CHARGE-TRANSFER COMPLEXES OF TETRACYANOETHYLENE WITH ALKYLNAPHTHALENES AND ALKENYLNAPHTHALENES AND RELATED-COMPOUNDS

Spectral characteristics, lambda(max) and epsilon, and equilibrium constants, K, for charge-transfer complexes of tetracyanoethylene (TCNE) with alkyl-substituted naphthalenes in dichloromethane are presented. Values of epsilon and K generally increase with alkyl substitution. All complexes exhibit two or three absorbance bands lambda1 550-885 nm, lambda2 425-585 nm, and lambda3 330-440 nm which are due to charge-transfer transitions from the three highest pi orbitals of the naphthalene ring to the pi* orbital of TCNE. Unhindered alpha- and beta-methyl substituents produce wavelength shifts of 36 and 25 nm per methyl in lambda1 and of 5 and 26 nm per methyl in lambda2 relative to naphthalene-TCNE (lambda1 550, lambda2 430 nm). Wavelength shifts are correlated with corresponding shifts in ionization energies of the methylnaphthalenes and with the symmetries of the pi donor orbitals. The wavelength shifts successfully predict lambda1 and lambda2 values of polymethylnaphthalenes without hindered methyls, indicating that the shifts are additive. The effects of peri-dimethyl steric interactions in naphthalenes on lambda(CT) values and the characteristics of complexes of TCNE with perylene, azulene, and some biphenylenes and bicycloalkenes are also presented.