W. Lester S. Andrews

Professor of Chemistry
B.S., Mississippi State University, 1963
Ph.D., University of California, Berkeley, 1966
Alfred P. Sloan Fellow, 1973-75
Coblentz Award, 1978
Science Research Council and Fulbright Research Fellowships,
Southampton, England, 1982-1983
Fellow, American Physical Society, 1993
Fulbright Senior Research Scholar, Oxford, England, 1994
Lippincott Award in Vibrational Spectroscopy, 2001
Docteur Honoris Causa, Université Paul Sabatier,
Toulouse, France, 2004
Pimentel Award in Matrix Iisolation Spectroscopy, 2007
University of Virginia Distinguished Scientist Award, 2008

Email: lsa at virginia.edu
Phone: (434) 924-6844

Spectroscopy and Photochemistry of Matrix Isolated Species

Normally inaccessible chemical species including free radicals, hydrogen-bonded complexes, unusual inorganic species, transition metal containing intermediates, metal hydrides, and molecular ions are under investigation using infrared matrix-isolation spectroscopy. These transient molecules are prepared by reactions of suitable atoms and/or molecules prediluted in argon by precursor photolysis, or by microwave discharge of the reagents during condensation at 7 K in a vacuum chamber. Solid argon isolates the reaction or photolysis products and preserves them for spectroscopic study at 7 K. Neon is used to isolate new reaction products on a 4 K substrate. Pure H2 and D2 are also be employed as a reagent and matrix for the investigation of novel metal hydrides. A new source of atoms that require high temperatures to generate, namely pulsed laser ablation from solid samples, has been developed for use in matrix-infrared spectroscopy in this laboratory. This method exploits two advantages: first, the ablated atoms contain excess energy which can activate reactions with small molecules, and second, collisions with matrix atoms during the condensation process relax energetic product molecules and allow them to be trapped in the solid matrix for spectroscopic study. In addition, laser-ablation also produces cations and electrons for reactions to make charged products.

The experimental apparatus used in hydrogen matrix investigations is sketched in the figure. Infrared spectra are recorded after co-depositing reagent and host matrix gases on the cold sample window and rotating by 90 degrees to face the infrared light beam.

These infrared spectroscopic matrix-isolation studies characterize the bonding and structure of chemical intermediates, interesting new inorganic molecules and complexes and molecular ions and often provide a useful complement and guide to high resolution gas phase work. Stable isotopes are used to determine assignments of the observed infrared absorptions to fundamental vibrational frequencies. Comparison of vibrational energies within related chemical species provides conclusions about the bonding of these newly observed chemical intermediates. Selection rules based upon molecular symmetry and vibrational analysis help determine the molecular geometry. Ab initio electronic structure calculations are done to find molecular structures compatible with the infrared spectrum. Agreement between calculated and observed isotopic vibrational spectra provides further evidence for the discovery of new transient molecular species.

Recent Representative Publications

Infrared Spectra of the WH₄(H₂)₄Complex in Solid Hydrogen. X. Wang, L. Andrews, I. Infante, and L. Gagliardi, J. Am. Chem. Soc. 2008, 130, 1972-1978.

Formation of Unprecedented Actinide≡Carbon Triple Bonds in Uranium Methylidyne Molecules. J. T. Lyon, L. Andrews, H.-S. Hu, and J. Li, Proc. Nat'l. Acad. Sci. 2007, 104, 18919-18924.

Mercury is a Transition Metal: The First Experimental Evidence for HgF₄. X. Wang, L. Andrews, S. Riedel, and M. Kaupp, Angew. Chem. 2007, 46, 8371-8375.

Methylidyne Molecules XC≡MX₃ (M = Cr, Mo, W; X = H, F, Cl) Diagnostic C-H and C-X Stretching Absorptions and Methylidene CH₂=MX₂ Analogs. J. T. Lyon, H.-G. Cho, and L. Andrews, Organometallics, 2007, 26, 6373-6387.

Infrared and DFT Investigations of the XC≡ReX₃ and HC≡ReX₃ Complexes: Jahn-Teller Distortion and the Methylidyn C-H(D) Stretching modes. J. T. Lyon, H.-G. Cho, L. Andrews, Inorg. Chem. 2007, 46, 8728-8738.

A Combined Experimental and Theoretical Study of Some Uranium Polyhydrides Shows that Sixteen Hydrogen Atoms Can Bind a Uranium Atom. J. Raab, R. H. Lindh, X. Wang, L. Andrews, and L. Gagliardi, J. Phys. Chem. A, 2007, 111: 6383-6387.

On the Agostic Interaction in the Methylidene Metal Dihydride Complexes H₂MCH₂ (M=Y, Zr, Nb, Mo, Ru, Th, or U). B. O. Roos, R. H. Lindh, H.-G. Cho, and L. Andrews, Phys. Chem. A, 2007, 111: 6420-6474.

Infrared Spectra and Theoretical Calculations of Lithium Hydride Clusters in Solid Hydrogen, Neon and Argon. X. Wang and L. Andrews, J. Phys. Chem. A, 2007, 111: 6008-6019.

Infrared Spectrum and Bonding in Uranium Methylidene Dihydride, CH₂=UH₂. J. T. Lyon, L. Andrews, P.- Å. Malmqvist, B. O. Roos, T. Yang and B. E. Bursten, Inorg. Chem, 2007, 46: 4917-4925.

Infrared Spectra of the CH₃−MX, CH₂=MHX, and CH≡MH₂X^- Complexes Formed by Reaction of Methyl Halides with Laser-Ablated Group 5 Metal Atoms. H.-G. Cho and L. Andrews, J. Phys. Chem. A, 2006 , 110: 10063-10077.

Contrasting Products in the Reactions of Cr, Mo, and W Atoms with H₂O₂: Argon Matrix Infrared Spectra and Theoretical Calculations. X. Wang and L. Andrews, J. Phys. Chem. A, 2006, 110: 10409-10418.

Matrix Preparation and Spectroscopic and Theoretical Investigations of Simple Methylidene and Methylidyne Complexes of Group 4, 5, and 6 Transition Metals. L. Andrews and H.-G. Cho, Organometallics, 2006, 25: 4040-4053.

Electron Deficient Carbon-Titanium Triple Bonds: Formation of Triplet XC÷TiX₃ Methylidyne Complexes. J. T. Lyon and L. Andrews, Inorg. Chem. 2006, 45: 9858-9863.

Formation and Characterization of the Uranium Methylidene Complexes CH₂=UHX(X = F, Cl, and Br). J. T. Lyon and L. Andrews, Inorg. Chem. 2006, 45: 1847-1852.

Formation and Characterization of Thorium Methylidene CH₂=ThHX Complexes. J. T. Lyon and L. Andrews, Inorg. Chem. 2005, 44: 8610-8616.

Infrared Spectrum and Structure of CH₂=ThH₂. L. Andrews and H.-G. Cho, J. Phys. Chem. A, 2005, 109: 6796-6798.

Infrared Spectrum and Structure of the Gold Dihydroxide Molecule. X. Wang and L. Andrews, Chem. Comm. 2005, 4001-4003.

Reactions of Methane with Hafnium Atoms: CH₂=HfH₂, Agostic Bonding and (CH₃)₂HfH₂. H.-G. Cho, X. Wang, and L. Andrews, Organometallics 2005, 24: 2854-2861.

Infrared Spectra of CH₃-MoH, CH₂=MoH₂, and CH≡MoH₃ Formed by Activation of CH₄ by Mo Atoms. H.-G. Cho and L. Andrews, J. Am. Chem. Soc. 2005, 127: 8226-8231.

Zinc and Cadmium Dihydroxide Molecules: Matrix Infrared Spectra and Theoretical Calculations. X. Wang and L. Andrews, J. Phys. Chem. A 2005, 109: 3849-3857.

Infrared Spectra and Electronic Structure Calculations for the Group 2 Metal M(OH)₂ Dihydroxide Molecules. X. Wang and L. Andrews, J. Phys. Chem. A 2005, 109: 2782-2792.

Reactions of Laser-Ablated Uranium Atoms with H₂O in Excess Argon: A Matrix Infrared and Relativistic DFT Investigation of Uranium Oxyhydrides. B. Liang, R. D. Hunt, G. P. Kushto, L. Andrews, J. Li, and B.E. Bursten, Inorg. Chem. 2005, 44: 2159-2168.

Formation of CH₃TiX, CH₂=TiHX, and (CH₃)₂TiX₂ by Reaction of Methyl Chloride and Bromide with Laser-Ablated Titanium Atoms: Photoreversible α-Hydrogen Migration. H.-G. Cho and L. Andrews, Inorg. Chem. 2005, 44: 979-988.

One-Dimensional BeH₂ Polymers: Infrared Spectra and Theoretical Calculations. X. Wang and L. Andrews, Inorg. Chem. 2005, 44: 610-614.

The C-H Activation of Methane by Laser-Ablated Zirconium Atoms: CH₂=ZrH₂, the Simplest Carbene Hydride Complex, Agostic Bonding, and (CH₃)₂ZrH₂. H.-G. Cho, X. Wang, and L. Andrews, J. Am. Chem. Soc. 2005, 127: 465-473.

Matrix Infrared Spectra and Density Functional Calculations of Transition Metal Hydrides and Dihydrogen Complexes. L. Andrews. Chem. Soc. Rev. 2004, 33: 123-132.

Infrared Spectra and Structures of the Stable CuH₂^-, AgH₂^-, AuH₂^-, and AuH₄^- Anions and the AuH₂ Molecule. L. Andrews and X. Wang. J. Am. Chem. Soc. 2003. 125: 11751-11760.

Infrared Spectra of Aluminum Hydrides in Solid Hydrogen: Al₂H₄ and Al₂H₆. X. Wang, L. Andrews, S. Tam, M. E. DeRose, and M. E. Fajardo. J. Am. Chem. Soc. 2003. 125: 9218-9228.

Chromium Hydrides and Dihydrogen Complexes in Solid Neon, Argon, and Hydrogen: Matrix Infrared Spectra and Quantum Chemical Calculations. X. Wang and L. Andrews. J. Phys. Chem. A 2003. 107: 570-578.

The Infrared Spectrum of Al₂H₆ in Solid Hydrogen. L. Andrews and X. Wang. Science 2003. 299: 2049-2052.

Noble Gas-Actinide Complexes of the CUO Molecule with Multiple Ar, Kr, and Xe Atoms in Noble-Gas Matrices. L. Andrews, B. Liang, J. Li, and B. E. Bursten. J. Am. Chem. Soc. 2003. 125: 3126-3139.

Homoleptic Tetrahydrometalate Anions MH₄^- (M = Sc, Y, La). Matrix Infrared Spectra and DFT Calculations. X. Wang and L. Andrews. J. Am. Chem. Soc. 2002. 124: 7610-7613.

Neon Matrix Infrared Spectrum of WH₆: A Distorted Trigonal Prism Structure. X. Wang and L. Andrews. J. Am. Chem. Soc. 2002. 124: 5636-5637.

Noble Gas-Actinide Compounds: Complexation of the CUO Molecule by Ar, Kr, and Xe Atoms in Noble Gas Matrices. J. Li, B. E. Bursten, B. Liang, and L. Andrews. Science 2002. 295: 2242-2245.

Infrared Spectra and Density Functional Theory Calculations on Transition Metal Nitrosyls. Vibrational Frequencies of Unsaturated Transition Metal Nitrosyls. L. Andrews and A. Citra. Chem. Rev. 2002. 102: 885-911.

Infrared Spectrum of the Hyponitrite Dianion, N₂O₂^2-, Isolated and Insulated from Stabilizing Metal Cations in Solid Argon. L. Andrews and B. Liang. J. Am. Chem. Soc. 2001. 123: 1997-2002.

Infrared Spectra and Density Functional Calculations of Platinum Hydrides. L. Andrews, X. Wang, and L. Manceron. J. Chem. Phys. 2001. 114: 1559-1566.

Infrared Spectra of cis- and trans-Peroxynitrite Anion, OONO^-, in Solid Argon. B. Liang and L. Andrews. J. Am. Chem. Soc. 2001. 123: 9848-9854.

Infrared Spectrum of the H₃N-HCl Complex in Solid Neon. L. Andrews, X. Wang, and Z. Mielke. J. Am. Chem. Soc. 2001. 123: 1499-1500.

Spectroscopic and Theoretical Investigations of Binary Unsaturated Transition Metal Carbonyl Cations, Neutrals and Anions. M. F. Zhou, L. Andrews, and C. W. Bauschlicher, Jr. Chem. Rev. 2001. 101: 1931-1961.

Infrared Spectra of UO₂, UO₂⁺, and UO₂^- in Solid Neon. M. F. Zhou, L. Andrews, N. Ismail, and C. Marsden. J. Phys. Chem. A 2000. 104: 5495-5502.

Reactions of Laser-Ablated Ni, Pd, and Pt Atoms with Carbon Monoxide: Matrix Infrared Spectra and Density Functional Calculations on M(CO)_n (n = 1-4), M(CO)_n^- (n = 1-3), and M(CO)_n⁺ (n = 1-2), (M = Ni, Pd, Pt). B. Liang, M. F. Zhou, and L. Andrews. J. Phys. Chem. A 2000. 104: 3905-3914.

Infrared Spectra of the CO₂- and C₂O₄- Anions Isolated in Solid Argon. M. F. Zhou and L. Andrews. J. Chem. Phys.1999. 110: 2414-2422.

Reactions of Laser-Ablated Co, Rh, and Ir with CO: Infrared Spectra and Density Functional Calculations of the Metal Carbonyl Molecules, Cations and Anions in Solid Neon. M. F. Zhou and L. Andrews. J. Phys. Chem. A 1999. 103: 7773-7784.

Infrared Spectra and Density Functional Calculations of the CrO₂-, MoO₂- and WO₂- Molecular Anions in Solid Neon. M. F. Zhou and L. Andrews. J. Chem. Phys. 1999. 111: 4230-4238.

Reactions of Laser-Ablated Uranium Atoms with CO: Infrared Spectra of the CUO, CUO-, OUCCO, ( n ²-C₂)UO₂, and U(CO)_x (x=1-6) Molecules in Solid Neon. M. F. Zhou, L. Andrews, J. Li, and B. E. Bursten. J. Am. Chem. Soc. 1999. 121: 9712-9721.

Matrix Infrared Spectra and Density Functional Calculations of Co(CO)_x- (x = 1,2,3,4) Anions. M. F. Zhou and L. Andrews. J. Phys Chem. A 1998. 102: 10250-10257.

Reactions of Laser-Ablated V, Cr, and Mn Atoms with Nitrogen Atoms and Molecules. Infrared Spectra and Density Functional Calculations on Metal Nitrides and Dinitrogen Complexes. L. Andrews, W. D. Bare, and G. V. Chertihin, J. Phys. Chem. A 1997. 101: 8417-8427.

Reactions of Laser-Ablated Iron Atoms with Oxygen Molecules: Matrix Infrared Spectra and Density Functional Calculations of OFeO, FeOO, and Fe(O₂). L. Andrews, G. V. Chertihin, A. Ricca and C. W. Bauschlicher, Jr. J. Am. Chem. Soc. 1996. 118: 467-470.

Reactions of Laser Ablated Be Atoms with O₂: Infrared Spectra of Beryllium Oxides in Solid Argon. C. A. Thompson and L. Andrews. J. Chem. Phys. 1994. 100: 8689-8699.

Pulsed Laser Evaporated Boron Atom Reactions with Acetylene. Infrared Spectra and Quantum Chemical Structure and Frequency Calculations for Several Novel BC₂H₂ and HBC₂ Molecules. L. Andrews, P. Hassanzadeh, J. M. L. Martin, and P. R. Taylor. J. Phys. Chem. 1993. 97: 5839-5847.

Pulsed Laser Assisted Reactions of B and N Atoms in a Condensing Nitrogen Stream. P. Hassanzadeh and L. Andrews. J. Phys. Chem. 1992. 96: 9177-9182.

Reactions of Boron Atoms with Molecular Oxygen. T. R. Burkholder and L. Andrews. J. Chem. Phys. 1991. 9:, 8697-8709.