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

This article dealt with the ruthenium and osmium derivatives of isomeric 1 H -indazole-3-carboxylic acid/2 H -indazole-3-carboxylic acid (H 2 L1) and 1 H -benzimidazole-2-carboxylic acid (H 2 L2) along with the π-acidic bpy (bpy = 2,2'-bipyridine) and pap (pap = 2-phenylazopyridine) 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) 2 Ru II (μ-L2 2- )Ru II (bpy) 2 ](ClO 4 ) 2 [ 6 ](ClO 4 ) 2 ) complexes. It also described modified L2' 2- (L2' 2- = 2,2'-bisbenzimidazolate)-bridged [(pap) 2 Ru II (μ-L2' 2- )Ru II (pap) 2 ](ClO 4 ) 2 [ 7 ](ClO 4 ) 2 , 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.