- Matrix effects and their role in the low-temperature photochemistry of (η-Aniline)Cr(CO)3
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The low-temperature chemistry and photochemistry of (η6- Aniline)Cr(CO)3 was investigated by matrix isolation techniques in frozen CH4 or N2. The spectroscopic properties of the matrix changed both during the de
- Alamiry, Mohammed H.,Long, Conor,Fidgeon, Padraig P.,Pryce, Mary T.
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- Adduct-Mediated Photochemistry. Evidence for Excited-State Reordering in (Acetophenone)tricarbonylchromium(0) upon Adduct Formation with Tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium(III)
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The electronic spectra of several (arene)tricarbonylchromium(0) complexes (arene = aniline, anisole, benzaldehyde, benzene, acetophenone, acenaphthene) and the photochemical reactivity of the latter three species have beeen investigated in isooctane solution in the absence and presence of the title europium(III) β-diketonate complex, Eu(fod)3.These complexes possess a band whose positional dependence on arene substituent leads to its assignment as predominantly Cr->arene charge transfer (MLCT).Addition of Eu(fod)3 produced spectroscopic changes only for the acetophenone and benzaldehyde complexes, red-shifting the λmax values of their MLCT bands by over 1000 cm-1 and shifting their IR terminal carbonyl stretching bands to higher energy by ca. 10 cm-1.These spectral changes are ascribed to adduct formation wherein the arene carbonyl oxygen atom, serving as a site of Lewis basicity, coordinates to the Lewis acid, Eu(fod)3.Spectrophotometric titrations support the presence of predominantly 1:1 adducts whose formation constants are ca. 103 M-1.Visible and near-UV photolysis of the benzene, acetophenone, and acenaphthene complexes in 1-pentene/isooctane solution results in the disappearance of the complexes, presumably through photosubstitution of CO by 1-pentene, with quantum efficiencies, φd, of ca. 0.7, 0.2, and 0.001, respectively.Addition of Eu(fod)3 affected φd for only the acetophenone complex: spectroscopic evidence indicates that the adduct undergoes the same photoreaction as the free complex but far less efficiently - φd is ca. 0.02.The decline in φd for the complexes examined roughly parallels the red-shift in their MLCT bands and is consistent with a model developed for other low-spin d6 systems: the MLCT excited state is believed to be inert toward substitution; as it is tuned to below a ligand field excited state whose population leads to substitution, φd diminishes.The adduct photoreactivity is readly subsumed in this excited-state reordering model.Implications of adduct-mediated perturbation of excited-state properties are discussed.
- Schreiner, Rodney,Ellis, Arthur B.
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- A laser flash photolysis, matrix isolation, and DFT investigation of (η6-C6H5Y)Cr(CO)3 (Y = NH2, OCH3, H, CHO, or CO2CH3)
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The quantum yield for arene displacement from (η6-C6H5Y)Cr(CO)3 was measured in 1,1,2-trifluorotrichloroethane (Y = NH2, OCH3, H, CHO, or CO2CH3). Values of 0.24, 0.27, 0.15, 0.17, and 0.32 were obtained respectively (λexc. = 355 nm). These values are significantly higher than those measured for photoinduced arene loss in hydrocarbon solvents using the same excitation wavelength. Laser flash photolysis of (η6-C6H5Y)Cr(CO)3 in 1,1,2-trifluorotrichloroethane (λexc. = 355 nm) resulted in the rapid formation (6. Matrix isolation experiments on (η6-C6H5Y)Cr(CO)3 (Y = H or CHO) at 12 K in CH4 or CO-doped CH4 matrixes using monochromatic irradiation confirmed the presence of two discrete excited states, one leading to CO-loss and the other to arene-loss. The results correlate with the calculated electron drift in the excited state derived from density functional theory and time dependent density functional theory calculations.
- Alamiry, Mohammed A.H.,Brennan, Peter,Long, Conor,Pryce, Mary T.
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- Protodeboronation of arylboronic acids and triarylboroxines in Bu2O/THF
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The arylboron compounds Ph3B3N3Me3, Ar3B3O3, or ArB(OH)2 (Ar = Ph, p-BrC6H4, p-MeC6H4, m-NH2C6H4) react with in refluxing Bu2O/THF (9:1) to afford the η6-arene)tricarbonylchromium(0) complexes of the protodeboronated substrates in yie
- Beckett, Michael A.,Gilmore, Robert J.,Idrees, Khalid
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- THE CONFORMATIONS OF SOME MONO-SUBSTITUTED DERIVATIVES OF (η6-BENZENE)TRICARBONYLCHROMIUM(0) FROM DIPOLE MOMENT AND ELECTRIC BIREFRINGENCE STUDIES
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Experimental dipole moments and molar Kerr constants (at 589 nm) are reported for (η6-C6H5Y)Cr(CO)3, where Y=CHO, COCH3, COOCH3, OCH3, NH2, N(CH3)2 and NH(CH3), examined as solutes in dioxan at 298 K.Analysis of these data in conjunction with i
- Aroney, M. J.,Cooper, M. K.,Englert, P. A.,Pierens, R. K.
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