Synthesis and crystal and molecular structure of the 2:1 molecular adduct between N,N′-(1,2-phenylene)bis(salicylaldiminato)copper(II) and 7,7,8,8-tetracyanoquinodimethane

Article abstract of DOI:10.1021/ic50205a018

A molecular adduct (2:1) between a tetradentate Schiff base complex, N,N′-(1,2-phenylene)bis(salicylaldiminato)copper(II) [Cu(salphen)], and 7,7,8,8-tetracyanoquinodimethane (TCNQ) is described. The conditions necessary to obtain this adduct are very critical, and the solution electronic spectra of the mixed component molecules show a new band at ～4300 ?, with respect to the spectra of the starting materials, only several hours after mixing. This adduct crystallizes in the triclinic system, space group P1, with cell constants a = 11.970 (4) ?, b = 12.567 (4) ?, c = 7.020 (2) ?, α = 103.44 (2)°, β = 92.35 (2)°, and γ = 92.48 (2)°. Least-squares refinement of the structure led to a final R factor (F basis) of 0.039 (R_w = 0.040) using 2384 independent reflections. The structure consists of stacks of centrosymmetrically related, nearly planar Cu(salphen) molecules, running in the c direction parallel to stacks of TCNQ molecules, whose spacing is twice that of the Cu(salphen) units. The geometry of the TCNQ molecule suggests the degree of charge transfer to be quite weak. Magnetic measurements from 9 to 295 K and the 77 K ESR spectrum show that there is no strong coupling between Cu(II) ions. The electrical conductivity, measured on a pressed powder at room temperature, σ = 10^-8 Ω^-1 cm^-1, is 10 to 100 times higher than that of the starting materials. The overlapping of molecules of Cu(salphen) with molecules of TCNQ in the solid state is discussed.