Bodenthin Y, Pietsch U, Grenzer J, Geue Th, Möhwald H, Kurth D G
University Potsdam, Department of Physics, P.O. Box 601553, D-14415 Potsdam, Germany, Max Planck Institute of Colloids and Interfaces, D-14424 Potsdam, Germany.
J Phys Chem B. 2005 Jul 7;109(26):12795-9. doi: 10.1021/jp0458001.
A detailed structural analysis of a Langmuir-Blodgett (LB) multilayer composed of a polyelectrolyte-amphiphile complex (PAC) is presented. The PAC is self-assembled from metal ions, ditopic bis-terpyridines, and amphiphiles. The vertical structure of the LB multilayer is investigated by X-ray reflectometry. The multilayer has a periodicity of 57 A, which corresponds to an architecture of flat lying metallo-supramolecular coordination polyelectrolyte (MEPE) rods and upright-standing amphiphiles (dihexadecyl phosphate, DHP). In-plane diffraction reveals hexagonal packing of the DHP molecules. Using extended X-ray absorption fine structure (EXAFS) experiments, we prove that the central metal ion is coordinated to the terpyridine moieties in a pseudo-octahedral coordination environment. The Fe-N bond distances are 1.82 and 2.0 A, respectively. Temperature resolved measurements indicate a reversible phase transition in a temperature range up to 55 degrees C. EXAFS measurements indicate a lengthening of the average Fe-N bond distance from 1.91 to 1.95 A. The widening of the coordination cage upon heating is expected to lower the ligand field stabilization, thus giving rise to spin transitions in these composite materials.
本文对由聚电解质 - 两亲物复合物（PAC）组成的朗缪尔 - 布洛杰特（LB）多层膜进行了详细的结构分析。PAC由金属离子、双齿双吡啶和两亲物自组装而成。通过X射线反射测量法研究了LB多层膜的垂直结构。该多层膜的周期为57 Å，对应于平躺的金属超分子配位聚电解质（MEPE）棒和直立的两亲物（磷酸二己酯，DHP）的结构。面内衍射显示DHP分子呈六方堆积。利用扩展X射线吸收精细结构（EXAFS）实验，我们证明中心金属离子在伪八面体配位环境中与吡啶基部分配位。Fe - N键距离分别为1.82 Å和2.0 Å。温度分辨测量表明在高达55℃的温度范围内存在可逆相变。EXAFS测量表明平均Fe - N键距离从1.91 Å延长至1.95 Å。加热时配位笼的加宽预计会降低配体场稳定化，从而在这些复合材料中引起自旋转变。
