Induced VCD analyzed in terms of molecular orbital contributions

PHYS 12

Valentin-Paul Nicu, nicu@few.vu.nl, Theoretical Chemistry, Theoretical Chemistry, Vrije Universiteit Amsterdam, de Boelelaan 1083, 1081HV, Amsterdam, Netherlands, Johannes Neugebauer, Johannes.Neugebauer@phys.chem.ethz,ch, Laboratory of Physical Chemistry, ETH Zurich, 8093 Zurich, Switzerland, Jochen Autschbach, jochena@buffalo.edu, Department of Chemistry, State University of New York at Buffalo, 312 Natural Sciences Complex, Buffalo, NY 14260-3000, and Evert Jan Baerends, baerends@chem.vu.nl, Theoretical Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, Netherlands.
To derive general rules relating features in VCD spectra to structural motifs in the systems under study a simple physical understanding of the sign and magnitude of the vibrational circular dichroism (VCD) intensities is needed. Such an understanding is difficult because the rotational strengths (R), which give the VCD intensities, depend on a large number of variables. To gain a deeper insight into the physical origins of VCD signals, we study various contributions to R for chiral molecules of different size: NHDT, trans-2,3 d2-oxirane, hexa- and hepta-helicenes. The electronic and nuclear contributions to the transition dipole moments are discussed. We show that a better understanding of the VCD spectra of these molecules can be achieved by correlating the nuclear motion in a given normal mode with the contributions to R per occupied orbital. This approach is then used to investigate the induced vibrational circular dichroism of the amphetamine – benzoyl-benzoic acid complex.
 

Implications and Applications of Chirality in Physical Chemistry
8:00 AM-12:00 PM, Sunday, March 25, 2007 McCormick Place South -- Room S401A, Level 4, Oral

Division of Physical Chemistry

The 233rd ACS National Meeting, Chicago, IL, March 25-29, 2007