A synthetic and computational approach to the design of new photoactive organometallic materials.

Abstract

Chapter one serves as an introduction to organometallic chemistry, specifically metal carbonyl complexes. The principles of photophysics are also introduced. This is followed by an outline of the techniques of matrix isolation and time-resolved infrared (TRIR) spectroscopy. The rapidly developing area of computational chemistry is then introduced. Specific emphasis is placed on the ab-intio and Density Functional Theory (DFT) levels of theory as well as the method of Time-dependent Density Functional Theory (TDDFT), used for predicting excited states. Chapter two begins with an introduction to the properties of the carbon-fluorine bond and a short review of recent reports of C-F bond activation in the literature. This is followed by a literature survey, which focuses on photochemistry and computational studies of a number of metal carbonyl compounds. The photochemistry of a series of fluorinated metal carbonyls of the type XMn(CO)5 (X = fluorinated substituent), was probed via matrix isolation studies at 20 K, using both IR and UV-vis as detectionmethods. Theoretical studies were performed, and compared to the experimental data. Chapter three involves a review of the photochemistry of M(C0)5 systems, where M = W, Cr, bound to pyridine or substituted pyridines. The photochemistry of systems of the type FpyW(CO)5, as then investigated using matrix isolation at 20 K in a number of matrix gases. Spectroscopic changes were monitored via UV-Vis and IR spectroscopy. Theoretical studies using TDDFT were also preformed. These are compared to the experimental data observed in matrix isolation studies. Chapter four begins with a review of the literature of cis-trans/trans-cis isomerisation, particularly in stilbene and butadiene type compounds. This is then followed by a literature review of the photochemistry of (arene)M(CO)s type compounds. For comparison a review of the photochemistry of a number of photoisomerisable Re(C0)3L complexes is also included, as these systems contain both isomerisable stilbene-like units and carbonyl units. .Predominantly the chapter centres on the photoinduced cis-trans isomerisation of ci~-(~~-1,2-di~hen~lethene)~r(~T0)h3e. photochemistry of these compounds is then examined using techniques such as, matrix isolation, time resolved infia red (TRLR) spectroscopy, and steady-state photolysis. These results are then compared to theoretical results achieved using quantum chemical calculations. The electrochemistry of these metal carbonyl systems is then briefly examined. Chapter five begins with a general introduction to Sonogashira-Hagihara type cross coupling reactions. This is then followed by a literature survey on the synthesis and photochemistry of luminescent organometallic dyad systems. The synthesis of these novel systems using the Sonogashira-Hagihara method is described. The photophysical properties are then examined using room and low temperature fluorescence and life-time studies. The photochemistry of the C02(C0)6 complexes are examined by steady-state photolysis studies in the presence of a trapping ligand. Electrochemical data is also included. Chapter six involves the study of organometallic pyrenyl-ferrocenyl dyad systems. This chapter begins with a brief review of the literature of organometallic ferrocene compounds as luminescent pyrenyl dyad systems are discussed in detail in chapter four. The effect, on the excited state, of the ferrocenyl moiety and the level of conjugation present is examined using fluorescence spectroscopy and electrochemistry. The results of photoinduced CO loss of the Co2(C0)6 complexes in the presence of the trapping ligand triphenylphisphine and are also discussed. Appendix: Experimental details for a number of metal carbonyl complexes and cyclopentenone complexes formed by a photochemically induced Pauson-Khand reaction. Matrix isolation sample preparation and matrix isolation studies for (n6-phenanthrene)Cr(CO)a~re also discussed