CRYSTAL AND MOLECULAR-STRUCTURE OF A CHARGE-TRANSFER COMPLEX BETWEEN ALPHA,ALPHA'-DIMETHYLQUATERTHIOPHENE AND 2,3,5,6-TETRAFLUORO-7,7,8,8-TETRACYANOQUINODIMETHANE

A 1:1 stoichiometric charge-transfer (CT) complex between alpha,alpha-dimethylquaterthiophene (DMQtT) and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (TCNQF(4)) crystallizes in the triclinic system with the space group P $($) over bar$$ 1, a = 10.185(6), b = 10.568(5), c = 6.842(3) Angstrom, alpha = 98.92(4), beta = 95.89(4), gamma = 67.24(4)degrees, Z = 1, U = 670.1 Angstrom(3) and D-c = 1.573 g cm(-3). The crystals comprise alternate mixed columns of DMQtT and TCNQF(4) with their molecular planes nearly parallel, this structural feature being characteristic of weak CT complexes. The crystal structure is compared with that of a related CT complex of non-substituted quaterthiophene and 7,7,8,8-tetracyanoquinodimethane (TCNQ) and the substituent effect on the crystal structure is discussed. The molecular structures of DMQtT and TCNQF(4) in the CT and neutral forms are also compared.