Synthesis and structural characterization of ruthenium(II) hydrido carbonyl triphenylphosphine α-diimine complexes with derivatives of 2,2'-bipyridine.

The structural and emission properties of two ruthenium(II) polypyridyl complexes, namely, carbonyl(4,4'-di-tert-butyl-2,2'-bypyridine)hydridobis(triphenylphosphine)ruthenium(II) hexafluorophosphate, [RuH(CHN)(CHP)(CO)]PF or [Ru(H)(CO)(dtbbpy)(PPh)]PF (dtbbpy is 4,4'-di-tert-butyl-2,2'-bipyridine), and (2,2'-biquinoline)carbonylhydridobis(triphenylphosphine)ruthenium(II) hexafluorophosphate, [RuH(CHN)(CHP)(CO)]PF or [Ru(H)(CO)(bq)(PPh)]PF (bq is 2,2'-biquinoline), were characterized by spectroscopic analysis, X-ray diffraction and density functional theory (DFT) <!?up><!?tlsb><!?down>computational methods, and compared to the parent [Ru(H)(CO)(bpy)(PPh)]PF complex (bpy is 2,2'-bipyridine). The X-ray analysis of these compounds showed a slightly distorted octahedral geometry of the Ru ion typical for this kind of complex. Classical hydrogen bonds are not observed in the crystals of the investigated complexes. Weak intermolecular C-H...F contacts and, as shown by the Hirshfeld surface analysis, H...H interactions have the dominant contributions in the molecular packing in both structures. In CHCl solution at 298 K, both complexes show a weak broad emission band attributed to S←MLCT transitions. At 77 K in frozen methanol/ethanol glass, the complexes exhibit strong luminescence of MLCT origin. DFT calculations confirm that the optimized geometries are in good agreement with the experimental structures. In the excited state, changes are observed in the metal-ligand bond lengths, which are consistent with a metal-to-ligand charge transfer (MLCT) character.