Design and synthesis of luminescent rhenium(I) diimine complexes with various receptor or carbene ligands

Abstract

Rhenium carbonyl diimine complexes are well-known to show intense and long-lived phosphorescence. In this thesis, the synthesis, characterization, photophysics and electrochemistry of a number of luminescent carbonyl rhenium(I) diimine complexes with different types of various ancillary ligands and functional diimine ligands are reported. First, a series of rhenium tricarbonyl complexes with acetylamino- and trifluoroacetylamino-containing 1,10-phenanthroline ligands with the general formula of [Re(CO)3(L)(phen-NHCOCX3)] (1: L = Br, X = F; 2: L = CN, X = F; 3: L = Br, X = H) have been synthesized, characterized and their photophysical and electrochemical properties studied. These complexes were found to show significant UV-vis and emission changes on addition of CN¯, F¯ and AcO¯ anions. Their reactivity towards CN¯, F¯ and AcO¯ anions was also investigated by UV-vis, emission and 1H NMR spectroscopy. The reaction product between the trifluoroacetylamino-containing 1,10-phenanthroline ligand and the CN¯ anion has also structurally characterized by X-ray crystallography. Second, a series of substituted bithiazole ligands have been synthesized and incorporated into rhenium(I) tricarbonyl and tetracarbonyl diimine complex systems. These complexes have been characterized by IR, NMR spectroscopy and elemental analysis. Their photophysical and electrochemical properties have also been studied. Detailed photophysical study on these bithiazole rhenium(I) complexes shows that the emission of rhenium(I) complexes with diimine ligand of very low-lying π* orbital could be blue-shifted with enhanced emission quantum efficiency and longer lived emission lifetimes through the incorporation of the strong π-accepting ancillary ligand. In addition, a series of rhenium(I) complexes with benzoxazol-2-ylidene ligand with general formula of {Re(CO)3(phen)[CN(X)C6H4-2-O]}+ and cis,trans-{Re(CO)2(phen)(L)[CN(H)C6H4-2-O]}+ (X = H, methyl; phen = 1,10-phenanthroline; L = PPh3, PPh2Me, P(OEt)3.) have been synthesized and characterized. The structures of most of the carbene complexes and some of their synthetic precursors have also been determined by X-ray crystallography. The photophysics and electrochemistry of these complexes were investigated. Detailed photophysical study shows that the carbene complexes in MeCN solutions display 3MLLCT [dπ(Re) → π*(phen)] phosphorescence at room temperature. The N-deprotonation of the benzoxazol-2-ylidene ligand in these complexes has been examined by UV-vis and emission spectroscopy.

Date of Award	3 Oct 2012
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Chi Chiu Vincent KO (Supervisor)