Fluorescent Small Molecules Are BIG Enough To Sense Biomacromolecule: Synthesis of Aromatic Thioesters and Understanding Their Interactions with ctDNA.

The visible fluorescent chromophoric moiety present in the water-soluble photoactive yellow protein (PYP) of is -hydroxycinnamic acid linked to the cysteine residue (Cys-69) by a thioester bond and it controls the key photoinduced biological processes of the host organism. In the present work, we have synthesized and characterized three structurally different thiophenyl esters [viz., hydroxycinnamic-thiophenyl ester (), -,-dimethylaminocinnamic-thiophenyl ester (), and -phenyl-3-(4-chlorophenyl)-3-(phenylthio)propanethioate ()] in addition to a novel (to the best of our knowledge) stilbene-type olefinic compound, ,,,-tetramethyl-1,2-bis(phenylthio)ethene-1,2-diamine (), under the same reaction condition.

Effect of an Electron-Donating Substituent at the 3',4'-position of 3-Hydroxyflavone: Photophysics in Bulk Solvents.

Introduction of the methylenedioxy substituent group in the 3',4'-position of 3-hydroxyflavone produced a significant impact on its proton-transfer response, much like the well-known 4'-N,N-dialkylamino group. The potential electron-donating property of the substituent helped sustain a high degree of charge separation in the excited enolic form of the molecule, which was stabilized in relatively polar solvents, whereupon the enol → tautomer excited state intramolecular proton-transfer (ESIPT) rate decreased. Hydrogen-bonding solvents caused further retardation by interfering with the intramolecular hydrogen bond that promotes ESIPT.