Photochemical synthesis of magnesium dihydride and methyl magnesium hydride in cryogenic matrixes

McCaffrey, John G.; Parnis, J. Mark; Ozin, Geoffrey A.; Breckenridge, W. H.

doi:10.1021/j100269a012

Cited by 65 publications

(53 citation statements)

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“…This ISC competes very efficiently with chemical quenching of singlet excited zinc which, as presented in the following paper in this issue, results in the insertion of a zinc atom into a C-H bond of ethane to form ethylzinc hydride. Although a definite mechanism for the ISC enhancement in the presence of the hydrocarbons has not been established, it is proposed, as observed in earlier Mg/CH 4 work, 28 that the enhanced production of triplet emission is a result of the initially attractive inserted reaction coordinate.…”

Section: Discussionmentioning

confidence: 93%

Spectroscopy and Photodissociation of Dimethylzinc in Solid Argon. 1. Vacuum UV Luminescence Detection/Synchrotron Radiation Photolysis

1997

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Absorption spectra of thin-film DMZ/Ar samples, prepared by condensing gaseous mixtures of dimethylzinc (DMZ) with argon at 12 K, were recorded in the region of the first dissociative absorptions of DMZ centered in the gas phase at 200 nm. Large blue shifts are observed in the matrix spectra which can be related to the Rydberg-like characteristics of these excited states of DMZ. The photochemistry of DMZ in an argon matrix was investigated either by subjecting samples to undispersed synchrotron irradiation using a quartz filter to select a wavelength range above 155 nm or to wavelength-specific irradiation. Steady-state and time-resolved luminescence spectroscopy of the dissociation products isolated in solid argon indicate the existence of atomic zinc strongly perturbed by a methyl radical in freshly photolyzed samples, which yields truly isolated atomic zinc upon annealing to 33 K. Dissociation threshold measurements indicate a barrier of 25 kcal/mol for direct cage escape of atomic zinc in the Ar lattice. The increased intensity of Zn( 3 P 1 )/Ar emission observed in photolyzed DMZ/Ar samples relative to pure Zn/Ar samples is explained in terms of the enhanced ISC of atomic zinc in the presence of hydrocarbon species in the former samples. This has been shown by codeposition of atomic zinc with Ar doped with CH 4 and C 2 H 6 .

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Section: Discussionmentioning

confidence: 93%

Spectroscopy and Photodissociation of Dimethylzinc in Solid Argon. 1. Vacuum UV Luminescence Detection/Synchrotron Radiation Photolysis

1997

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“…[1][2][3][4][5][6][7][8][9][10] The ground state reaction Mg-( 1 S 0 ) + H 2 (g) f MgH 2 is endoergic and is inhibited by a large barrier. [10][11][12] It is generally accepted that MgH 2 is an intermediate in the gas-phase reactions Mg( 1 S 0 or 1 P 1 ) + H 2 f MgH + H. [1][2][3][4][5][6][7][8][9][10] However, despite its detection by infrared spectroscopy in low-temperature rare-gas matrixes, 13,14 stable gaseous MgH 2 was not observed until the work of Shayesteh et al in 2003. 15 Their high-resolution Fourier transform infrared emission spectroscopy studies yielded band origins and rotational constants for four vibrational bands of MgH 2 and one of MgD 2 .…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic Properties of MgH₂, MgD₂, and MgHD Calculated from a New ab Initio Potential Energy Surface

Roy

2007

J. Phys. Chem. A

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A three-dimensional potential energy surface for the ground electronic state of MgH 2 has been constructed from 9030 symmetry-unique ab initio points calculated using the icMRCI+Q method with aug-cc-pVnZ basis sets for n ) 3, 4, and 5, with core-electron correlation calculated at the MR-ACPF level of theory using cc-pCVnZ basis sets, with both calculations being extrapolated to the complete basis set limit. Calculated spectroscopic constants of MgH 2 and MgD 2 are in excellent agreement with recent experimental results: for four bands of MgH 2 and one band of MgD 2 the root-mean-square (rms) band origin discrepancies were only 0.44 and 0.06 cm -1 , respectively, and the rms relative discrepancies in the inertial rotational constants (B [V] ) were only 0.0196% and 0.0058%, respectively. Spectroscopic constants for MgHD were predicted using the same potential surface.

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“…As for the minor reaction pathway, the H atom should depart from a linear HMgH intermediate, of which the Mg atom lies in the center. The linear structure in the ground state has been identified to be stable at 12 K. 11 Thus the excess energy carried in the intermediate is presumed to have dissipated before decomposition, and thereby the resulting MgH may stay in the quantum states of low rotation and low vibration. 4 It should be noted that the impulsive model [12][13][14] accounts for the breaking apart between the single atom and the remaining diatomic molecule in a three-atom system depending upon the initial bond angle.…”

Section: Introductionmentioning

confidence: 99%

Ab initio calculation for potential energy surfaces relevant to the microscopic reaction pathways for Mg(3s3p1P1)+H2→MgH(2Σ+)+H

Liu

Lin

1998

The Journal of Chemical Physics

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Two ab initio methods have been employed to calculate the dynamical potential energy surfaces (PES’s) for the excited (B21 or A'1) and the ground (A11 or A'1) states in the Mg(3s3p1P1)–H2 reaction. The obtained PES’s information reveals that the production of MgH in the Σ+2 state, as Mg(1P1) approaches H2 in a bent configuration, involves a nonadiabatic transition. The MgH2 intermediate around the surface crossing then elicits two distinct reaction pathways. In the first one, the bent intermediate, affected by a strong anisotropy of the interaction potential, decomposes via a linear HMgH geometry. The resulting MgH is anticipated to populate in the quantum states of rotational and vibrational excitation. In contrast, the second pathway produces MgH in the low rotational and vibrational states, as a result of the intermediate decomposition along the stretching coordinate of the Mg–H elongation. These two tracks may account for the previous experimental findings for the MgH distribution, which the impulsive model has failed to comprehend. By far, different interpretations have been proposed especially for the low-N MgH product. The supply of a detailed PES’s information in this work helps to clarify the ambiguity. It is also conducive to an interpretation of the isotope and temperature effects on the product rotational distribution.

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Photochemical synthesis of magnesium dihydride and methyl magnesium hydride in cryogenic matrixes

Cited by 65 publications

References 1 publication

Spectroscopy and Photodissociation of Dimethylzinc in Solid Argon. 1. Vacuum UV Luminescence Detection/Synchrotron Radiation Photolysis

Spectroscopy and Photodissociation of Dimethylzinc in Solid Argon. 1. Vacuum UV Luminescence Detection/Synchrotron Radiation Photolysis

Spectroscopic Properties of MgH₂, MgD₂, and MgHD Calculated from a New ab Initio Potential Energy Surface

Ab initio calculation for potential energy surfaces relevant to the microscopic reaction pathways for Mg(3s3p1P1)+H2→MgH(2Σ+)+H

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Photochemical synthesis of magnesium dihydride and methyl magnesium hydride in cryogenic matrixes

Cited by 65 publications

References 1 publication

Spectroscopy and Photodissociation of Dimethylzinc in Solid Argon. 1. Vacuum UV Luminescence Detection/Synchrotron Radiation Photolysis

Spectroscopy and Photodissociation of Dimethylzinc in Solid Argon. 1. Vacuum UV Luminescence Detection/Synchrotron Radiation Photolysis

Spectroscopic Properties of MgH2, MgD2, and MgHD Calculated from a New ab Initio Potential Energy Surface

Ab initio calculation for potential energy surfaces relevant to the microscopic reaction pathways for Mg(3s3p1P1)+H2→MgH(2Σ+)+H

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Spectroscopic Properties of MgH₂, MgD₂, and MgHD Calculated from a New ab Initio Potential Energy Surface