Unexpected linkage isomerism in chiral tetranuclear bis-tridentate (1,2,3-triazol-4-yl)-picolinamide (tzpa) grids

Abstract

Two chiral [2 × 2] tetranuclear CuII square grid complexes are prepared from a (1,2,3-triazol-4-yl)-picolinamide (tzpa) ligand. Linkage isomerism through the amide is observed accompanying an in situ deprotonation and CuI → CuII oxidation process.

Formation of lanthanide luminescent di-metallic helicates in solution using a bis-tridentate (1,2,3-triazol-4-yl)-picolinamide (tzpa) ligand

“…23 With that in mind we recently combined these two coordination environments within a single ligand motif, the result being the formation of a new class of bis-tridentate (1,2,3-triazol-4-yl)picolinamide (tzpa) ligands. [24][25][26] Up until now, our effort has focused on exploring some of the coordination chemistry of the tzpa ligands with d-metal ions, which included the formation of chiral tetranuclear Cu(II) supramolecular assembly (M 4 L 4 ) grids, using 1 (Figure 1). 26 However, no evidence for the formation of circular helicates was observed in the solid state using either Cu(II) or Fe(II) with tzpa ligands.…”

“…[24][25][26] Up until now, our effort has focused on exploring some of the coordination chemistry of the tzpa ligands with d-metal ions, which included the formation of chiral tetranuclear Cu(II) supramolecular assembly (M 4 L 4 ) grids, using 1 (Figure 1). 26 However, no evidence for the formation of circular helicates was observed in the solid state using either Cu(II) or Fe(II) with tzpa ligands. 25,26 We thus speculated that due to the coordination similarity with bis-tridentate pda ligands, 18,19 the use of f-metal ions might yield such helical selfassemblies.…”

“…Fig.1(a) The chiral bis-tridentate (1,2,3-triazol-4-yl)-picolinamide (tzpa) ligand 1 used in the current study, and the 'half' ligand 2, which was formed as a model ligand. The solid state structures of the tetranuclear [2 &Â 2] square grids formed from 1 in our previous study using:(b) Cu(NO 3 ) 2 Á 3 H 2 O and (c) [Cu(MeCN) 4 ](PF 6 ), respectively 26. …”

“…1). 26 However, no evidence for the formation of circular helicates was observed in the solid state using either Cu( ii ) or Fe( ii ) with tzpa ligands. 25,26 We thus speculated that due to the coordination similarity with bis-tridentate pda ligands, 18,19 the use of f-metal ions might yield such helical self-assemblies.…”

“…26 However, no evidence for the formation of circular helicates was observed in the solid state using either Cu( ii ) or Fe( ii ) with tzpa ligands. 25,26 We thus speculated that due to the coordination similarity with bis-tridentate pda ligands, 18,19 the use of f-metal ions might yield such helical self-assemblies. Herein, we present the results from our investigation, and the first example of the use of tzpa ligands in the formation of lanthanide di-metallic helicates by using Tb( iii ) and 1 (and ligand 2 , as a ‘half-helical’ model compound).…”