Planar 2-Pyridyl-1,2,3-triazole Derived Metallo-ligands: Self-assembly with PdCl₂ and Photocatalysis

Self-assembled metallosupramolecular architectures (MSAs) with built-in functionalities such as light-harvesting metal centers are a promising approach for developing emergent properties within discrete molecular systems. Herein we describe the synthesis of two new but simple "click" ligands featuring a bidentate 2-pyridyl-1,2,3-triazole chelate pocket linked to a monodentate pyridyl (either 3- or 4-substituted, L1 and L2) unit. The ligands and the corresponding four Pd^II and Pt^II metallo-ligands (Pd1, Pd2, Pt1 and Pt2) were synthesized and characterized using nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and X-ray crystallography. Solid-state characterization of the series of ligands and metallo-ligands revealed that these compounds display a co-planar conformation of all the aryl units. The Pt^II containing metallo-ligands (Pt1 and Pt2) were found to assemble into square (Sqr) and triangular (Tri) shaped architectures when combined with neutral PdCl₂ linker units. Additionally, the ability of the Pt^II metallo-ligands and Tri to photocatalyze the cycloaddition of singlet oxygen to anthracene was investigated.