title: Heterospin pi-heterocyclic radical-anion salt: synthesis, structure, and magnetic properties of decamethylchromocenium [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazolidyl.
abstract: Decamethylchromocene, Cr(II)(eta(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)).
authors.affiliation: Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia.
authors.forename: Nikolay A
authors.initials: NA
authors.lastname: Semenov
authors.forename: Nikolay A
authors.initials: NA
authors.lastname: Pushkarevsky
authors.forename: Anton V
authors.initials: AV
authors.lastname: Lonchakov
authors.forename: Artem S
authors.initials: AS
authors.lastname: Bogomyakov
authors.forename: Elena A
authors.initials: EA
authors.lastname: Pritchina
authors.forename: Elizaveta A
authors.initials: EA
authors.lastname: Suturina
authors.forename: Nina P
authors.initials: NP
authors.lastname: Gritsan
authors.forename: Sergey N
authors.initials: SN
authors.lastname: Konchenko
authors.forename: Ruediger
authors.initials: R
authors.lastname: Mews
authors.forename: Victor I
authors.initials: VI
authors.lastname: Ovcharenko
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Zibarev