A spectroscopic study on the coordination and solution structures of the interaction systems between biperoxidovanadate complexes and the pyrazolylpyridine-like ligands

NSF of China [21172066, 21201062, 51103122]; Ministry of Science and Technology [2011CB808505]; Scientific Research Fund of Hunan Provincial Education Department [12K101]; Hunan Provincial Natural Science Foundation of China [11JJ2007]; State Key Laboratory of Physical Chemistry of Solid Surfaces (Xiamen University) [201309]; Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan ProvinceIn order to understand the substitution effects of pyrazolylpyridine (pzpy) on the coordination reaction equilibria, the interactions between a series of pzpy-like ligands and biperoxidovanadate ([OV(O-2)(2)(D2O)](-)/[OV(O-2)(2)(HOD)](-), abbrv. bpV) have been explored using a combination of multinuclear (H-1, C-13, and V-51) magnetic resonance, heteronuclear single quantum coherence (HSQC), and variable temperature NMR in a 0.15 mol L-1 NaCl D2O solution that mimics the physiological conditions. Both the direct NMR data and the equilibrium constants are reported for the first time. A series of new hepta-coordinated peroxidovanadate species [OV(O-2)(2)L](-) (L = pzpy-like chelating ligands) are formed due to several competitive coordination interactions. According to the equilibrium constants for products between bpV and the pzpy-like ligands, the relative affinity of the ligands is found to be pzpy >2-Ester-pzpy approximate to 2-Me-pzpy approximate to 2-Amide-pzpy > 2-Et-pzpy. In the interaction system between bpV and pzpy, a pair of isomers (Isomers A and B) are observed in aqueous solution, which are attributed to different types of coordination modes between the metal center and the ligands, while the crystal structure of NH4[OV(O-2)(2)(pzpy)]center dot 6H(2)O (CCDC 898554) has the same coordination structure as Isomer A (the main product for pzpy). For the N-substituted ligands, however, Isomer A or B type complexes can also be observed in solution but the molar ratios of the isomer are reversed (i.e., Isomer B type is the main product). These results demonstrate that when the N atom in the pyrazole ring has a substitution group, hydrogen bonding (from the H atom in the pyrazole ring), the steric effect (from alkyl) and the solvation effect (from the ester or amide group) can jointly affect the coordination reaction equilibrium

The investigation of the interaction between Tropicamide and bovine serum albumin by spectroscopic methods

Scientific Research Fund of Hunan Provincial Education Department [12K101]; National Natural Science Foundation of China [21172066]; Hunan Provincial Natural Science Foundation of China [11JJ2007]; Opening Project of State Key Laboratory of Physical Chemistry of Solid Surfaces (Xiamen University) [201309]; Aid program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan ProvinceThe fluorescence and ultraviolet-visible (UV-Vis) spectroscopy were explored to study the interaction between Tropicamide (TA) and bovine serum albumin (BSA) at three different temperatures (292, 301 and 310 K) under imitated physiological conditions. The experimental results showed that the fluorescence quenching mechanism between TA and BSA was static quenching procedure. The binding constant (K-a), binding sites (n) were obtained. The corresponding thermodynamic parameters (Delta H, Delta S and Delta G) of the interaction system were calculated at different temperatures. The results revealed that the binding process is spontaneous, hydrogen binds and vander Waals were the main force to stabilize the complex. According to Forster non-radiation energy transfer theory, the binding distance between TA and BSA was calculated to be 4.90 nm. Synchronous fluorescence spectroscopy indicated the conformation of BSA changed in the presence of TA. Furthermore, the effect of some common metal ions (Mg2+, Ca2+, Cu2+, and Ni2+) on the binding constants between TA and BSA were examined. (C) 2013 Elsevier B.V. All rights reserved

NMR and theoretical study on the coordination interactions between peroxovanadium(V) complex and bisubstituted pyridine ligands

National Natural Science Foundation of China [21201062, 21172066]; Scientific Research Fund of Hunan Provincial Education Department [12K101, 12C0115]; Hunan Provincial Natural Science Foundation of China [11JJ2007]; State Key Laboratory of Physical Chemistry of Solid Surfaces (Xiamen University) [201309]; Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan ProvinceTo understand the substitution effects of pyridine ligands on coordination equilibrium, the coordination interactions between a series of bisubstituted pyridine ligands and peroxovanadium(V) [OV(O-2)(2)(D2O)](-)/[OV(O-2)(2)(HOD)](-) in solution have been investigated by multinuclear (H-1, C-13, and V-51) magnetic resonance and HSQC. A series of new six-coordinate peroxovanadate complexes [OV(O-2)(2)L] (n) (-) (L=2, 3, 4, n=1 or 3) have been observed, and the coordination ability of the bisubstituted pyridines to peroxovanadium(V) is 3,4-dimethylpyridine (2)>3,5-dimethylpyridine (3)>pyridine-3,5-dicarboxylate (4)>> 2,3-dimethylpyridine (1). The coordination interactions among title system have been further studied by DFT (density functional theory) calculations, and the results indicate that solvent may play an important role in these coordination interactions

High-Capacity Gas Storage by a Microporous Oxalamide-Functionalized NbO-Type Metal–Organic Framework

A microporous oxalamide-functionalized NbO-type metal–organic framework, HNUST-3, has been designed and synthesized by self-assembling [Cu₂(COO)₄] paddlewheel SBUs and a novel tetracarboxylate ligand with linking oxalamide groups. HNUST-3 represents the first example of a porous oxalamide-functionalized MOF, which exhibits a high BET surface area of 2412 m²·g^–1, large H₂ uptake (unsaturated total capacity of 6.1 wt % at 20 bar and 77 K), and excellent CH₄ storage (135.8 cm³(STP)­cm^–3 at 20 bar and 298 K) as well as high CO₂ adsorption capacity (20.2 mmol·g^–1 at 20 bar and 298 K) with good selectivity for CO₂ over CH₄ (7.9) and N₂ (26.1) at 298 K