Investigation and Control of Single Molecular Structures of meso-meso Linked Long Porphyrin Arrays.

We have investigated conformational structures of meso-meso linked porphyrin arrays (Zn) by single molecule fluorescence spectroscopy. Modulation depths (M values) were measured by excitation polarization fluorescence spectroscopy. The M value decreases from 0.85 to 0.46 as the number of porphyrin units increases from 3 to 128, indicating that longer arrays exhibit coiled structures. Such conformational changes depending on the length have been confirmed by coarse-grained simulation. The histograms of M values and traces of centroid position of emitting sites by localization microscopy showed that the structures of longer arrays changed to more stretched after solvent vapor annealing with tetrahydrofuran.