Page 84 - Photoreactive Organic Thin Films

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PHOTOISOMERIZATION

ZOUHEIR SEKKAT
Department of Applied Physics, Osaka University, Suita, Osaka 565-0871, Japan
School of Science and Engineering, Al Akhawayn University in Ifrane, 53000 Ifrane, Morocco

3.1 INTRODUCTION
3.2 PHOTOISOMERIZATION OF AZOBENZENES
3.3 PHOTO-ORIENTATION BY PHOTOISOMERIZATION
3.3.1 Base Ground Work
3.3.2 Theory of Photo-Orientation
3.4 PHOTO-ORIENTATION OF AZOBENZENES:
INDIVIDUAUZABLE ISOMERS
3.4.1 Reorientation within the trans —> cis Photoisomerization
3.4.2 Reorientation within the cis -> trans Thermal Isomerization
3.5 PHOTO-ORIENTATION OFAZO DYES: SPECTRALLY
OVERLAPPING ISOMERS
3.6 PHOTO-ORIENTATION OF PHOTOCHROMIC
SPIROPYRANSAND DIARYLETHENES
3.6.1 Photoisomerization of Spiropyrans and Diarylethenes
3.6.2 Spectral Features of Photo-Orientation
3.6.3 Photo-Orientation Dynamics and Transitions Symmetry
3.7 CONCLUSION
APPENDIX 3A: QUANTUM YIELDS DETERMINATION
APPENDIX 3B: DEMONSTRATION OF EQUATIONS 3.12
THROUGH 3.15

ABSTRACT

In this chapter, I discuss the phenomenon of molecular orientation induced
by photoisomerization whereby experiment merges with theory to assess
molecular movement during isomerization. The theory unifies photochemistry
with optics, and it provides rigourous analytical tools for powerful quan-
tification of coupled photoisomerization and photo-orientation. Experiments
on spectrally distinguishable isomers detail the mechanisms of chromophore
reorientation during photo- and thermal isomerization. In particular, I

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