Remarkable Steric Effects and Influence of Monodentate Axial Ligands L on the Spin-Crossover Properties of trans-[FeII(N4 ligand)L] Complexes
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- 作者：José ; Sá ; nchez Costa ; Kristian Lappalainen ; Graham de Ruiter ; Manuel Quesada ; Jinkui Tang ; Ilpo Mutikainen ; Urho Turpeinen ; C. Matthias Grunert ; Philipp Gü ; tlich ; Hanane Zhor Lazar ; Je
- 刊名：Inorganic Chemistry
- 出版年：2007
- 出版时间：May 14, 2007
- 年：2007
- 卷：46
- 期：10
- 页码：Gütlich, Hanane
- 全文大小：343K
- 年卷期：v.46,no.10(May 14, 2007)
- ISSN：1520-510X
文摘
Iron(II) complexes obtained from tetradentate, rigid, linear N4 ligands have been investigated to appraise the influenceof steric effects and the impact of trans-coordinated anions on the spin-transition behavior. As expected, the well-designed ligands embrace the metal center, resulting in octahedral iron(II) complexes where the basal plane is fullyoccupied by the pyridine/pyrazole N4 ligand, while anions or solvent molecules are exclusively axially coordinated.Precursor complexes, namely, [Fe(bpzbpy)(MeOH)2](BF4)2 (where bpzbpy symbolizes the ligand 6,6'-bis(N-pyrazolylmethyl)-2,2'-bipyridine) and [Fe(mbpzbpy)(MeOH)2](BF4)2 (where mbpzbpy symbolizes the ligand 6,6'-bis(3,5-dimethyl-N-pyrazolmethyl)-2,2'-bipyridine), have been used for the in situ preparation of a series of structuralanalogues via the exchange of the weakly coordinated trans methanol molecules by various anions, such asthiocyanate, selenocyanate, or dicyanamide. The magnetic properties of all seven iron(II) compounds thus obtainedhave been investigated. Two iron(II) complexes, i.e., [Fe(bpzbpy)(NCS)2] and [Fe(bpzbpy)(NCSe)2], exhibit gradualspin-crossover (SCO) properties typical of isolated mononuclear species with weak cooperative interaction. Thesetwo SCO materials have been studied by Mössbauer spectroscopy, and the light-induced excited spin state trappingeffect has been investigated, revealing the possibility to induce the spin-transition both by temperature variationand by light irradiation. A correlation between steric/anion effect and SCO behavior is suggested.