Salts of vanadyl phthalocyanine {VIVO(Pc•3−)}− anions with decamethylmetallocenium cations (Cp*2M+, M = CrIII and CoIII). Ferromagnetic coupling in the [(Cp*2Cr+){VIVO(Pc•3−)}−]2 assemblies

Abstract

Vanadyl phthalocyanine {VIVO(Pc2−)}0 was reduced by decamethylchromocene or decamethylcobaltocene (Cp*2MII), and the crystals of the complexes were precipitated by n-hexane. Reduction of this phthalocyanine is centered on the macrocycle providing the formation of the {VIVO(Pc•3−)}− anions containing two paramagnetic VIV and Pc•3− centers with an S = 1/2 spin state. These paramagnetic anions coexist in (Cp*2Cr+){VIVO(Pc•3−)}−·3C6H4Cl2 (1) with the high-spin (S = 3/2) Cp*2Cr+ counter cations. Nearly isolated assemblies in which two Cp*2Cr+ cations are sandwiched between two {VIVO(Pc•3−)}− anions are formed in 1. Effective magnetic moment of 1 of 4.57 μB at 300 K corresponds to the contribution of noninteracting VIV, Pc•3− and CrIII spins. Weiss temperature of +4 K indicates weak ferromagnetic coupling of spins. Effective magnetic moment of 1 increases upon cooling up to 4.78 μB at 8 K and then drastically falls down. Such magnetic behavior is described well by ferromagnetic coupling between the VIV and Pc•3− spins with J1 = + 4.75 cm−1 and weaker ferromagnetic interactions between Pc•3− and CrIII spins through the Cp* ligand with J2 = +1.08 cm−1. Weak antiferromagnetic coupling with J3 = −0.76 cm−1 is also present between the CrIII spins. Complexes (Cp*2Co+){VIVO(Pc•3−)}−·1.5C6H4Cl2 (2) and (Cp*2Co+) {VIVO(Pc•3−)}−·C6H4Cl2 (3) with the diamagnetic Cp*2Co+ counter cations (S = 0) were also obtained allowing to study their crystal structures and optical properties.