Semi-Experimental Equilibrium Structures for Molecules of Biological Significance
EMSL Project ID
41294
Abstract
Polyenes are important in vision, in natural pigments, and in light-harvesting for photosynthesis. Putting fluorine substituents in medicinal substances has become an important strategy for tuning potency and increasing the lifetime of drugs in competition with metabolic processes. The goal of the project is to gain a better understanding of the structures of simple polyenes and fluorine-substituted ones. We do so by determining exact equilibrium structures (good to 0.001 angstrom with atoms seemingly at rest; as distinct from standard methods, such a x-ray, which give ~0.02 angstrom resolution because of zero point vibrations of the atoms) for molecules where effects of pi-electron delocalization and fluorine substitution may have significant effects on bond lengths and bond angles in comparison with reference substances. These equilibrium structures are also useful in assessing the quality of high-level quantum chemical (QC) calculations of molecular properties. Equilibrium structures (re) come from equilibrium rotational constants, which are determined from ground state rotational constants secured from the analysis of high-resolution spectra and from the QC calculation of the vibration-rotation constants (alphas). Full sets of 13C and 2H isotopomers must be synthesized for this work. Two molecular systems are being studied: the cis and trans isomers of 1,3,5-hexatriene and the three isomers of 1,4-difluorobutadiene.
Project Details
Project type
Exploratory Research
Start Date
2010-11-09
End Date
2011-11-13
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Craig NC, HA Fuson, T Hengfeng, and TA Blake. 2012. "Analysis of the rotational structure in the high-resolution infrared spectra of trans-hexatriene-1,1-d2 and -cis-1-d1." PNNL-SA-84964, Pacific Northwest National Laboratory, Richland, WA.
Craig NC, H Tian, and TA Blake. 2012. "Analysis of the Rotational Structure in the High-Resolution Infrared Spectrum of trans-Hexatriene-1-13C1; a Semiexperimental Equilibrium Structure for the C6 Backbone for trans-Hexatriene." Journal of Physical Chemistry A 116(12):3148-3155. doi:10.1021/jp211791r