Laser Dye Complexes and Their Polymorphic Relationships


Our current efforts are directed toward a better understanding of the correlation between the structural, theoretical and photophysical properties of laser dye molecules, assemblies and polymorphs in three classes structurally related to the coumarin, fluorene and methene moieties, respectively. Our focus is being directed toward investigating a theoretical approach to predicting crystal structures based on systematically searching for densely packed structures within the common planar organic species related to these laser dye cluster species. The crystallographic data will serve as a starting point for these investigations providing coordinates of the most stable cluster form corresponding to the global minimum in the lattice energy. This will ensure confidence that the most stable crystal structure will be found as a model for the forces that bind the molecules together for a crystal.

Based on our prior efforts and results with the coumarin based molecules and clusters, we are moving in a new direction concentrating on understanding the structural and theoretical nature of recently observed polymorphism in coumarin related systems and in two new classes of laser dye derivatives defined by the presence of the flourene and methene structual units, respectively. Polymorphism in laser dye compounds was first identified in our laboratory when we reported the polymorphic crystalline structures of Coumarin 152 1 and Coumarin 138.2Within the past three years two additional polymorphic species of coumarin compounds have been reported.3-7 It would appear that additional members of the coumarin family of laser dye compounds may also exhibit similar behavior. It is our aim to further investigate these phenomena as well as search for similar effects in two new classes of laser dye compounds and further relate these results to crystal structure predictability. We have achieved some success in studying two of the flourene based molecular assemblies in the crystalline state. The single crystal structural analysis of Exalite 384 and Exalite 404 has been completed.8 By engaging in a coordinated approach emphasizing both experimental and theoretical fundamental techniques, we hope to provide a better understanding of the photophysical processes that occur in these systems. Six papers1,2,9-12, in the preparation stages and seven presented papes have resulted from the work performed on this project in our laboratory in the recent past. The proposed work includes the development of a theoretical framework whereby one can probe the intra and inter molecular nature of the interactions of these systems as well as provide insight into the nature of the various discriminatory and conformational energies that they tend to display. A potential outcome of this effort may aid in the methodology of the possible design and implementation of additional new types of laser dye materials.


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The New England Molecular Structure Center