Patel, D. G., Paquette M. E., Kopelman, R. A., Kaminsky, W., Ferguson, M. J., Frank, * N. L. Solution and Solid State Investigation of Medium Effects on Charge Separation in Metastable Photomerocyanines J. Am. Chem. Soc. 2010 132,12568-12586 (SEP 15 2010). DOI: 10.1021/0100238h
Photochromes have found utility in smart optical coatings, and as witching elements in energy transfer and electron transfer processes for molecular electronics. Structure-activity relationships for the effect of environmental dielectric on electronic structure and thermal relaxation kinetics in spirooxazine negative photochromes is investigated through synthesis, spectroscopy, and computational modeling. We report the first X-ray diffraction (XRD) analyses of the photomerocyanine form. Structural differences observed in pseudopolymorphs of 2-PMC suggest that the degree of charge-separated character in the solid state is correlated with a higher dielectric of the environment. In nonpolar environments, the PMC has more quinoidal character, while in media of high dielectric, the PMC forms are more zwitterionic. These studies provide insight into the control of structure, thermodynamics, and kinetics in photochromes through modification of the environment.