Self-assembled nanoscale photomimetic models: structure and related dynamics

Abstract

Using static and time-resolved measurements, dynamics of non-radiative relaxation processes have been studied in self-assembled porphyrin triads of various geometry, containing the main biomimetic components, Zn-porphyrin di mers, free-base extra-ligands (porphyrin, chlorin or tetrahydroporphyrin), and electron acceptors A (quinone or pyromellitimide). The strong quenching of the dimer fluorescence is due to energy and sequential electron transfer (ET) processes to the extra-ligand (~0.9-1.7 ps), which are faster than a slower ET (34-135 ps) from the dimer to covalently linked A in toluene at 293 K. The extra-ligand Si -state decay (sS = 940-2670 ps) is governed by competing processes: a bridge (dimer) mediated long-range (rDA = 18-24 A) superexchange ET to an acceptor, and photoinduced hole transfer from the excited extra-ligand to the dimer followed by possible superexchange ET steps to low-lying charge transfer states of the triads. The subsequent ET steps dimer ! monomer ! A taking place in the triads, mimic the sequence of primary ET reactions in photosynthetic reaction centers in vivo.

Multistep photoinduced electron transfer in self-organised nanoscale porphyrin triads

“…2). The detailed analysis of femtosecond spectral-kinetic data (presented in our forthcoming papers [11,12]) shows that the formation of charge transfer (CT) states could be appropriately detected, and the primary fast deactivation of the locally excited S 1 -states of interacting subunits (the dimer and extra-ligand) is caused by the competition between the energy migration and sequential electron=hole transfer.…”

Deactivation of Excited States in Nanostructures Containing Cu-Porphyrin Subunit

“…The "keylock" principle is based on the complexation of central Zn ions of porphyrin chemical dimers or trimers with suitable extra-ligands (tetrapyridyl substituted tetrapyrrolic macrocycles, in our case) via two-fold non-covalent coordination. [74,77,[81][82][83][84] One principal moment should be taken into account in this case: the matching geometry between nitrogen atoms in meso-pyridyl containing extra-ligands and Zn-Zn distance in the dimers and trimers plays the essential role in the formation of triads and pentads with relatively well-defined conformational rigidity. [74,77,80] The structure of the complexes under discussion will be shown below.…”

Laser Confocal and Spatially-Resolved Fluorescence Spectroscopy of Porphyrin Distribution on Plasma Deposited Polymer Films

“…These values are typical for monomeric porphyrins of various types in liquid solvents in the presence of dissolved oxygen. [12,13,36,38] This situation may be explained by two ways: i) TAPP molecules are in monomeric form presumably in the spot; ii) there is a distribution of monomers and aggregates in the spot, but intercenter monomer-aggregate distances are relatively large and the effective energy transfer "monomer®aggregate" does not realise. The statistical analysis of time-correlated single photon counting measurements being obtained for various spots and concentrations of TAPP and DAPEP molecules on PP surface is under the way.…”

“…At present, synthetic porphyrins and phthalocyanines being fixed on synthetic polymer carries by various methods [1][2][3][4][5][6][7][8] or being polymers themselves [9][10][11][12] are the subject of interest both as model compounds of natural polymer-bonded tetrapyrroles (chlorophyll, hemoglobin, cytochrome), [13][14][15][16][17][18][19] new biological and catalytically active materials [2][3][4][5] as well as modified membranes and sensors. [20][21][22][23][24] The fixation of porphyrins on polymer carrier allows to realize some advantages which are absent when using nonbonded porphyrins.…”