Persistent spectral hole‐burning study on dendrimer porphyrins

Abstract

We report the first results of persistent spectral hole burning of dendrimer porphyrins having three‐, four‐, or five‐layered aryl ether dendritic arrays. We evaluate structural relaxations of dendrimer framework around the porphyrin core at low temperatures. A large environmental change around the porphyrin core, as evaluated from the hole area, was suppressed in dendrimer porphyrins of higher generation numbers, whereas a small environmental change, as evaluated from hole width, showed no dependence on the number of generations. The dendrimer porphyrins showed sharp holes at 20 K, suggesting a long dephasing time and the suppression of spontaneous spectral diffusion. The results of dendrimer‐embedded polymer sample indicated that the structural relaxation of polymer chain outside the dendrimer does not have an influence on the resonant frequency of the porphyrin core. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 210–215, 2002

Nanoscopic Aggregation in Random Copolymer Bulk Films Studied with Photochemical Hole Burning and Transmission Electron Microscopy

“…12b The effective distance within which the porphyrin molecule can sense the structural relaxation of surrounding polymer chains was also ascertained to be 2.5 nm by PHB of dendrimers with a TPP core. 17 We confirmed that PHB is very useful for studying the nanoenvironments around the chromophores. The nanoscopic aggregation in bulk films of the amphiphilic random copolymers already reported by TEM 11 has been recently confirmed by PHB temperature cycle experiments.…”

“…The hole widths of the unimers in PVA were independent of the unimers radii, which suggested the structural relaxation detected by PHB temperature cycle experiments was effective within 2.3 nm 12b. The effective distance within which the porphyrin molecule can sense the structural relaxation of surrounding polymer chains was also ascertained to be 2.5 nm by PHB of dendrimers with a TPP core . We confirmed that PHB is very useful for studying the nanoenvironments around the chromophores.…”

Porphyrin-Cored 2,2-Bis(methylol)propionic Acid Dendrimers

“…The studies have dealt with for example light harvesting, 21,26,27 energy transfer, 8,28-31 and site isolation. 3,15,[32][33][34][35][36] A large number of different dendrimers 26,[28][29][30][37][38][39] have been utilized, ranging from Fre ´chet-type benzyl ether dendrimers 35,[40][41][42][43] to glutamic dendrimers. 15,36,44 Very little work has been conducted with the bis-MPA (2,2-bis(methylol)propionic acid) repeating unit.…”