title: Free base tetraazaporphine isolated in inert gas hosts: matrix influence on its spectroscopic and photochemical properties.
abstract: The absorption, fluorescence, and excitation spectra of free base tetraazaporphine (H2TAP) trapped in Ne, N2, and Ar matrices have been recorded at cryogenic temperatures. Normal Raman spectra of H2TAP were recorded in KBr discs and predicted with density functional theory (DFT) using large basis sets calculations. The vibrational frequencies observed in the Raman Spectrum exhibit reasonable agreement with those deduced from the emission spectra, as well as with frequencies predicted from large basis set DFT computations. The upper state vibrational frequencies, obtained from highly resolved, site selected excitation spectra, are consistently lower than the ground state frequencies. This contrasts with the situation in free base phthalocyanine, where the upper state shows little changes in vibrational frequencies and geometry when compared with the ground state. Investigations of the photochemical properties of H2TAP isolated in the three matrices have been performed using the method of persistent spectral hole-burning (PSHB). This technique has been used to reveal sites corresponding to distinct N-H tautomers which were not evident in the absorption spectra. An analysis of the holes and antiholes produced with PSHB in the Qx (0-0) absorption band made it possible to identify inter-conversion of distinct host sites.
authors.affiliation: Department of Chemistry, National University of Ireland - Maynooth, Maynooth, County Kildare, Ireland.
authors.forename: Chris
authors.initials: C
authors.lastname: Henchy
authors.affiliation: Department of Chemistry, National University of Ireland - Maynooth, Maynooth, County Kildare, Ireland.
authors.forename: John G
authors.initials: JG
authors.lastname: McCaffrey
authors.affiliation: Department of Chemistry, Belarussian State Agrarian Technical University, Minsk, Belarus.
authors.forename: Serguei
authors.initials: S
authors.lastname: Arabei
authors.affiliation: B.I. Stepanov Institute of Physics, Minsk, Belarus.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Pavich
authors.affiliation: Laboratoire Aimé Cotton, UPR3321 CNRS - Université Paris-Sud 11, F-91405 Orsay, France.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Galaup
authors.affiliation: Institut des Sciences Moléculaires d'Orsay, UMR8214 CNRS - Université Paris-Sud 11, F-91405 Orsay, France.
authors.forename: Niloufar
authors.initials: N
authors.lastname: Shafizadeh
authors.affiliation: Institut des Sciences Moléculaires d'Orsay, UMR8214 CNRS - Université Paris-Sud 11, F-91405 Orsay, France.
authors.forename: Claudine
authors.initials: C
authors.lastname: Crépin