Molecular structure, optical and magnetic properties of the {SnIVPc(3-)Cl2}•- radical anions containing negatively charged Pc ligands

Radical anion salt (PPN+){(SnPc)-Pc-IV(3-)Cl-2}(center dot-) (1) was obtained by the reduction of tin(IV) phthalocyanine dichloride {(SnPc)-Pc-IV(2-)Cl-2} with (PPN+)(C-60(center dot-)) (PPN+ is bis(triphenylphosphoranylidene)ammonium cation). It was shown that the reduction is centered mainly on the Pc ligand providing the appearance of a new band in the spectrum of 1 in the NIR range at 1006 nm and blue-shift of Soret and Q-bands of (SnPc)-Pc-IV(2-)Cl-2. The alternation of short and long C-N imine bonds for two oppositely located isoindole units in 1 indicates possible disruption of aromaticity of the Pc ligand under reduction. Salt 1 has effective magnetic moment of 1.69 mu(B) at 300 K corresponding to the contribution of one non-interacting S = 1/2 spin per formula unit and manifests antiferromagnetic coupling of spins with Weiss temperature of -7.3 K in the 400-30 K range. The salt shows a broad EPR signal with g = 1.9957 and linewidth of 19.3 mT at room temperature. The signal splits into two components below 120 K. Strong broadening of the EPR signal and shift of g-factors to smaller values in comparison with the EPR signal from radical anions of metal-free phthalocyanine {H2Pc(3-)}(center dot-) were attributed to the contribution of the {(SnPc)-Pc-III(2-)Cl-2}-admixture with paramagnetic Sn-III. There are pi-pi stacking one-dimensional chains composed of {(SnPc)-Pc-IV(3-)Cl-2}(center dot-) in 1 along the a axis with weak overlapping between phenylene groups of phthalocyanine radical anions. The calculated HOMO-HOMO overlap integral is 0.0033 and the SOMO-SOMO overlap integral is only 0.0004. Metallic conductivity is not realized in 1 most probably due to weak SOMO-SOMO overlapping.