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An investigation on the excited state dynamics and two-photon absorption properties of four novel linked porphyrin dimers in toluene is presented. The results indicate that the fused porphyrin dimers exhibit extremely increased two-photon absorption cross-section values (12000-15000 GM) porphyrin monomers owing to much enhanced pi-electron delocalization throughout the porphyrin dimers ring.

The photoinduced energy transfer processes in 1,4-phenylene, 1,3-phenylene, 1,2-phenylene, and 4,4'-bi-phenylene-linked and directly-linked zinc(II) free-base porphyrins heterodimers in THF were investigated by femtosecond transient absorption spectroscopy. The results indicate that even for the covalently-linked models the relative contribution of the through-space Coulombic interaction becomes increasingly important upon the decrease of the center-to-center separation.

Time-resolved fluorescence and transient absorption techniques are used to investigate the energy relaxation dynamics of the photoexcited [2+2]-bridged C60 dimer in 0-dichlorobenzene. The absorption and fluorescence spectra of the C60 dimer show that the monomeric moieties of C60 are only weakly interacting with each other, which indicates that the C60 dimer can be considered as a nearly decoupled bichromophoric molecular system in the ground state.

The ensemble and single-molecule spectroscopy technique is employed to explain the molecular structures and photophysical properties of the zinc(II) porphyrin dendrimers with and without guest binding. The analysis reveals that the use of appropriate bidentate guests can easily help in controlling the porphyrin dendritic structures in poor environmental conditions.

The studies of two-photon absorption (TPA) phenomena of a series of single-strand as well as supramolecular self-assembled ladders and prisms of highly conjugated ethyne bridged multiporphyrin dimer, trimer, and star shaped pentamer are described. The results suggested that the TPA maximum position is determined by the [pi]-delocalization pathway and the TPA property of the pentamer arise from its basic trimer unit rather than the entire molecule.

The excitation energy transfer process of meso-meso linked zinc(II) porphyrin arrays are examined by using the on-the-fly filtered propagator path integral method. The studies have shown that the coherence length is the result of electronic and environmental effect rather than the structure disorder.

The article presents the synthesis, STM detection and the efficient energy hopping (EEH) in near-infrared region of cyclic and hexagonal prismatic porphyrin arrays. Two-dimensional cyclic arrays are found to be excellent for EEH processes for artificial biomimic light harvesting apparatus.

The unusual proximity of the porphyrin units through meso-meso direct linkage and the dihedral angel change between the porphyrin units exhibit new electronic absorptions due to strong orbital interactions. It is found that most orbital overlap occurred at the C(sub alpha) and C(sub beta) positions in the charge resonance transition and the vibration modes involving the v(C(sub aplha)C(sub beta)) and v(C(sub(beta)(Sub beta)) motions are dominantly enhanced by excitation of the charge resonance transition.

Intramolecular charge transfer (ICT) processes in two-photon (TP) allowed states were investigated using three pyrene derivatives N1, N2C, and N2T, which have different molecular symmetry depending on the number and position of N,N-dimethylaniline donating substituents. On the basis of steady-state and nondegenerate two-photon absorption measurements, we investigated femtosecond transient absorption (TA) spectra by one-photon (OPE) and two-photon excitation (TPE). In the analysis of TA spectra, we discovered that the transfer rate from locally excited state to the ICT state by TPE is slower than that by OPE, indicating that the energy barrier between the TP and ICT states is higher than that between the one-photon (OP) allowed and ICT states. Furthermore, we demonstrated that ICT dynamics in a TP state are affected by molecular symmetry through the disappearance of stimulated emission from the locally excited state in the TA spectra of N2T obtained by TPE. We believe that our findings will provide fundamental information for a better understanding of excited-state ICT dynamics. [ABSTRACT FROM AUTHOR]