Tuning zinc(II) coordination architectures by rigid long bis(triazole) and different carboxylates: Synthesis, structures and fluorescence properties

Study of interaction of metal ions with methylthymol blue by chemometrics and quantum chemical calculations

In this study, we determine the acidity constants of methylthymol blue (MTB) and association constants of its complexes with the ZnII, CuII, and FeII metal ions (MIs), through theoretical and experimental means. The complexes were characterized using UV-Visible absorption spectroscopy combined with soft/hard chemometrics methods and quantum chemical calculations. Quantum chemical calculations revealed that electronic transitions in the UV-Visible spectra of MTB have mixed n → π* and π → π* characters. The results of molar ratio and multivariate curve resolution alternating least squares (MCR-ALS) revealed the formation of successive 1:2 and 1:1 complexes (MI:MTB) for the ZnII and CuII systems. However, the formation of successive 1:1 and 2:1 complexes are suggested for FeII by the molar ratio and MCR-ALS. The majority of transitions observed in the UV-Visible spectra of the Zn(MTB) and Cu(MTB) complexes have ligand-to-ligand charge transfer (LLCT) characters. However, the transitions in the UV-Visible spectrum of the Fe(MTB) complex have LLCT and metal-to-ligand charge transfer (MLCT) characters. For the Fe2(MTB) complex, the lowest energy transition of has an LLCT character. However, its higher energy transitions are a mixture of LLCT, MLCT, and metal-to-metal charge transfer (MMCT) characters. The correlation between experimental and computed wavelengths revealed that the 1:1 complexes of ZnII and CuII prefer square pyramidal geometries. However, the FeII complexes always show octahedral geometry.

Three-dimensional nanocomposites with Co3O4 nanosheets parallelly embedded in carbon network walls for enhanced lithium-ion storage

Three-dimensional Co3O4/C nanocomposites are synthesized via a hydrogel assisted synthesis route. The carbon has a three-dimensional interconnected network structure, and ultrathin Co3O4 nanosheets (≈5.0 nm) are parallelly and uniformly embedded in the two-dimensional carbon network walls. This unique structure restricts the aggregation and pulverization of active materials, and ensures the continuity and efficiency of electron and ion transmission during the lithiation/delithiation process. As a result, the Co3O4/C nanocomposites exhibit excellent cycling performance at different current densities. The discharge capacities remain at 905 mA h g-1 after 190 cycles at the current density of 100 mA g-1 and 561 mA h g-1 after 500 cycles at the current density of 2000 mA g-1. Since this approach is facile and large-scale, it is a rational way to engineer high capacity anodes to achieve improved electrochemical performances.

Luminescence, electrochemical and photocatalytic properties of sub-micron nickel(II) and cobalt(II) coordination polymers synthesized by sonochemical process

Submicron structures of Ni^II/Co^II-based coordination polymers (CPs) [Ni(L1)(mip)·H₂O]_n (1) and {[Co(L2)(mip)]·0·.5H₂O}_n(2) (L1=1,6-bis(5,6-dimethylbenzimidazole)hexane, L2=1,6-bis(benzimidazole)hexane, H₂mip=5-methylisophthalic acid) were obtained by ultrasonic irradiation and structurally characterized by elemental analysis, powder X-ray diffraction and scanning electron microscopy. Structural analysis show that two CPs feature uninodal 3-connected 2D hcb layer, whilst CP 2 is further extended into a 3D complicated supramolecular network by C14-H14⋯O2 hydrogen bonds. Ultrasonic time and power influencing morphology of sub-micron sized CPs, were also discussed. Besides that, thermal stability, luminescence, electrochemical properties and photocatalytic activity of sub-micron sized 1 and 2 were presented in detail. Moreover, sub-micron sized 1 manifests the higher photocatalytic activity than sub-micron sized 2 for decomposition of methylene blue (MB) under UV irradiation.