Synthesis and Photophysical Properties of S, N and Se-modified Methyl Salicylate Derivatives

Abstract Three different S, N and Se-modified methyl salicylate derivatives, methyl 2-hydroxy-4-(pyridin-2-yl)benzoate (MHPB), methyl 2-hydroxy-4-(thiophen-2-yl)benzoate (MHTB) and methyl 2-hydroxy-4-(selenophen-2-yl)benzoate (MHSB) have been synthesized and their photophysical properties are examined in dichloromethane. The three derivatives produce absorption spectra with different shapes spanning over 260 – 370 nm region. The UV excitation of the derivatives produces characteristic emission features, associated with the Franck-Condon (FC) excited-state configuration at high-energy side and excited state intramolecular proton transfer configuration at low-energy side. For MHPB, two emission bands peaking at around 380 and 450 nm are observed with relatively strong intensities. However, for MHTB the intensity of the blue emission is significantly reduced and for MHSB the emission is significantly quenched. Quantum mechanical calculations on the structural geometry and the electronic transition are performed to reveal the effect of the substituent moieties on the photophysical properties.