Photochemistry of RuII 4,4'-bi-1,2,3-triazolyl (btz) complexes: crystallographic characterization of the photoreactive ligand-loss intermediate trans-[Ru(bpy)(?2-btz)(?1-btz)(NCMe)]2+.

ABSTRACT: We report the unprecedented observation and unequivocal crystallographic characterization of the meta-stable ligand loss intermediate solvento complex trans-[Ru(bpy)(?(2) -btz)(?(1) -btz)(NCMe)](2+) (1?a) that contains a monodentate chelate ligand. This and analogous complexes can be observed during the photolysis reactions of a family of complexes of the form [Ru({NN})(btz)(2)](2+) (1?a-d: btz=1,1'-dibenzyl-4,4'-bi-1,2,3-triazolyl; {NN}=a)?2,2'-bipyridyl (bpy), b)?4,4'-dimethyl-2,2'-bipyridyl (dmbpy), c)?4,4'-dimethoxy-2,2'-bipyridyl (dmeobpy), d)?1,10-phenanthroline (phen)). In acetonitrile solutions, 1?a-d eventually convert to the bis-solvento complexes trans-[Ru({NN})(btz)(NCMe)(2)](2+) (3?a-d) along with one equivalent of free btz, in a process in which the remaining coordinated bidentate ligands undergo a new rearrangement such that they become coplanar. X-ray crystal structure of 3?a and 3?d confirmed the co-planar arrangement of the {NN} and btz ligands and the trans coordination of two solvent molecules. These conversions proceed via the observed intermediate complexes 2?a-d, which are formed quantitatively from 1?a-d in a matter of minutes and to which they slowly revert back on being left to stand in the dark over several days. The remarkably long lifetime of the intermediate complexes (>12?h at 40?°C) allowed the isolation of 2?a in the solid state, and the complex to be crystallographically characterized. Similarly to the structures adopted by complexes 3?a and d, the bpy and ?(2) -btz ligands in 2?a coordinate in a square-planar fashion with the second monodentate btz ligand coordinated trans to an acetonitrile ligand.

SUBMITTER: Welby CE 

PROVIDER: S-EPMC4506527 | biostudies-other | 2014 Jul

REPOSITORIES: biostudies-other