FTIR Spectroscopic and Theoretical Study of the Photochemistry of Matrix‐isolated Coumarin

Abstract

The infrared spectrum of monomeric unsubstituted coumarin (C9H6O2; 2H-1-benzopyran-2-one), isolated in solid argon at 10 K is presented and assigned. The UV-induced (lambda>200 nm) unimolecular photochemistry of the matrix-isolated compound was studied experimentally. Three main photoreactions were observed: (a) decarboxylation of the compound and formation of benzocyclobutadiene and CO2, with the Dewar form of coumarin as intermediate; (b) isomerization of the compound, leading to production of a conjugated ketene; and (c) decarbonylation, leading to formation of CO and benzofuran complex. Further decomposition of benzofuran to produce ethynol is suggested. Photochannels (a) and (b) correspond to those previously observed for matrix-isolated alpha-pyrone and its sulfur analogs (Phys. Chem. Chem. Phys. 2004, 6, 929; J. Phys. Chem. A 2006, 110, 6415), while route (c) is similar to the UV-induced photochemistry of coumarin in the gaseous phase (J. Phys. Chem. A 2000, 104, 1095). Interpretation of the experimental data is supported by extensive calculations performed at the B3LYP/6-311++G(d,p), MP2/6-31G(d,p) and MP2/6-311++G(d,p) levels.

Theoretical and Experimental Infrared Spectrum Analysis of 1-Ethyl-3-Methylimidazolium Cation

“…1 and EMIM-2 (0.520), reveals the relatively low degree of aromaticity of the imidazolium ring in these compounds, which is similar to the one of the -pyrone ring (0.526) in coumarin [20].…”

The effect of chalcogen substitution on the structure and spectroscopy of 4,7-dimethyl-2H-chromen-2-one/thione analogues

“…For compound 1, the most salient features are the νC=O and νC1-O stretching modes, appearing as intense absorptions at 1717 (1698 cm -1 in Raman) and 1149 cm -1 (1148 cm -1 in Raman), respectively, in good agreement with the values reported for related species. 46 The computed values are 1798 and 1151 cm -1 , suggesting that the relatively low frequency value experimentally observed for the νC=O is related with intermolecular interactions involving the carbonyl group in the crystalline compound 1.…”

High‐Efficiency Luminescent Solar Concentrators Based on Antifogging and Frost‐Resisting Fluorescent Polymers: Adding Multiple Functions for Sustained Performance

“…Indeed, no signal characteristic of CC stretching in methacrylate monomers (1637 cm −1 ) was detected after polymerization, while the signals at 1612, 1388, and 1152 cm −1 , associated to CC stretching in pyrone ring, CC stretching in aromatic ring, and CH bending of aromatic carbons, respectively, were found to proportionally increase with coumarin content. [38] Gel permeation chromatography (GPC) analyses evidenced a sharp decrease in the number average molecular weight (M n ) with the increase in CMA feed molar content likely ascribable to the bulkiness of coumarin side groups that inhibits chain growth (see Table 1).…”