Spectroscopy and Photochemistry of Nickel(II), Palladium(II), and Platinum(II) .beta.-Diketonates

Abstract

The spectroscopy and photochemistry of several group 10(11) /3-diketonates have been investigated. The spectral shifts observed upon replacing the methyl groups of the acetylacetonate ligand with phenyl groups have been correlated with the changes in frontier orbital energies and the allowed electronic transitions calculated using the semiempirical INDO/S-SCF-Cl (ZINDO) algorithm. All of the group 10(11) /3-diketonates undergo inefficient decomposition upon 254 nm irradiation in ethanol or dichloromethane solution to produce free metal and /3-diketone.Photoisomerization of cisand frans-platinum(II) benzoylacetonate is more efficient than photodecomposition. Irradiation of the platinum /3-diketonates in the presence of hydrosilanes or olefins results in the formation of primary products which revert to starting material in the dark and can be converted to free metal and /3-diketone by continued irradiation or heating. Reaction with added hydrosilane effectively inhibits photoisomerization. Both the efficiency of intermediate formation and its dark stability are dependent upon the structure of the hydrosilane or olefin and the /3-diketonate ligand. A mechanism is proposed in which one-bond cleavage results in the formation of a short-lived three-coordinate intermediate which can recombine with retention or inversion of configuration, react with solvent to form unstable intermediates, or react with added hydrosilanes or olefins to form primary photoproducts of variable stability. Possible structures for the primary photoproducts are discussed.

Dynamic NMR spectroscopy in studies of the kinetics of photoinduced chemical exchange in solutions

“…X obs is the radiospectroscopic observation channel ( 1 H, 13 C, 19 F nuclei, etc. ), X dec is the radiospectroscopic channel of selective homonuclear decoupling of the second signal at the frequency ν 2 , and hν denotes the irradiation channel (electromagnetic radiation in the visible, IR, or UV spectral region) for the chemical system under study.…”

“…Pulse sequence for the PICE kinetic studies using NMR lineshape analysis under irradiation with light (a) and in the dark (b). X obs denotes the radiospectroscopic observation chan nel ( 1 H,13 C,19 F nuclei, etc.) and hν denotes the irradiation channel (electromagnetic radiation in the visible, IR, or UV spectral region) for the system under study.…”

NMR application for a study of reversible photochemical kinetics: A multisite case

“…The study of photochemical reactions is one of the many interesting applications of nuclear magnetic resonance (NMR) spectroscopy (1)(2)(3)(4). In particular, NMR is used to measure quantum yields for irreversible photochemical reactions (1) and, in addition, NMR branch of photochemically induced polarization of nuclei provides detection of short-lived radicals arising in flash photolysis of substances (2).…”

“…In particular, NMR is used to measure quantum yields for irreversible photochemical reactions (1) and, in addition, NMR branch of photochemically induced polarization of nuclei provides detection of short-lived radicals arising in flash photolysis of substances (2). Being a well-developed NMR tool, dynamic NMR spectroscopy (DNMR) is commonly used to obtain kinetic parameters of dark reversible chemical reactions in solutions (5,6).…”

Synthesis, Characterization and Antimicrobial Screening of 1,3-Dione with their Metal Complexes

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General structure of enol form of 1,3-diones 1,3-Dione metal complexes are used as catalyst in reaction of olefin oxidation and epoxidation [11,12]. Europium(III)-diketonates have excellent luminescent property [13].

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