Ian Carmichael University of Glasgow, Scotland, B.Sc.Hons ('71) Ph.D. ('74) Director - Notre Dame Radiation Laboratory Tel. (574) 631-4502 e-mail: carmichael.1@nd.edu Theoretical Studies of Reactive Intermediates

Scientific Interests

Quantum chemistry of reactive intermediates — structure and properties of radicals, radical ions and excited states in solution and on surfaces

Magnetic interactions in molecular species — EPR splittings; NMR spin-coupling constants and chemical shifts; nuclear quadroplar couplings

Theory of radiation and photochemical transformations — photophysical processes; transient absorption spectroscopy

Recent Accomplishments | Top |

Water on alumina — The first molecular water on dry alumina (0001) is calculated by Density Functional Theory (DFT) methods to sit roughly parallel to the surface, O atop Al. Physisorption is predicted to proceed via competitive O–Al and H–O interactions terminating in a hexagonal, ice-like layer at a coverage of two waters per surface Al. However, dissociative adsorption to produce a hydroxylated surface appears energetically favorable.

Radiation damage in MX — Intensity loss from radiation damage during room-temperature X-ray characterization of lysozyme unexpectedly showed that the dose tolerated by a crystal is dependent on the dose rate according to a positive linear relationship (99% correlation coefficient); a 60% increase in dose rate gave a 4-fold increase in crystal lifetime over the range (6-10 Gy s⁻¹) studied.

Muonic radicals — Reliable estimates of hyperfine interaction tensors in a number of small muonium-bearing radicals were obtained from DFT. The importance of proper vibrational averaging over modes in which the muon is active was demonstrated.

Geminal organodimetallic complexes — Complexes [({Ph₂P(NSiMe₃)}₂C)₂M₄], where M₄=Na₄; Li₂Na₂; LiNa₃; Li₂K₂; Na₂K₂, and Na₃K, are prepared and characterized by single-crystal X-ray diffraction as forming a homologous series of dimeric structures in the solid-state. ¹H, ¹³C, ⁷Li, ³¹P, and ²⁹Si multinuclear NMR spectroscopic studies, cryoscopic measurements, and electrospray ionization-mass spectroscopic studies are consistent with the dimers being retained in solution. Dynamic solution behavior was discovered for Li₂Na₂ complex in which all five possible tetrametallic derivatives Li₄, Li₃Na, Li₂Na₂, LiNa₃ and Na₄ coexist. DFT calculations indicate that he smaller cations are more effective in localizing the double negative charge on the carbanion leading to differences in the distribution of the electron density within the ligand backbones. In turn, a complex interplay of hyperconjugation, electrostatics and metal-ligand interactions is found to control the resulting electronic structures.

NMR spin couplings in biomolecules — Internal electronegative substituents (IES) effects are calculated to phase shift ³J_COCC Karplus curves (~15°) suggesting that the two types of inter-residue C-O-C-C coupling pathways observed in many oligosaccharides cannot be treated using the same generalized ³J_COCC Karplus equation. DFT calculations of ³J_HCOH, ³J_CCOH, and ²J_COH values involving exchangeable hydroxyl protons support the use of a generalized Karplus equation to treat ³J_HCOH involving the non-anomeric OH groups. IES effects in ³J_H1,O1H again mandate a separate treatment of this coupling. ³J_CCOH values are shown to depend not only on the C-C-O-H torsion angle but also on the orientation of terminal substituents on the coupled carbon, necessitating three distinct Karplus equations for non-anomeric ³J_CCOH coupling. IES effects on ³J_C2,O1H also require a separate parameterization. ²J_COH values showed no systematic dependence on C–O torsions and are thus not structurally useful.

V.A. Ranea, I. Carmichael and W.F. Schneider
DFT characterization of coverage dependent molecular water absorption on α-Al₂O₃(0001)
Surf. Sci. 2008 602, 268-75 link

H. Zhao, I. Carmichael and A.S. Serianni
Oligosaccharide trans-glycoside ³J_COCC Karplus curves are not equivalent: Effects of internal electronegative substituents
J. Org. Chem. 2008 73, 3255-7 link

K.L. Hull, I. Carmichael, B.C. Noll and K.W. Henderson
Homo- and heterodimetallic geminal dianions derived from the bisphosphinimine {Ph₂P(Me₃Si)N}₂CH₂ and the alkali metals Li, Na and K
Chem. Eur. J. 2008 14, 3939-53 link

R.J. Southworth-Davis, M.A. Medina, I. Carmichael and E.F. Garman
Observation of decreased radiation damage at higher dose rates in room temperature protein crystallography
Structure 2007 15, 1531-41 link

H. Zhao, I. Carmichael and A.S. Serianni
Density functional calculations of ²J_COH, ³J_HCOH, and ³J_CCOH NMR spin-spin coupling constants in saccharides
J. Org. Chem. 2007 72, 7071-82 link

S.L. Thomas and I. Carmichael
Hyperfine interactions in muonium-containing radicals
Physica B 2006 374-5, 290-4 link

Supported by the Division of
Chemical Sciences
Office of
Basic Energy Sciences
at the
U.S. Department of Energy

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Last Modified: 05/06/2008