Spectrum and Structure of Spiropyran
Abstract
Photochromic materials are of interest to the Air Force for a variety of potential applications including high resolution photography, optical devices, holographic systems and variable transmission devices. The photochemical and structural characteristics of two organic photochromes, specifically indoline-spiro-benzopyran and benzothiazoline-spiro-benzopyran, have been studied by computational chemistry techniques. Both quantum mechanical and classical methods were used. Irradiation of spiropyran by UV light causes molecular rearrangement, thus yielding merocyanine whose absorption band lies in the visible region. This is the basis of the photochromic nature of the spiropyran. Several chromophore based devices would benefit from a material whose visible absorption spectrum was red shifted and whose structure and properties in various environments was fully understood. The absorption spectra of both indoline-spiro-benzopyran and benzothiazoline-spiro-benzopyran were calculated. Spectroscopic calculations reveal that the absorption spectrum is determined by two factors: the choice of substituent and the geometry of the chromophore. Both electron withdrawing and electron donating substituents were strategically placed on the chromophore. Maximum red shifts may be achieved in the merocyanine by attaching (at the proper position) strongly electron donating substituents which force rotations about double bonds while limiting the rotation about single bonds. Two force fields have been developed to allow classical calculations on large photochromic systems (solvated chromophores or polymer substituted chromophores). The agreement of these classical force fields with quantum mechanical methods for the unsubstituted indoline-benzopyran merocyanine has been shown. These force fields were used in molecular dynamics simulations to explore the effect of the solvent polarity on
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1994
- Accession Number
- ADA332921
Entities
People
- B. L. Farmer
- J. A. Young
- W. W. Adams
Organizations
- University of Virginia