Charge transfer complexes of metal-free phthalocyanine radical anions with decamethylmetallocenium cations: (Cp*2Co+)(H2Pc•-)·solvent and (Cp*2Cr+)(H2Pc•-)·4C6H4Cl2

Abstract

Charge transfer complexes (Cp*2Co+)(H2Pc•-)·0.5C6H4Cl2·0.7C6H5CN·0.3C6H14 (1) and (Cp*2Cr+)(H2Pc•-)·4C6H4Cl2 (2) have been obtained as single crystals. Both complexes contain metal-free phthalocyanine (Pc) radical anions and decamethylmetallocenium cations. Reduction of the Pc macrocycle leads to the appearance of new bands at 1026-1030 nm in the NIR range and blue shifts of both Soret and Q-bands of H2Pc in the spectra of 1 and 2. The geometry of the Pc macrocycles supports the formation of H2Pc•- by the alternation of shorter and longer C-N(imine) bonds in the macrocycles in 2. Complex 1 contains pairs of H2Pc•- having effective π-π interactions with two sandwiched Cp*2Co+ cations, whereas complex 2 contains stacks composed of alternating Cp*2Cr+ and H2Pc•- ions. The magnetic moment of 1 is 1.64 μB at 300 K due to the contribution of the H2Pc•- spins with the S = 1/2 state and diamagnetism of Cp*2Co+. This is supported by the observation of a narrow EPR signal of 1 with g = 2.0032-2.0036 characteristic of H2Pc•-. Strong antiferromagnetic coupling of spins with a Weiss temperature of −23 K is observed between H2Pc•- in 1. This coupling is probably mediated by the Cp*2Co+ cations. The magnetic moment of 2 is 4.18 μB at 300 K indicating the contribution of both paramagnetic H2Pc•- (S = 1/2) and Cp*2Cr+ (S = 3/2) species. In spite of the presence of stacks of alternating ions in 2, only weak magnetic coupling is observed with a Weiss temperature of −4 K most probably due to ineffective π-π interactions between Cp*2Cr+ and H2Pc•-. The EPR spectrum of 2 contains an asymmetric signal attributed to CrIII (g1 = 3.9059-3.9220) and a narrow Lorentzian signal from H2Pc•- with g2 = 1.9943-1.9961. In addition to these signals, a broad EPR signal grows in intensity below 80 K with g4 = 2.1085-2.2438 which can be attributed to both paramagnetic Cp*2Cr+ and H2Pc•- species having exchange interactions.