Synthesis and electric properties of one-dimensional polymers of metallophthalocyanine with octakis-substituents of acceptor groups

ELSEVIER

Synthetic

Metals

84 (1997)

353-354

Synthesis and electric properties of one-dimensional polymers of metallophthalocyanine with octakis-substituents of acceptor groups Kazuki Morimoto, Graduate

school

ofBio-Applications 2-24-16

Soo-Jong Kim and Kiyotaka Shigehara & Systems Nakacho,

Engineering, Tokyo University Koganei, To&o 184, Japan

of Agriculture

& Technology

Abstract One-dimensional metallophthalocyanine polymers adopt a favorable conformation for the enhancement of electric conductivity. Metallophthalocyanine derivatives with octakis-substituents of donor or acceptor groups, especially with octa-cyano substituents as acceptor groups are also known to increase the electric conductivity. In the present study, octacyanometallophthalocyanine (MPcOC, M=Si, Fe) monomeric and polymeric complexes were synthesized and their electric and electrochemical properties were investigated. Each complex showed reversible redox wave at near 0 volt, exhibiting the strong acceptor properties. The polymeric complexes gave electric conductivity of 10 - ’ S/cm without any doping process. Kqvwords:OctacyanophthaIocyanine,

Phthaloqvanine

Polymer,

Electric

l.Introduction

Conductivi&

2.Experimental

Cyclic

voltammetry

Details

Synthesis of Silicon Octacyanophthalocyanine(SiPcOC) yen Metallophthalocyanines (MPc), which have macrocyclic 18rr electronic structure are known as very stable organic (photo) semiconductor. Although conductivity appears when planner molecules such as Mpc are stacking as column form, their electric properties greatly vary because of their polymorphism. One-dimensional coordination polymers composed of MPc molecules bridged with axial ligands adopt the enforced and show relatively high electric tetragonal packing conductivity. Thus far, authors have reported electric and electrochemical properties of o&&is-substituted MPc with donor or acceptor groups.[l] Although it have become apparent that introduction of peripheral substituents is not necessarily effective in order to enhance their conductivity due to decreased intermolecular interaction, octacyanometallo ( or free-base ) phthalocyanines exhibited relatively high conductivity without doping. In this study, improvement of electric conductivity is attempted by units polymerizing octacyanometallophthalocyanine into one-dimensional molecular ally. The synthetic routes to silicon or iron phthalocyanine monomeric and polymeric complexes with octacyano substituents as acceptor groups are presented and their electric and electrochemical properties are discussed. 0379-5779197R17.00 0 1997 Elsevier Science S.A. All rights reserved PII SO379-6779(96)03934-3

Bu142000C under VPC”“rn

m

cm

CN R - Me, n-Pr , n-Her

cx

cx

Scheme 1 Synthetic route of SiPcOC monomeric complexes.

and polymeric

354

K. Morimoto

et al. /SynthetxMetals

Silicon octacyanophthalocyanine complexes were synthesized by the reaction between 5,6-dicyano-1,3-diiminoisoindolenine (halfindolenine) and tetrachlorosilane in S-picoline at 130°C for 1 hour. (HO)2SiPcOC were obtained by the hydrolysis of Clz SiPcOC in water. For the convenience of characterization, bis(trialkylsiloxy1) axial substituted SiPcOC were synthesized. The polymerization of (HO)2SiPcOC was carried out in vacua at 200” C for 24 hours. Synthesis of Iron@) Octacyanophthalocyanlne(FePcOC) Iron(B) octacyanoF-? phthalocyanine complex was synthesized by the reaction between tetracyanobenzene (TCB) and iron@)acetate with cyclohexylamine in sulforane at 130°C for 3 hours. The coordination polymer with pyrazine were obtained by stirring the equivalent mixture of FePcOC and pyrazine in DMF at 80°C for 20 hours. The structure and purity were confirmed by FePcOC monomeric and elemental analysis, 1R, polymeric complexes. UV-Vis and FAB-mass spectroscopy. Electric and Electrochemical Measurements Electric conductivity measurement was conducted by AC method. Electrochemical measurement was run by cyclicvoltammometry. The cyclicvoltammograms were recorded at basalplane pyrolytic graphite electrode coated with h4PcOC complexes (F=10-emol/cm2) vs. Ag-AgC1, scanned at 100 mV/sec. in pH1 HCl-KC1 buffer. 3.Results and Discussion SiPcOC The products of the reaction between halfindolenine and tetrachlorosilane showed lR absorption at about 2200cm-i derived from stretching vibration of cyano groups. The reaction between TCB and silicon reagents such as tetrachlorosilane or tetrakis(dimethylamino)silane didn’t occur. The monomeric complexes, (RaSiO)nSiPcOC (R=n-hexyl) were soluble in DMF, THF and acetone and the THF solution showed Q-band absorption maxima at 686nm (Fig.2, ca.20nm bathochromic shift compared with peripheral unsubstituted (RaSiO)2SiPcs). The both of monomeric and polymeric complexes gave distinct and reversible redox wave at about -0.2V (Fig.1 a, Epa=-0.17, Epc=-0.22V). In the case of octacyanophthalocyanines, it is reported that the redox potential shifts to negative compared to free-base PcOC (at near OV) when transitional metals were chosen for the central metal.[2] The polymeric complexes gave electric conductivity of 1.7

84 (1997)

-0.4

4.2

353-354

0

0.2

V vs. ApA%CI

Fig1 Cyclicvoltammograms (b)FePcOC

-0.4

0 -0.2 V vs. A%-A&I

of (a)[Si(PcOC)O]n

0.2

and

1

Fig.2 UV-Vis spectrums of SiPcOC (upper) and FePcOC(lower). Both spectrums display the monomeric complex( -) and the polymeric complex(-----). ~10~“S/cm without doping, this value is 3 orders higher than the monomeric complexes. The electric conductivities depend on purity and degree of polymerization. FePcOC The reaction between TCB and iron acetate occurred readily. The product is soluble in DIG’, and showed Q-band absorption maxima at 694nm. The Q-band absorption of coordination polymer with pyrazine became broad (Fig.2). The redox potential of FePcOC also appeared at -0.2V (Fig.1 b, Epa=-0.22, Epc=-0.24V). The electric conductivity of coordination polymer was lo-*S/cm. Such values were usually found, in the case where pyrazine was used for a u-ligand. 4.Conclusion In the case of SiPcOC, the enhancement of electric conductivity was recognized by polymerization. In order to achieve further enhancement, the doping of alkali metals such as Li or Na will be required and the results will be reported elsewhere. References 1. KShigehara, et.al., SynMet., 71, 2303(1995) 2. D.Wohrle, etal., J.Electrochem.Soc., 132,9,2144(1985)