Novel hexanuclear and octanuclear zinc alkyl cages derived from a bis-oxamidate ligand

Photodegradation of Brilliant Green Dye by a Zinc bioMOF and Crystallographic Visualization of Resulting CO2

We present a novel bio-friendly water-stable Zn-based MOF (1), derived from the natural amino acid L-serine, which was able to efficiently photodegrade water solutions of brilliant green dye in only 120 min. The total degradation was followed by UV-Vis spectroscopy and further confirmed by single-crystal X-ray crystallography, revealing the presence of CO2 within its channels. Reusability studies further demonstrate the structural and performance robustness of 1.

A Trinuclear Zinc Coordination Cluster Exhibiting Fluorescence, Colorimetric Sensitivity, and Recycling of Silver Ion and Detection of Cupric Ion

The detection and reusage of transition-metal ions play a crucial role in human health and environmental protection. Recently, various analytical methods and substances have been successfully applied to probe or sense silver ions; however, rare representative examples have been presented regarding the simultaneous detection of silver and silver recycling with the elemental silver powder form. Herein, an unparalleled sensing mechanism for silver ions and recycling silver in its elemental form is exemplified by a fluorescent trinuclear zinc coordination cluster possessing the dual function of colorimetric sensing of silver and responding cupric ions. A Schiff-base-based trinuclear zinc coordination cluster, 1, with formula Zn₃(L₁)₂(CH₃COO)₂(H₂O)₂, has been successfully synthesized by the initial exploration of multidentate ligand H₂L₁-((E)-2,4-di-tert-butyl-6-((2-hydroxy-3-methoxybenzy-lidene)amino)phenol) with various metal ions under self-assembly reactions. Complex 1 is highly fluorescent in solution and as a solid, in addition to acting as a fluorescence sensor toward Ag^I in ethanol media. Compound 1 displays distinctive sensing of Ag^I through the fluorescence quenching effect at 576 nm and signal augment at 446 nm over 11 kinds of cations in the absence of interference. The proposed sensing mechanism is attributed to the ligands in 1 which interact with Ag^I; the ligands undergo oxidation cyclization reaction, leading to the formation of 2 with the formula Zn₃(L₂)₄(CH₃COO)₂·2CH₃CH₂OH·H₂O, and Ag^I reduction to elemental Ag powder. Compound 1 presents specific selectivity and sensitivity for Ag^I in ethanolic solution with a detection limit of 0.1722 μM. The orange color of 1 changes to colorless during the mixing of a small amount of Ag^I, revealing its potential practical application in naked-eye detection of Ag^I. Furthermore, 2 exhibits obvious fluorescence emission at 448 nm (λ_ex = 380 nm) and selectively responds to Cu^II over 11 kinds of metal ions with the fluorescence "turn-off" owing to the formation of 3 in ethanolic solution; it also has a detection limit of 0.0226 μM.

Crystal structure of trans-N,N'-bis-(3,5-di-tert-butyl-2-hy-droxy-phen-yl)oxamide methanol monosolvate

The here crystallized oxamide was previously characterized as an unsolvated species [Jímenez-Pérez et al. (2000 ▸). J. Organomet. Chem. 614-615, 283-293], and is now reported with methanol as a solvent of crystallization, C30H44N2O4·CH3OH, in a different space group. The introduction of the solvent influences neither the mol-ecular symmetry of the oxamide, which remains centrosymmetric, nor the mol-ecular conformation. However, the unsolvated mol-ecule crystallized as an ordered system, while many parts of the solvated crystal are disordered. The hy-droxy group in the oxamide is disordered over two chemically equivalent positions, with occupancies 0.696 (4):0.304 (4); one tert-butyl group is disordered by rotation about the C-C bond, and was modelled with three sites for each methyl group, each one with occupancy 1/3. Finally, the methanol solvent, which lies on a twofold axis, is disordered by symmetry. The disorder affecting hy-droxy groups and the solvent of crystallization allows the formation of numerous supra-molecular motifs using four hydrogen bonds, with N-H and O-H groups as donors and the oxamide and methanol mol-ecule as acceptors.