Homoleptic Iron(II) Complexes with the Ionogenic Ligand 6,6鈥?Bis(1H-tetrazol-5-yl)-2,2鈥?bipyridine: Spin Crossover Behavior in a Singular 2D Spin Crossover Coordination Polymer
详细信息 查看全文
- 作者：Maksym Seredyuk ; Luc铆a Pi帽eiro-L贸pez ; M. Carmen Mu帽oz ; Francisco J. Mart铆nez-Casado ; G谩bor Moln谩r ; Jos茅 Alberto Rodriguez-Velamaz谩n ; Azzedine Bousseksou ; Jos茅 Antonio Real
- 刊名：Inorganic Chemistry
- 出版年：2015
- 出版时间：August 3, 2015
- 年：2015
- 卷：54
- 期：15
- 页码：7424-7432
- 全文大小：560K
- ISSN：1520-510X
文摘
Deprotonation of the ionogenic tetradentate ligand 6,6鈥?bis(1H-tetrazol-5-yl)-2,2鈥?bipyridine [H2bipy(ttr)2] in the presence of FeII in solution has afforded an anionic mononuclear complex and a neutral two-dimensional coordination polymer formulated as, respectively, NEt3H{Fe[bipy(ttr)2][Hbipy(ttr)2]}路3MeOH (1) and {Fe[bipy(ttr)2]}n (2). The anions [Hbipy(ttr)2]鈭?/sup> and [bipy(ttr)2]2鈥?/sup> embrace the FeII centers defining discrete molecular units 1 with the FeII ion lying in a distorted bisdisphenoid dodecahedron, a rare example of octacoordination in the coordination environment of this cation. The magnetic behavior of 1 shows that the FeII is high-spin, and its M枚ssbauer spectrum is characterized by a relatively large average quadrupole splitting, 螖EQ = 3.42 mm s鈥?. Compound 2 defines a strongly distorted octahedral environment for FeII in which one [bipy(ttr)2]鈭?/sup> anion coordinates the equatorial positions of the FeII center, while the axial positions are occupied by peripheral N-tetrazole atoms of two adjacent {Fe[bipy(ttr)2]}0 moieties thereby generating an infinite double-layer sheet. Compound 2 undergoes an almost complete spin crossover transition between the high-spin and low-spin states centered at about 221 K characterized by an average variation of enthalpy and entropy 螖Hav = 8.27 kJ mol鈥?, 螖Sav = 37.5 J K鈥? mol鈥?, obtained from calorimetric DSC measurements. Photomagnetic measurements of 2 at 10 K show an almost complete light-induced spin state trapping (LIESST) effect which denotes occurrence of antiferromagnetic coupling between the excited high-spin species and TLIESST = 52 K. The crystal structure of 2 has been investigated in detail at various temperatures and discussed.