PECULIARITY OF ETHYLENEDIOXY GROUP IN FORMATION OF CONDUCTIVE CHARGE-TRANSFER COMPLEXES OF BIS(ETHYLENEDIOXY)-DIBENZOTETRATHIAFULVALENE (BEDO-DBTTF)

The electronic and molecular structures and charge transfer (CT) compl ex formation of a new electron donor molecule; bis(ethylenedioxy)-dibe nzotetrathiafulvalene (BEDO-DBTTF), were studied from the point of the peculiar ability of ethylenedioxy group in delivering conductive soli d complexes. The BEDO-DBTTF molecules afforded 37 solid complexes with 40 kinds of electron acceptor molecules belonging to 5 systems; TCNQ, quinone, fluorene, percyano and nitrophenyl systems. The infrared and ultraviolet-visible-near infrared spectra of the complexes were exami ned to study the ionicity of their ground states in solid. A plot of C T transition energies and the difference of redox potentials; Delta E( DA), of donor and acceptor molecules indicated that 10 complexes have neutral ground state. No definitely identified back CT bands were obse rved in the 4 complexes of completely ionic ground state. 23 complexes of partially ionic ground state gave CT transitions below 5x10(3) cm( -1) and are highly conductive. The presence of the ethylenedioxy group in BEDO-DBTTF provided wide variety of conductive complexes regardles s the size and shape of acceptor molecules, with smaller degree of CT (gamma greater than or equal to 0.3), from combination with much weake r acceptor molecules (Delta E(DA) less than or equal to 0.53) than exp ected for conventional TTF.TCNQ system (gamma greater than or equal to 0.5, Delta E(DA) less than or equal to 0.34) and with donor molecule excess in content. These features are very much resemblance to those o f BEDO-TTF which affords a number of metallic complexes and are ascrib ed to peculiar ability of ethylenedioxy group to assemble self-aggrega ted donor assemblies. In spite of such similarity, the partially ionic complexes of BEDO-DBTTF are not metallic, maybe due to the lack of th e side-by-side intermolecular sulfur...sulfur short contacts that is p redicted based on the molecular geometry consideration. Single crystal growth of BEDO-DBTTF complexes was not much successful. 2,5-Dimethyl- and 2,5-dimethoxy-TCNQ complexes, which reside near the boundary of t he partial CT and neutral states, afforded complexes with different io nicities, conductivities and optical properties. The crystal structure s of neutral complexes of 2,5-dimethyl- and 2,5-dimethoxy-TCNQ as well as that of neutral donor molecules were determined.