COMPLEXES OF AZOBISINDOLES WITH PI-ORGANIC ACCEPTORS

Complexes of azobisindoles with tetracyanoethylene and tetracyanoquino dimethane were studied by UV-Vis, FT-IR, Raman, NMR and X-ray spectros copies. FT-IR and Raman spectra, as well as X-ray analysis, gave usefu l information on the participation of various sites to the association , through analysis of CN and N = N vibrational modes, while UV-Vis and NMR spectra were less helpful. The crystal structure of complexes hen yl-3-(1-ethyl-2-phenyl-3-azoindole)indole/TCNE, 3a and -diphenyl-3-(1, 2-diphenyl-3-azoindole)indole/TCNQ, 5b are reported. In the two comple xes, the distances between donor and acceptor planes range between 3.4 and 3.5 Angstrom; in 3a tetracyanoethylene faces the phenyl ring of t he indole, while in 5b the superposition of tetracyanoquinodimethane w ith the donor is negligible. Compound 3a, P-I, a = 9.504(2), b = 9.513 (3), c = 8.941(2) Angstrom, alpha = 97.81(4), beta = 103.38(3), gamma = 84.14(2)degrees, Z = 2, D-calc = 2.55 g cm(-3); compound 5b, P-1, a = 12.648(3), b = 12.205(2), c = 7.263(3) Angstrom, alpha = 103.69(2), beta = 91.23(3), gamma = 110.61(2)degrees, Z = 2, D-calc = 2.53 g cm(- 3).