The stable structure and photophysical properties of a Schiff base Pt(II) foldamer was experimentally examined via spectroscopic techniques and X-ray crystallographic analysis. The influence of solid photoluminescence of the Schiff base Pt(II) foldamer was evaluated by comparing microcrystals with poly(4-vinylpyridine) matrix.
A series of bis(tridentate Schiff base platinum) complex (Pt2L2) linked with 2-methylenepropane-1,3-diyl were synthesized, and their photophysical properties were examined to analyze different solid states. X-ray crystallographic analysis indicated that Pt2L2 containing 4-vinylpyridine (Pt2L24VP) as a ligand had a helically-folded structure. It caused upfield chemical shifts and a redshift in UV-Vis absorption spectra compared to the analogous mononuclear complex. Pt2L2 containing dimethylsulfoxide (Pt2L2DMSO) had no such helically-folded structure due to the steric repulsion of DMSO. Pt2L24VP did not exhibit solid photoluminescence owing to the crystal packing. The mixture of poly(4-vinylpyridine) (P4VP) and Pt2L2DMSO (Pt2L2DMSO−P4VP) showed a similar redshift in UV-Vis absorption and excitation spectra to Pt2L24VP, implying the helically-folded structure of Pt2L2 with P4VP coordination. The Pt2L2DMSO−P4VP exhibited solid photoluminescence with a longer phosphorescence lifetime (2.4 μs) than the Pt2L24VP crystals (0.5 μs), indicating regulated aggregation of the Pt2L2 frames in the P4VP matrix.Zum Volltext