title: Trans- and cis-stilbene isolated in cryogenic argon and xenon matrices.
abstract: Monomers of trans- (TS) and cis-stilbene (CS) were isolated in cryogenic argon and xenon matrices, and their infrared (IR) spectra were fully assigned and interpreted. The interpretation of the vibrational spectra received support from theoretical calculations undertaken at the DFT(B3LYP)/6-311++G(d,p) level of theory. In situ broadband UV irradiation of the matrix-isolated CS led to its isomerization to TS, which appeared in the photolysed matrices in both non-planar and planar configurations. The non-planar species was found to convert into the more stable planar form upon subsequent annealing of the matrices at higher temperature. TS was found to be photostable under the used experimental conditions. The structure of the non-planar TS form was assigned based on the comparison of its observed IR spectrum with those theoretically predicted for different conformations of TS. Chemometrics was used to make this assignment. Additional reasoning on the structure of the studied stilbenes is presented taking as basis results of the Natural Bond Orbital analysis.
authors.affiliation: Department of Chemistry, University of Coimbra, P-3004-535 Coimbra, Portugal; Department of Physics, Faculty of Sciences, University of Istanbul, Turkey.
authors.forename: Ozan
authors.initials: O
authors.lastname: Ünsalan
authors.affiliation: Department of Chemistry, University of Coimbra, P-3004-535 Coimbra, Portugal; Department of Physics, Anadolu University, Eskişehir, Turkey.
authors.forename: Nihal
authors.initials: N
authors.lastname: Kuş
authors.affiliation: Department of Chemistry, University of Coimbra, P-3004-535 Coimbra, Portugal.
authors.forename: Susana
authors.initials: S
authors.lastname: Jarmelo
authors.affiliation: Department of Chemistry, University of Coimbra, P-3004-535 Coimbra, Portugal. Electronic address: rfausto@ci.uc.pt.
authors.forename: Rui
authors.initials: R
authors.lastname: Fausto
mesh_terms: D001128:Argon / Q000737:chemistry; D007536:Isomerism; D015394:Molecular Structure; D010777:Photochemistry / Q000379:methods; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013267:Stilbenes / Q000737:chemistry* / Q000302:isolation & purification; D014466:Ultraviolet Rays; D014732:Vibration; D014978:Xenon / Q000737:chemistry
chemical_list: D013267:Stilbenes; D014978:Xenon; D001128:Argon
keywords: Cis→trans photoisomerization; DFT(B3LYP)/6-311++G(d,p) calculations; Matrix isolation IR spectroscopy; Trans- and cis-stilbene