This award in the Inorganic, Bioinorganic, and Organometallic Chemistry Program provides continued support for photochemical research by Dr. Peter C. Ford, Chemistry Department, University of California, Santa Barbara. Work will focus on two classes of compounds: metal nitrosyl and nitrito complexes, and polynuclear copper(I) complexes. The goal of the first project is to elucidate the photochemical mechanisms of nitric oxide (NO) generation as well as the dynamics of NO reactions with metal centers of bioinorganic interest. Flash and continuous photolysis of various mononuclear metal nitrosyl and metal nitrito complexes will be conducted, placing particular emphasis on compounds that may serve as precursors for the photochemical delivery of NO to desired targets on demand. In addition, the synthesis and photochemical-photophysical characterization of dual chromophore systems that might serve as luminactive sensors for detection of NO will be studied. The second project will investigate the photoluminescent behavior of mononuclear and cluster compounds containing d-10 metal centers, primarily copper(I), including how the excited state properties respond to perturbations in the properties of the media. When light is absorbed by a molecule, the energy that the molecule acquires is sometimes used to initiate a chemical reaction and sometimes is re-emitted as light of a different wavelength (luminescence). The methods used in this study enable changes of both types to be determined. Nitric oxide(NO) affects bioregulatory and immune response and medical benefits could be derived from controlled release of NO at specific targets. This study will contribute to the understanding of the interaction of NO with biomolecules and the ability to monitor its effects. Studies of the changes of excited state properties of metal clusters are relevant to the design, optimization, and application of photooptical devices and photocatalysts.