Phosphorescence and Fluorescence of Phthalocyanines

Abstract

For the first time, phosphorescence has been observed from and clearly assigned to the molecular triplet of several metallophthalocyanine (Pc) molecules. The Pc's of Pt, Pd, Cu, Zn, and Cd have O–O bands in solution (77°K) at the extraordinarily low energies of 10 590, 10 100, 9390, 9150, and 9120 cm−1, respectively, while those of Mg and VO have possible transitions at ∼9000 and 8500–8800 cm−1. Half-widths, lifetimes, approximate quantum efficiencies, triplet absorption, and excitation spectra, and vibrational substructure are reported, together with oxygenation and heavy atom effects. The lifetimes were very short (varying from 1 msec to less than 3 μsec), so room temperature phosphorescence was seen, as was radiation from the separate triplet sublevels at 4°K and below. Yields were very low (∼10−2 to ∼10−5) because of very strong radiationless transitions, and various other Pc complexes did not seem to phosphoresce at all. Both tripdoublet and quartet luminescence were seen from CuPc, and the intersystem crossing time was estimated to be ∼1 nsec. Fluorescence is reported from several of the complexes, including PdPc.

Single-Molecule Investigation of Energy Dynamics in a Coupled Plasmon-Exciton System

“…The I/I0 spectra of MgPc shows only one doubly-degenerate molecular resonance at 1.89 eV (Q state), which is between the Qx (1.81 eV) and Qy (1.92 eV) states of H2Pc. This observation is consistent with the four-fold molecular symmetry and the previously results of conventional spectroscopy 28 . The apparently symmetric dip structure in the I/I0 spectrum of MgPc is reasonable in the coupled plasmonexciton system 2,6-8 where the interference condition depends on the relative energy of the plasmon and exciton 6 .…”

Decorating graphene nanosheets with electron accepting pyridyl-phthalocyanines

“…The quantum yields are 0.23, 0.18, and 0.12 for 1, 2, and 3, respectively, and slightly lower than the quantum yield of 0.3 seen for the ZnPc reference. 52 As a complement, Time-Correlated Single Photon Counting (TCSPC) measurements were performed following 403 nm excitation - Fig. S1 in the ESI.…”

Coherent control of biomolecules

“…This difference explains the shift of the maximum of the ESA signal in the blue region of the measured spectrum, which is due to the decay of population in the S 1 state, concurrent with the population growth in the T 1 state. The 2.8 ns lifetime of the S 1 state determined from the fit matches well with previous studies [128,137,155], and the effective fluorescence lifetime measured in this study. The position found for the SE spectrum is red shifted by 8 nm, with respect to the peak of the bleach (672 nm), congruent with the Stokes shift found in the steady-state fluorescence measurements.…”

“…Several experimental studies on the photophysics of ZnPc and similar compounds (derivatives or different metallophthalocyanines) in solution have been reported [130][131][132][133][134][135][136][137][138][139][140][141], but so far the results fail to depict a coherent picture of the overall photophysics. The generally accepted energy-flow model includes three major intramolecular relaxation pathways from the initially excited S 1 state.…”