Studies of the charge-transfer complexes of 2-dicyanomethyleneindane-1,3-dione

Abstract

A novel electron acceptor 2-dicyanomethyleneindane-1,3-dione has been prepared and its charge-transfer spectra with π-donors examined. The association constants, extinction coefficients, oscillator strengths, and transition dipole moments for its hexamethylbenzene, pentamethylbenzene, and pyrene complexes have been determined. The bonding enthalpy (6·95 kcal. mole^–1) and the energy of the charge-transfer transition for the hexamethylbenzene complex lead to estimated contribution of the dative form of 11% in the ground and 84% in the first excited state. The average electron affinity of 2-dicyanomethyleneindane-1,3-dione, E_A= 1·36 eV, was computed from spectral and polarographic reduction studies. Anion radicals of the dione were studied by e.s.r. The hyperfine structure of the dione radical anion sodium salt shows two equivalent nitrogen and four equivalent hydrogen atoms. The solid complex of the lithium salt was also isolated.