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A novel series of mononuclear five-coordinated pseudohalido-Cu(II) complexes displaying distorted square bipyramidal: [Cu(L1)(NCS)2] (1), [Cu(L2)(NCS)2] (2) and [Cu(L3)(NCS)]ClO4 (5) as well as distorted trigonal bipyramidal: [Cu(isp3tren)(N3)]ClO4 (3), [Cu(isp3tren)(dca)]ClO4 (4) and [Cu(tedmpza)(dca)]ClO4·0.67H2O (6) geometries had been synthesized and structurally characterized using X-ray single crystal crystallography, elemental microanalysis, IR and UV-vis spectroscopy, and molar conductivity measurements. Different N-donor amine skeletons including tridentate: L1 = [(2-pyridyl)-2-ethyl)-(3,4-dimethoxy)-2-methylpyridyl]methylamine and L2 = [(2-pyridyl)-2-ethyl)-(3,5-dimethyl-4-methoxy)-2-methyl-pyridyl]methylamine, and tetradentate: L3 = bis(2-ethyl-di(3,5-dimethyl-1H-pyrazol-1-yl)-[2-(3,4-dimethoxy-pyridylmethyl)]amine, tedmpza = tris[(2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl]amine and isp3tren = tris[(2-isopropylamino)ethyl)]amine ligands were employed. Molecular structural parameters such as nature of coligand, its chelate ring size and steric environment incorporated into its skeleton, which lead to adopting one of the two limiting geometries in these complexes and other reported compounds are analyzed and correlated to their assigned geometries in solutions. Similar analysis were extended to other five-coordinated halido-Cu(II) complexes.

The organic ligand 1,10-phenanthroline-2,9-dicarboxylic acid (H 2 L) was used to react with ZnSO 4 ·7H 2 O at 140 °C for two days to obtain the complex [Zn 6 (L) 6 (H 2 SO 4 )]·3CH 3 CN·Et 3 N ( 1 ). The structure of complex is confirmed by X-ray crystallography, TG and PXRD. The structure suggested that six ligands chelated with six Zn 2+ ions. Every five-coordinated Zn(II) ion is surrounded by two N atoms and three O atoms (one sulfate radical or three ligands) with the N 2 O 3 coordination environment. Each Zn(II) ion in the structure of complex 1 binds only one L 2− ligand. The metal center Zn2 and Zn3 are bridged by SO 4 2− . The photoluminescence of complex 1 is obvious. Moreover, in the presence of Cd 2+ ions, the complex exhibits an efficient recognition ability, and it realizes the recognition of toxic metal ions.

N-methylbenzimidazole-2-methanol (Hmbm) and Zn(NO3)2·6H2O were reacted in acetonitrile solvothermal at 80 °C for 48 h to obtain a six-nuclear Zn(II) cluster ([ZnII6(Hmbm)2(mbm)8(NO3)4]·12H2O·2CH3CN (Zn6)). Structural analysis indicated that Zn(II) in the above Zn6 clusters showed pentacoordinates. The metal centers Zn1 and Zn2 are both in the N2O3 coordination environment, and both show a triangular bipyramid configuration. Zn3 is in a NO4 coordination environment, which is also shown as a triangular bipyramid configuration. The ion source voltage of high-resolution electrospray ionization mass spectrometry (HRESI-MS) was further adjusted to bombard the Zn6 cluster, and seven major key intermediates were identified. Furthermore, we proposed that the gradual fragmentation mechanism is Zn6 → [ZnII6(mbm)8(NO3)3]+ → [ZnII5(mbm)7(NO3)2]+ → [ZnII4(mbm)6(NO3)]+ → [ZnII3(mbm)4(NO3)]+ → [ZnII2(mbm)3]+ → [ZnII2(mbm)2(OH)(H2O)2(DMSO)]+ → [ZnII(mbm)]+. In order to understand the gradual formation of Zn6 clusters, herein, we track the changes of species in the solution in different time periods by HRESI-MS. The nine key intermediates were identified and further combined with its gradual fragmentation mechanism. We proposed the gradual assembly mechanism of [ZnII(mbm)]+ → [ZnII(mbm)(Hmbm)]+ → [ZnII2(mbm)2(NO3)]+ → [ZnII2(mbm)3]+ → [ZnII3(mbm)4(NO3)]+ → [ZnII4(mbm)5(NO3)2]+ → [ZnII4(mbm)6(NO3)]+ → [ZnII5(mbm)7(NO3)2]+ → [ZnII6(mbm)8(NO3)3]+ → Zn6. To the best of our knowledge, this is the first time that a decomposition and assembly binding strategy has been used to resolve the stepwise formation of Zn(II) clusters. Photoluminescence measurements indicate that the cluster Zn6 exhibits a strong emission peak at 300 nm and an emission shoulder at 600 nm.