Rhenium(I) tricarbonyl complexes: Synthesis, photophysics, switching and recognition properties

This dissertation research explores the design and properties of rhenium(I) tricarbonyl complexes and their possible applications as chemical sensors and photoswitching devices. A series of aryl(pyridyl)methanone rhenium(I) complexes have been prepared for the purpose of examining their photophysical, electrochemical and kinetic properties as well as to evaluate their potential effectiveness as molecular sensors of anions, including cyanide and acetate ions. It is established that the photophysical behavior of these systems is highly dependent on the solvent and that they undergo ligand exchange processes. Two binuclear Re(I) complexes covalently linked to rigid macrocyclic phenylacetylene ligands have been successfully synthesized and their photophysical and electrochemical properties have been studied to explore their host-guest chemistry. These complexes display recognition properties for inorganic anions, viz. fluoride, acetate, cyanide and phosphate. It is also found that nitro-substituted aromatic compounds effectively quench their luminescence intensities. Furthermore, a series of binuclear (diimine) rhenium(I) tricarbonyl complexes linked by a stilbene-like ligand have been synthesized and characterized. The complexes show interesting photoswitching features, where the luminescence from the complexes can be switched on and off by photoinduced ligand isomerization. Finally, rhenium(I) complexes of monodentate para-substituted azo-pyridine and styrylpyridine have been synthesized. The para-hydroxyphenyl azopyridine complex exhibits spectral changes upon addition of common anions, including fluoride and acetate, and their binding constants have been determined. It is also been found that both para-hydroxyphenyl azopyridine and para-aminophenyl styrylpyridine complexes undergo spectral changes upon pH change.