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Three polycyclic chromeno[2,3-b]indolecontaining indole and naphthalene rings fused by a pyran ring were synthesized by metal-free C–H functionalization method and their photophysical studies were done. Steady state absorption spectra do not show solvent effect while fluorescence spectra exhibit solvatochromic shift. The molecules exhibit ultra-high Stokes shift of the order of 3.07 eV (24,696 cm−1) in acetonitrile and 2.12 eV (17,054 cm−1) in ethyl acetate. To corroborate experimental observation, we performed computational investigation both in gas and solvent phases. The computed results are in good agreement with the experimental observation. Analysis of the frontier molecular orbitals as well as natural transition orbitals depicts intramolecular charge transfer in the molecules. Further, gas phase as well as solvent phases optimized structures in the ground and excited states of all chosen molecules show increase in planarity in the excited state. An excited state intramolecular charge transfer accompanied by structural relaxation leading to planarity in the excited state has been suggested to cause large Stokes shifted fluorescence emission in these molecules. [ABSTRACT FROM AUTHOR]

Quantum dynamical calculations on HOD subjected to different combinations of IR and UV pulses have been made to isolate field attributes which maximise selectivity and yield in the photodissociation of the desired O-H/O-D bond. Results from IR+UV pulse combinations which provide very high selectivity and/or yield are analysed in detail using population transfer, probability density flow, and flux variations to obtain microdynamic details favouring selectivity and yield. The expectation values for stretch and momentum in O-H and O-D bonds of the H-O-D molecule subjected to UV pulses effecting selective cleavage of these bonds have been analysed to decipher the mechanistic basis of selective dissociation. Fully quantum dynamical calculations using both the ground and excited potential energy surfaces with different initial states and UV pulses reveal that prior stretch in a bond before transferring it to the repulsive first excited state ensures preferential dissociation of this bond. The sampling of large stretch values and a quick downhill motion in the channel corresponding to dissociation of the prestretched bond on the upper surface are seen to underlie this preferential dissociation. [ABSTRACT FROM AUTHOR]