CuII and CuI Coordination Complexes Involving Two Tetrathiafulvalene-1,3-benzothiazole Hybrid Ligands and Their Radical Cation Salts

Preparations, crystal structure analyses, and magnetic property investigations on a new CuII(hfac)2 complex coordinated with two TTFCHCHBTA ligands, where hfac is hexafluoroacetylacetonate, TTF is tetrathiafulvalene, and BTA is 1,3-benzothiazole, are reported together with those of its dicationic AsF6– salt, [Cu­(hfac)2(TTFCHCHBTA)2]­(AsF6)2, in which each TTF part is in a radical cation state. In these CuII(hfac)2 complexes, two ligands are bonded to the central Cu atom of the Cu­(hfac)2 part through the nitrogen atom of the 1,3-benzothiazole ring and occupy the two apical positions of the Cu­(hfac)2 complex with an elongated octahedral geometry. These two ligands are located parallelly in a transverse head-to-tail manner, and the Cu­(hfac)2 moiety is closely sandwiched by these two ligands. In the AsF6– salt of the Cu­(hfac)2 complex, each TTF dimer is separated by the AsF6– anions and has no overlap with each other within the one-dimensional arrays, resulting in an insulating behavior. Both Cu­(hfac)2 complexes showed the simple Curie-like temperature dependence of paramagnetic susceptibilities (χM), indicating that no interaction exists between the paramagnetic CuII d spins. Furthermore, crystal structure analysis and magnetic/conducting properties of a radical cation ReO4– salt of the CuI complex with two TTFCHCHBTA ligands, [Cu­(TTFCHCHBTA)2]­(ReO4)2, are also described. Two nitrogen atoms of the ligands are connected to the central CuI in a linear dicoordination with a Cu–N bond length of 1.879(9) Å. Two TTF parts of the neighboring complexes form a dimerized structure, and such a TTF dimer forms a one-dimensional uniform array along the a direction with a short S–S contact of 3.88 Å. Magnetic property measurement suggested the existence of a strongly antiferromagnetic one-dimensional uniform chain of S = 1/2 spins that originate from the radical cation states of the TTF dimers. Due to the construction of the one-dimensional uniform array of the radical cation state of the TTF dimer along the a axis, a semiconducting behavior is observed with σrt = of 6 × 10–5 S cm–1 and an activation energy of Ea = 0.16 eV.