Research Interests – David L. Cooper

Current main research areas:

• Theoretical studies of small molecules and of molecular processes
• Momentum-space concepts

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Theoretical studies of small molecules and of molecular processes

Concepts taken from electronic structure theory have been of immense importance in the historical development of chemistry, and continue to play a key role in the modern understanding of molecular electronic structure and reactivity. Such concepts not only allow us to rationalize but also to make predictions for whole classes of new systems. Much of our research work involves the development and applications of modern valence bond approaches to electronic structure – especially the spin-coupled (SC) approach, which provides a simple highly visual model of the behaviour of correlated electrons in molecules, whilst also producing results of high accuracy. Current applications include:

• Studies of organic reaction pathways, typically for electrocyclic reactions. Most recently we have been examinings SN2 identity reactions, addition reactions of singlet dihalocarbenes, aromatic versus diradical character in Cope rearrangements, and hetero-Diels-Alder reactions.

  Main collaborator: Peter Karadakov at the University of York. See, especially, here for some nice pictures and explanations.

• Charge transfer processes in astrophysical environments (planetary nebulae, supernova remnants, interstellar medium, jupiter atmosphere, ...) and in laboratory plasmas (scrap-off and divertor regions in tokamak fusion devices). Most recently, we have been studying collisions of O³⁺ with molecular hydrogen and of O⁷⁺ with helium.

  Main collaborator: Phillip Stancil at the University of Georgia.

• Developing new 'auxiliary' tools for analyzing the wavefunctions, electron densities and density matrices from high-level calculations (using SC calculations as a testing ground). Most recently we have been using "generalized population analysis" to re-examine models that invoke three-centre bonding to describe electron-deficient and electron-rich molecules.

  Main collaborator: Robert Ponec in Prague.

We use various computational strategies, including the CASVB algorithms that have been released for general use via MOLPRO and also via MOLCAS. The most recent version is included in MOLPRO2009.1. CASVB can be used either to perform fully-variational optimization of fairly general types of (multiconfigurational) modern VB wavefunctions or to generate representations of CASSCF wavefunctions in modern VB form, using overlap-based (relatively inexpensive) or energy-based criteria.

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Momentum-space concepts

Most chemists feel much more 'comfortable' when visualizing molecular electronic structure in terms of position-space (r–space) quantities rather than via the complementary momentum-space (p–space) representation, but the latter offers a number of useful features. Current applications include:

• p–space quantum molecular similarity studies. Quantum molecular similarity attempts to answer quantitatively the general question: How similar are two molecules?. In our approach, molecular similarity and dissimilarity indices are obtained from numerical comparisons of p–space electron densities. The p–space approach is particularly suited to problems for which the molecular activity depends less on the details of the bonding topology than on features of the long-range slowly-varying valence electron density. For example: anti-HIV activity of various phospholipids in C8166 T–lymphoblastoid cells.

  Main collaborator: Neil L. Allan at the University of Bristol.

• Development of p–space molecular descriptors for QSAR and QSPR. Having obtained useful correlations for a range of property and activity data, such as gas-chromatography retention times, gas-hexadecane partition coefficients and tadpole narcosis concentrations, we are currently modelling the partitioning of organic solutes across the blood-brain barrier. Preliminary results are encouraging.

  Main collaborator: Jabir H. Al-Fahemi (PhD student) at the University of Liverpool.

See also: Publications
Other collaborators