Spin-crossover phenomenon of the assembled iron complexes with 1,2-bis(4-pyridyl)ethane as bridging ligand studied by Mössbauer spectroscopy.

The transition temperatures between high- and low-spin states of the assembled spin-crossover complexes, Fe(NCX)2(bpa)2(guest) (X = S, Se, BH3; bpa = 1,2-bis(4-pyridyl)ethane; guest = biphenyl, 2-nitrobiphenyl, diphenylmethane, or 1,4-dichlorobenzene), were compared with the Mössbauer parameters. The transition temperature increases when the QS value of FeII high-spin state becomes small. The transition temperature also increases by changing the anion from NCS to NCSe and then to NCBH3. [ABSTRACT FROM AUTHOR]