Translocation and Confinement of Tetraamines in Adaptable Microporous Cavities.

Metal-Organic Frameworks can be grafted with amines by coordination to metal vacancies to create amine-appended solid adsorbents, which are being considered as an alternative to using aqueous amine solutions for CO2 capture. In this study, we propose an alternative mechanism that does not rely on the use of neutral metal vacancies as binding sites but is enabled by the structural adaptability of heterobimetallic Ti2Ca2 clusters. The combination of hard (Ti4+) and soft (Ca2+) metal centers in the inorganic nodes of the framework enables MUV-10 to adapt its pore windows to the presence of triethylenetetramine molecules. This dynamic cluster response facilitates the translocation and binding of tetraamine inside the microporous cavities to enable the formation of bis-coordinate adducts that are stable in water. The extension of this grafting concept from MUV-10 to larger cavities not restrictive to CO2 diffusion will complement other strategies available for the design of molecular sorbents for decarbonization applications.

Synthesis and crystal structure of trans-di-aqua(1,4,8,11-tetra-aza-undeca-ne)copper(II) isophthalate monohydrate.

In the title hydrated mol-ecular salt, [Cu(C7H20N4)(H2O)2](C8H4O4)·H2O, the metal ion is coordinated by the two primary and two secondary N atoms of the amine ligand and the mutually trans O atoms of the water mol-ecules in a tetra-gonally distorted octa-hedral geometry. The average equatorial Cu-N bond lengths (2.013 and 2.026 Šfor Cu-Nprim and Cu-Nsec, respectively) are substanti-ally shorter than the average axial Cu-O bond length (2.518 Å). The tetra-amine ligand adopts its energetically favored conformation with its five- and six-membered chelate rings in gauche and chair conformations, respectively. In the crystal, the N-H donor groups of the tetra-amine, the acceptor carboxyl-ate groups of the isophthalate dianion and both the coordinated water mol-ecules and the water mol-ecule of crystallization are involved in numerous N-H⋯O and O-H⋯O hydrogen bonds, resulting in the formation of electroneutral layers oriented parallel to the ac plane.

Preparation and testing of a tetra-amine copper(II) chitosan bead system for enhanced phosphate remediation.

A tetra-amine copper(II) chitosan bead system (TAC@CS composite beads) was developed by grafting tetra-amine copper(II) (TAC) with chitosan (CS) and utilized for phosphate removal. The prepared TAC@CS composite beads possess enhanced phosphate sorption capacity (SC) of 41.42 ±â€¯0.071 mg/g than copper grafted chitosan (Cu@CS) composite, TAC and chitosan which were found to be 37.01 ±â€¯0.803, 33.20 ±â€¯0.650 and 7.24 ±â€¯0.059 mg/g respectively. In batch mode, various adsorption influencing parameters like contact time, initial phosphate concentration, solution pH, co-anions and temperature were optimized for maximum phosphate sorption. The prepared adsorbents were characterized by FTIR, XRD, UV-Visible, SEM and EDAX analysis. The adsorption isotherms and thermodynamic parameters of the adsorbent were studied. The feasible phosphate uptake mechanism of TAC@CS biocomposite beads was reported. The reusability studies of TAC@CS composite beads were carried out using NaOH as elutant. The suitability of TAC@CS composite beads at field conditions was tested with phosphate contaminated field water samples collected from nearby areas of Dindigul district.

A novel thiol-affinity micropipette tip method using zinc(II)-cyclen-attached agarose beads for enrichment of cysteine-containing molecules.

Cysteine-containing biomolecules are attractive targets in the study of thiol biology. Here we introduce a novel method for the selective enrichment of thiol-containing molecules using a thiol-capture zinc(II) complex of 1,4,7,10-tetraazacyclododecane (Zn(2+)-cyclen). Recognition of N-acetylcysteine amide by Zn(2+)-cyclen has been studied by potentiometric pH titration, revealing formation of a 1:1 thiolate-bound Zn(2+)-cyclen complex with a large thiolate-affinity constant of 10(6.2)M(-1) at 25°C and I=0.10M (NaCl). The Zn(2+)-bound thiolate anion is unexpectedly stable in aqueous solution at pH 7.8 under atmospheric conditions for a few days. These findings have contributed to the development of a convenient method for separation of thiol compounds by using a micropipette tip. A 200µL micropipette tip containing 10µL of hydrophilic cross-linked agarose beads attached to Zn(2+)-cyclen moieties was prepared. All steps for thiol-affinity separation (binding, washing, and eluting) are conducted using aqueous buffers at room temperature. The entire separation protocol requires less than 15min per sample. We demonstrate practical example separations of cysteine-containing molecules. This micropipette tip method would be used preferentially as an alternative to existing tools for reliable enrichment of thiol-containing molecules.