete theory of this method of measurement can be found 
in Chem. Phys. 173 (1993), 305-314, Chem. Phys. 173 (1993), 99-108, and J. 
Phys. Chem. 96 (1992), 9724-9730. Of significance in addition to the 
hyper-polarizability (.beta..sub.0) is the parameter .mu..sub.g 
.beta..sub.0 (.mu..sub.g =dipole moment in ground state), which is 
relevant for polymeric nonlinear optical systems, since .mu..sub.g 
.beta..sub.0 is directly proportional to the 2nd order susceptibility. The 
measured .mu..sub.g .beta..sub.0 values are listed below in Table 2 in 
comparison with p-nitroaniline. 
TABLE 2 
______________________________________ 
.beta..sub.0 10.sup.-50 Cm.sup.3 V.sup.-2 ! 
.mu..sub.g .beta..sub.0 10.sup.-80 C.sup.2 m.sup.4 
V.sup.-2 ! 
______________________________________ 
Ex. No. 1 127 4830 
p-Nitroaniline 95 
______________________________________ 
The relevant parameter .mu..sub.g .beta..sub.0 of the methine dye of the 
present invention is about 50 times larger than in the 
literature-described compound and hence impressively underlines the 
suitability of the novel dyes for use in nonlinear optics.