Crystal Structure of a Supramolecular Complex Formed between 1-bromo-2-iodo-tetrafluoroethane and N,N,N′,N′-tetramethyl-ethylenediamine

X-ray analysis has revealed that N,N,N′,N′-tetramethyl-ethylenediamine 1 form donor–acceptor complex 3 with 1-bromo-2-iodo-tetrafluoroethane 2, in which the N X (X = Br, I) distances are longer than the average covalent bond length between X and N, but are also definitively shorter than the sum of the corresponding van der Waals radii of X and N, thus that indicating weak interactions between the nitrogen and bromine or iodine atoms. In our experimental section, a valuable method for recrystallization and collect X-ray data from crystals that easily exhibit decay and can be cracked is reported.     

Two Polymorphs of (Anilinium)(18-Crown-6)[Ni(dmit)2]: Structure and Magnetic Properties

Two polymorphs of monovalent [Ni(dmit)₂]⁻ (dmit²⁻=2-thioxo-1,3-dithiole-4,5-dithiolate) crystals A and B, (anilinium)(18-crown-6)[Ni(dmit)₂], were prepared, and the structure and magnetic properties were investigated. In these crystals, the [Ni(dmit)₂]⁻ molecules form dimers, which arranged into chains between the supramolecular cation structure (anilinium)(18-crown-6). In crystal A, supramolecular cation formed a regular stack, inducing ladder structure of [Ni(dmit)₂], whose magnetism had been well fitted by spin ladder equation with the spin gap of Δ=190 K. Crystal B is ca. 3% more densely packed compared to crystal A. Due to the dense packing, supramolecular cation stack is distorted, which prevented the intermolecular interaction between [Ni(dmit)₂]⁻ dimers in direction corresponds to the ladder-leg direction in crystal A. Reflecting the [Ni(dmit)₂]⁻ arrangement, crystal B showed a temperature dependence of magnetic susceptibility well reproduced by the singlet-triplet thermal activation model, whose antiferromagnetic exchange interaction (2J) was 140 K.     

Two‐ and Three‐Dimensional Molecular Organization of Schiff‐Base Derivatives

We have designed and synthesized a series of Schiff base derivatives, and studied their structural features in two‐dimensional (2D) and three‐dimensional (3D) states by combining scanning tunneling microscopy (STM) and X‐ray diffraction experiments. The Schiff‐base derivatives with short alkyl chains crystallize easily, which allows a detailed structural analysis by X‐ray diffraction. Due to the strong adsorbate–substrate interactions, those bases with long alkyl chains easily form 2D assemblies on highly oriented pyrolytic graphite (HOPG). The STM images indicate also that the introduction of two methoxy groups into the molecule can change the structure of these 2D assemblies as a result of the increased steric hindrances, for example: the Schiff‐base derivative, bearing both methoxy groups and C₁₆H₃₃ tails, forms 2D Moiré patterns, and an alignment of pairing Schiff‐base molecules may be easily resolved. Conversely, the Schiff base derivative, bearing solely C₁₆H₃₃ tails, forms 2D non‐Moiré patterns. It is demonstrated that the 3D structural features result from the compromise of intermolecular interactions of different molecular moieties. However, there is one more factor, which also governs the 2D structure: the adsorbate‐substrate interaction. The 3D crystal structure may thus help to understand many factors involved in the formation of 2D structures, and would be helpful for designing new molecular assemblies with tailoring functions.     

Stable Hydrogen-Bonded Spherical Capsules Formed from Self-Assembly of Pyrogallol[4]arenes

The self-assemblies of two pyrogallol[4]arenes held together by 48 intermolecular hydrogen bonds stably associate in the form of spherical hexameric capsules. The molecular structures of two hexameric capsules with large interior space were analyzed by single crystal X-ray crystallography.     

Cover Picture: Trimeric Perfluoro‐ortho‐phenylenemercury: A Versatile Lewis Acidic Host (Chem. Eur. J. 21/2003)

The cover picture shows how trimeric perfluoro‐ortho‐phenylene mercury (center), one of the simplest trifunctional Lewis acidic hosts, interacts with organic molecules to afford various adducts. The planarity of this trinuclear complex as well as its overall polarizability compounded with relativistic effects at mercury permits the occurrence of noncovalent interactions and accounts for the tendency of this compound to form cofacial dimers as observed in the structure of the acetone adduct (top left). With a triply coordinated acetone molecule, the structure of this adduct also substantiates the cooperative effects that arise from the proximity and accessibility of the mercury centers. The complexation of arenes, such as benzene (bottom left) and naphthalene (bottom right), also occurs and leads to the formation of binary stacks in which the arene establishes multiple linkages with the mercury centers of the trifunctional Lewis acids. In addition to displaying unusual coordination environment, the arene units present in those stacks exhibit remarkable phosphorescent properties. For more details, see the paper by F. P. Gabbaï, R. E. Taylor, and M. R. Haneline on p. 5188 ff.     

Design and self-assembly of ditopic and tetratopic cavitand complexes

The self-assembly of open ditopic and tetratopic cavitand complexes has been investigated by using monofunctionalized cavitand ligands and suitable metal precursors. In the case of ditopic complexes, self-assembly protocols, leading exclusively to the formation of both thermodynamically stable cis-Pt square-planar complexes 8 and 9 and the kinetically inert fac-Re octahedral complex 14, have been elaborated. The use of cis-[Pt(CH3)CN)2Cl2] as metal precursor led to the formation of monotopic trans-10 and ditopic trans-11 cavitand complexes, while cis-[Pt(dmso)2Cl2] afforded both cis-13 and trans-11 isomers. The self-assembly of tetratopic cavitand complexes has been achieved by using mononuclear [Pd(CH3CN)4(BF4)2] and dinuclear [M2(tppb)(OTf)4] (19: M = Pt; 20: M = Pd) metal precursors. Only the tetratopic dinuclear complexes 21 and 22 were stable. The ligand configuration with two phosphorus and two cavitand ligands at the metal centers is the most appropriate to build tetratopic cavitand complexes with sufficient kinetic stability.     

Effect of axial ligation or pi-pi-type interactions on photochemical charge stabilization in "two-point" bound supramolecular porphyrin-fullerene conjugates

Two types of structurally well-defined, self-assembled zinc porphyrin-fullerene conjugates were formed by "two-point" binding strategies to probe the effect of axial ligation or pi-pi-type interactions on the photochemical charge stabilization in the supramolecular dyads. To achieve this, meso-tetraphenylporphyrin was functionalized to possess one or four [18]crown-6 moieties at different locations on the porphyrin macrocycle while fullerene was functionalized to possess an alkyl ammonium cation, and a pyridine or phenyl entities. As a result of the crown ether-ammonium cation complexation, and zinc-pyridine coordination or pi-pi-type interactions, stable zinc porphyrin-fullerene conjugates with defined distance and orientation were formed. Evidence for the zinc-pyridine complexation or pi-pi-type interactions was obtained from the spectral and computational studies. Steady-state and time-resolved emission studies revealed efficient quenching of the zinc-porphyrin singlet excited state in these dyads, and the measured rates of charge separation, k(CS) were found to be slightly better in the case of the dyads held by axial coordination and crown ether-cation complexation. Nanosecond transient absorption studies provided evidence for the electron transfer reactions, and these studies also revealed charge stabilization in these dyads. The lifetimes of the radical ion pairs were found to depend upon the type of porphyrins utilized to form the dyads, that is, porphyrin possessing the crown ether moiety at the ortho position of one of the phenyl rings yielded prolonged charge stabilized states. Addition of pyridine to the supramolecular dyads eliminated the zinc-pyridine coordination or pi-pi-type interactions of the "two-point" bound systems due to the formation of a new zinc-pyridine axial bond thus giving a unique opportunity to probe the effect of axial coordination or pi-pi interactions on k(CS) and k(CR). Under these conditions, the measured electron transfer rates revealed faster k(CS) and slower k(CR) as compared to those obtained in the absence of added pyridine. The evaluated lifetimes of the radical ion-pairs were found to be hundreds of nanoseconds and were longer in the presence of pyridine.     

Prediction of H-Bonding Motifs for Pyrazoles and Oximes Using the Cambridge Structural Database

H-bonding motifs for pyrazoles and oximes have been examined in the Cambridge Structural Database. The accessible surface of the N atoms has been found to be useful as a discriminator to divide structures into dimer and catemer motifs for both pyrazoles and oximes. Low accessibility favors dimers and tetramers and high values favor catemers and trimers. Total molecular volume shows some correlation for oximes, while high values favor dimers. Empirical rules were successfully applied to predict the motifs of eight new structures in the subsequent release of the CSD.     

TiO2/Eu-MCM纳米超分子材料的组装和光催化性能

利用有机相-水相界面共沉淀溶胶支持自组装方法制备粒径为15 nm、孔径为8 nm的分子筛Eu-MCM, 它拥有734 m²/g的比表面积和1.49 cm³/g的比孔容. 把TiO₂组装到Eu-MCM的孔道中, 组装成TiO₂/Eu-MCM纳米复合材料. XRD, RAMAN和选区电子衍射花样分析表明纳米复合材料中的TiO₂为锐钛型. TiO₂/Eu-MCM的发光表现为Eu^3＋离子的特征光谱, 激发峰分别为342 (⁵L₁₀), 358 (⁵L₉), 378 (⁵L₇), 390 (⁵L₆), 411 (⁵D₃), 462 (⁵D₂)和524 (⁵D₁) nm; 发射峰为579, 592, 613, 653和701 nm, 归属于⁵D₀→⁷F_J (J＝0, 1, 2, 3, 4)组态间的跃迁. 纳米复合材料的发光强度都要比Eu-MCM的发光强, 其中43%TiO₂/Eu-MCM的发光最强. 荧光和紫外漫反射结果表明客体TiO₂对主体分子筛存在能量传递效应. 在微弱的紫外灯光照射下, TiO₂/Eu-MCM纳米复合材料对苯酚的光催化氧化性能和其发光强度具有一定的相关性. 29%TiO₂/Eu-MCM的纳米复合材料拥有的比表面积、孔容和孔径分别为204 m²/g, 0.24 cm³/g和4.7 nm. 29%TiO₂/Eu- MCM对苯酚具有68%的最高光催化氧化产率和85%催化氧化选择性.