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Sensing of carbon monoxide via luminescence of ruthenium complexes containing a hemilabile phosphine pyrenyl ether ligand

University of British Columbia

Our laboratory previously reported a Ru2 + complex with a hemilabile phosphine ether ligand tcc-RuCl2(POC4Pyr-P,O)2 (14) (POC4Pyr = 4-{2- (diphenylphosphino)phenoxy}butylpyrene). This complex reacts rapidly with carbon monoxide to produce a significant luminescence response in which the monomer: excimer emission ratio changes dramatically. The reaction with CO is accompanied by a geometric isomerization from the initial trans-dicarbonyl product, ttt- RuCl2(CO)2(POC4Pyr-P)2 , to the cis-dicarbonyl product, crt-RuCl2(CO)2(POC4Pyr-P)2. However, an OFF-ON response was not achieved. Two methodologies are explored in this thesis to obtain the desirable OFF-ON response by promoting pyrene fluorescence quenching before exposure to CO. Attempts are reported to synthesize ligands with tether lengths less than four carbon atoms in length in order to probe the effect of tether length between the pyrene moiety and the rest of the complex on fluorescence quenching. Although a ligand with a one-carbon tether ({2-(diphenylphosphino)phenoxy}methylpyrene) was not successfully synthesized, a ligand with a two-carbon tether (2-{2- (diphenylphosphino)phenoxy}ethylpyrene) was obtained. However, attempts to coordinate this ligand with Ru were unsuccessful. A second strategy explored in this thesis is the effect of changing the halide ligands of complex 14 to either bromo (22) (tcc-RuBr2(POC4Pyr-P,O)2) or iodo ligands (23) (tcc-Rul2(POC4Pyr-P,O)2). The different halogen ligands are expected to change the energies of the metal d-orbitals and possibly result in fluorescence quenching. This series of complexes with different halogen ligands has been fully characterized by NMR, MS, UV-vis and fluorescence spectroscopies and their reactivity toward CO studied. A similar geometric isomerization from the ttt isomer to the cct isomer was observed for 22 and 23 as for 14. Furthermore, fluorescence experiments were undertaken in order to explore the changes in fluorescence properties that accompany the reaction with CO. No excimer emission is observed even at high concentration before reaction with CO for 14, 22 or 23. After reaction with CO, excimer emission is observed for all complexes. From excitation, steady-state emission, and UV-vis spectroscopies, it has been determined that both inter- and intra-molecular excimers are observed that originate from loosely coupled or transient molecular pairs.

Thesis/Dissertation

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2009-11-24

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http://hdl.handle.net/2429/15717

Chemistry

University of British Columbia

UBCV

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