Time- and Space-Resolved Spectroscopic Investigation on Pi-Conjugated Nanostructures - 2.

摘要

Highly conjugated pi-molecular systems show attractive semiconducting and optical properties, which makes them highly attractive materials for applications in organic electronic devices and molecular electronics as their optical phenomena may be manipulated in ways not possible with bulk materials. This research investigates photophysical properties of fused linear and macrocyclic porphyrin arrays by integrated time- and space-resolved spectroscopic methodologies to understand the effect of pi-conjugation and molecular structure in excited-state dynamic systems. This is the first study to demonstrate that the electronic deactivation overtakes vibrational relaxation processes in the energy relaxation processes from initially excited vibronic state manifolds in highly conjugated molecular systems. The report also includes an examination of structural properties and fluorescent trapping sites at the single-molecule level. Defocused wide-field fluorescence (DWFI) microscopy suggests that molecular heterogeneities and flexibilities clearly depend on ring size and that site selection for fluorescent trapping is related to the nature of the surrounding chromophore environment. The direct observation of prevailing molecular conformations and the location of fluorescent trapping sites in multichromophoric macrocycles using single-molecule spectroscopic methods provides not only a new level of understanding, but will also stimulate other experimental and computational studies on related multichromophoric systems.