Syntheses and photophysics of luminescent mono- and dinuclear rhenium complexes containing functional ligands

by Wong, Man-chung

Abstract (Summary)
(Uncorrected OCR) Abstract of thesis entitled ?YNTHESES AND PHOTOPHYSICS OF LUMINESCENT MONO- AND DINUCLEAR RHENIUM COMPLEXES CONTAINING FUNCTIONAL LIGANDS?Submitted by Wong Man Chung for the degree of Doctor of Philosophy at The University of Hong Kong ABSTRACT With the growing interest in the exploration of inorganic/ organometallic sensing materials, a series of mononuclear rhenium(I) and rhenium(V) and dinuclear rhenium(I) complexes with crown ether pendants of formula [Re(CO)3(DIC-18-C-6)Cl], [{Re(CO)3Cl}2(DDIC)], [Re(CO)3(DIC-S)Cl], [Re(CO)3(DIC-3S)Cl], [Re(CO)3(DIC-Se)Cl], [Re(CO)3(DPPZC)Cl] and [ReV(PPh3)2(C=C-benzo-15-crown-5)2] have been synthesized. The photophysical, electrochemical and cation-binding properties of these systems have been studied. The structure of [Re(CO)3(DIC-Se)Cl] has been established by X-ray crystallography. The electronic absorption energies of the rhenium(I) complexes were found to be sensitive to the presence of metal cations. The stability constants of [Re(CO)3(DIC-18-C-6)Cl] and [{Re(CO)3Cl}2(DDIC)] for alkali and alkaline-earth metal cations have been determined by UV-visible spectrophotometry. The complexes [Re(CO)3(DIC-S)Cl], [Re(CO)3(DIC-3S)Cl] and [Re(CO)3(DIC-Se)Cl] showed a downfield shift of methylene protons adjacent to the sulphur or selenium atom on the crown ether moiety upon addition of silver ion in deuterated acetonitrile. Their stability constants for silver ion have also been determined by UV-visible and 1H NMR spectroscopies. Direct evidences for the formation of the inclusion species between the crown ether-containing rhenium(V) complex [ReV(PPh3)2(C=C-benzo-15-crown-5)2] and lithium or sodium ions were obtained from electrospray ionization-mass spectrometry. A series of mononuclear and dinuclear rhenium(I) complexes with thiolate and selenolate ligands, [Re(CO)3(N-N)(S-C6H4-X-p)] and [{Re(CO)3(N-N)}2(?S-C6H4-X- p)]+, have been synthesized (N-N = bpy, Me2-bpy, tBu2-bpy, phen; X = CH3, OCH3, C(CH3)3, Cl, F). Unsymmetrical dinuclear rhenium(I) thiolate complexes have been prepared by utilizing the mononuclear complexes as precursors. Their electrochemical properties have also been studied. The photophysical behaviour of the dinuclear complexes has been studied. Attempts to investigate the photophysical behaviour of the mononuclear counterparts were unsuccessful owing to their low photo-stability. The crystal structures of the complexes [Re(CO)3(phen)(SC6H4-OCH3-p)], [Re(CO)3(tBu2-bpy)(SePh)], [{Re(CO)3(bpy)}2(?SC6H4-CH3-p)]OTf, [Re(CO)3(phen)(?SC6H4-OMe-p)Re(CO)3(bpy)]OTf and [Re(CO)3(Me2-bpy)(?SC6H4-Me-p)Re(CO)3(NO2-phen)]OTf have also been determined. Besides, a series of luminescent rhenium(I) acetylide complexes with diimine ligands, [Re(CO)3(N-N)(C=C-R)] (N-N = bpy, Me2-bpy, phen, NO2-phen; R = Ph, C6H4-Cl-p, C6H4-C8H17-p, C6H4-C=CH-p, C6H4-N=N-C6H4-OC12H25, EEME), have been synthesized and their photophysical and electrochemical properties studied. The X-ray crystal structure of [Re(CO)3(bpy)(C=C-Ph)] has been determined. An unsymmetrical dinuclear complex, [(bpy)(CO)3Re-C=C-C6H4-C=C-C=C-C6H4-C=C-Re(CO)3(tBu2-bpy)] has been prepared by the coupling reaction of the respective precursors, [Re(CO)3(bpy)(C=C-C6H4-C=CH-p)] and [Re(CO)3(tBu2-bpy)(C=C-C6H4-C=CH-p)]. Attempts to employ the versatile starting material, [Re(CO)3(bpy)(MeCN)]+ to prepare luminescent rhenium(I) tricarbonyl monoacetylide complexes yielded unexpectedly the dinuclear complex [{Re(CO)3(bpy)}2{NHC(CH3)CHCN}]OTf through the reaction of the rhenium(I) starting material with the sodium salt of the acetylide, prepared from sodium hydride and the corresponding acetylide in THF solution. The same dinuclear complex has also been obtained from the reaction of the rhenium(I) starting material with sodium hydride. The complex has been characterized by 1H NMR, 13C NMR, IR, FAB-MS, elemental analyses, and X-ray crystallography. A reaction mechanism has been proposed for its formation and its photophysical and electrochemical properties have been studied. Both 1H and 13C NMR experiments revealed the presence of two rotamers, suggestive of the existence of an equilibrium between the cis- and the trans-conformations in solution.
Bibliographical Information:


School:The University of Hong Kong

School Location:China - Hong Kong SAR

Source Type:Master's Thesis

Keywords:rhenium compounds synthesis


Date of Publication:01/01/1999

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