Spin Crossover in a Vacuum-Deposited Submonolayer of a Molecular Iron(II) Complex

Spin-state switching of transition-metal complexes (spin crossover) is sensitive to a variety of tiny perturbations. It is often found to be suppressed for molecules directly adsorbed on solid surfaces. We present X-ray absorption spectroscopy measurements of a submonolayer of [Fe^II(NCS)₂L] (L: 1-{6-[1,1-di­(pyridin-2-yl)­ethyl]-pyridin-2-yl}-<i>N</i>,<i>N</i>-dimethylmethanamine) deposited on a highly oriented pyrolytic graphite substrate in ultrahigh vacuum. These molecules undergo a thermally induced, fully reversible, gradual spin crossover with a transition temperature of <i>T</i>_1/2 = 235(6) K and a transition width of Δ<i>T</i>₈₀ = 115(8) K. Our results show that by using a carbon-based substrate the spin-crossover behavior can be preserved even for molecules that are in direct contact with a solid surface