Photophysics of a solvent sensitive keto-tetrahydrocarbazole based fluorophore and its interaction with triethylamine: A spectroscopic inquest under surfactant and β-CD confinement

• Quantum yield of DMMTCO is higher in polar aprotic solvents.
• Excited state of DMMTCO is sensitive to solvent polarity and H-bonding.
• Fluorescence maximum of DMMTCO is red shifted in more polar and protic solvent.
• DMMTCO have higher fluorescence yield in micelles and β-cyclodextrin.
• Organic base quenches DMMTCO fluorescence on photoexcitation.

In this communication, we wish to report solution phase photophysics of 6,7-dimethoxy-3-methyl-2,3,4,9-tetrahydro-1H-carbazol-1-one (DMMTCO) and its interaction with a simple aliphatic organic donor, triethylamine (TEA) in different environments using absorption, steady-state and time-resolved fluorescence techniques. We have chosen ten solvents of varied nature and have observed that the fluorescence emission maximum of the compound is sensitive to the ET(30) value of the solvent. Quantum yield of the fluorophore is found to be higher in polar aprotic solvents like DMSO, DMF and ACN. When the fluorophore interacts with an anionic surfactant solution of sodium dodecyl sulphate (SDS), a hypsochromic shift of 17 nm is observed with respect to pure aqueous medium as the concentration of the surfactant increases. On switching over to the neutral surfactant of Triton X-100, a hypsochromic shift of 29 nm with respect to pure aqueous medium is witnessed as the concentration surges. Likewise, with the increase in concentration of β-cyclodextrin, we have noted a hypsochromic shift of 26 nm. In all of the above mentioned occasions, we have perceived hypsochromic shifts along with concomitant increase in fluorescence intensity. These observations regarding the organised media indicate that the immediate surrounding around the probe gets modified with the increase in surfactant and β-cyclodextrin concentration. TEA is a simple organic molecule that interacts with DMMTCO in a differing manner when we change the atmosphere from purely homogeneous to surfactant environment. In the confined medium, we observe the formation of a ground state complex, which is not that much appreciable in the case of homogeneous solvents.

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