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Salts of Tetraselenatetracene and Bis(ethylenedithio)tetrathiafulvalene with Metal Hexafluoroacetylacetonate Anions: MnII(hfac)3–, CoII(hfac)2Cl–, and PrIII(hfac)4–
Oxidation of tetraselenatetracene (TSeT) and bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) by p-chloranil in the presence of metal hexafluoroacetylacetonates: MnII(hfac)2, CoII(hfac)2 and PrIII(hfac)3 followed by precipitation of crystals by n-hexane produces (TSeT1.5)+{MnII(hfac)3–} (1), (TSeT1.5)+{PrIII(hfac)4–} (3), (TSeT2)+{CoII(hfac)2Cl–} (4), and (ET3)+{MnII(hfac)3–} (5). Thioindigo dye is introduced into (TSeT1.5)+ (Thioindigo1.5){MnII(hfac)3–} (2) due to the appearance of specific C═O···(Se–Se bond) interactions accompanied by the formation of short O···Se contacts of 2.85–3.04 Å length. Formal charges on TSeT are +0.666 and +0.5 in 1-3, and 4, respectively, and +0.333 on BEDT-TTF in 5. Crystal structures and optical and magnetic properties were studied for 1–5, and conductivity measurements and zone structure calculations were carried out for 3. Salts 1–4 contain 1D stacks formed by TSeT, and salt 5 contains 2D layers formed by BEDT-TTF. Essential dimerization yields alternation of dimers and monomers within the stacks. Positive charges are localized on the dimers, which transfer to a diamagnetic singlet state in 1, 2, and 4, preserving this state up to room temperature (RT). Only in 3 with weakly dimerized TSeT stacks positive charge is localized on both monomers and dimers, and the triplet state of the dimers is populated above 180 K (the singlet–triplet gap is 420 K). As a result, semiconducting behavior is observed for the oriented single crystal of 3 with the activation energy of 83 meV. According to the length of the central C═C bond in BEDT-TTF, charge separation is observed in the layers of 5. As a result, neutral BEDT-TTF molecules surround BEDT-TTF•+. High-spin MnII(hfac)3– anions (S = 5/2) in 1 and 2 have no exchange due to long distances between them and the absence of spins on the TSeT sublattice. The CoII ions in CoII(hfac)2Cl– (4) have a square pyramid surrounding and show a rather high zero field splitting parameter D of 80 cm–1. Despite that, slow magnetic relaxation is not observed in the 1–1500 Hz range. The PrIII(hfac)4– anions with the 3H4 state for PrIII in 3 show rather strong antiferromagnetic coupling of spins, and most probably TSeT•+ monomers are also involved in this coupling. The MnII(hfac)3– anions are isolated in 5, whereas weak antiferromagnetic coupling of spins is observed between BEDT-TTF•+ within the layers with an estimated exchange interaction characterized by J = −3.17 cm–1.