Photoisomerization within a novel synthesized photoswitchable dyad: Experimental and theoretical approaches

Abstract

Photoswitchable characteristics of a novel dyad, 1-(4-chloro-phenyl)-3-(1-methoxy-3,4-dihydro-naphthalen-2-yl)propenone (MNCADH) have been investigated both experimentally and theoretically. In the ground state MNCADH is found exclusively as ‘trans’ isomer. From experimental findings, obtained by steady state and time resolved spectroscopic techniques, it is apparent that both ‘cis’ and ‘trans’ isomers are present in the excited state. ‘Trans’ isomer prefers to populate in polar medium, whereas ‘cis’ isomer mainly populates in nonpolar medium. Potential energy surface calculations at density functional theory level for trans–cis isomerism, in ground and excited states, unveil that the interconversion energy barrier is quite high in ground state as compared to that of excited state, so that switching form one conformer to another only becomes possible in excited state. Natural bond orbital analysis also supports the similar mechanism of interconversion processes.