Monitoring spin-crossover phenomena via Re(I) luminescence in hybrid Fe(II) silica coated nanoparticles

Bare (1) and silica coated (1@SiO2) spin crossover (SCO) nanoparticles based on the polymer {[Fe(NH(2)Trz)(3)](BF4)(2)}(n) have been prepared following a water-in-oil synthetic procedure. For 1, the critical temperatures of the spin transition are T-C down arrow = 214.6 K and T-C up arrow = 220.9 K. For 1@SiO2, the abruptness of the transition is enhanced and the critical temperatures are centred at room temperature (T-C down arrow = 292.1 K and T-C up arrow = 296.3 K). An inert Re(I) complex of formula [Re(phen)(CO)(3)(PETES)](PF6) (phen = 1, 10-phenanthroline; PETES = 2(4-pyridylethyl)triethoxysilane) (Re) was also synthesized yielding intense green emission centred at lambda(em) = 560 nm. The grafting of this complex on the silica shell of 1@SiO2 led to a bifunctional SCO-luminescence composite (1@SiO2/Re) whose luminescence properties were tuned by the spin state switching. Temperature-variable photophysical studies showed that luminescence and spin transition were synchronized through a radiative (trivial) energy transfer mechanism between the Re(I) and the Fe(II)-LS (LS, Low Spin) centres.

Automated summary

Nanoparticles based on polymer were prepared, with the silica-coated ones showing enhanced abruptness of spin transition. A Re(I) complex with intense green emission was synthesized, and its grafting onto the silica shell led to a bifunctional SCO-luminescence composite whose properties were tuned by spin state switching. Photophysical studies demonstrated synchronized luminescence and spin transition through a radiative energy transfer mechanism between different centers.