Heterospin π-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)).

Metal-radical coordination complexes of thiazyl and selenazyl ligands

“…However, species incorporating the 125TDA can be reduced by one electron to resonance stabilized radical anions, and ionic compounds involving 125TDA radical anions can be prepared and isolated as crystalline solids [107][108][109][110]. As observed with thiazyl radical cations (vide supra), ionic complexes of 125TDA radical anions that incorporate a metal-containing counterion may also exhibit structural features consistent with coordination between the thiazyl radical and the metal.…”

Fused 1,2,3-Dithiazoles: Convenient Synthesis, Structural Characterization, and Electrochemical Properties

“…Amongst compounds synthesized in this work napthoquinone-fused derivatives 13 and 15 are especially interesting in the context of RAs since one may expect some concentration of a negative charge on the C=O moieties (ultimately leading to the C–O − bonding situation) enlarging their ability to coordinate metal cations. This might be a new approach to the design and synthesis of sulfur-nitrogen π-heterocyclic RA salts as potential building blocks of magnetic functional materials [25,26,27,28,29].…”

Stable heterocyclic radicals

“…31 As a rule, 1,2,3-dithiazolyl radicals 14 ± 16 are obtained by the reduction of the corresponding 1,2,3-dithiazolium salts 18 ± 21 with decamethylferrocene 30, 31 or triphenylantimony. 29,31 The radical species also form in the oxidation of 1,2,5thiadiazolo-1,2,3-dithiazolopyrazine (22). 32 The best result among the oxidants studied (S 2 Cl 2 , SO 2 Cl 2 , bromine, chlorine) was obtained with sulfur monochloride in boiling chlorobenzene.…”

“…Chemistry and materials science of the former is the subject of numerous reviews (e.g., see Refs 20,21 and others of this specialized issue).The study of the latter isolated as thermally stable salts of various cations is just at the beginning (see, e.g., Ref. 22 and papers cited therein). Collected here are data on the other types of heterocyclic radicals mainly over the last 15 years.…”