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Project Descriptions:

Potential Energy Surfaces

Solvated Species

CH5+

Porous Crystalline Species

Temperature Effects on Structure

Photodissociation Dynamics

Computational Drug Design

Osteoporosis

Hydrogen Bonding

 

 

Hydrogen Bonding

(with Prof Janet Del Bene, Ohio)

Our research investigates environmental effects on the structures and spectroscopic properties of hydrogen-bonded complexes.  In particular, we are interested in NMR spin-spin coupling constants across hydrogen bonds. Our quest has been to better understand these properties, to elucidate relationships among structures, IR and NMR properties, and to provide a firm theoretical basis for the interpretation of relevant experimental data.

We have completed studies of environmental effects on the structures and IR and NMR properties of the hydrogen-bonded ClH:pyridine and ClH: and BrH:trimethylammonia complexes.  These studies support the use of NMR spin-spin coupling constants as a fingerprint of hydrogen-bond structure.  We have initiated systematic studies of spin-spin coupling constants across hydrogen bonds in an effort to assess the factors that are important in determining the magnitude of such coupling constants, and the relationships between coupling constant and structure.  For example, it is well known that vibrational averaging can influence spin-spin coupling constants. We have generated potential energy surfaces and coupling constant surfaces in order to estimate the effects of zero-point motion and thermal vibrational averaging on coupling constants in the CNH:NCH hydrogen bonded complex and the FHF ion.  To our knowledge, this is the first time such studies have ever been performed.  The FHF ion has, for many years, presented a major theoretical challenge, and these studies are the first to accurately predict FF spin-spin coupling constants in this system.

We have seen further evidence of correlation between NMR parameters and hydrogen bond type in more detailed investigations of coupling across N-H-N hydrogen bonds.  These investigations have also allowed us to determine the conditions under which a ‘proton-shared’ hydrogen bond can form.  Specifically we have shown that such a hydrogen bond is unlikely to form in neutral species.

Our contributions to the field include:

1. A rigorous and robust method for computing vibrational frequencies in ‘floppy’ hydrogen-bonded complexes.

2. Use of electric fields to model the environment of hydrogen bonded complexes and to show the influence of the environment on the structures and spectra of such complexes.

3. Evaluation of NMR XY spin-spin coupling constants across X-H-Y hydrogen bonds and identification of the factors that determine the magnitude of these coupling constants.

4. Elucidation of the relationships among hydrogen bond types, structures, the IR proton-stretching frequency and the NMR properties of chemical shift and XY spin-spin coupling constant across the hydrogen bond. We are the first to make the connection between IR and NMR properties and to show how the XY spin-spin coupling constant may be used to determine hydrogen bond type and intermolecular distance.

5. Evaluation of the effects of zero-point motion and thermal vibrational averaging on spin-spin coupling constants and the isotropic chemical shielding constant for the hydrogen-bonded proton.

Although this work is still in its infancy it has already provided insight into the interpretation of relevant experimental data.  The findings of this research have already led to a better understanding of the structures and vibrational spectroscopy of the hydrogen bond, and how these properties may be influenced by the environment.  Given the ubiquitousness of the hydrogen bond, this work has far-reaching consequences in many areas.  The demonstration that the XY spin-spin coupling constant across an X-H-Y hydrogen bond is dominated by the distance dependent Fermi contact term will have an impact on the interpretation of NMR data obtained in a wide range of disciplines.  This work will provide sound theoretical foundation for the interpretation of NMR and IR data, and structure determination from these data.

 

Publications

M. J. T. Jordan and K. C. Thompson “The Response of a Molecule to an External Electric Field: Predicting Structural and Spectroscopic Change”, Chem. Phys. Lett. 370, 14-20 (2003). pdf (961 kB)

J. E. Del Bene and M. J. T. Jordan “ To What Extent Do External Fields and Vibrational and Isotopic Effects Influence NMR Coupling Constants?  Two-Bond Cl-N Spin-Spin Coupling Constants (2hJCl-N) in Model ClH:NH3 Complexes” J. Phys. Chem. A 106, 5385-5392 (2002).

J. S.-S. Toh, M. J. T. Jordan, B. Husowitz and J. E. Del Bene “Can proton-shared or ion-pair hydrogen bonds be produced in uncharged complexes? A systematic ab initio study of the structures and selected NMR and IR properties of complexes with N-H-N hydrogen bonds” J. Phys. Chem. A. 105, 10906-10914 (2001).

M. J. T. Jordan, J. S.-S. Toh and J. E. Del Bene, “Vibrational averaging of NMR properties for an N-H-N hydrogen bond” Chem Phys Lett. 346 288-192 (2001).

J. E. Del Bene, M. J. T. Jordan, S. A. Perera and R. J. Bartlett, “Vibrational effects on the F-F spin-spin coupling constant (2hJFF) in FHF- and FDF-”, J. Phys. Chem A, 105, 8399-8402 (2001).

J. E. Del Bene and M. J. T. Jordan, “What a difference a decade makes: progress in ab initio studies of the hydrogen bond”, invited paper for a special issue of Theochem to celebrate the 10th CCTCC, Theochem, 573, 11-23 (2001).

K. Chapman, D. Crittenden, J. Bevitt, M. J. T. Jordan and J. E. Del Bene, “Relating environmental effects and structures, IR and NMR properties of hydrogen-bonded complexes: ClH:pyridine”, J. Phys. Chem. A., 105, 5442-5449 (2001).

J. E. Del Bene and M. J. T. Jordan, “Vibrational spectroscopic and NMR properties of hydrogen-bonded complexes: do they tell us the same thing?”, J. Am. Chem. Soc., 122, 4794-4797 (2000).

M. J. T. Jordan and J. E. Del Bene, “Unravelling environmental effects on hydrogen-bonded complexes: matrix effects on the structures and proton stretching frequencies of hydrogen-halide complexes with ammonia and trimethylamine”, J. Am. Chem. Soc., 122, 2101-2115 (2000).

J. E. Del Bene and M. J. T. Jordan, “Vibrational Spectroscopy of the Hydrogen Bond: An Ab Initio Chemical Perspective”, Int. Rev. in Phys. Chem., Vol. 18, no. 1, 119-162 (1999). Invited review article, edited by D.C. Clary.

J. E. Del Bene and M. J. T. Jordan, “A comparative study of vibrational anharmonicity in the bihalide anions XHX: X=F, Cl and Br”, Spectrochimica Acta, Part A, 55, 719-729 (1999). An invited paper in a special issue entitled “Theoretical Spectroscopy: State of the Science” edited by T.J. Lee and M. Head-Gordon.

J. E. Del Bene and M. J. T. Jordan, “A comparative study of anharmonicity and matrix effects on the complexes XH:NH3, X=F, Cl and Br”, J. Chem. Phys., 108, 3205-3212 (1998).

J. E. Del Bene, M. J. T. Jordan, P. M. W. Gill and A. D. Buckingham, “An ab initio study of anharmonicity and matrix effects on the hydrogen-bonded BrH:NH3 complex”, Mol. Phys., 92, 429-439 (1997). Invited contribution to a special issue of Molecular Physics in honour of Professor John Pople, Nobel Laureate in Chemistry, ed N. C. Handy.