Photophysical properties of an environment sensitive fluorophore 1-keto-6,7-dimethoxy-1,2,3,4-tetrahydrocarbazole and its excited state interaction with N,N-dimethylaniline: A spectroscopic investigation

Photophysical properties of a fluorophore 1-keto-6,7-dimethoxy-1,2,3,4-tetrahydrocarbazole (KTHC-67) have been studied in a number of organic solvents. The profile of the fluorescence spectrum and the wavelength at which fluorescence intensity maximizes are found to vary with the nature of the solvent. The photophysics of KTHC-67 is much more influenced by the hydrogen bond donor and acceptor abilities of the solvents rather than their polarity of the solvent. Excited state interactions of KTHC-67 with N,N-dimethylaniline (DMA) have also been investigated in three homogeneous solvents, acetonitrile (ACN), dimethyl sulphoxide (DMSO) and ethanol (EtOH). Photoinduced electron transfer from DMA to KTHC-67 is evident from the subsequent changes in the fluorescence intensity, fluorescence lifetime and transient absorbance of KTHC-67 in presence of DMA.

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► Excited state dipole moment of KTHC-67 is 3.197 D higher than that in ground state.
► Fluorescence maximum of KTHC-67 is red-shifted by 71 nm from 1,4-dioxane to EtOH.
► Fluorescence maximum of KTHC-67 is red-shifted by 47 nm from DMSO to MeOH.
► Photophysics of KTHC-67 is mostly controlled by H-bond donor ability of solvent.
► Photoinduced electron transfer is liable for the interaction of KTHC-67 with DMA.