Phase transitions in a metal–organic coordination polymer: [Zn₂(C₈H₄O₄)₂(C₆H₁₂N₂)] with guest molecules. Thermal effects and molecular mobility

<p>Thermal effects of a series of [Zn₂(C₈H₄O₄)₂(C₆H₁₂N₂)] porous compound with the guest molecules located in the pores were studied using differential scanning calorimetry combined with solid-state ¹H nuclear magnetic resonance spectroscopy. The intercalation of the molecules was shown to produce various thermal anomalies and phase transitions, which were characterized and analyzed.</p

Fast Interchange of Coordinated and Guest Dimethylformamide Molecules in the Zinc(II) Lactate Terephthalate Metal–Organic Framework

Mobility of <i>N</i>,<i>N</i>-dimethylformamide (dmf) molecules in a homochiral metal–organic framework [Zn₂(bdc)­(<i>S</i>-lac)­(dmf)]·dmf (bdc = 1,4-benzenedicarboxylate; <i>S</i>-lac = <i>L</i>-(−)-lactate) has been studied using ¹³C, ¹H, and ²H solid-state NMR and DSC experiments. The compound exhibits a phase transition in the vicinity of 240 K, associated with disordering of the dmf molecules. In the high-temperature phase, the dmf molecules undergo intense diffusion accompanied by the exchange between the molecules coordinated with Zn and guest molecules in the framework pores. The activation energy of the molecular migration including exchange between coordinated and guest molecules was estimated to be 37 kJ/mol

Facile Substitution of Bridging SO₂^2– Ligands in Re₁₂ Bioctahedral Cluster Complexes

Selective substitution of μ-SO₂^2– groups by either O^2– or Se^2– ions occurs upon heating the bioctahedral rhenium cluster complex K₆[Re₁₂CS₁₄(μ-SO₂)₃(CN)₆] in air atmosphere or in the presence of a Se source, respectively, manifesting the remarkable lability of SO₂^2– ligands bound to a transition-metal cluster. A series of compounds based on the new mixed-ligand anions, [Re₁₂CS₁₄(μ-O)₃(CN)₆]^6–, [Re₁₂CS₁₄(μ-Se)₃(CN)₆]^6–, and [Re₁₂CS₁₄(μ-O)₃(OH)₆]^6–, were isolated and their solid-state structures were elucidated by single-crystal X-ray diffraction analysis. Along with the previously reported μ-sulfide clusters, the new species constitute a series of rhenium anionic complexes with the common formula [Re₁₂CS₁₄(μ-Q)₃L₆]^6– (Q = O, S, Se, L = CN^–; Q = O, S, L = OH^–), within which the total charge and number of cluster valence electrons (CVEs) are constant. The article presents insights into the mechanistic and synthetic aspects of the substitution process, and it comprehensively discusses the influence of inner ligand environment on the structure, spectroscopic characteristics, and electrochemical behavior of the novel compounds

Selective Two-Step Oxidation of μ₂-S Ligands in Trigonal Prismatic Unit {Re₃(μ₆-C)(μ₂-S)₃Re₃} of the Bioctahedral Cluster Anion [Re₁₂CS₁₇(CN)₆]^6–

An oxidation of cluster anion [Re₁₂CS₁₇(CN)₆]^6– by H₂O₂ in water has been investigated. It was shown that selective two-step oxidation of bridging μ₂-S-ligands in trigonal prismatic unit {Re₃(μ₆-C)­(μ₂-S)₃Re₃} takes place. The first stage runs rapidly, whereas the speed of the second stage depends on intensity of ultraviolet irradiation of the reaction mixture. Each stage of the reaction is accompanied by a change in the solution’s color. In the first stage of the oxidation, the cluster anion [Re₁₂CS₁₄(SO₂)₃(CN)₆]^6– is produced, in which all bridging S-ligands are turned into bridging SO₂-ligands. The second stage of the oxidation leads to formation of the anion [Re₁₂CS₁₄(SO₂)₂(SO₃)­(CN)₆]^6–, in which one of the SO₂-ligands underwent further oxidation forming the bridging SO₃-ligand. Seven compounds containing these anions were synthesized and characterized by a set of different methods, elemental analyses, IR and UV/vis spectroscopy, and quantum-chemical calculations. Structures of some compounds based on similar cluster anions, [Cu­(NH₃)₅]₃[Re₁₂CS₁₄(SO₂)₃(CN)₆]·9.5H₂O, [Ni­(NH₃)₆]₃[Re₁₂CS₁₄(SO₂)₃(CN)₆]·4H₂O, and [Cu­(NH₃)₅]_2.6[Re₁₂CS₁₄(SO₂)₃(CN)₆]_0.6[{Re₁₂CS₁₄(SO₂)₂(SO₃)­(CN)₅(μ-CN)}­{Cu­(NH₃)₄}]_0.4·5H₂O, were investigated by X-ray analysis of single crystals