Magnetic circular dichroism and absorption spectrum of zinc phthalocyanine in an argon matrix between 14700 and 74000 cm-1

Abstract

Fund, and the allocation of computer time from the Computer Center of the University of New Brunswick. functional approximation used in the computations. There are very few computations for arene-metal complexes that are of sufficient quality to predict their bond and total energies accurately. In order to determine whether the LCAO-LSD method can generally predict these properties, more computations on a whole series of arene-metal compounds must be performed and compared with accurate experimental data.The magnetic circular dichroism (MCD) and absorption spectra of zinc phthalocyanine (ZnPc) isolated in an Ar matrix have been studied over the range 14700-74000 cm-I. Synchrotron radiation, from the electron storage ring at the Synchrotron Radiation Center, Madison, WI, was used for energies above 33 000 cm-I. The spectra are well resolved, and the MCD permits the determination of excited-state magnetic moments. There is strong evidence that the Pc rings are preferentially oriented with the molecular planes parallel to the deposition window. The data can be reasonably correlated with the old Peel calculation of Henriksson et al., but there is a compelling need for a new calculation that extends to higher energy and includes extensive configuration interaction. (4) Bondybey, V. E.; English, J. H. J . Am. Chem. SOC. 1979, 101, (5) Huang, T. H.; Reickhoff, K. E.; Voigt, E. M. J. Chem. Phys. 1982, (6) Huang, T. H.; Rieckhoff, K. E.; Voigt, E. M.

Laser-Desorption Supersonic Jet Spectroscopy of Phthalocyanines

“…In the Shpol'skii excitation spectra of H 2 Pc, MgPc, and ZnPc, Huang et al (7) observed intense broad structures in the 1600-cm Ϫ1 region which they assigned to a 1 (n*) state of A 2u symmetry. In the MCD spectrum of ZnPc in an argon matrix (8), an underlying electronic transition was also observed in this region of the Q band, the MCD of which was consistent with the assignment of Huang et al In the jet spectrum of H 2 Pc, Fitch et al (3) also observed a region of congested vibronic structure at about 1600 cm Ϫ1 above the origin, which they attributed to the onset of the S 1 y state. However, this may in fact be due to the QЈ state, with the onset of the S 1 y state corresponding to another region of dense vibronic structure at about 1000 cm Ϫ1 , as discussed below.…”

“…The transition at 103 cm Ϫ1 in ZnPc (94 cm Ϫ1 in H 2 Pc) cannot be accounted for in terms of vibronic coupling between the S 1 and S 2 states, and we must invoke another intensity-lending state, the so-called QЈ state. There is evidence from low-temperature matrix studies (7,8) for the existence of the QЈ state, a 1 (n*)…”

“…On this basis, the vibronic intervals observed are plausibly similar to those in the S 1 x spectrum. The spectrum is rather weak compared with that of S 1 ; this indicates a substantially lower fluorescence quantum yield, since the oscillator strength of the S 2 -S 0 transition is expected to be greater than that of S 1 -S 0 (2,8). The linewidth of the vibronic transitions in this region is ca.…”

“…Bondybey and English (6) reported the fluorescence excitation and emission spectra of H 2 Pc in an argon matrix at 4.2 K; Huang et al (7) reported fluorescence excitation and emission spectra of several phthalocyanines in Shpol'skii matrices at 4.2 K; and VanCott et al (8) reported magnetic circular dichroism and absorption spectra of ZnPc in an argon matrix at 5 K. These spectra are considerably more complex than the jet spectra. Multiple 0 0 0 transitions are observed as a result of multiple site occupancy; the 0 0 0 transitions of the metallophthalocyanines are split into doublets by the crystal field stabilized Jahn-Teller effect; and the 0 0 0 of H 2 Pc is split because of the existence of two tautomeric forms.…”

Ground and excited states of zinc phthalocyanine, zinc tetrabenzoporphyrin, and azaporphyrin analogs using DFT and TDDFT with Franck-Condon analysis

“…[14][15][16] There have been ZnPc studies proposing a symmetry forbidden n-π * transition blue-shifted from the highest energy states of the Q band region. [17][18][19][20] Even though the additional assignments in the first four bands have been debated in literature, Gouterman and Edwards made a key observation in 1970. They noted that the Q band, in particular, would be subject to Franck-Condon (FC) [21][22][23] vibrational displacement, and point to an earlier publication by Gouterman and Fulton, in which the higher energy bands were believed to take on much more peculiar shapes, especially at the investigated temperature of 0 K. 24 Some believe the four orbital model is simplistic, but the framework is generally still reliable for the major transitions, and is used in this present work.…”