Interplay between Dopant Species and a Spin-Crossover Host Lattice during Light-Induced Excited-Spin-State Trapping Probed by Electron Paramagnetic Resonance Spectroscopy

Q-band electron paramagnetic resonance (EPR) data conclusively demonstrate that the iron and cobalt centers in the solid solution [Fe(bpp)₂]₀.₉₇[Co(terpy)₂]₀.₀₃[BF₄]₂ (bpp = 2,6-dipyrazol-1-ylpyridine) undergo allosteric spin-state switching during light-induced excited-spin-state trapping (LIESST) at 20 K and thermal relaxation around 80 K. EPR of [Cu(terpy)₂]²⁺ and [Cu(bpp)₂]²⁺, doped into the same host lattice, also indicates expansion of the copper coordination sphere during LIESST excitation