Electronic communication between fluorescent pyrene excimers and spin crossover complexes in nanocomposite particles

Abstract

Bistable [Fe(H-trz)₂(trz)]BF₄ core and silica shell hybrid nanoparticles with different sizes between 50–150 nm were grafted with a pyrene-derivative fluorophore. The fluorescent composites exhibited both monomer and excimer luminescence (with a controllable ratio), whilst their spin transition properties remained unaltered. When switching the particles from the diamagnetic to the paramagnetic state the excimer lifetime and luminescence intensity increased and the emission spectra were redshifted, while the monomer emission exhibited negligible spin-state dependence. The strong coupling of the pyrene excimers with the spin-state of the ferrous ions was shown to occur via a non-radiative mechanism, brought about, to a large extent, by the spin transition induced mechanical strain.