Salts of Tetraselenatetraceneand Bis(ethylenedithio)tetrathiafulvalenewith Metal Hexafluoroacetylacetonate Anions: Mn^II(hfac)₃^–, Co^II(hfac)₂Cl^–, and Pr^III(hfac)₄<

Oxidation of tetraselenatetracene (TSeT) and bis­(ethylenedithio)­tetrathiafulvalene (BEDT-TTF) by <i>p</i>-chloranil in the presence of metal hexafluoroacetylacetonates: Mn^II(hfac)_2, Co^II(hfac)₂ and Pr^III(hfac)₃ followed by precipitation of crystals by <i>n</i>-hexane produces (TSeT_1.5)⁺{Mn^II(hfac)₃^–} (<b>1</b>), (TSeT_1.5)⁺{Pr^III(hfac)₄^–} (<b>3</b>), (TSeT₂)⁺{Co^II(hfac)₂Cl^–} (<b>4</b>), and (ET₃)⁺{Mn^II(hfac)₃^–} (<b>5</b>). Thioindigo dye is introduced into (TSeT_1.5)⁺ (Thioindigo_1.5)­{Mn^II(hfac)₃^–} (<b>2</b>) 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 <b>1</b>-<b>3</b>, and <b>4</b>, respectively, and +0.333 on BEDT-TTF in <b>5</b>. Crystal structures and optical and magnetic properties were studied for <b>1</b><b>–</b><b>5</b>, and conductivity measurements and zone structure calculations were carried out for <b>3</b>. Salts <b>1</b><b>–</b><b>4</b> contain 1D stacks formed by TSeT, and salt <b>5</b> contain<b>s</b> 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 <b>1</b>, <b>2</b>, and <b>4</b>, preserving this state up to room temperature (RT). Only in <b>3</b> 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 <b>3</b> 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 <b>5. A</b>s a result, neutral BEDT-TTF molecules surround BEDT-TTF^•+. High-spin Mn^II(hfac)₃^– anions (<i>S</i> = 5/2) in <b>1</b> and <b>2</b> have no exchange due to long distances between them and the absence of spins on the TSeT sublattice. The Co^II ions in Co^II(hfac)₂Cl^– (<b>4</b>) have a square pyramid surrounding and show a rather high zero field splitting parameter <i>D</i> of 80 cm^–1. Despite that, slow magnetic relaxation is not observed in the 1–1500 Hz range. The Pr^III(hfac)₄^– anions with the ³H₄ state for Pr^III in <b>3</b> show rather strong antiferromagnetic coupling of spins, and most probably TSeT^•+ monomers are also involved in this coupling. The Mn^II(hfac)₃^– anions are isolated in <b>5</b>, whereas weak antiferromagnetic coupling of spins is observed between BEDT-TTF^•+ within the layers with an estimated exchange interaction characterized by <i>J</i> = −3.17 cm^–1.