Experimental and TheoreticalStudy on the PhotophysicalProperties of 90° and 60° Bimetallic Platinum Complexes.

The 90° and 60° bimetallic platinum complexeswith specialstructures are widely used in coordination-driven self-assembled metallosupramoleculararchitectures, and these complexes are the key components of triangular,rectangular, and polygonal metallacycle and metallocage supramolecules.Therefore, spectroscopic techniques and quantum chemistry calculationswere employed in this article to investigate the photophysical propertiesof these bimetallic platinum complexes. Compared with spectra forthe ligands, the absorption spectra of these Pt complexes are red-shifted,and the fluorescence spectra become wider and are also red-shifted.Moreover, the reasons for the low fluorescence quantum yields andshort fluorescence lifetimes of these compounds were investigatedusing quantum chemistry calculations. We demonstrate that the fluorescentstates of the bimetallic platinum complexes can be considered as localexcited states, and that they possess a ligand-centered π–π*transition feature. Meanwhile, the platinum metals act as perturbationfor these transitions, whereas the nonfluorescent states are classifiedas intramolecular charge-transfer states. Furthermore, a new fluorescencemodulation mechanism is developed to explain the different emissionprocesses of these complexes with different ligands. [ABSTRACT FROM AUTHOR]