15680-13-4Relevant academic research and scientific papers
Photosubstitution reactions of M(CO)4(1,10-phenanthroline) (M = Mo, W). Influence of entering ligand, irradiation wavelength, and pressure
Fu, Wen-Fu,Van Eldik, Rudi
, p. 572 - 578 (1997)
The influence of the entering nucleophile, irradiation wavelength, and pressure on the quantum yield for the photosubstitution of M(CO)4phen (M = Mo, W) to produce M(CO)3-(L)phen (L = PMe3, PPh3) was investigated in toluene at 298 K. From the pressure dependence of the quantum yield apparent volumes of activation could be determined as a function of irradiation wavelength. These could be analyzed in terms of contributions arising from dissociative ligand field excitation and associative metal-to-ligand charge transfer excitation. The influence of steric hindrance on the entering ligand (PPh3 > PEt3 > PMe3) controls the contribution of the associative charge-transfer photosubstitution reaction. An overall mechanistic picture is presented and discussed in reference to available literature data.
A biphasic displacement of [60]fullerene from fac-(dihapto-[60]fullerene) (dihapto-1,10-phenanthroline) tricarbonyl molybdenum (0)
Ocasio-Delgado, Yessenia,De Jesús-Segarra, Jonathan,Cortés-Figueroa, José E.
, p. 3366 - 3372 (2007/10/03)
The Lewis bases (=L) triphenylphosphine (PPh3) and tricyclohexyl phosphine (P(Cy)3) displace [60]fullerene (C60) from the complex fac-(η2-C60)(η2-phen)Mo(CO) 3 (phen = 1,10-phenanthroline). The progress of the reactions was followed observing the decrease of the absorbance values at 440 nm and by monitoring the stretching carbonyl region from 1700 to 2100 cm-1. The plots of absorbance vs. time were biexponential, indicative of a biphasic behavior, for reactions under flooding conditions where [L] ? [fac-(η2-C60)(η2-phen)Mo(CO) 3]. The plot of absorbance vs. time consisted of two consecutive segments: the first segment of the plot was a decrease of absorbance with time followed by a second segment where the absorbance increased with time. The first segment of the biphasic plot was ascribed to the solvent-assisted displacement of C60 from fac-(η2-C60)(η2- phen)Mo(CO)3 and the second segment to decomposition of the complex fac-(η1-L)(η2-phen)Mo(CO)3 produced in the first of the two consecutive reactions. The rate constant values corresponding to the first segment of the biphasic plot are independent of the chemical nature of L, the molar concentration of L, and the molar concentration of C60 but dependent on the chemical nature of the solvent.
Systematic Tuning of the Photosubstitution Mechanism of M(CO)4(1,10-phenanthroline) by Variation of the Metal, Entering Nucleophile, Excitation Wavelength, and Pressure
Fu, Wen-Fu,Van Eldik, Rudi
, p. 1044 - 1050 (2008/10/08)
The photosubstitution reactions of M(CO)4(phen) (M = Cr, Mo, W; phen = 1,10-phenanthroline) with PR3 (R = Me, Bun, Ph) to form M(CO)3(PR3(phen) were studied as a function of excitation wavelength, entering nucleophile concentration, and pressure. Ligand field photolysis in general results in a dissociative substitution mechanism. whereas charge-transfer photolysis can, depending on the nature of M and PR3, proceed according to an associative mechanism. The chemical and physical variables studied result in a systematic tuning of the photosubstitution mechanism. Nucleophile concentration, excitation wavelength, and pressure dependencies reveal unique mechanistic information. The results are discussed in reference to available literature data, and a complete mechanistic analysis is presented.
Emission and photochemistry of M(CO)4(diimine) (M = Cr, Mo, W) complexes in room-temperature solution
Manuta, David M.,Lees, Alistair J.
, p. 1354 - 1359 (2008/10/08)
Electronic absorption, emission, and photochemical data are reported for a series of M(CO)4L complexes, where M = Cr, Mo, or W and L = 2,2′-bipyridine, 1,10-phenanthroline, or a derivative diimine ligand. Low-energy ligand field (LF) and intense metal-to-ligand charge-transfer (MLCT) transitions are observed in the electronic absorption spectra. The energy positions of the MLCT transitions are extremely sensitive to the nature of ligand substituent and solvent medium. Each complex exhibits dual emission features at 298 K in the 500-850-nm region and two low-lying M → π*(L) transitions are implicated in the radiative decay process. Quantum efficiencies for photosubstitution (φ) have been determined following excitation into the low-lying excited states. The photoreaction efficiences depend substantially on the irradiation wavelength; e.g., for W(CO)4(bpy) in benzene LF excitation at λ = 395 nm yields φ = 1.2 × 10-2, whereas MLCT excitation at λ = 514 nm yields φ = 5.4 × 10-5. Photosubstitution data indicate that a LF state is largely responsible for the photochemistry in these M(CO)4L complexes. The photoefficiencies following MLCT excitation at 514 nm are only slightly temperature-dependent, indicating that either the MLCT state is intrinsically photoactive or another excited state lies close in energy and contributes to the photochemistry. The suggestion of photoreaction from the low-lying LF triplet state (1A → 3E) is discussed. An excited-state scheme relating the photochemical and emission data is presented.
