Accession Number : ADA332921

Title :   Spectrum and Structure of Spiropyran

Descriptive Note : Final rept. 1 Sep 92-15 Aug 94

Corporate Author : VIRGINIA UNIV CHARLOTTESVILLE DEPT OF MATERIALS SCIENCE AND ENGINEERING

Personal Author(s) : Young, J. A. ; Farmer, B. L. ; Adams, W. W.

PDF Url : ADA332921

Report Date : AUG 1994

Pagination or Media Count : 84

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

Descriptors :   *ABSORPTION SPECTRA, *PHOTOCHROMIC MATERIALS, COMPUTATIONS, CHROMOPHORES, QUANTUM THEORY, SOLVENTS, POLARITY, ROTATION(CHEMICAL BONDS), SPIRO COMPOUNDS.

Subject Categories : Radiation and Nuclear Chemistry
      Atomic and Molecular Physics and Spectroscopy
      Quantum Theory and Relativity

Distribution Statement : APPROVED FOR PUBLIC RELEASE