Computational Quantum Chemical Studies of Electron Transfer, Diels-Alder Stereoselectivity & cytochrome c mechanisms; Computational Quantum Chemical Studies of Electron Transfer and Diels-Alder Facial Stereoselectivity

This proposal will employ an arsenal of modern computational techniques to study two important areas of chemical research, namely electron transfer and pi-facial stereoselectivity. We will investigate the energetics and geometrical changes that accompany electron transfer reactions and to what extent molecular vibrations influence the dynamics of electron transfer. The results will have widespread applicability and will be relevant to biological electron transfer processes (such as photosynthesis). pi-Facial stereoselectivity plays an important role in controlling the stereochemistry of products of reactions and is relevant to the design and synthesis of new drugs. By computing transition structures for cycloaddition reactions, we will develop simple intuitive models for predicting pi-facial selectivity. Our computations are extremely numerically intensive and can only be carried out using facilities such as APAC NF. ; This proposal will employ an arsenal of modern computational techniques to study two important areas of chemical research, namely electron transfer and pi-facial stereoselectivity. We will investigate the energetics and geometrical changes that accompany electron transfer reactions and to what extent molecular vibrations influence the dynamics of electron transfer. The results will have widespread applicability and will be relevant to biological electron transfer processes (such as photosynthesis). pi-Facial stereoselectivity plays an important role in controlling the stereochemistry of products of reactions and is relevant to the design and synthesis of new drugs. By computing transition structures for cycloaddition reactions, we will develop simple intuitive models for predicting pi-facial selectivity. Our computations are extremely numerically intensive and can only be carried out using facilities such as APAC NF.

Principal Investigator

Michael Paddon-Row
Dept of Chemistry
University of NSW

Project

d38, e12

Co-Investigators

Damian Moran
School of Chemistry
University of Sydney

RFCD Codes

250303

Significant Achievements, Anticipated Outcomes and Future Work

(1) A massive computational study of the intramolecular Diels-Alder (IMDA) reactions has been completed. Over 230 transition structures have been calculated at the B3LYP/6-31G(d) level and this constitutes the largest computational study ever carried out on this synthetically important reaction. Of particular significance, the results of this computational study has enabled us to develop a simple model which not only explains a large body of extant experimental data, but which also has predictive power.

(2) A new type of Diels-Alder reaction, namely the double Diels-Alder reaction, has been studied, both computationally (Paddon-Row) and experimentally (Sherburn, ANU), with the aim of devising strategies for controlling both site selectivity and facial selectivity. This project is at the early stages but already, it has led to predictions of stereoselectivity that have been subsequently confirmed experimentally by the Sherburn group at the ANU. (3) We have made significant progress in developing models for explaining and predicting remote π-facial stereoselectivity in intramolecular Diels-Alder reactions. The computational work has led to the proposal of a simple model of predictive power. (4) The calculation of properties relevant to electron transfer (ET) is an ongoing and fruitful project. A joint time-dependent density functional (TD-DFT) computational and experimental study has opened the way for using certain chromophores in molecular electronic devices. TD-DFT and spin-orbit coupling calculations have also been carried out to explain the very long lifetimes of triplet charge-separated states of a rigid donor-bridge-acceptor molecule. Calculations of the magnitude of electronic coupling in very large U-shaped donor-acceptor system have been carried out and correlated with experimental observations. The agreement between theory and experiment is good. New and important insights into the role of solvent effects on electron tunnelling have been obtained from this study.

 

Computational Techniques Used

The projects involve quantum chemical calculations of molecular electronic structure and reactivity., specifically, the calculation of the geometries, molecular orbitals, energies and vibrational frequencies of important species lying on potential energy surfaces for Diels-Alder reactions. These highly cpu-intensive calculations are carried out using the GAUSSIAN 03 quantum chemical package.

 

Publications, Awards and External Funding

External Funding and Awards

(1) Understanding Electron Transfer through Surface Bound Rigid Molecular Constructs: DP0556397 , 2005-2009 ($780,000).

(2) New horizons in Diels- Alder chemistry. DP0344445, 2003–2005 ($420,000).

(3) Experimental-Computational Investigations into Diels–Alder Sequences: DP0665161, 2006-20-8 ($270,000).ith None.

Publications

1 On the Origin of Cis/trans Stereoselectivity in Intramolecular Diels–Alder Reactions of Substituted Pentadienyl Acrylates: A Comprehensive Density Functional Study. Paddon-Row, M. N.; Moran, D.; Payne, A. D.; Jones, G. A.; Sherburn, M. S. J. Org. Chem.. 2005, 70, 5561-5570.
2 On the Diels–Alder reactions of pentadienyl maleates and citraconates. Cayzer, T. N.; Lilly, M. J.; Paddon-Row, M. N.; Williamson, R. M.; Sherburn, M. S. Org. Biol. Chem. 2005, 3, 1302-1307.
3 Double Diels–Alder Reactions of Linear Conjugated Tetraenes. Turner, C. L.; Paddon-Row, M. N.; Willis, A. C.; Sherburn, M. S. J. Org. Chem . 2005, 70, 1154-1163.
4 Intramolecular Diels–Alder Reactions of Ester Linked 1,3,8-Nonatrienes. Cayzer, T. N.; Paddon-Row, M. N.; Moran, D.; Payne, A. D.; Sherburn, M. S.; Turner, P. J. Org. Chem. 2005, 70, 5561-5570.
5 Allylic Stereocontrol of the Intramolecular Diels–Alder Reaction. Lilly,, M. J.; Miller, N. A.; Edwards, A. J.; Willis,, A. C.; Turner, P.; Paddon-Row, M. N.; Sherburn, M. S. Chem. Eur. J. 2005, 11, 2525 - 2536.
6 Achieving Direct Electrical Connection to Glucose Oxidase using Aligned Single Walled Carbon Nanotube Arrays. Liu, J; Paddon-Row, M. N.; Gooding, J. J. Electroanalysis, 2005, 17, 38 - 46.
7 Unusually Rapid Heterogeneous Electron Transfer through a Saturated Bridge 18 Bonds in Length. Liu, J.;, Gooding, J. J.; Paddon-Row, M. N. Chem. Comm. 2005, 631- 633.
8 Length Dependence of Charge Transport in Nanoscopic Molecular Junctions Incorporating a Series of Rigid Thiol- Terminated Norbornylogs. Beebe, J. M.; Engelkes, V. B.; Liu, J.; Gooding, J. J.; Eggers, P. K.; Jun, Y.; Zhu, X.; Paddon-Row, M. N.; Frisbie, C. D. J. Phys. Chem. B 2005, 109, 5207 - 5215.
9 Surface Reconstitution of Glucose Oxidase onto a Norbornylogous Bridge Self-Assembled Monolayer. Liu, J.; Paddon-Row, M. N.; Gooding, J. J. Liu, J.; Paddon-Row, M. N.; Gooding, J. J. Chem. Phys. 2005 in presss.
10 Pendant Unit Effect on Electron Tunneling in U-Shaped Molecules. Liu, M.; Chakrabarti, S.; Waldeck, D. H.; Oliver, A. M.; Paddon-Row, M. N. Chem. Phys. in press.
11 Solvent Friction Effect on Intramolecular Electron Transfer. Liu, M.; Ito, N.; Maroncelli, M.; Waldec, D. H.; Oliver, A. M.; Paddon-Row, M. N. J. Am. Chem. Soc. 2005, 127, 17867-17876.
12 Conformational and Photophysical Studies on Porphyrin-Containing Donor-Bridge-Acceptor Compounds. Charge Shift in Micellar Nanoreactors. Martinez- Junza, V.; Rizzi, A.; Jolliffe, K. A.; Head, N. J.; Paddon-Row, M. N.; Braslavsky1, S. E. Phys. Chem. Chem. Phys. 2005, 7, 4114-4125.