Spectra of porphyrins

The Journal of Chemical Physics

2003

Laser induced fluorescence spectroscopy of free-base (H 2 Pc) and zinc (ZnPc) phthalocyanines trapped in rare gas and nitrogen matrices reveals a quite unexpected phenomenon with a moderate increase in the laser intensity. In all matrices except Xe, a huge increase occurs in the intensity of an emission band near 755 nm when pumping the S 1 ' S 0 transition. The band involves a vibrational mode of the ground state, located at 1550 and 1525 cm À1 for H 2 Pc and ZnPc, respectively. Many of the characteristics of amplified emission (AE) are exhibited by this vibronic transition. Excitation scans recorded for the AE band yield greatly enhanced site selectivity compared to what is obtained in normal fluorescence excitation scans.

Section: Absorptionsupporting

confidence: 73%

A pair-potentials analysis of the emission spectroscopy of P13 state atomic mercury isolated in solid Ar, Kr, and Xe

Collier

The Journal of Chemical Physics

2003

“…The phthalocyanines have been examined in the solid state, [7][8][9][10][11] in the gas phase, [12][13][14] free expansions, 15,16 and in helium droplets. 17,18 In contrast, high resolution spectroscopy of the parent molecule H 2 TAP appears to have only been studied in Shpol'skii organic matrices [19][20][21][22] where large (∼53 cm −1 ) siteinduced tautomeric splitting complicates the analysis of the fluorescence spectra.…”

Section: Introductionmentioning

confidence: 99%

Free base tetraazaporphine isolated in inert gas hosts: Matrix influence on its spectroscopic and photochemical properties

Henchy

The Journal of Chemical Physics

Arabei

et al. 2014

The absorption, fluorescence, and excitation spectra of free base tetraazaporphine (H 2 TAP) trapped in Ne, N 2 , and Ar matrices have been recorded at cryogenic temperatures. Normal Raman spectra of H 2 TAP 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 H 2 TAP 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 Q x (0-0) absorption band made it possible to identify inter-conversion of distinct host sites. © 2014 AIP Publishing LLC.

“…Visible absorption spectra of H 2 Pc and ZnPc isolated in a variety of matrices were first reported by Bajema et al 17 A detailed lineshape analysis of H 2 Pc in Ar has been presented by Geissinger et al 26 The emission and excitation spectra of H 2 Pc have been studied in Ar matrices by Bondybey and English. 18 In contrast, the Ne and N 2 systems have not yet received much attention.…”

Section: Introductionmentioning

confidence: 99%

“…11 The two molecules have also been studied in cryogenic matrices: either in Shpol'skii organic matrices [12][13][14] or isolated in the solid rare gases. [15][16][17][18] In a detailed magnetic circularly polarised luminescence (MCPL) study of ZnPc, Schatz and co-workers 19 identified the presence of both crystal field splitting and Jahn-Teller coupling on the degenerate first excited singlet state. IR and Raman spectra for H 2 Pc in thin films 20 and for ZnPc in KBr discs 21 have been presented and theoretical predictions for both molecules have also been published.…”

Section: Introductionmentioning

confidence: 99%

Visible luminescence spectroscopy of free-base and zinc phthalocyanines isolated in cryogenic matrices

Murray

Dozova

Phys. Chem. Chem. Phys.

et al. 2011

The absorption, emission and excitation spectra of ZnPc and H 2 Pc trapped in Ne, N 2 , Ar, Kr and Xe matrices have been recorded in the region of the Q states. A comparison of the matrix fluorescence spectra with Raman spectra recorded in KBr pellets reveals very strong similarities. This is entirely consistent with the selection rules and points to the occurrence of only fundamental vibrational transitions in the emission spectra. Based on this behaviour, the vibronic modes in emission have been assigned using results obtained recently on the ground state with large basis-set DFT calculations [Murray et al. PCCP, 12, 10406 (2010)]. Furthermore, the very strong mirror symmetry between excitation and emission has allowed these assignments to be extended to the excitation (absorption) bands. While this approach works well for ZnPc, coupling between the band origin of the S 2 (Q Y ) state and vibrationally excited levels of S 1 (Q X ), limits the range of its application in H 2 Pc. The Q X /Q Y state coupling is analysed from data obtained from site-selective excitation spectra, revealing pronounced matrix and site effects. From this analysis, the splitting of the Q X and Q Y states has been determined more accurately than in any previous attempts.