Excitation energy migration processes in various multi-porphyrin assemblies

Abstract

The electronic interactions and excitation energy transfer (EET) processes of a variety of multi-porphyrin arrays with linear, cyclic and box architectures have been explored. Directly meso-meso linked linear arrays (Z N ) exhibit strong excitonic coupling with an exciton coherence length of approximately 6 porphyrin units, while fused linear arrays (T N ) exhibit extensive p-conjugation over the whole array. The excitonic coherence length in directly linked cyclic porphyrin rings (CZ N ) was determined to be approximately 2.7 porphyrin units by simultaneous analysis of fluorescence intensities and lifetimes at the single-molecule level. By performing transient absorption (TA) and TA anisotropy decay measurements, the EET rates in m-phenylene linked cyclic porphyrin wheels C12ZA and C24ZB were determined to be 4 and 36 ps −1 , respectively. With increasing the size of C N ZA, the EET efficiencies decrease owing to the structural distortions that produce considerable non-radiative decay pathways. Finally, the EET rates of self-assembled porphyrin boxes consisting of directly linked diporphyrins, B1A, B2A and B3A, are 48, 98 and 361 ps −1 , respectively. The EET rates of porphyrin boxes consisting of alkynylenebridged diporphyrins, B2B and B4B, depend on the conformation of building blocks (planar or orthogonal) rather than the length of alkynylene linkers.

Triplet State Delocalization in a Conjugated Porphyrin Dimer Probed by Transient Electron Paramagnetic Resonance Techniques

“… 7 , 8 Porphyrins, which are closely related to the chlorophyll and bacteriochlorophyll molecules found in plants and photosynthetic bacteria, have often been used as building blocks for these materials and have been designed with a wide range of different linkers and linking geometries. 9 − 16 Electronic π-conjugation, the fundamental phenomenon required for most applications, has been investigated in porphyrin chain systems using many different techniques, including electron paramagnetic resonance (EPR). 13 , 14 , 17 − 26 …”

Tracing coherences of quantum states by ultrafast laser spectroscopy

“…Additionally, the approach has already been used while analyzing exciton coherence in the bacterial light harvesting complex LH1 and reaction center of Photosystem II, thin film and crystalline C60, as well as conjugate polymers [59]. Recently, it has also been used while studying artificial lightharvesting aggregates of porphyrin [62][63][64][65].…”

Panchromatic light funneling through the synergy in hexabenzocoronene–(metallo)porphyrin–fullerene assemblies to realize the separation of charges

“…[20][21][22][23][24][25][26] Porphyrin (homo/hetero) dimers linked by p-conjugated oligomeric bridges have been studied extensively, not only with regard to their spectroscopic properties, but also to their propensity to build supramolecular architectures and mediate charge transport between different porphyrins. [27][28][29][30][31][32][33][34][35][36][37] Another way of tailoring porphyrins is to couple polycyclic aromatic hydrocarbons, PAHs, directly to the porphyrin core (e.g. tetraphenylporphyrins, TPPs).…”