Electronic absorption, MCD, and luminescence properties of porphyrin J-aggregates

In this paper, we have investigated electronic absorption, magnetic circular dichroism, fluorescence, and phosphorescence spectra for a protonated form of H 2 TPPS 4( H 4 TPPS 4) and the J-aggregates of H 4 TPPS 4. The J-aggregation induces a large red-shift in the B (Soret) and Q absorption bands, while the phosphorescence peaks of H 4 TPPS 4 and its J-aggregates are almost entirely similar. The large red-shift of the B-band is quantitatively explained by the exciton interactions. Thus, the exciton interactions in the J-aggregates are proposed as a useful approach to decrease the energy splitting between the fluorescent and phosphorescent states.

A NOVEL GREEN LONG-LASTING PHOSPHOR Ca2ZnSi2O7:Eu2+

A new green emitting long-lasting phosphor Ca2ZnSi2O7:Eu2+ has been synthesized through the high temperature solid-state method. The excitation spectrum of [Formula: see text] shows a broadband attributed to 8S7/2–4f65d1 transition of Eu2+ ions. Both of the fluorescence and phosphorescence spectra showed a broadband centered at 528 nm, corresponding the only one Ca2+ site in Ca2ZnSi2O7 . The relationship of emission wavelength and Eu–O distance is investigated. Its afterglow can be seen with the naked eye in the dark clearly for 2 h after removal of the excitation source. Oxygen vacancy [Formula: see text] and zinc vacancy [Formula: see text], two different kinds of traps are proposed and their contrary influence on afterglow is discussed.

Distorted forms of metalloporphyrins probed by methods of highly resolved spectroscopy

The spectral manifestations of the distorted forms of sterically unconstrained metallocomplexes of porphyrin in rare gas and Shpol'skii matrices at cryogenic temperatures were detected. The planar and two kinds of distorted conformations of the Mg - and Zn -porphyrins in rare gas matrices have been measured simultaneously in the fluorescence and phosphorescence spectra due to external heavy atom effect. The distinctly different frequencies of the vibronic transitions have been revealed for planar and distorted forms. In the phosphorescence spectra of the Pd -porphyrin the manifestation of the two forms in the ground state has been proven also, with one of them being planar and the other being saddle-type distorted. The ratio of the planar and non-planar forms was shown to depend on the deuteration of both meso-positions of the porphyrin and n-alkane matrix. The appearance of the out-of-plane modes in the phosphorescence spectra of the Pd - and Pt -porphyrin has been demonstrated.

Effect of Substituents on the Viscosity Dependence of Fluorescence and on the S1 - T1 Energy Gap of Donor-Acceptor Substituted Trans-Stilbenes

The dependence of fluorescence quantum yields and S1-lifetimes of donor-acceptor substituted trans-stilbenes on temperature was measured in the temperature range from 298 to 100 K, using solutions of stilbenes in 3-methylpentane (3-MP). Measurements of fluorescence and phosphorescence spectra show that the triplet energy is almost independent of the acceptor. The S1-energy and the S1-T1 energy gap decrease with increasing acceptor strength. For all compounds intersystem crossing (ISC) S1 → T1, is negligible