Spin Transition Charted in a Fluorophore-Tagged Thermochromic Dinuclear Iron(II) Complex

The first crystal structures of a dinuclear iron(II) complex with three N1,N2-1,2,4-triazole bridges in the high-spin and low-spin states are reported. Its sharp spin transition, which was probed using X-ray, calorimetric, magnetic, and Fe-57 Mossbauer analyses, is also delineated in the crystalline state by variable-temperature fluorimetry for the first time.