Two ways of spin crossover in an iron(ii) coordination polymer associated with conformational changes of a bridging ligand

Abstract

<p>Structural phase transition in [Fe(<bold>bbtre</bold>)₃](ClO₄)₂·2CH₃CN (<bold>bbtre</bold> = 1,4-di(1-ethyl-1,2,3-triazol-5-yl)butane) plays the role of a switch, allowing spin crossover to be carried out in two ways.</p>

Does the Structural Preorganization Contribute to the “Two-Way” Spin Crossover in 1,1′-Di(tetrazol-1-ylo)methane-Based Fe(II) Coordination Polymer Containing Conformationally Labile Adiponitrile Coligand?

“…In comparison with 1-substituted tetrazole derivatives, studies on the family of 1,ω-di(tetrazol-2yl)alkanes (ω = 2, 50,51 6 52−54 ) also revealed their predisposition to form the heteroleptic systems in which N4 nitrogen atoms of four tetrazole rings create the equatorial plane of the coordination octahedron, whereas axial positions are saturated by nitrile molecules. Similarly to 2-substituted tetrazoles, also mono 1-substituted-1,2,3-triazoles 55−59 as well as their 1,5disubstituted derivatives 35,37,60 can form both homo-and heteroleptic complexes in which the Fe(II) ion is coordinated with six azoles 55,57,59 or with four 1,2,3-triazole rings and two axially coordinated nitriles. 35,37,58 It was also found in the 1,2,3-triazole-based family of coordination polymers that the presence of an alkyl spacer can be an origin of ligand flexibility.…”

“…37 Studies on the regioisomeric ligand, that is, 1,4-di(1-ethyl-1,2,3-triazol-5yl)butane (bbtre), revealed that in this case the occurrence of multiway spin crossover is also related to an ability of bbtre molecules to conformationally change. 60 In coordination compounds of the type [Fe-(azolyl) 4 (RCN) 2 ] (azolyl = tetrazol-2-yl, 1,2,3-triazol-1-yl, RCN = organic nitrile), an origin of structural liability can also be, besides flexible bridging ligands, the presence of coordinated nitriles. It was established that two structural features of coordinated nitriles can affect the spin crossover behavior.…”

Extremely Slow Thermally‐Induced Spin Crossover in the Two‐Dimensional Network [Fe(bbtr)3](BF4)2

“…[29] Also regioisomeric 1,4-di(1-ethyl-1,2,3-triazol-5-yl)butane (bbtre) forms with Fe(II) a 3D net [Fe-(bbtre) 3 ](ClO 4 ) 2 • 2CH 3 CN exhibiting an ability of multi way spin transitions accompanied by structural alterations. [30] Thus, structurally diverse coordination compounds based on ligands of common feature, that is, depending on linking two 1,2,3triazole rings through 1,4-butylene spacer, exhibit structural lability interconnected with spin crossover properties. The precursor of these compounds is the simplest ligand 1,4di(1,2,3-triazol-1-yl)butane (bbtr).…”

Two stages in one-step spin crossover in [Fe(bbtr)3](CF3SO3)2

“…The occurrence of uncommon spin transitions in these complexes is associated with significant structural changes. An application of regioisomeric ligand bbtre leads to forming a three-dimensional coordination network in which the multi-way spin crossover is strongly related to conformational changes of the bridging ligands [5].Studies of bbtr-based coordination polymers revealed the importance of counterion. Therefore, we have expanded our studies on the application of triflate derivatives.…”

“…The occurrence of uncommon spin transitions in these complexes is associated with significant structural changes. An application of regioisomeric ligand bbtre leads to forming a three-dimensional coordination network in which the multi-way spin crossover is strongly related to conformational changes of the bridging ligands [5].…”