Synthesis and structural studies of 1,4-di(2-pyridyl)-1,2,3-triazole dpt and its transition metal complexes; a versatile and subtly unsymmetric ligand

The synthesis of the 'click' derived 1,4-di(2-pyridyl)-1,2,3-triazole (dpt) chelator/ligand from 2-azidopyridine and 2-ethynylpyridine using Cu(I) and TBTA by microwave assisted synthesis is presented. The complexes of the subtly unsymmetric dpt ligand with Cu(I), Pt(II), Co(II), and Ag(I) were structurally characterised by using conventional methods, as well as using single crystal and powder diffraction analysis. The results of the studies showed formation of discrete molecules displaying preferential binding of the d-metal cations through the pyridyl nitrogen N1 and the proximal triazolyl nitrogen N2 i.e. the 2-(1H-1,2,3-triazol-4-yl)pyridine or 'regular' chelate moiety despite the presence of a second potential binding pocket i.e. the 2-(1H-1,2,3-triazol-1-yl)pyridine chelate or 'inverse' moiety. This binding selectivity was corroborated through the study of the self-assembly of dpt with Cu(I) and Ag(I) using H-1 NMR titration in CD3CN solution, as well as using UV-Vis absorption titrations; the former showing a broadening of the proton peaks associated with that chelate pocket.