Excitation wavelength-dependent EPR study on the influence of the conformation of multiporphyrin arrays on triplet state delocalization

The optoelectronic properties of conjugated porphyrin arrays render them excellent candidates for use in a variety of molecular electronic devices. Understanding the factors controlling the electron delocalization in these systems is important for further developments in this field. Here, we use transient EPR and ENDOR (Electron Nuclear Double Resonance) to study the extent of electronic delocalization in the photoexcited triplet states of a series of butadiyne-linked porphyrin oligomers. We are able to distinguish between planar and twisted arrangements of adjacent porphyrin units, as the different conformations are preferentially excited at different wavelengths in the visible range. We show that the extent of triplet state delocalization is modulated by the torsional angle between the porphyrins and therefore by the excitation wavelength. These results have implications for the design of supramolecular systems with fine-tuned excitonic interactions and for the control of charge transport.

The 3D [(Cu2Br2){μ-EtS(CH2)4SEt}]n material: a rare example of a coordination polymer exhibiting triplet–triplet annihilation

A very rare case of excitation energy migration has been observed for an inorganic material.

A bifurcated molecular pentad capable of sequential electronic energy transfer and intramolecular charge transfer

The title compound absorbs strongly over much of the solar range and undergoes a variety of photophysical events under illumination.

Molecular tweezer based on zinc porphyrin-substituted diarylethene

A molecular tweezer, zinc porphyrin-dithienylethene-zinc porphyrin (ZnP-DTE-ZnP) triad, has been prepared. Triad ZnPor-DTE-ZnPor showed a little electronic communication among the chromophores judged from the comparison of the steady-state absorption and fluorescence spectra for triads and their component compounds. Irradiation of ZnPor-DTE-ZnPor with UV light converts dithienylethene moiety from open form to closed form. The complexation of ZnP-DTE-ZnP with 4,4'-bipyridyl were investigated by absorption and fluorescence spectroscopic measurements. ZnP-DTE-ZnP forms a 1:1 complex with 4,4'-bipyridyl. The stability constants of log K=4.0 and 4.2 mol(-1)dm3 were determined by absorption and fluorescence spectral changes, respectively.

Large Two-Photon Absorption (TPA) Cross-Section of Directly Linked Fused Diporphyrins

The excited state dynamics and two-photon absorption properties of four novel triply linked porphyrin dimers in toluene have been investigated. The fused porphyrin dimers exhibit extremely increased two-photon absorption cross-section values (12,000-15,000 GM) compared with porphyrin monomers owing to much enhanced pi-electron delocalization throughout the porphyrin dimer ring.