Chirality organization of ferrocenes bearing podand dipeptide chains: synthesis and structural characterization

A variety of ferrocenes bearing podand dipeptide chains have been synthesized to form an ordered structure in both solid and solution states and have been investigated by 1H NMR, FT-IR, CD, and X-ray crystallographic analyses. Conformational enantiomerization through chirality organization was achieved by the intramolecular hydrogen bondings between the podand dipeptide chains. The single-crystal X-ray structure determination of the ferrocene 2 bearing the podand dipeptide chains (-D-Ala-D-Pro-OEt) revealed two C2-symmetric intramolecular hydrogen bondings between CO (Ala) and NH (another Ala) of each podand dipeptide chain to induce the chirality-organized structure. The molecular structures of the ferrocene 1 composed of the podand L-dipeptide chains (-L-Ala-L-Pro-OEt) and 2 are in a good mirror image relationship, indicating that they are conformational enantiomers. An opposite helically ordered molecular arrangement was formed in the crystal packing of 2 as compared with 1. The ferrocene 2 exhibited induced circular dichroism (CD), which appeared at the absorbance of the ferrocene moiety. The mirror image of the CD signals between 1 and 2 was observed, suggesting that the chirality-organized structure via intramolecular hydrogen bondings is present even in solution. The ferrocene 4 bearing the podand dipeptide chains (-Gly-L-Leu-OEt) also showed an ordered structure in the crystal based on two intramolecular hydrogen bondings between CO (Gly) and NH (another Gly) of each podand dipeptide chain, together with intermolecular hydrogen bondings between CO adjacent to the ferrocene unit and NH (neighboring Leu) to create the highly organized self-assembly. A different self-assembly was observed in the crystal of the ferrocene 5 composed of the podand dipeptide chains (-Gly-L-Phe-OEt), wherein each molecule is bonded to two neighboring molecules through two pairs of symmetrical intermolecular hydrogen bonds to form a 14-membered intermolecularly hydrogen-bonded ring. These ordered structures based on the intramolecular hydrogen bondings in the solution state are also confirmed by 1H NMR and FT-IR.     

Anderson型杂多酸-DABCO复合二维相变晶体材料的合成及介电性质

以1.4-二氮杂二环[2.2.2]辛烷(DABCO)氟硼酸盐与(NH4)3[FeMo6 O24 H6]·7H2 O多酸盐为原料,通过H管水溶液界面扩散方式合成一种新颖的Anderson型超分子化合物(H2 DABCO)2[FeMo6 O24 H4]·4H2 O(1).并通过红外光谱、单晶X衍射、元素分析、XRD粉末衍射...     

Interactions of water-soluble polymers with small molecules I: Poly(2-diethylaminoethyl methacrylate)-orange II and ethyl orange systems

The interactions between poly(2-diethylaminoethyl methacrylate) (PDEAEMA) and orange II (OII) or ethyl orange (EO) have been examined in detail by measuring the transmittance and the specific conductance of the solutions. The mechanisms of flocculation and deflocculation have been investigated by changing the intrinsic viscosity, the degree of neutralization and alkyl groups of PDEAEMA or by adding NaCl, urea or alcohols. The complexation of PDEAEMA with dyes is completed at the same mole ratio but is not dependent on the molecular weight of PDEAEMA. OII molecules bind with PDEAEMA by electrostatic interactions, followed by flocculation through hydrogen bondings between hydroxyl groups on OII molecules bound. EO molecules first interact with PDEAEMA electrostatically in the same ways as OII, but flocculation occurs by hydrophobic interactions between ethyl groups on EO molecules bound. By further addition of dyes to the complex, OII or EO molecules already bound can interact with free OII or EO molecules newly added through hydrogen/hydrophobic interaction between OII or EO molecules. Deflocculation occurs by the electrostatic repulsion between anions of dyes bound, such as (PDEAEMA-OII)-hydrogen bonding-(OII-anions) or (PDEAEMA-EO)-hydrophobic bonding-(EO-anions) newly formed.     

Hydrogen‐Bonded Liquid Crystalline Materials: Supramolecular Polymeric Assembly and the Induction of Dynamic Function

Liquid crystals are molecular materials that combine anisotropy with dynamic nature. Recently, the use of hydrogen bonding for the design of functional liquid crystalline materials has been shown to be a versatile approach toward the control of simple molecularly assembled structures and the induction of dynamic function. A variety of hydrogen‐bonded liquid crystals has been prepared by molecular self‐assembly processes via hydrogen bond formation. Rod‐like and disk‐like low‐molecular weight complexes and polymers with side‐chain, main‐chain, network, and guest‐host structures have been built by the complexation of complimentary and identical hydrogen‐bonded molecules. These materials consist of closed‐type hydrogen bondings. Another type of hydrogen‐bonded liquid crystals consists of open‐type hydrogen bonding. In this case, the introduction of hydrogen bonding moieties, such as hydroxyl groups, induces microphase segregation leading to liquid crystalline molecular order. Moreover, liquid crystalline physical gels have been prepared by the molecular aggregation of hydrogen‐bonded molecules in non‐hydrogen‐bonded liquid crystals. They show significant electrooptical properties. An anisotropic gel is a new type of anisotropic materials forming heterogeneous structures.     

The influence of isomerism on the self-assembly behavior and complexation property of 1,3-alternate tetraaminopyridyl-thiacalix[4]arene derivatives

A series of 1,3-alternate conformation thiacalix[4]arenes containing different isomeric aminopyridyl pendent arms have been synthesized. It was found that their self-assembly behaviors and complexation properties strongly depended on the structures of aminopyridyl pendent arms. The crystal structures demonstrate that tetra(meta-aminopyridyl)-thiacalix[4]arene motif is capable of forming intramolecular hydrogen bondings between the sp² nitrogen donors in the meta position of the aminopyridyl groups and the facing amide N-H of the adjacent aminopyridyl groups, and self-assembles via C-H?O weak hydrogen bondings and C-H?π interaction to generate a double stranded rectilineal networks. By contrast, in the case of tetra(para-aminopyridyl)-thiacalix[4]arene, the presence of para-aminopyridyl units enables the formation of N-H?N strong hydrogen bondings between the individual molecules leading to the solid-state structure with water-bridged double strands. Their complexation properties had been also studied by measurement of the stability constants for their complexation in a range of metal cations and investigation of their binding models via ¹H NMR titration and ESI-MS experiments. It was found that the three ligands exhibited high and selective extractability toward Ag⁺, and their stoichiometry of ligand to Ag⁺ was 1:1, while the meta-aminopyridyl derivative showed the best extraction capacity and possessed the most efficient binding sites.     

Über Wasserstoffbrücken im α-KZnBr3 · 2 H2O

Hydrogen Bondings in α-KZnBr₃ · 2 H₂O The positions of the hydrogen atoms and the system of hydrogen bondings in the crystal structure of α-KZnBr₃ · 2 H₂O are discussed. The hydrogen atoms have been located by FOURIER difference synthesis. IR-spectra have given some information about the strength of the various hydrogen bondings O? H …? H and O? H …? Br.     

A novel method for superimposing molecules and receptor mapping

Superposition of molecules on a three-dimensional computer graphic display is an efficient means to compare three-dimensional molecular structures. Biologically active molecules, which are presumed to bind to the same receptor site, are thought to have common structural features. But, it is the physical and chemical properties arranged spatially through chemical structures that are important for specific binding to a receptor. Therefore, for the purpose of studies on biological activities, molecules should be superposed to those properties, not to the atomic positions as in the traditional methods. We have developed a program system for realizing this new concept. The concept stands on the general perceptions of organic chemists about hydrogen bondings and chemical isosterisms. The 'goodness of fit' values, which are estimated in realtime on the basis of spatial similarity of those properties between molecules, are displayed and updated throughout the superposing process. This program can construct a receptor cavity model and provide with the cavity size and shape, surface electrostatic potentials, hydrogen bonding sites and so on, by using all information supplied by the superposed molecules. This model can be modified by further superposing of another molecule. These constructed models would be of help for rational drug design, when the receptor structures are not yet known.     

Hydrogen storage inside a toroidal carbon nanostructure C120: Density functional theory computer simulation

Ab initio density functional calculations were performed for a toroidal carbon C₁₂₀ nanostructure. Hydrogen molecules, n = 1–15, were added inside the nanotorus and for each one of these systems a geometry optimization was obtained. The cohesive energy shows that these structures are energetically stable. For example, the binding energies are ?34.95 and ?36.19 Hartrees and the interatomic distances H? H are 0.753 and 0.772 Å for 1 and 14 molecules, respectively. Considering only molecular hydrogen, we have always seen so far weak physisorption into the C₁₂₀ nanotorus. There is no chemisorption until the number oh hydrogen molecules are increased to 14. In this case, four hydrogen atoms are chemisorbed. With 15 molecules, there are 10 hydrogen atoms chemisorbed just at the inner nanotorus surface forming 10 H? C bondings with bond length close to that in methane. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2495–2508, 2010     

药物在pH敏感聚甲基丙烯酸-poloxamer水凝胶中的扩散行为

平衡溶胀率;药物扩散;药物在pH敏感聚甲基丙烯酸-poloxamer水凝胶中的扩散行为     

Encapsulation of anionic guests in a new hydantoinylamido molecular capsule

Resorcin[4]arene-based tetrakis(N-hydantoinylamido)cavitand 1 forms a stable molecular capsule in the presence of suitable anionic guests such as CH(3)OSO(3)(-) or BF(4)(-) in C(2)D(2)Cl(4). Molecular capsule G(2)@1(2) is stabilized by the eight intermolecular imide N-H···O═C hydrogen bondings, two from each four paired hydantoinyl units, and the eight intramolecular amide N-H···O-CH(2)-O hydrogen bondings, four on each two cavitands. The formations of molecular capsules were confirmed by (1)H, 2D NOESY, and 2D-DOSY NMR.     

Intermolecular-medium and intramolecular-weak hydrogen bonding chains in the crystals of chiral trifluoromethylated amino alcohols

A structural feature of hydrogen bonding chains found in the crystals of trifluoromethylated amino alcohols is reported. Hydrogen bondings of 3-(N,N-dialkylamino)-1,1,1-trifluoro-2-propanols construct chiral spiral hydrogen bonding chains. Lone pairs on the nitrogen atoms of the amino alcohols participate in two hydrogen bondings. Detailed structural analysis of the hydrogen bonds of the 3-(N,N-dimethylamino)-1,1,1-trifluoro-2-propanol suggested that the chain built up with alternating intermolecular-medium and intramolecular-weak hydrogen bonds. The medium intermolecular hydrogen bond, which transfers a proton from the hydroxy group to the amino nitrogen, would make a tentative zwitterionic form of the molecule. Then, electrostatic attraction between the charges in the zwitterion centers induced a weak intramolecular hydrogen bond.     

Hydrazide as a new hydrogen-bonding motif for resorcin[4]arene-based molecular capsules

The resorcin[4]arene-based benzoylhydrazide cavitands formed stable molecular capsules in nonpolar solvents by the eight intermolecular N-H...O=C hydrogen bondings, two from each four paired hydrazides, and the four intramolecular O-H2C-O...H-N hydrogen bondings on each cavitand. The stability of these molecular capsules depends on the encapsulated guest in the following order: CH3SO3(-) > CH3CO2(-) > CH3CH2NH2 x HCl approximately = CH3NH2 x HCl > (CH3)4N(+) > toluene > C2D2Cl4.     

Narcissistic aggregation of steroid compounds in diluted solution elucidated by CSI-MS, PFG NMR and X-ray analysis

Large-scale aggregated chain structures of progesterone, estrone, cortisone, hydrocortisone and cholic acid were observed in diluted solution by means of cold-spray ionization mass spectrometry (CSI-MS) and pulsed field gradient (PFG) NMR. The crystal structures were determined by X-ray crystallography, and the relationship between the crystal and solution structures is discussed. It is suggested that the intermolecular hydrogen bondings observed in the crystal might be partly retained in diluted solution.     

Self-assembly of [Et,Et]-bacteriochlorophyll cF on highly oriented pyrolytic graphite revealed by scanning tunneling microscopy

The chlorosomal light-harvesting antennae of green phototrophic bacteria consist of large supramolecular aggregates of bacteriochlorophyll c (BChl c). The supramolecular structure of (3(1)-R/S)-BChl c on highly oriented pyrolytic graphite (HOPG) and molybdenum disulfide (MoS2) has been investigated by scanning tunneling microscopy (STM). On MoS2, we observed single BChl c molecules, dimers or tetramers, depending on the polarity of the solvent. On HOPG, we observed extensive self-assembly of the dimers and tetramers. We propose C=O...H-O...Mg bonding networks for the observed dimer chains, in agreement with former ultraviolet-visible and infrared spectroscopic work. The BChl c moieties in the tetramers are probably linked by four C=O...H-O hydrogen bonds to form a circle and further stabilized by Mg...O-H bondings to underlying BChl c layers. The tetramers form highly ordered, distinct chains and extended two-dimensional networks. We investigated semisynthetic chlorins for comparison by STM but observed that only BChl c self-assembles to well-structured large aggregates on HOPG. The results on the synthetic chlorins support our structure proposition.     

The X-ray crystal and molecular structure of 5′-bromo-5′-deoxythymidine

5′-Bromo-5′-deoxythymidine (1) crystallizes with four molecules in a monoclinic unit cell of space group C2. The ribose ring adopts an envelope conformation, transient between T and E₀ (O4′-exo), with the C1′ atom being in the flap position. In the crystal lattice, the molecules are connected by intermolecular one-dimensional chains of hydrogen bondings from the hydroxyl hydrogen H3′(O3′) to the carbonyl oxygen O4. The differences in conformation and a hydrogen-bonding system of 1 with comparison to the structure of thymidine are observed. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9: 591–596, 1998     

An unprecedented example of a cis-phosphonodithioato nickel(II) complex built by an extensive hydrogen bonding supramolecular network

The P-N bond hydrolysis of the 4-methoxyphenyl-ammonium ethylamido-phosphonodithioato ligand during its complexation to NiII leads to the first example of phosphonodithioato nickel(II) complex having a cis configuration; this complex is stabilised in the solid state by an extensive and intricate network of hydrogen bondings involving the released ethylenediamine and a water molecule.     

Dipeptide-induced chirality organization

This review describes an outline of dipeptide-induced chirality organization by using molecular scaffolds. A variety of ferrocene-dipeptide conjugates as bioorganometallics are designed to induce chirality-organized structures of peptides. The ferrocene serves as a reliable organometallic scaffold with a central reverse-turn unit for the construction of protein secondary structures via intramolecular hydrogen bondings, wherein the attached dipeptide strands are constrained within the appropriate dimensions. Another interesting feature of ferrocene-dipeptide conjugates is their strong tendency to self-assemble through contribution of available hydrogen bonding sites for helical architectures in solid states. Symmetrical introduction of two dipeptide chains into a urea molecular scaffold is performed to induce the formation of the chiral hydrogen-bonded duplex, wherein each hydrogen-bonded duplex is connected by continuous intermolecular hydrogen bonds to form a double helix-like arrangement.     

Note on EPR study of decomposition of polymeric hydroperoxide with polyamines in styrene

Decomposition of polypropylene hydroperoxide in styrene with triethylenetetramine, diethylenetriamine and ethylenediamine at 23–80 was studied by electron paramagnetic resonance measurements. The hfs parameters for isotropic EPR spectra of aminoalkylnitroxy radicals from these polyamines were determined. The supposed complex formation of polymeric hydroperoxide with polyamine by two hydrogen bondings facilitates its decomposition with styrene.     

系列双磷维生素B1离子盐化合物的合成、结构及分子构象

将Ni(ClO4)2和NH4PF6分别与硫胺素焦磷酸在甲醇体系中反应, 得到了两个新的离子盐型化合物[TPP·ClO4·H2O](1)和[TPP·PF6·CH3OH](2)(TPP为硫胺素焦磷酸酯). 通过元素分析、红外光谱及X射线衍射等方法对它们进行了表征. 结构分析表明, 它们属于离子型化合物, 而且硫胺素焦磷酸与高氯酸根, 六氟磷酸根形成了大量的氢键网络结构. 结合计算结果进一步分析了化合物的活性及电子结构特征.     

Atomistic insights on the LCST behavior of PMEO2MA in water by molecular dynamics simulations

Fully atomistic molecular dynamics simulations of poly(2‐[2‐methoxyethoxy]ethyl methacrylate) (PMEO₂MA) in water at temperatures below and above its lower critical solution temperature (LCST) were performed to improve the understanding of its LCST behavior. Atomic trajectories were used to calculate various structural and dynamic properties. Simulation results show that PMEO₂MA undergo a distinct coil‐to‐globule transition above LCST. Detailed analyses of the number of first hydration shell water molecules around various atomic regions are revealed that the water solubility of PMEO₂MA below LCST is mainly provided by the hydrophobic hydration around the side chain carbon atoms. This is achieved by the cage‐like water network formations which are disrupted when the temperature is increased above LCST, accompanied by significant amount of water molecule release and local water‐ordering reduction, which leads to the LCST phase transition. Furthermore, other analyses such as the number of hydrogen bonds and hydrogen bond lifetimes suggest that intermolecular hydrogen bondings between polymer and water molecules have little effect on the phase transition. Our results will contribute to a better understanding on the LCST phase transition of oligo(ethylene glycol) methyl ether methacrylate (OEGMA)‐based homopolymers at atomistic level that will be useful when designing homo‐ and co‐polymers of OEGMAs with desired properties. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 429–441