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Cobaltocenium [1,2,5]Thiadiazolo[3,4‐ c ][1,2,5]thiadiazolidyl: Synthesis, Structure, and Magnetic Properties
Author(s) -
Konchenko Sergey N.,
Gritsan Nina P.,
Lonchakov Anton V.,
Irtegova Irina G.,
Mews Ruediger,
Ovcharenko Victor I.,
Radius Udo,
Zibarev Andrey V.
Publication year - 2008
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200800390
Subject(s) - chemistry , antiferromagnetism , cobaltocene , crystallography , heisenberg model , magnetic susceptibility , exchange interaction , spins , yield (engineering) , atmospheric temperature range , condensed matter physics , ferromagnetism , thermodynamics , physics , ferrocene , electrode , electrochemistry
Cobaltocene, [Co II (η 5 ‐C 5 H 5 ) 2 ], readily reduced [1,2,5]thiadiazolo[3,4‐ c ][1,2,5]thiadiazole ( 2 ) to the [1,2,5]thiadiazolo[3,4‐ c ][1,2,5]thiadiazolidyl radical anion ( 1 ) which was isolated in the form of the thermally stable salt [Co III (η 5 ‐C 5 H 5 ) 2 ][ 1 ] ( 5 ) in 93 % yield. The XRD structure of 5 displays layers of radical anions 1 , with S ··· N contacts of 358.2 and 366.0 pm between neighboring species. The salt was further characterized by ESR spectroscopy in the solid state as well as in solution. The temperature dependence of its magnetic susceptibility ( χ ) in the range of 2–300 K with a maximum at (9.7 ± 0.5) K indicates antiferromagnetic ordering of the spin system. The magnetic structure of 5 was analyzed in terms of dimeric exchange integrals calculated by a spin‐unrestricted broken‐symmetry approach at the DFT/UB3LYP/6‐31+G(d) level of theory and was found to be 2D. Further analysis of the χ ( T ) dependence was performed by using the low‐ and high‐temperature series expansion methods for the S = 1/2 square lattice antiferromagnetic Heisenberg model. The exchange interactions between radical anions 1 were estimated to be J = (–4.2 ± 0.7) cm –1 . With the general form of the Van Vleck equation for a [3 × 4] grid of spins 1/2, the best fit of the experimental χ ( T ) was achieved with J 1 = –5.0 cm –1 and J 2 = –0.23 cm –1 . Thus, the exchange interactions in 5 are stronger than those observed for previously studied salts of 1 . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)