Photoswitching of Quadratic Nonlinearities

METAL-BASED QUADRATIC NONLINEAR OPTICAL MATERIALS 

PSS closed forms the /u/ o value for the open form is very small, in agreement with the absence of Tt-conjugation between the two thiophene rings of the DTE fragment. Upon conversion to the closed form in the photosta-tionary state, the NLO activity dramatically increased, from 160 to 

1800 X 10 esu. Thus, the huge enhancement of clearly reflects the efficient delocalisation of the 7i-electron system in the closed forms and demonstrates an efficient ON/OFF switching of the NLO responses. 

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