Unique Metal–Ligand Interplay in Directing Discrete and Polymeric Derivatives of Isomeric Azole-Carboxylate. Varying Electronic Form, C–C Coupling, and Receptor Feature

Abstract

This article dealt with the ruthenium and osmium derivatives of isomeric 1H-indazole-3-carboxylic acid/2H-indazole-3carboxylic acid (H 2 L1) and 1H-benzimidazole-2-carboxylic acid (H 2 L2) along with the π-acidic bpy (bpy = 2,2′-bipyridine) and pap (pap = 2phenylazopyridine) co-ligands. It thus extended structurally authenticated monomeric ([(bpy) 2 Ru II (HL1 − )]ClO 4 [1]ClO 4 , (pap) 2 Ru II (L1 2− ) 2, (bpy) 2 Os II (L1 2− ) 3, (pap) 2 Os II (L1 2− ) 4, (bpy) 2 Ru II (L2 2− ) 5, (bpy) 2 Os II (L2 2− ) 8, and (pap) 2 Os II (L2 2− ) 9) and dimeric ([(bpy, where L2′ 2− was developed selectively with the {Ru(pap) 2 } metal fragment via in situ intermolecular C−C coupling of the two units of decarboxylated benzimidazolate. Moreover, chemical oxidation (Os II to Os III ) of (bpy) 2 Os II (L1 2− ) 3 (E 0 = 0.11 V versus SCE) and (bpy) 2 Os II (L2 2− ) 8 (E 0 = 0.12 V versus SCE) by AgClO 4 yielded unprecedented Os III -Ag I derived polymeric {[(bpy) 2 Os III -L1 2− -Ag I (CH 3 CN)](ClO 4 ) 2 } n {[10](ClO 4 ) 2 } n and dimeric [(bpy) 2 Os III -L2 2− -Ag I (CH 3 CN)](ClO 4 ) 2 [11](ClO 4 ) 2 complexes as a function of trans and cis orientations of the active N2 donor with special reference to the carboxylate O2 of L 2− , respectively. Microscopic (FE-SEM, TEM−EDX, and AFM) and DLS experiments suggested a homogeneously dispersed hollow spherical shaped morphology of {[10](ClO 4 ) 2 } n with an average particle size of 200−400 nm as well as its non-dissociative feature in the aprotic medium. Experimental (structure, spectroscopy, and electrochemistry) and theoretical (DFT/TD-DFT) explorations revealed a redox non-innocent feature of L 2− in the present coordination situations and the selective anion sensing (X = F − , CN − , and OAc − ) event of [1]ClO 4 involving a free NH group at the backface of HL1 − , which proceeded via the NH•••X hydrogen bonding interaction.

Effect of Terminal Substituents of 2-Aminobenzimidazoles on Non-Covalent Molecular Interactions in Their Transition Metal Coordination Compounds. Evaluation of Their Biological Activity

“…In the presence of a reducing agent, these compounds induce DNA damage by ROS generation. Cytotoxicity studies with different cancer cell lines revealed that complexes [Cu(tnz) 2 (µ-Cl)Cl] 2 and [Cu(tnz) 2 Br 2 ] showed the highest cytotoxicity, while being moderately toxic to normal cells [26,27] Generally, the reported cytotoxic transition metal compounds have been synthesized using chelating ligands [28][29][30][31][32][33][34]. The results with non-chelating ligands, tinidazole and clotrimazole [35][36][37][38][39][40][41][42], have shown that weak interactions, such as hydrogen bonding, electrostatic interactions, π stacking, lp•••π or hydrophobic contacts, as well as geometry and redox properties, have an important role in the biological activity of coordination compounds with monocoordinated ligands.…”