Excitonic Coupling Strength and Coherence Length in the Singlet and Triplet Excited States of meso–meso Directly Linked Zn(II)porphyrin Arrays

Abstract

Excitation-energy transport (EET) phenomena in meso-meso directly linked Zn(II)porphyrin arrays in the singlet and triplet excited states were investigated with a view to electronic coupling strength and coherence length by steady-state and time-resolved spectroscopic measurements. To investigate energy transfer in the triplet states, we modified the Zn(II)porphyrin arrays with bromo substituents at both ends. The coupling strength of the Soret bands of the arrays was estimated to be about 2200 cm-1, and that of the Q bands is about 570 cm-1. The coherence length in the S1 state of the Zn(II)porphyrin arrays was determined to be 4-5 porphyrin units, which is comparable to that of the well-ordered two-dimensional circular structure B850 in the peripheral light-harvesting antenna (LH2) in photosynthetic purple bacteria. This indicates that the Zn(II)porphyrin arrays are well suited for mimicking natural light-harvesting antenna complexes. On the other hand, the rate of energy transfer in the triplet state is estimated to be on the order of 100 microseconds-1, and the very weak coupling between the triplet states (ca. 0.003 cm-1), indicates that the triplet excitation energy is essentially localized on a single porphyrin moiety.

Intramolecular and intermolecular energy transfers in donor-acceptor linear porphyrin arrays

“…570 cm −1 from the absorption spectra. 41 Close inspection of the absorption and emission spectra shows that the pattern observed for the B …”

Self-assembly and photoconductivity of binary porphyrin nanostructures of meso -tetrakis(4-sulfonatophenyl)porphine and Co(III) meso -tetra(4-pyridyl)porphine chloride

“…Investigations of the electronic properties of porphyrin tectonic matter can help in understanding and utilizing the electronic transport in these nanoscale materials for the development of biomimicking nanoarchitectonics in the fields of photo(electro)catalysis [34][35][36][37][38], sensors [39,40], and organic photoconducting materials [41][42][43]. In this regard, we report on the self-assembly, morphological, spectral, and photoconductivity properties of binary nanostructures in the system of water-soluble porphyrins: meso-tetrakis(4sulfonatophenyl)porphine and Co(III) meso-tetra(4-pyridyl)porphine chloride.…”

A nonpolymeric highly emissive ESIPT organogelator with neither dendritic structures nor long alkyl/alkoxy chains

“…Long-range ordering in well-defined aggregates of p-conjugated structures is crucial for carrier transport in organic electronic devices, [1][2][3][4] as well as for efficient light harvesting [5][6][7][8][9][10] in artificial antenna systems. Controlling the molecular alignments into ordered self-assemblies at nano or micro scales has attracted considerable interest in promoting the well-known bottom-up technology in organic electronics.…”