School of Chemistry, University of Bristol, Bristol BS8 1TS, UK.
Inorg Chem. 2011 Nov 7;50(21):10633-42. doi: 10.1021/ic200932w. Epub 2011 Oct 5.
Two new isostructural two-dimensional (2D) coordination polymers exhibiting spin crossover (SCO) behavior of formulation [Fe(4,4'-bipy)(2)(NCX)(2)]·4CHCl(3) (4,4'-bipy = 4,4'-bipyridine; X = S [1·4CHCl(3)], Se [2·4CHCl(3)]) have been synthesized and characterized, and both undergo cooperative spin transitions (ST). For 1·4CHCl(3) the ST takes place in two steps with critical temperatures of T(c1)(down) = 143.1 K, T(c2)(down) = 91.2 K, T(c1)(up) = 150.7 K, and T(c2)(up) = 112.2 K. 2·4CHCl(3) displays half ST characterized by T(c)(down) = 161.7 K and T(c)(up) = 168.3 K. The average enthalpy and entropy variations and cooperativity parameters associated with the ST have been estimated to be ΔH(1)(av) = 5.18 kJ mol(-1), ΔS(1)(av) = 35 J K(-1) mol(-1), and Γ(1) = 2.8 kJ mol(-1) and ΔH(2)(av) = 3.55 kJ mol(-1), ΔS(2)(av) = 35 J K(-1) mol(-1), and Γ(2) = 2.6 kJ mol(-1) for 1·4CHCl(3), and ΔH(av) = 6.25 kJ mol(-1), ΔS(av) = 38.1 J K(-1) mol(-1), and Γ = 3.2 kJ mol(-1) for 2·4CHCl(3). At T > [T(c1) (1·4CHCl(3)); T(c) (2·4CHCl(3))], both compounds are in the space group P2/c while at T < [T(c1) (1·4CHCl(3)); T(c) (2·4CHCl(3))] they change to the C2/c space group and display an ordered checkerboard-like arrangement of iron(II) sites where the high- and low-spin states coexist at 50%.
已经合成并表征了两个新的同构二维（2D）配位聚合物，它们表现出[Fe(4,4'-bipy)(2)(NCX)(2)]·4CHCl(3)（4,4'-bipy=4,4'-联吡啶；X=S[1·4CHCl(3)]，Se[2·4CHCl(3)])的自旋交叉（SCO）行为，并且都经历了协同自旋转变（ST）。对于 1·4CHCl(3)，ST 发生在两个步骤中，临界温度 T(c1)(down)=143.1 K，T(c2)(down)=91.2 K，T(c1)(up)=150.7 K，T(c2)(up)=112.2 K。2·4CHCl(3)表现出由 T(c)(down)=161.7 K 和 T(c)(up)=168.3 K 表征的半 ST。与 ST 相关的平均焓变、熵变和协同参数已被估计为 ΔH(1)(av)=5.18 kJ mol(-1)，ΔS(1)(av)=35 J K(-1) mol(-1)，Γ(1)=2.8 kJ mol(-1)和 ΔH(2)(av)=3.55 kJ mol(-1)，ΔS(2)(av)=35 J K(-1) mol(-1)，Γ(2)=2.6 kJ mol(-1)用于 1·4CHCl(3)，以及 ΔH(av)=6.25 kJ mol(-1)，ΔS(av)=38.1 J K(-1) mol(-1)，Γ=3.2 kJ mol(-1)用于 2·4CHCl(3)。在 T > [T(c1)(1·4CHCl(3))；T(c)(2·4CHCl(3))]时，这两种化合物都处于 P2/c 空间群，而在 T < [T(c1)(1·4CHCl(3))；T(c)(2·4CHCl(3))]时，它们转变为 C2/c 空间群，并显示出铁(II)位点的有序棋盘式排列，其中高低自旋态共存 50%。
