Design and applications of luminescent inorganic complexes

Citation

McCleskey, T. Mark (1994) Design and applications of luminescent inorganic complexes. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/kqh2-zq63. https://resolver.caltech.edu/CaltechETD:etd-07202005-153301

Abstract

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A series of Au(I) phosphine complexes were designed and synthesized to investigate the possibility of room temperature phosphorescence in solution from three different types of transitions: metal-to-ligand-charge-transfer in four coordinate monomers, [...] in Au(I) dimers, and [...] in two and three coordinate monomers. Solution emission was only observed from the three coordinate Au(I) complexes. The complex [...] (dcpe = 1,2-bis-dicyclohexylphosphinoethane) has two isolated AuP3 units and emits at 508 nm in acetonitrile solution with a lifetime of 21 [...] and a quantum yield of 0.8 (366 nm excitation). The emission has been assigned as a [...] transition with the corresponding absorption band at 370 nm. The excited state is a powerful reductant capable of reducing aryl halides.

Electron transfer (ET) rates were studied from the excited [...] to a series of substituted pyridiniums (py+). The low excited state reduction potential (Au(II)/Au(I)) of -2.3 V made it possible to study ET rates at driving forces as high as 2.1 eV. High driving force, bimolecular ET rates were also studied with [Ir(cod)(pz)]2 (IR2; cod = cyclooctadiene, pz = pyrazole). The forward ET rates from Ir2 to py+ increase to the diffusion limit and remain diffusion limited at driving forces as high as 1.60 eV. The recombination ET rates from py to Ir2+ show inverted behavior (rates decrease as the driving force increases) at driving forces > 0.85 eV, representing the first observation of inverted behavior for a bimolecular system. The discrepancy between the forward ET and recombination ET rates is explained by ET to low lying excited states.

On the basis of the emission observed from three coordinate Au(I) complexes, Au(I) was used as a probe for the coordination environment of the active site in Pseudomonas auruginosa azurin. The active site consists a copper center strongly bound to two histidines and a cysteine in a trigonal plane with a disputed axial interaction to [...] away. The Au(I)-WT-azurin is stable and emits at 580 nm, indicating that there is little or no interaction with the Metl2l.

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