Search results for "Van der Waals force"
showing 10 items of 170 documents
Directed Assembly of Cellulose Nanocrystals in Their Native Solid-State Template of a Processed Fiber Cell Wall
2021
Funding Information: I.S. thanks The Academy of Finland (grant no. 300364) for funding this work. C.D. acknowledges funding from FAPESP (grant 13/07932‐6). P.A.P. thanks the Emil Aaltonen Foundation and Academy of Finland (grant no. 315768) for funding and ESRF for beamtime at beamline D2am (experiment 02‐01‐885). Rita Hatakka is acknowledged for her assistance with the GPC measurements. Work of M.L. was supported by the Jane and Aatos Erkko Foundation. The work is a part of the FinnCERES Bioeconomy ecosystem. Publisher Copyright: © 2021 The Authors. Macromolecular Rapid Communications published by Wiley-VCH GmbH Copyright: Copyright 2021 Elsevier B.V., All rights reserved. Nanoparticle ass…
N ‐Annulated Perylene Bisimides to Bias the Differentiation of Metastable Supramolecular Assemblies into J‐ and H‐Aggregates
2020
The unique self-assembling features of N-annulated perylene bisimides (PBIs) 1 and 2 are reported. The stability of the aggregates of diester 1, in which no H-bonding interactions are operative, corroborates the significance of long-range van der Waals and dipole-dipole electrostatic interactions in the construction of stable supramolecular assemblies. The incorporation of amide functional groups within the N-annulated PBI in 2 stimulates pathway differentiation to achieve up to three J-type aggregates and a fourth H-type aggregate depending on the experimental conditions. The results presented demonstrate unprecedented levels of control over synthetic supramolecular self-assembly and the r…
Configurational effects in17O NMR chemical shifts of hydroxyl-substituted, bicyclo [2.2.1]heptenes and -heptanes, their methylated derivatives and so…
1993
Well resolved natural abundance 17O NMR spectra of 27 mono-, di-, tri- and tetrahydroxybicyclo[2.2.1]heptenes and -heptanes (norbornenes or norbornanes), their methylated derivatives and some related compounds were measured for 0.5 M or saturated solutions in acetonitrile at 65°C. In addition, the 17O NMR chemical shifts of 14 aliphatic and alicyclic alcohols were also determined for reference purposes. The 17O NMR chemical shifts of all compounds were assigned. Both methyl- and hydroxyl-induced deshielding β-effects were consistent with those reported in the literature. Similarly, observed shielding γ-effects were in agreement with the earlier observations and characteristic especially for…
1,1-Dichloroethane: a molecular crystal structure without van der Waals contacts?
2008
Isochoric and isobaric freezing of 1,1-dichloroethane, CH3CHCl2, mp = 176.19 K, yielded the orthorhombic structure, space group Pnma, with the fully ordered molecules, in the staggered conformation, located on mirror planes. The CH3CHCl2 ambient-pressure (0.1 MPa) structures were determined at 160 and 100 K, whereas the 295 K high-pressure structures were determined at 0.59 and 1.51 GPa. At 0.1 MPa, all intermolecular distances are considerably longer than the sums of the van der Waals radii, and only a pressure of about 1.5 GPa squeezed the Cl···Cl and Cl···H contacts to distances commensurate with these sums. The exceptionally large difference between the melting points of isomeric 1,1- a…
Recurrence of the oxazole motif in tubulin colchicine site inhibitors with anti-tumor activity
2021
Abstract Because of its wide spectrum of targets and biological activities, the oxazole ring is a valuable heterocyclic scaffold in the design of new therapeutic agents with anticancer, antiviral, antibacterial, anti-inflammatory, neuroprotective, antidiabetic and antidepressant properties. The presence of two heteroatoms, oxygen and nitrogen, offers possible interactions (hydrogen, hydrophobic, van der Waals or dipoles bonds) with a broad range of receptors and enzymes. Furthermore, the oxazole core conjugates low cytotoxicity with improved compound solubility and is well suited to structural modifications such as substitution with different groups and condensation to aromatic, heteroaroma…
Copper(II) complexes of 3-aminopropanols. Synthesis and structure of (3-aminopropanolato)formatocopper(II)
1987
Abstract The crystal and molecular structure of the title compound has been determined from single-crystal X-ray data and refined to a final R value of 0.030 for 971 reflections. The compound crystallizes in the monoclinic space group P21/c with two dimeric molecules in a cell of dimensions a=856.9(1), b= 887.7(1), c=837.0(1) pm and β=99.55(1)°. The blue crystals of Cu(ap)(HCOO) (ap=3-aminopropanolato ion) are made of centrosymmetric dialkoxy bridged dimers (Cu…Cu 296.4(1) pm). The dimers are polymerized along the c axis into chains via two NHO hydrogen bonds (Cu…Cu 547.9(1) pm). These chains are joined together along the b axis by CuOCOCu bridges and NHO hydrogen bonds (Cu…Cu 462.2(1) pm…
Host–guest inclusion complexes between peracetylated β-cyclodextrin and diphenyl(4-phenylphenyl)phosphine : computational studies
2006
PM3 and molecular dynamic calculations were performed upon the inclusion complexation of peracetylated β-cyclodextrin (Per-Ac-β-CD) with diphenyl(4-phenylphenyl)phosphine (DBP). Results show that the 4-phenylphenyl part of the DBP phosphine fits tightly in the cavity of the Per-Ac-β-CD, leading to the formation of stable inclusion complexes. Complexation energies indicate that the complex formed via the primary side of the Per-Ac-β-CD is more stable than that formed via the secondary side. Electrostatic potential mapping and frontier orbital analysis suggest that van der Waals interaction constitute a major driving force in the complexation of the DBP and Per-Ac-β-CD.
Spectrophotometric determination of binding constants between some aminocyclodextrins and nitrobenzene derivatives at various pH values
2002
Abstract The inclusion capacity of three modified cyclodextrins—namely mono-(6- N , N -dimethylamino-6-deoxy)- ( 3 ), mono-6-(2-aminoethyl)-amino-6-deoxy- ( 4 ) and mono-6-(2- N , N -dimethylaminoethyl)-amino-6-deoxy- ( 5 ) β-cyclodextrin, with six para -substituted nitrobenzenes ( A – F ) has been investigated at three different pH values. Molecular interactions in inclusion complexes have also been investigated by means of molecular mechanics (MM2/QD) models. The desolvation of the cyclodextrin is the most important factor in determining the binding ability of the various hosts. However, for a given host, electrostatic and van der Waals interactions and the formation of a hydrogen bond be…
Graphene related magnetic materials: micromechanical exfoliation of 2D layered magnets based on bimetallic anilate complexes with inserted [FeIII(aca…
2015
The syntheses, structures and magnetic properties of the coordination compounds of formula [FeIII(acac2-trien)][MnIICrIII(Cl2 An)3]·(CH3CN)2 (1), [FeIII(acac2-trien)][MnIICrIII(Br2An)3]·(CH3CN)2 (2) and [GaIII(acac2-trien)][MnIICrIII(Br2An)3]·(CH3CN)2 (3) are reported. They exhibit a 2D anionic network formed by Mn(II) and Cr(III) ions linked through anilate ligands, while the [FeIII(acac2-trien)]+ or [GaIII(acac2-trien)]+ charge-compensating cations are placed inside the hexagonal channels of the 2D network, instead of being inserted in the interlamellar spacing. Thus, these crystals are formed by hybrid layers assembled through van der Waals interactions. The magnetic properties indicate …
Structure Formation of Polymeric Building Blocks: Complex Polymer Architectures
2013
This chapter describes macromolecules with a complex structure, their defined aggregation in solution, their adsorption to surfaces, and their possible aggregation on surfaces. The term “complex structure” implies that the macromolecules show different, distinct structural elements or building blocks on a supra-atomic length scale. Key to understanding the complex structure of macromolecules, their aggregation, and adsorption to surfaces are intra- and intermolecular interactions such as van der Waals, electrostatic, π–π interactions, and hydrogen bonds.