Comparative Study of Structures and Luminescent Properties of Three Ag(I) Complexes Utilizing an Achiral Bipyridyl-N or Its Axially Chiral N-Oxide Analogue

Abstract

An achiral 2,2′-bipyridyl-3,3′-dicarboxylate (H2LN) can be oxidized to a C 2 axially chiral N-oxide analogy (R,S)-2,2′-bipyridyl-3,3′-dicarboxylate-1,1′-dioxide ((R,S)-H2LNO), converting normal bipyridyl-N to a charge-separated N-oxide group. The achiral H2LN connects the Ag­(I) ions into a 4-connected mesomeric 3D network [Ag4(LN)2·(H2O)]·3H2O (1). However, as expected, with the introduction of N-oxide groups, {Ag4­[(R,S)-LNO]2·2­(H2O)}·H2O (2) and {Ag2­[(R,S)-LNO]}·H2O (3) contain right- and left-handedness homochiral layers. Such opposite handedness layers are linked together to give a racemic compound in 2 but meso double-layers in 3. Notably, both ligands in 1–3 support argentophilic interactions. Moreover, a luminescent comparison of 1–3, pyridyl-N, and its functional N-oxide ligands is also investigated in detail.

Does Proton Transfer Always Take Place in Molecules of 2-Substituted Pyridine-N-oxides? The Case of 2-Aminopyridine-N-oxide Crystal Structure and Its 3,5-Dinitrobenzoic Acid Co-crystal

“…The chemistry and application of aromatic heterocyclic N -oxides is fundamental in today’s scientific advances. The importance of these compounds is due to their role as synthetic intermediates, directing or protecting groups, − effective ligands, and components of metal–organic frameworks (MOF) and host–guest complexes − in catalysis and organic chemistry. − These compounds are also very interesting because of their biological importance. − Some derivatives of pyridine N -oxide have been reported as ingredients in pharmaceutical co-crystals. − …”