P K Bhowmik
University of Nevada Las Vegas, USA
Title: Synthesis, optical spectroscopy and laser potential of pyrylium tosylates
Biography
Biography: P K Bhowmik
Abstract
Pyrylium salts are an important class of organic molecules containing trivalent oxygen atom in six-membered aromatic ring. Versatile methods for the synthesis of a series of four 2,4,6-triaryl-substitued pyrylium tosylate salts with different substituents are reported. The synthesis methods use p-toluenesulfonic acid monohydrate instead of conventional acid catalysts including perchloric acid or boron trifluoride diethyl etherate that pose explosion danger and difficult storage problem, respectively. The chemical structures of these salts were established using Fourier transform infrared, 1H and 13C nuclear magnetic resonance spectroscopic techniques and elemental analysis. Their solubility in different organic solvents was dependent on the substituents in 2nd and 6th positions of phenyl groups. Their thermal stability and thermal property were studied using thermogravimetric analysis and differential scanning calorimeter, respectively. It was observed that, solutions of all four pyrylium tosylate salts absorbed strongly in the blue-near-ultraviolet spectral range and emitted efficiently in the blue-green spectral range depending on the substituent in 2nd and 6th positions of phenyl groups. The fluorescence quantum yield of the salts ranged from 0.56 to 0.33 and under intense ultrashort laser pumping, the solution of the salt, (2,4,6-triphenylpyrylium tosylate), which was having the highest quantum yield demonstrated stimulated emission and laser action with only nominal feedback.