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21

Cation Binding PropertiesofBenzo-type
Crown Ethers.3.i-2)
EffectofLarge Ring Sizeupon Complexation Phenomena ofCrown-9 and Crown-10 Derivatives3)
Mikio OUCHI,Department

andofMaterials

HiromitsuYOSHIDA
Scienceand Chemistry

Graduate School ofEngineering
Abstract
The cation-bindingby two 1argering-sizeda solventof monovalent

extraction

metal

benzo-27-crown-9
and benzo-30-crown-1Ohas been evaluated by
K', Rb", Cs'F',Ag', and Tl') betweenwater andpicrates(Na',dichlolomethane.The effect of ring size and benzo group upon the cation binding ability is discussed.Theresults
arecomparedwith benzo-type crown-6-8
benzo-21-crown-7 and(benzo-IS-orown-6,benzo-24-crown-8) and simple unsubstituted crown-6-8
ethers (18-crown-6,21-crown-7 and 24-crown-8).
The cation-binding ability and complex formationare discussedin yiew of the size of the crown ether ringand
the basieityof oxygen
atoms.
Key Words: crownethers, solvent extraction.

supramolecularchemistry

1. Introduction
variety of fimctionalizedcrownether cornpounds
have been synthesized te control thc complexation
still givesthe idea of
phenomena with cations, The eriginal papar by Pedersen'spioneering work in 1967 [3]the appreach forthe design of supramolecularsystems, The interestin thisfieldby our group isto explore thecharacterof benzo-type crownethers. We
have recently reperted
the cation-binding
abilities
ofless-symmetricalbenzo-type crown ethers and found that dibenzo-crown-6 derivativeswere superior tomonobenzo-crown-ethersin view of cation binding and cation selectivity [1].
And the cation-binding
abilityof largering-sized benzo-crown-7 and crown-8
ethers (1,2,5,6)
has been evaluated by solvent extraction ofmetalThe
results
werecomparedwith
thosederivatives(9-IO).
In general,largeofcrown-6
picrates[4].
ring-sized
benzo-crown-7,and crown-8 ethers have a lower eation-binding
abilityas the ring size increases,
and a cation selectivity forlange
cations (Cs'and Tl'). By determiningthe overall extraction equilibrium
constants
itwas fbund that 1 and 2 tend to form 1i1 crown ether-cation
complexes
underthe conditions(1(E.),of the presentexperimental
study
For furtherdiscussionen the ring-size and thecation-binding ability3 wereportin this paper the syntheses
andcation-binding
ability of largering-sizedmono-benzo-crownethers,benzo-27-crown-9 (3)and benzo-30-crown-10 (4).Their syntheses are described.and their cation-binding
abilities
have been evaluatedby solvent extractionof aqueous
metal picrates.
The results were comparedwiththose of simple crown ethers 27-crown-9 (7),30-crown-10 (8),benzo-18-orown-6 (9),and commerciallyavailable 18-crown-6(10)A wide

2. ExperimentalDetails

Infrared
spectra were

JASCO A-1OO grating spectrophotometer,

Mass spectra were measured
270 spectrometer
NMR spectra were recorded
on a JEOL JNM-EX
inchloroform-dsolution containing
1% tetramethylsilane
as internalstandard. UVLVIS spectra were recorded
ona HitachiU-3500 spectrophotometer.
Melting pointswere measured
with a MEL-TEMP
apparatus
and arefrom sodium hydride, Commerciallyavailable
uncorrected.
Solventtetrahydrofuran(THF)was distilled
reagents
ftirtherunIessnoted
otherwise.
were used in the fbllowing syntheses without
purification
Syntheses.The reagents of the crown ether syntheses are preparedby the synthetic method according tothe similar reported method[2].
usingobtained

Shimazu GCMS-QP5000,

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SCHOOL OF ENGINEERING, UNIVERSITY OF HYOGO No.59(2e06)

REPORTS OF GRADUATE

2,2'-[1,2-Phenylenebis(oxyethyleneoxy)]diethanol
wasSynthesis.
(11)

synthesized

fromcatechol

andetherin the presence of NaOH in 30% yield according
to the similar
glycol mono-2-chloroethyliH
3.87-3.9i
4.13-4.17
6.90
NMR
6
3.66-3.74[5].
(m.4H),(t.8H),(t.4H), (s.4H).
oligoethylene
Oligoethyleneglycol ditesylateswere synthesized from the corresponding
glycol andin 83-89% yieldaccerdingto the reported method
chloride in THF in the presenceofNaOH
p-toluenesulfbnyl
from the authors' group [6].

ethylenerepertedmethod.

Sf.e.
"ao"os(gLot/(PO5: n==16:1: m=12:m

n==27:

F23:

m=34:

n=38:

m=4

n=4

Ooio g g)yoV

Ooioo(oyoVo)

109

Benzo-27-Crown-9
flaskequippedwith.

intoa 2-L three
KOH (3.4g,O.06rnol)
and THF (200mL)were introduced(3).

neckeddroppingfunnel,and nitrogen
inlettube. [Ibthestirred suspension
at 66 ℃ wasadded
2,2'-[1,2-Phenylenebis(oxyethyleneoxy)ldiethanol(ll)(1.8g,O.O06mol) in THF (200mL),
and stirring was continued
for 1 h with consecutive
bubblingof nitrogen.
[IbtaraethyleneO.O065mol) in THF(150mL) was then added
dropwise to the stirred
glycol ditosylate(3.3g,mixture over 3 h, and the stirring was continued
for2 daysat 66 ℃ under a nitrogen atmosphere. The solventa magnetic

stirreg refluxcondenseg

the residue
wasextracted
withchlorofbrm.
The chlorofbrm
extract was dried overAfter
itwasbycolumnchromatographymagnesium
sulfate and the solvent was evaporated.
work-up,puTifiediHNMRS
chloroform-hexane2il) to give O.79g (2g%)
of the product 3 as the oily product.:(alumina.
3.53-3.71(s.28H).
4.15-4.18(t.4H),
6.90 (s.4H);
MS m!e 467 (Mi'+Na").
O.O028mol) and pentaethyleneglycol ditosylate
Benzo-30-Crown-10 (4)was synthesized from 11 (1.67g,O,039mol) in 18% (O.25g)
O.O034mol) in THF in the presence ef KOH (2.18g,
as the oily(l.88g,yieldiH
tothedescribedabove.
NMR
63.53-3.71
4.l4-4.20
6.90
according
product
procedure(t.32H),(t.4H),MS mle 511 (M'+Na').
(s.4H);
27-Crown-9 (7)was synthesizedfrom pentaetyleneglycol (23.gg,O.lmol) and pentaetliylene
glyeolO.09mel)
inTHF
inKOH
O.25mel)in7%
according
toditosylate
theof(47.7g,
presence(16.5g,(2.8g)
yieldItwas
distillation
under
reducedbp
16g-172℃
the similar procedure describedabove.
purifiedby
pressure.
fO.2Torr;iH NMR 6 3.6i (s.28H);
IR (neat)
2850, 1450, 1250, 11OO cm-i; MS 396 ()vC).
30-Crown-10
from pentaetylene glycol (23.8g,O.lmol) and pentaethylene glycol(8)was synthesized
wasevaporated

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ftN.S" :Cation
Binding
Propertiesof Benzo-t･ype
CrewnEthers,
3,Effectof Large
RingSiza
upon Complexation
Phenomenaef
of Crown9 and Crown-10
Derivatives23

ditosylateO.09mol)inTHF inthe presenceof KOH(47.7g,O.25mol) in8% (3.4g)(16.5g,yield ac ¢ ording totheproceduredescribedabove. bp 200℃ fO.3Torr;iH NMR S 3.67 (s.32H);
IR (neat)
2850, 1450, 1350,'124o, 11oocm'i;
Ms 44o (M").
SolventExtraction.The generalextraction proceduresemployed
are similar
to thosepreviously presented [7].
Disti11eddichloromethaneand demineralizedwater
The solvents were saturated with each otherwere used.
before use in order to preventvolume changes of the phase during extraction. Equal volumes(10mL) ofdichloromethane solution of the respective crown ether (3.0mM)and of an aqueoussolutionofthecorresponding
metalmM)
10
wereshakenfbr
minutes
at25℃
inaTaiyo
MIOOL
incubator.
Thepicrate (3.0mixture
wasthen allowed to stand fbr at }east90 minutes
at thattemperature in order
to complete phaseseparation. The organio phase was separated by fi1tration
filterNo.IPS).
Sincethe picrates(Whatman paper
do not dissolvein dichloromethane,the molar extinction
coefficientsin l:1mixtureof dichloromethane
andacetonitrile were determined.
The concentration of alkali
and heavymetal picrat¢ in the organic
phase wasdeterminedfrom absorbance at 375 nm in a. mixture of dichlorometkane and acetonitrile.
The molar
extinctiDncoefficientsat the absorption
maximumof 375 nm
fbrsodium,potassium, rubidiurn, cesium, silver,
and thallium picrates
are l8600, 19000, I8800, 18500, 18800, and 18900 M-icm'i,respectively.
Resultsand Discussion
Synthesis.
The generalidea of the synthesis

has been presented in Pedersen's
converted
to 11 by reaction of[8]
incatechol and ethylene glycolmono-2-chloroethyl
ether
thepresenceof KOH in 28% yield.
The eompound
11 has two side chains possessing oxyethylene chains that would be thecomponentof the crownether hng.
Thus 11 is the starting material of the synthesis
oflargeringmono-benzeethers.
¢ rownBenzo-27-crown-9
in THF in the presenceofKOH
in 289/6yield.
(3)was synthesized from 11 and tetraethylene glycolditosylate
Benzo-30-Crown-IO (4)was synthesizedfrom 11 and pentaethyiene glycol ditosylate
in THF in the presenceofKOH
in I8% yield.
No attempt was made to maximize
theyields
ofthe products.
Unsubstitutedlargering-sizedcrown ethers, 27-oronw-9 (7)was synthesized from pentaetyleneglycoland
in THF in the presenceof KOH in 7% (2.8g)
pentaethyleneglycol ditosylate
yield. Likewise,30-crown-IO
wassynthesized
fromditosylate
in THF in thepresenceof(8)
pentaetyleneglyeol,andpentaethyleneglycol
KOH in 8% yield.The oily products7 and 8 were purifiedby disti11ation
under
reducedpressure.
Though the generalidea of the above synthetic'methods
has been already reported by other and our groups
the characteristic infbrrnationsof the compounds
have not been describedin detail.As well as the[5,9],
reported
data of crown-7andcrown-8compounds
the presentresults would give the detailedstrategic[2],ideaand directionin ease of synthesizing largering-sized macrocyclic compounds.
SolventExtraction.A wide variety of rneasurement
techniques fbr evaluating the characters of macrocyclic
compounds
have been reported. Notable among them are ion-selective electrode techniques, NMR methods,ethers,
solvent
extraction
techniquesand solvent extraction. For crownare quitepepular and convenientInrnethod to evaluate catien binding ability
the presentstudM aqueous some alkaliand heavy metal picrates
solution ofthe crownethers(Na',K", Rb', Cs', Ag', and Tl')were extraoted at 25 ℃ with dichloromethane
in1.
The
extractabilities
obtainedareshown
Table
In
thestudM
dataobtainedby
thissolvent(1-10).
presentextraction of metal picrates
arc presentedforgeneraldiscussion.
As seen from Table 1, largering-sizedcrown-9andcrown-10
fbr K',(3,4,7,8)
possesshigh extractability
workandtheprevious report

Rb" and Tl' whilecrown-7

etherscrown-8and crown-6(1,2,S,6)

wasderivatives
also possess high(9,10)

Tl".Generallyit was found that largering-sized
benzo-crown ethers have lower
with thoseof 9 and 1O,,and cation
selectivity fbr largecation
hasbeenobserved.
This would be clearly explained by the generallyaccepted size-fit cencept [8]and unusualhighTl'bindingabilityof the ring
size [1O].
Compared with benzo-crownformost crown ethers irrespective
ethersandunsubstitutedorown
etherswiththesamering
size,
thecationbindingabilityofbenzo-crown
(3,4)
(7,8)
ethersare generally lower than the corresponding
unsubstituted
crownethers;e.g. the dataof 3 vs. 7 and thoseisNa' fbr4. which isthe same as those foT2 discussed
of4vs. 8. The exception
inthe previousreport [2].
As repQrted in the previouspaper [2,4],
the results are explained by thebasicityof oxygen atom of thecrownether ring as this has been also alreadyreported fbr small ring-sized crown-5
and 6 ethers. Basicityof
oxygenatom
next
to the benzene ringof 3 and 4 islewer tlranthat of 7 and 8 whichcausesthe low binding
extractability

cationfbr K' andandof mono-benzo-crown[21.In thepresent studyl catecholbindingability as compared,Tl'NII-Electronic
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24No.59 (20e6)

abilityof the crownethers fic}rcations,
The above explanation isbased on the fbrmationof 1:1crownether-cation
complexandthe absenceof any
betweencrown ether and cation.
insightintothe elibct of benzo-type
thatthedatain Table 1 provideinteresting
crowntype complex

sandwich

It should

be noted

ether ring size upon the extracabilityof cations. For Na' and Ag', the cation-binding
abilityis strongest withbenzo-24-crown-8 (2)and other cation-binding ability (K',Rb', Cs',and Tl') of benzo-type crownethersfrom benzo-18-crown-6
decreases
again withbenzo-27-crown-9(9)to benzo-24-crown-8(2)and increases(3)
andbenzo-30-crown-IO (4).
As has alreacly reported
in the paper from other group [5],thisresult would

thatcrovvn ether ring no longerremains planarbuidistorts
to accommodate
cations whichwouldether ring. To get the clear-cut evidence,
thefmiierextraction experiments
the extraction equilibrium constants (Kex)determine
should be needed.
suggestto fitin the crownsmal1

Since the size-fit eoncept

has been mainly

solutiondiscussien
on thelargesimple

chemistrMbe neededshouldmorewithregard

to cation

Tahle 1.Solvent
ExtractionofMetal
Ligandlc)2c)

Na'K'

discussedin the caseselectivity

andofstmctured,complexthe crown-4,beto5, and 6 derivatives
in the-10 ethers

ring-sizedcrown-7,8,9,andfbrmationof crownether

chemistry.

Picratesa)%Extractabilityb)
Rb'

Cs'

Ag'

Tl'

1.7lL23.05.23.25.12.93.32.96.3
19.713,720,428.824.916230.939.743.069.0
33.118.525.738.843.122.426.645.328.657.6
36.418.421.127.752232.426.13L517.036.7
9.022.2ILI13.822.419.915.013.118231.3
52,841.939.449.663.648.449.957.05S.

345c)6c)789c)loc)a) Ibmperature 25 ℃ ;aqueousphase

Organic Phase (CH2C12,(1Oml):[picrate]=3mM.

10rnl):[Ligand]=3mh.

b)Definedas percentpicrateextracted intothe organic phase.Ayerageof two independerit
nms.c)

Ref 2

References
SZrhoolof[1]Part 1: M. Ouchi, T. Kinashi,H. Ueda, M. Kejima, and R. Miyoshi, Reports ofGraduate

Eleigineering,
Uhiversity
57,36 (2004),
of.llyogo,
Part
2.
M.
Ouchi,M.
Kojima,YOtoshi,H. Ybshida,and H. Shibata,
ReportsofGraduate
Strhool[2]ofEhgineering,Universityof Hyoge, 58, 16 (2005).
[3]Preliminaryresults of thework have been presented:M. Ouchi,H. Ydshida,H. Sakarnoto,and K. Kimura
Abstractsof the 55thAnnualMeetingof theJapanSociety
fbrAnalyticalChemistrMp.368.0saka,2006.
M.
Ouchi,M.
Kojima,YlOtoshi,H.
Ybshida,T.
Ybkohara,andH.
Shibata,Sblv Illxin
Res. Dev .ipn.,13,[4]155 (2006).
[5]B.R Czech,A. Czech,B.E. Knudsen, and R.A. Bartsch, Gametta Chimica Italiczna,117,717 (1987).
[6]M. Ouchi, Y Inoue, Liu,S. Nagamune, S. Nakamura, K. Wada, and r Hakushi,Bull.eneue.Sbc..ipn.,
63, 1260 (1990).
T, Hakushi, and E. Webeg J 0rg. Chem., 52, 2490 (1987).
I7]M. Ouchi,Y Inoue.K. Wada, S.lketani,C.J.
Pedersen,
X
Am.
Chem.
Sbc..
89,7017[8](1967).
[9]M. Ouchi,Y Inoue,T, Kanzaki,and T, Hakushi,X Org. enem., 49, 1408 (1984).
M. Ouchi,and T. Hakushi.Coo,ztenene.Rev.,148, 171 (1996).
[1Ol,'ll

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