The first neutral 0D and 1D heterometallic assemblies based on orbitally degenerate heptacyanidorhenate(IV) were prepared and structurally characterized. An analysis of the magnetic data of polycrystalline samples showed that both compounds display slow magnetization relaxation at temperatures below 5 K. The very low temperature measurements of the magnetization on the single crystals demonstrate that for the 1D compound {[Mn(SB2+)Re(CN)7]·7H2O}n (1) and the 0D complex [Mn(SB2+)(H2O)Re(CN)7]·2H2O (2), the hysteresis loops open just below 2.2 and 1.8 K, respectively. Thus, heterometallic polymer 1 is the first single-chain magnet involving a pentagonal bipyramidal [ReIV(CN)7]3− synthon, and the binuclear complex 2 represents a single-molecule magnet.
Two novel applications of functionalized 2,1,3-benzothiadiazoles for metal coordination chemistry and crystal engineering of organic solids are presented. 4-Amino-2,1,3-benzothiadiazole (1) forms a 2 : 1 complex with ZnCl 2 (complex 2) and a 1 : 1 complex with 4-nitro-2,1,3-benzothiadiazole (3) (complex 4). The structures of compounds 1-4 were confirmed by single-crystal X-ray diffraction and studied by UV-Vis and IR spectroscopy, and DFT and QTAIM calculations. Complex 2 is the first structurally defined Zn complex with 2,1,3-benzothiadiazole ligands. In this complex, both molecules 1 are coordinated to Zn only by amino groups, thus revealing a novel type of coordination of this ligand to the metal center.According to 1 H NMR data, complex 2 dissociates in CHCl 3 , THF or DMSO solutions. There are only a few examples of similar complexes, which are also considered to dissociate in solutions. In crystalline complex 4, molecules 1 and 3 form infinite alternating p-stacks connected by lateral S/N interactions between the neighboring stacks. Intermolecular S/N interactions are also observed in the crystals of individual 1 and 3 but the packing motifs are different from those in 4. DFT calculations predict a small charge transfer (CT, $0.02e at B97-D3 level) from 1 to 3 upon the formation of 4, which therefore is an unprecedented CT complex where both donor and acceptor moieties are the derivatives of the 2,1,3benzothiadiazole ring system. This finding creates some new prospects for the crystal engineering of organic solids. Crystalline complex 4 is characterized by an intense CT absorption band with a maximum at $550 nm. However, according to DFT and QTAIM calculations the complex is weakly bonded and its formation is not observed in CH 2 Cl 2 solution with 1 H NMR and UV-Vis techniques.
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