First Gallium and Indium Crystal Structures of Curcuminoid Homoleptic Complexes: All-Different Ligand Stereochemistry and Cytotoxic Potential.

The crystal structure determination of metal complexes of curcuminoids is a relevant topic to assess their unequivocal molecular structure. We report herein the first two X-ray crystal structures of homoleptic metal complexes of a curcuminoid, namely Dimethoxycurcumin (DiMeOC), with gallium and indium. Such successful achievement can be attributed to the suppression of interactions from the phenolic groups, which favor an appropriate molecular setup, rendering Dimethoxycurcumin gallium ((DiMeOC)2-Ga) and Dimethoxycurcumin indium ((DiMeOC)3-In) crystals. Surprisingly, the conformation of ligands in the crystal structures shows differences in each metal complex. Thus, the ligands in the (DiMeOC)2-Ga complex show two different conformers in the two molecules of the asymmetric unit. However, the ligands in the (DiMeOC)3-In complex exhibit three different conformations within the same molecule of the asymmetric unit, constituting the first such case described for an ML3 complex. The cytotoxic activity of the (DiMeOC)2-Ga complex is 4-fold higher than cisplatin against the K562 cell line and has comparable activity towards U251 and PC-3 cell lines. Interestingly, this complex exhibit three times lesser toxicity than cisplatin and even slightly lesser cytotoxicity than curcumin itself.

Gallium hydride and monovalent indium compounds that feature tris(pyrazolyl)hydroborate ligands.

The tris(pyrazolyl)hydroborate compounds [tris(3,5-dimethyl-1H-pyrazol-1-yl-κN(2))hydroborato]indium(I), [In(C15H22BN6)], abbreviated as [Tp(Me2)]In, and [tris(3-tert-butyl-5-methyl-1H-pyrazol-1-yl-κN(2))hydroborato]indium(I), [In(C24H40BN6)], abbreviated as [Tp(Bu(t),Me)]In, represent well defined examples of three-coordinate monovalent indium. In both compounds, the geometry at indium is pyramidal and natural bond orbital (NBO) calculations indicate that the indium lone pair occupies an orbital that is primarily 5s in character. The trivalent gallium hydride compound hydrido[tris(3-tert-butyl-5-methyl-1H-pyrazol-1-yl-κN(2))hydroborato]gallium(III) tetrachloridogallium(III), [Ga(C24H40BN6)H][GaCl4], abbreviated as {[Tp(Bu(t),Me)]GaH}[GaCl4], is obtained via reaction of [Tp(Bu(t),Me)]Tl with [HGaCl2]2, and the Ga-H bond length of 1.49 (6) Šcompares favorably with the mean value of 1.50 Šfor structurally characterized gallium hydride compounds that are listed in the Cambridge Structural Database.

A Highly Stable 3D Luminescent Indium-Polycarboxylic Framework for the Turn-off Detection of UO22+, Ru3+, and Biomolecule Thiamines.

Hydrothermal reaction of the multidentate organic ligand (H6TTHA) with indium chloride (InCl3) produced a highly stable 3D luminescent indium-organic framework [In2(OH)2(H2TTHA)(H2O)2]n (1). Complex 1 exhibits remarkable luminescent properties, especially the multifunction sensitivity and selectivity for detecting Ru3+, UO22+; as well as small biomolecules thiamines (TPP, TMP, and TCl) based on a "turn-off" manner. In particular, the pyrophosphate groups of TPP and the phosphate groups of TMP could further affect the quenching rate, leading to different luminescent responds. In addition, we also discussed and proved the luminescence quenching mechanism in detail through comparative test and PXRD characterization. Therefore, complex 1 could be used as a kind of excellent luminescence sensor to detect Ru3+, UO22+, and thiamines (TPP, TMP, and TCl).