The magnetic and structural elucidation of 3,5-bis(2-pyridyl)-1,2,4-triazolate-bridged dinuclear iron(II) spin crossover compounds |
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| Institution: | 1. School of Chemistry, Monash University, Building 23, Clayton, Vic. 3800, Australia;2. School of Physics, Monash University, Building 27, Clayton, Vic. 3800, Australia |
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| Abstract: | Variable temperature magnetic susceptibility, Mössbauer spectroscopic and X-ray crystallographic studies are described on two structurally similar families of dinuclear iron(II) spin crossover (SCO) complexes of formula Fe(NCX)(py)]2(μ-L)2, where L is either a 3,5-bis(2-pyridyl)-pyrazolate bridging ligand, bpypz?, examples of which have been earlier reported by Kaizaki and coworkers, or a corresponding 3,5-bis(2-pyridyl)-1,2,4-triazolate, bpytz?. Compounds synthesised were Fe(NCS)(py)]2(μ-bpypz)2 (1), Fe(NCSe)(py)]2(μ-bpypz)2 (2), Fe(NCS)(py)]2(μ-bpytz)2 (3), Fe(NCSe)(py)]2(μ-bpytz)2 (4), Fe(NCBH3)(py)]2(μ-bpytz)2 (5). The crystal and molecular structures of 1 and 3 are very similar in their HS–HS forms (HS = high spin d6). In contrast to reported SCO behaviour for precipitated samples of 1, also repeated here, crystals of 1 show only HS–HS behaviour with no spin crossover transition. Complex 3 likewise displays HS–HS magnetism, with very weak antiferromagnetic coupling. Compound 5 displays a well resolved two-step, full spin transition from HS–HS to LS–LS states while compound 2 shows a one step transition. The Mössbauer data for 2 and 5 show unusual features at low temperatures. |
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