Heterospin π-heterocyclic radical-anion salt: Synthesis, structure, and magnetic properties of decamethylchromocenium [1,2,5]Thiadiazolo[3,4-c ][1,2,5]thiadiazolidyl

摘要

Decamethylchromocene, Cr~(II)(η~5-C _5(CH_3)_5)_2 (2), readily reduced [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (1) in a tetrahydrofuran solvent at ambient temperature with the formation of radical-anion salt [2] ~+[1]~- (3) isolated in 97% yield. The heterospin salt 3 ([2]~+, S = ~3/_2; [1]~-, S = ~1/_2) was characterized by single-crystal X-ray diffraction as well as magnetic susceptibility measurements in the temperature range 2-300 K. The experimental data together with theoretical analysis of the salt-s magnetic structure within the CASSCF and spin-unrestricted broken-symmetry (BS) density functional theory (DFT) approaches revealed antiferromagnetic (AF) interactions in the crystalline 3: significant between anions [1]~-, weak between cations [2]~+, and very weak between [1]~- and [2]~+. Experimental temperature dependences of the magnetic susceptibility and the effective magnetic moment of 3 were very well reproduced in the assumption of the AF-coupled [1]~-?[1]~- (J_1 = -40 ± 9 cm~(-1)) and [2]~+? [2]~+ (J_2 = -0.58 ± 0.03 cm~(-1)) pairs. The experimental J_1 value is in reasonable agreement with the value calculated using BS UB3LYP/6-31+G(d) (-61 cm~(-1)) and CASSCF(10,10)/6-31+G(d) (-15.3 cm~(-1)) approaches. The experimental J_2 value is also in agreement with that calculated using the BS DFT approach (-0.33 cm~(-1)).