Iron(II) and 1,1,1-Tris(2-pyridyl)nonadecane Complex Showing an Order–Disorder-Type Structural Transition and Spin-Crossover Synchronized over Both Conformers

The title compound (Me4N)[Fe{(2-py)3C-n-C18H37}(NCS)3] having a C18 chain underwent spin-crossover (SCO). There are two crystallographically independent molecules in a triclinic cell at 100 K but only one in a monoclinic cell at 300 K. The complex showed a gradual one-step SCO in the same temperature region as that of the structural transition. The SCO is supported with the 57Fe Mossbauer spectroscopy. The molecules are differentiated on cooling, but the SCO was synchronized.