Spectroscopy, simulation and structure of molecular clusters: A molecular view of solvation.

Format:

Book

Thesis/Dissertation

Author/Creator:

Andrews, Peter M.

Contributor:

Topp, Michael R., advisor.

University of Pennsylvania.

Language:

English

Subjects (All):

Chemistry, Physical and theoretical.

0494.

Penn dissertations--Chemistry.

Chemistry--Penn dissertations.

Local Subjects:

Penn dissertations--Chemistry.

Chemistry--Penn dissertations.

0494.

Physical Description:

319 pages

Contained In:

Dissertation Abstracts International 58-11B.

System Details:

Mode of access: World Wide Web.

text file

Summary:

The understanding of cluster formation, the energetics of structural relaxation and the formation of multiple conformers of a several aggregates are explored. These include the alcohol and halobenzene complexes of perylene, the water complexes of the coumarin dyes as well as several other test systems. The results of experimental structural measurement are compared and/or supplemented by computational algorithms to assist in understanding the dominant forces which govern the complex formation. Experimental studies on these systems are performed by using fluorescence excitation, dispersed fluorescence, hole burning and rotational coherence spectroscopy. These results are compared to several commercially available computational algorithms, including ab-initio, semi-empirical and molecular mechanics methods.

The results of these studies show that the molecular mechanics algorithms reproduce the experimental structures well, giving good qualitative agreement. This includes the prediction of multiple conformers of several complexes, as seen in the alcohol complexes of perylene, as well as the existence of multiple conformers of the solvent species for a given solute/solvent complex. For the case of the (1:1) water complex of the coumarin dye, Coumarin 151, the complex shows a low energy barrier to relaxation. This is evident by a large Stokes shift in the emission and a pronounced red shift upon complexation. The Stokes shift is proposed to exist due to a facile rearrangement of the water molecule to an adjacent sit on the coumarin molecule. The complex of perylene/p-dichlorobenzene also shows relaxation when given excess vibrational energy in the excited state. The molecular mechanics algorithms are further utilized to predict those structures where directional hydrogen bonding dominates and affords the complexing species two equivalent adjacent sites for binding.

In conclusion, it has been found that the combined approach of measuring structures of aggregates with experimental techniques and computational methods works well for several of the complexes studied. These techniques resulted in good qualitative agreement, and in several cases good quantitative agreement and helped to establish the interplay between aggregate structure and relaxation dynamics.

Notes:

Thesis (Ph.D. in Chemistry) -- University of Pennsylvania, 1997.

Source: Dissertation Abstracts International, Volume: 58-11, Section: B, page: 5980.

Supervisor: Michael R. Topp.

Local Notes:

School code: 0175.

ISBN:

9780591659481

Access Restriction:

Restricted for use by site license.