Synthesis and UV-light induced oligomerization of a benzofulvene-based neutral platinum(II) complex

Neutral platinum(II) complex 2-PTPC-BF3a was easily prepared from benzofulvene derivative 2-Pyr-BF3a in order to evaluate the effects in the aggregation/polymerization behavior of a bulky substituent capable of establishing intermolecular metal-metal interactions in the close proximity of the putative polymerization center. Complex 2-PTPC-BF3a was found to aggregate into an ordered crystalline solid-state without significant spontaneous polymerization, but the UV-light irradiation of its dispersions in chloroform produced corresponding oligomers, which were characterized by NMR spectroscopy and MALDI-TOF mass spectrometry. On the other hand, the UV-irradiation of the platinum complex in the solid-state produced different results probably depending on the aggregate architecture. Notably, the crystalline films deposited from THF solutions on quartz substrates showed weak emissions, which progressively increased upon irradiation with the formation of oligomers devoid of the aggregation-induced quenching sites that seemed to affect the emission of poly-2-PTPC-BF3a. Finally, DFT calculations were performed on platinum complex 2-PTPC-BF3a in the aim of rationalizing the observed photophysical features.