Abstract
The investigation of new spin-crossover (SCO) compounds plays an important role in understanding the key design factors involved, informing the synthesis of materials for future applications in electronic and sensing devices. In this report, three bis-bidentate ligands were synthesized by Schiff base condensation of imidazole-4-carbaldehyde with 4,4-diaminodiphenylmethane (L1), 4,4′-diaminodiphenyl sulfide (L2) and 4,4′-diaminodiphenyl ether (L3) respectively. Their dinuclear Fe(II) triple helicates were obtained by complexation with Fe(BF4)2·6H2O in acetonitrile. The aim of this study was to examine the influence of the steric nature of the ligand central atom (–X–, where X = CH2, S or O) on the spin-crossover profile of the compound. The magnetic behaviours of these compounds were investigated and subsequently correlated to the structural information from single-crystal X-ray crystallographic experiments. All compounds [Fe2(L1)3](BF4)2 (1), [Fe2(L2)3](BF4)2 (2) and [Fe2(L3)3](BF4)2 (3), demonstrated approximately half-spin transitions, with T1/2 values of 155, 115 and 150 K respectively, corresponding to one high-spin (HS) and one low-spin (LS) Fe(II) centre in a [LS–HS] state at 50 K. This was also confirmed by crystallographic studies, for example, bond lengths and the octahedral distortion parameter (∑) at 100 K. The three-dimensional arrangement of the HS and LS Fe(II) centres throughout the crystal lattice was different for the three compounds, and differing extents of intermolecular interactions between BF4− counter ions and imidazole N–H were present. The three compounds displayed similar spin-transition profiles, with 2 (–S–) possessing the steepest nature. The shape of the spin transition can be altered in this manner, and this is likely due to the subtle effects that the steric nature of the central atom has on the crystal packing (and thus inter-helical Fe–Fe separation), intermolecular interactions and Fe–Fe intra-helical separations.
Highlights
The design of new spin-crossover (SCO) coordination complexes is a challenge at the forefront of the field of magnetic molecular materials [1,2,3,4,5,6]
The ability to understand and control the SCO properties of molecular materials has been of ongoing interest and research
Spin transition is generally observed in first-row transition metal coordination complexes with electronic configurations in the range d4 –d7 [9,10]
Summary
The design of new spin-crossover (SCO) coordination complexes is a challenge at the forefront of the field of magnetic molecular materials [1,2,3,4,5,6]. Spin transition is generally observed in first-row transition metal coordination complexes with electronic configurations in the range d4 –d7 [9,10]. These transitions produce a change in the magnetic, optical and structural properties of the material.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
