Synthesis, Characterization, Photo-physical Evaluation and Crystal Structure of 2-Methoxy-1-Methylquinolinium Tetrafluoroborate, a Potentially Selective Agent for the Quantitative Measurement of Biologically Relevant Thiols

Abstract

We report the quantitative and facile conversion of 2-chloro-1-methylquinolinium tetrafluoroborate to 2-methoxy-1-methylquinolinium tetrafluoroborate via stirring in methanol at room temperature. The resulting compound was evaluated for use as a selective tag for biologically relevant thiols. The results displayed a fivefold increase in fluorescent quantum yield (ФFLUOR = 0.20) and an increased stability in pH when compared to 2-chloro-1-methylquinolinium tetrafluoroborate (ФFLUOR = 0.04), however, results demonstrated that it did not offer an improvement to 2-chloro-1-methylquinolinium tetrafluoroborate as a thiol specific tag. The compound was fully characterised by 1HNMR, ESI mass spectroscopy and by single-crystal X-ray diffraction. The title compound crystallizes in the monoclinic space group P21/m with a = 8.2420(3) A, b = 6.6751(2) A, c = 10.8415 A and β = 105.164(2)°, Z = 2, V = 575.69(3) A3. Work is on-going to synthesise and evaluate other such analogues for their potential use as thiol tags. The authors present the crystal structure of 2-methoxy-1-methylquinolinium tetrafluoroborate, a potentially selective agent for the quantitative measurement of biologically relevant thiols.