| 1. |
- Adnan, Muhammad, et al.
(författare)
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Fine Tuning the Optoelectronic Properties of Triphenylamine Based Donor Molecules for Organic Solar Cells
- 2017
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Ingår i: Zeitschrift fur physikalische Chemie (Munchen. 1991). - : Walter de Gruyter GmbH. - 0942-9352 .- 2196-7156. ; 231:6, s. 1127-1139
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Tidskriftsartikel (refereegranskat)abstract
- Geometrical parameters, electronic structures and photophysical properties of three new triphenylamine (TPA) and diphenylamine (DPA) based electron donor materials M1-M3 (for organic solar cells) have been investigated through density functional theory (DFT) methods at the B3LYP/6-31G(d) level of the theory. TPA and DPA are used as donor moieties due to their electron donating ability while benzothiazole, cyanide and cyanomethylacetate (CMA) moieties have been taken as acceptor moieties. The time dependent-DFT (TD-DFT) method has been employed [TD-B3LYP/6-31G (d)] for the computation of excited state properties in the gas phase and in solvent (chloroform). The polarization continuum model is applied for calculations in the solvent phase. The designed molecules exhibited broad absorption in the visible and near infra-red region of spectrum with respect to a reference molecule "R" of a similar class of compounds. Based on reorganization energies calculations, these materials could act as excellent hole transport materials.
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| 2. |
- Chakraborty, I, et al.
(författare)
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Ion-Selective Ligands: How Colloidal Nano- and Micro-Particles Can Introduce New Functionalities
- 2018
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Ingår i: ZEITSCHRIFT FUR PHYSIKALISCHE CHEMIE-INTERNATIONAL JOURNAL OF RESEARCH IN PHYSICAL CHEMISTRY & CHEMICAL PHYSICS. - : Walter de Gruyter GmbH. - 0942-9352. ; 232:9-11, s. 1307-1317
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Colloidal nano- and micro-particles can introduce new properties and functionalities to existing materials and thus are a valuable building block for the construction of novel materials. This is discussed for the case of ion-selective ligands, hence molecules that can bind specifically ions of one type. First, in case ion-selective fluorescent ligands are attached to the surface of particles, these fluorophores sense the local ion concentration at the particle surface and not the bulk ion concentration. Thus, the ion-response of the ligands can be tuned by attaching them to the surface of particles. Second, in case ligands specific for particular ions are bound to the surface of particles, these ions can provide contrast and thus the particles can be imaged. This involves for example Gd-ions, which provide contrast for magnetic resonance imaging (MRI), and 111In-ions, which provide contrast for imaging of radioactivity. By attaching the ligands to the surface of particles, their physicochemical properties (as for example size and solubility) are changed, which affects their interaction with cells and, consequently, biodistribution. Attachment of ion-chelators for imaging to particles thus allows for tuning their biodistribution. Third, ion-specific ligands can be also attached to the surface of magnetic particles. In this case ions bound to the ligands can be extracted with magnetic field gradients and magnetic separation becomes possible. Therefore, magnetic particles provide a handle to the ligands, which enables the extraction of ions from solution. These examples demonstrate how the attachment of different types of colloidal particles to one existing class of molecules, ion-selective ligands, can open new fields of applications of these molecules.
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| 3. |
- Cheung, Kitt, et al.
(författare)
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Fabrication of Protein Microparticles and Microcapsules with Biomolecular Tools
- 2018
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Ingår i: Zeitschrift fur physikalische Chemie (Munchen. 1991). - : WALTER DE GRUYTER GMBH. - 0942-9352 .- 2196-7156. ; 232:5-6, s. 759-771
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Tidskriftsartikel (refereegranskat)abstract
- Microparticles have attracted much attention for medical, analytical and biological applications. Calcium carbonate (CaCO3) templating method with the advantages of having narrow size distribution, controlled morphology and good biocompatibility that has been widely used for the synthesis of various protein-based microparticles. Despite CaCO3 template is biocompatible, most of the conventional methods to create stable protein microparticles are mainly driven by chemical crosslink reagents which may induce potential harmful effect and remains undesirable especially for biomedical or clinical applications. In this article, we demonstrate the fabrication of protein microparticles and microcapsules with an innovative method using biomolecular tools such as enzymes and affinity molecules to trigger the assembling of protein molecules within a porous CaCO3 template followed by a template removal step. We demonstrated the enzyme-assisted fabrication of collagen microparticles triggered by transglutaminase, as well as the affinity-assisted fabrication of BSA-biotin avidin microcapsules triggered by biotin-avidin affinity interaction, respectively. Based on the different protein assemble mechanisms, the collagen microparticles appeared as a solid-structured particles, while the BSA-biotin avidin microcapsules appeared as hollow-structured morphology. The fabrication procedures are simple and robust that allows producing protein microparticles or microcapsules under mild conditions at physiological pH and temperature. In addition, the microparticle morphologies, protein compositions and the assemble mechanisms were studied. Our technology provides a facile approach to design and fabricate protein microparticles and microcapsules that are useful in the area of biomaterials, pharmaceuticals and analytical chemistry.
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| 4. |
- Heard, Christopher, 1988, et al.
(författare)
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Charge and Compositional Effects on the 2D-3D Transition in Octameric AgAu Clusters
- 2016
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Ingår i: Zeitschrift für Physikalische Chemie. - : Walter de Gruyter GmbH. - 0942-9352 .- 2196-7156. ; 230:5-7, s. 955-975
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Tidskriftsartikel (refereegranskat)abstract
- The unbiased density functional-based Birmingham Cluster Genetic Algorithm is employed to locate the global minima of all neutral and mono-ionic silver-gold octamer clusters. Structural, energetic and electronic trends are determined across the series, in order to clarify the role of composition and charge on the position of the 2D-3D transition in ultrasmall coinage metal systems. Our calculations indicate a preference for three dimensional structures at high silver concentrations, which varies significantly with charge. The minimum in composition dependent mixing energies is independent of the charge, however, with a preference tor the maximally mixed clusters, AgiAii4v for all charge states v. The sensitivity of isomeric preference to v is found to he greater for electron-rich and electron-deficient clusters, implying a complexity of unambiguous determination of cluster motifs in related experiments. Vertical ionization potentials and detachment energies are calculated to probe electronic behaviour, providing numerical predictions for future spectroscopic studies.
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| 5. |
- Jabbari, Mostafa, et al.
(författare)
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Finding solvent for polyamide 11 using a computer software
- 2019
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Ingår i: Zeitschrift für Physikalische Chemie. - : Walter de Gruyter GmbH. - 0942-9352 .- 2196-7156.
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Tidskriftsartikel (refereegranskat)abstract
- The solvent finding step has always been a time-consuming job in chemical-involved processes. The source of difficulty mainly comes from the trial-and-errors, as a repetitive process of chosing solvents and mixing them in different proportions. Computers are good at doing repetitive processes; however, they can only deal with numerical values, rather than qulitative scales. Numerification of qualitative parameters (like solubility) has already been introduced. The most recent one is the Hansen solubility parameters (HSPs). Using the HSPs could provide a solvent or solvent-mixture. In our previous study, we introduced a computer-aided model and a software to find a solvent mixture. In this study, we have used the computer-aided solvent selection model to find some solvent mixtures for polyamide 11, a biobased polymer which has attracted enormous attention recently. Using this numerical model significantly diminished the time of solvent development experimentation by decreasing the possible/necessary trials.
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| 6. |
- Jackalin, Lukas, et al.
(författare)
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Natural Abundance Nitrogen-15 NMR in Thermotropic Liquid Crystals With Cyano-Group
- 2017
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Ingår i: Zeitschrift fur physikalische Chemie (Munchen. 1991). - : WALTER DE GRUYTER GMBH. - 0942-9352 .- 2196-7156. ; 231:4, s. 795-808
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Tidskriftsartikel (refereegranskat)abstract
- We present natural abundance nitrogen-15 (NAN15) NMR spectroscopy in thermotropic liquid crystals. It is demonstrated that high resolution NAN15 NMR spectra in mesophases can be accurately recorded in non-spinning samples with a high orientational molecular order and strong anisotropic spin interactions. In this technique, due to low demand on radio-frequency decoupling power, standard solution-state probes can be used, which generally provide superior sensitivity and spectroscopic resolution in comparison to solid-state probes. We show that N-15 chemical shift anisotropy (CSA) can be used as a sensitive probe of molecular orientational dynamics in liquid crystals. This method is exploited here to measure the orientational molecular order parameter of the nematic 4-pentyl-4'-cyanobiphenyl (5CB). Since the nitrogen spectra are obtained from the molecules constituting the mesophase rather than from probe molecules, the information is direct and the analysis and interpretation is straightforward. Nitrogen CSA of immobilized molecules, required in the analysis, is obtained using a DFT calculation. The approach provided consistent results for the order parameter in the nematic 5CB in the whole temperature range, in good agreement with literature data.
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| 7. |
- Kovačević, Goran, et al.
(författare)
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Revised atomistic models of the crystal structure of C-S-H with high C/S ratio
- 2016
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Ingår i: Zeitschrift fur Physikalische Chemie. - : Walter de Gruyter GmbH. - 0942-9352 .- 2196-7156. ; 230:9, s. 1411-1424
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Tidskriftsartikel (refereegranskat)abstract
- The atomic structure of calcium-silicate-hydrate (C1.67-S-Hx) has been studied. Atomistic C-S-H models suggested in our previous study have been revised in order to perform a direct comparison of energetic stability of the diferent structures. An extensive set of periodic structures of C-S-H with variation of water content was created, and then optimized using molecular dynamics with reactive force feld ReaxFF and quantum chemical semiempirical method PM6. All models show organization of water molecules inside the structure of C-S-H. The new geometries of C-S-H, reported in this paper, show lower relative energy with respect to the geometries from the original defnition of C-S-H models. Model that corresponds to calcium enriched tobermorite structure has the lowest relative energy and the density closest to the experimental values.
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| 8. |
- Medronho, Bruno, et al.
(författare)
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Transient and Steady-State Shear Banding in a Lamellar Phase as Studied by Rheo-NMR
- 2012
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Ingår i: Zeitschrift für Physikalische Chemie. - : Walter de Gruyter GmbH. - 0942-9352 .- 2196-7156. ; 226:11-12, s. 1293-1313
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Tidskriftsartikel (refereegranskat)abstract
- Flow fields and shear-induced structures in the lamellar (L-alpha) phase of the system triethylene glycol mono n-decyl ether (C10E3)/water were investigated by NMR velocimetry, diffusometry, and H-2 NMR spectroscopy. The transformation from multilamellar vesicles (MLVs) to aligned planar lamellae is accompanied by a transient gradient shear banding. A high-shear-rate band of aligned lamellae forms next to the moving inner wall of the cylindrical Couette shear cell while a low-shear-rate band of the initial MLV structure remains close to the outer stationary wall. The band of layers grows at the expense of the band of MLVs until the transformation is completed. This process scales with the applied strain. Wall slip is a characteristic of the MLV state, while aligned layers show no deviation from Newtonian flow. The homogeneous nature of the opposite transformation from well aligned layers to MLVs via an intermediate structure resembling undulated multilamellar cylinders is confirmed. The strain dependence of this transformation appears to be independent of temperature. The shear diagram, which represents the shear-induced structures as a function of temperature and shear rate, contains a transition region between stable layers and stable MLVs. The steady-state structures in the transition region show a continuous change from layer-like at high temperature to MLV-like at lower temperature. These structures are homogeneous on a length scale above a few micrometers.
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| 9. |
- Riest, Jonas, et al.
(författare)
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Coarse-Graining of Ionic Microgels: Theory and Experiment
- 2012
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Ingår i: Zeitschrift für Physikalische Chemie. - : Walter de Gruyter GmbH. - 0942-9352 .- 2196-7156. ; 226:7-8, s. 711-735
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we discuss the statistical mechanics of many-body systems consisting of electrically charged microgels, and we show that their collective behavior is determined by an interplay between the screened electrostatic and the elastic contributions to their effective interaction potential. The former is derived by means of a statistical-mechanical approach due to Denton [A. R. Denton, Phys. Rev. E 67, 011804 (2003)], and it includes the screened electrostatic potential between penetrable spheres and the counterion entropic contribution. The latter is based on the Hertzian model of the theory of elasticity. Comparisons with experimental results demonstrate the realistic nature of the coarse-graining procedure, which makes it possible to put forward theoretical predictions on the phase diagram of ionic microgels and on the behavior of soft, neutral microgels under confinement in narrow pores.
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| 10. |
- Sharifi, Soheil, et al.
(författare)
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Variations in Structure Explain the Viscometric Behavior of AOT Microemulsions at Low Water/AOT Molar Ratios
- 2012
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Ingår i: Zeitschrift Fur Physikalische Chemie-International Journal of Research in Physical Chemistry & Chemical Physics. - : Walter de Gruyter GmbH. - 0942-9352. ; 226:3, s. 201-218
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Tidskriftsartikel (refereegranskat)abstract
- The viscosity of AOT/water/decane water-in-oil microemulsions exhibits a well-known maximum as a function of water/AOT molar ratio, which is usually attributed to increased attractions among nearly spherical droplets. The maximum can be removed by adding salt or by changing the oil to CCl4. Systematic small-angle X-ray scattering (SAXS) measurements have been used to monitor the structure of the microemulsion droplets in the composition regime where the maximum appears. On increasing the droplet concentration, the scattering intensity is found to scale with the inverse of the wavevector, a behavior which is consistent with cylindrical structures. The inverse wavevector scaling is not observed when the molar ratio is changed, moving the system away from the value corresponding to the viscosity maximum. It is also not present in the scattering from systems containing enough added salt to essentially eliminate the viscosity maximum. An asymptotic analysis of the SAXS data, complemented by some quantitative modeling, is consistent with cylindrical growth of droplets as their concentration is increased. Such elongated structures are familiar from related AOT systems in which the sodium counterion has been exchanged for a divalent one. However, the results of this study suggest that the formation of non-spherical aggregates at low molar ratios is an intrinsic property of AOT.
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| 11. |
- Skepö, Marie, et al.
(författare)
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Adsorption of the Flexible Salivary Proteins Statherin and PRP-1 to Negatively Charged Surfaces. A Monte Carlo Simulation and Ellipsometric Study
- 2007
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Ingår i: Zeitschrift fur physikalische Chemie (Munchen. 1991). - : Oldenbourg Wissenschaftsverlag, München. - 0942-9352 .- 2196-7156. ; 221:1, s. 21-46
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Tidskriftsartikel (refereegranskat)abstract
- The structural properties of the salivary proteins, acidic proline rich PRP-1 and statherin, adsorbed onto negatively charged surfaces have been studied by Monte Carlo simulations and ellipsometry. It is shown that both proteins adsorb to negatively charged surfaces, although their net charges are negative. Experimentally, an initial fast mass-controlled film build-up was detected for both proteins, and plateaus were reached within 10 minutes. The isotherm shape and the adsorbed amounts were similar for PRP-1 to hydrophilic and hydrophobic surfaces, while statherin adsorbs to a greater extent to the hydrophobic surface. These results could be explained from the simulation results by considering the proteins as diblock polyampholytes. It has also been shown that the adsorption of PRP-1 to a negatively charged surface may be purely electrostatically driven, while pure electrostatic interaction is not sufficient to drive adsorption of statherin, i.e., an extra short-ranged attractive interaction is necessary to account for the experimental observations.
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| 12. |
- Sugiyama, Jun, et al.
(författare)
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How Li diffusion in spinel Li[Ni1/2Mn3/2]O4 is seen with μ ±SR
- 2021
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Ingår i: Zeitschrift fur physikalische Chemie (Munchen. 1991). - : Walter de Gruyter GmbH. - 0942-9352 .- 2196-7156.
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Tidskriftsartikel (refereegranskat)abstract
- The diffusive behavior in a spinel-type Li+ ion battery material, Li[Ni1/2Mn3/2]O4, has been studied with positive and negative muon spin rotation and relaxation (μ±SR) measurements in the temperature range between 200 and 400 K using a powder sample. The implanted μ+ locates at an interstitial site near O2- ion so as to form a O-H like bond, while the implanted μ- is mainly captured by an oxygen nucleus, resulting in the formation of muonic oxygen. This means that local magnetic environments in Li[Ni1/2Mn3/2]O4 were investigated from the two different sites in the lattice, i.e., one is an interstitial site for μ+SR and the other is an oxygen site for μ-SR. Since both μ+SR and μ-SR detected an increase in the fluctuation rate of a nuclear magnetic field for temperatures above 200 K, the origin of this increase is clearly confirmed as Li diffusion. Assuming a random walk process with the hopping of thermally activated Li+ between a regular Li site and the nearest neighboring vacant octahedral sites, a self-diffusion coefficient of Li+ was found to range above 10-11 cm2/s at temperatures above 250 K with an activation energy of about 0.06 eV.
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| 13. |
- Svendsen, Ida, et al.
(författare)
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Lactoperoxidase and Histatin 5 : their Adsorption Behaviour on Silica and Hydrophobized Silica Surfaces, and Implications on their Role in the Initial Salivary Film Formation
- 2007
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Ingår i: Zeitschrift fur physikalische Chemie (Munchen. 1991). - : Oldenbourg Wissenschaftsverlag, München. - 0942-9352 .- 2196-7156. ; 221, s. 65-73
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Tidskriftsartikel (refereegranskat)abstract
- The acquired pellicle is the thin salivary film that covers all oral surfaces, formed by selective adsorption of primarily salivary proteins. Several cationic proteins, such as lactoferrin, lactoperoxidase, lysozyme and histatin 5 have been identified in the pellicle. This study focused on the adsorption of lactoperoxidase and histatin 5, to investigate their possible importance in the initial salivary film formation. The adsorption was investigated by means of in situ ellipsometry, to both pure (hydrophilic) and methylated (hydrophobized) silica substrates, at concentrations relevant in saliva. The adsorption was investigated in terms of surface area per molecule and influence of surface wettability. Mass transport controlled adsorption in relation to the initial adsorption from human whole saliva and glandular saliva was also investigated. Results showed that lactoperoxidase adsorbed in larger amounts on pure silica compared to methylated surfaces. Histatin 5 adsorbed to the same extent to the two types of surfaces, but to a lesser extent compared to lactoperoxidase. The mass transport calculated adsorption rates of lactoperoxidase and histatin 5 showed that histatin 5 might potentially have a significant role in the initial adsorption from saliva, whereas lactoperoxidase may also adsorb but is not a dominating component.
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| 14. |
- Bessarab, Pavel F., et al.
(författare)
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Potential Energy Surfaces and Rates of Spin Transitions
- 2013
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Ingår i: Zeitschrift fur physikalische Chemie (Munchen. 1991). - : Walter de Gruyter. - 0942-9352. ; 227:9-11, s. 1543-1557
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Tidskriftsartikel (refereegranskat)abstract
- The stability of magnetic states and the mechanism for magnetic transitions can be analyzed in terms of the shape of the energy surface, which gives the energy as a function of the angles determining the orientation of the magnetic moments. Minima on the energy surface correspond to stable or metastable magnetic states and can represent parallel, antiparallel or, more generally, non-collinear arrangements. A rate theory has been developed for systems with arbitrary number, N, of magnetic moments, to estimate the thermal stability of magnetic states and the mechanism for magnetic transitions based on a transition state theory approach. The minimum energy path on the 2N-dimensional energy surface is determined to identify the transition mechanism and estimate the activation energy barrier. A pre-exponential factor in the rate expression is obtained from the Landau-Lifshitz-Gilbert equation for spin dynamics. The velocity is zero at saddle points so it is particularly important in this context to realize that the transition state is a dividing surface with 2N -1 degrees of freedom, not just a saddle point. An application of this rate theory to nanoscale Fe islands on W(110) has revealed how the transition mechanism and rate depend on island shape and size. Qualitative agreement is obtained with experimental measurements both for the activation energy and the pre-exponential factor. In particular, a distinct maximum is observed in the pre-exponential factor for islands where two possible transition mechanisms are competing: Uniform rotation and the formation of a temporary domain wall. The entropy of the transition state is enhanced for those islands making the pre-exponential factor more than an order of magnitude larger than for islands were only the uniform rotation is viable.
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| 15. |
- Hammarstrom, L, et al.
(författare)
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Mimicking photosystem II reactions in artificial photosynthesis
- 1999
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Ingår i: ZEITSCHRIFT FUR PHYSIKALISCHE CHEMIE-INTERNATIONAL JOURNAL OF RESEARCH IN PHYSICAL CHEMISTRY & CHEMICAL PHYSICS. - : R OLDENBOURG VERLAG. - 0942-9352. ; 213, s. 157-163
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Tidskriftsartikel (refereegranskat)abstract
- The paper describes a project aiming at the construction of functional mimics of the oxygen evolving complex of Photosystem II, coupled to photoinduced charge separation. Biomimetic electron donors - manganese complexes and tyrosine - have been linked to
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| 16. |
- Hammarström, Leif, et al.
(författare)
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Mimicking Photosystem II Reactions in Artificial Photosynthesis
- 1999
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Ingår i: Zeitschrift für Physikalische Chemie. - 0942-9352. ; 213:2, s. 157-163
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Tidskriftsartikel (refereegranskat)abstract
- The paper describes a project aiming at the construction of functional mimics of the oxygen evolving complex of Photosystem II, coupled to photoinduced charge separation. Biomimetic electron donors - manganese complexes and tyrosine - have been linked to a Ru(II)-polypyridine photosensitizer. Oxidation of the donors by intramolecular electron transfer from the photo-oxidized Ru(III) complex was demonstrated using optical flash photolysis and EPR experiments. A step-wise electron transfer Mn → tyrosine → Ru(III) was demonstrated, in a sequence analogous to reactions of the PSII donor side.
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| 17. |
- Iqbal, Z., et al.
(författare)
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Photocatalytic degradation of dyes in aqueous media by gum shellac stabilized selenium nanoparticles
- 2023
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Ingår i: Zeitschrift Fur Physikalische Chemie-International Journal of Research in Physical Chemistry & Chemical Physics. - 0942-9352. ; 237:8, s. 1139-1152
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Tidskriftsartikel (refereegranskat)abstract
- The present work outlines the successful synthesis of selenium nanoparticles (Se NPs) stabilized with gum shellac (GS) and their use as photocatalyst for the enhanced degradation of dyes. Se NPs were synthesized by a simple and cost effective chemical reduction method using selenious acid, GS and sodium borohydride. Gum shellac was used as stabilizing agent. The orange red gum shellac-selenium nanoparticles (GS-Se NPs) were characterized by UV-Vis spectroscopy, Fourier transform infra-red (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The morphology of these particles appeared to be uniform and spherical as observed in SEM images. Energy dispersive X-ray spectroscopic profile showed the presence of elemental selenium, carbon and oxygen. The synthesized GS-Se NPs were investigated for their photo-catalytic efficiency towards degradation of methylene blue (MB) and methyl orange (MO) dye in aqueous media. Absorbance was measured at ?(max) 665 nm and 455 nm for MB and MO, respectively. Maximum degradation of MB in-comparison with MO obtained at 50 mg/L were 81.72 % and 71.42 % respectively. A very slow degradation rate was observed for the MO and MB in the absence of synthesized photocatalyst whereas greater percentage degradation was observed for the GS-Se NPs.
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| 18. |
- Olovsson, Ivar
(författare)
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Comparison of the proton transfer path in hydrogen bonds from theoretical potential energy surfaces and the concept of conservation of bond order
- 2006
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Ingår i: Zeitschrift fur physikalische Chemie (Munchen. 1991). - : Walter de Gruyter GmbH. - 0942-9352. ; 220:7, s. 797-810
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Tidskriftsartikel (refereegranskat)abstract
- The 'quantum-mechanically derived reaction coordinates' (QMRC) for the proton transfer in hydrogen bonds involving fluorine, oxygen and chlorine have been derived from earlier ab initio calculations of potential energy surfaces. A comparison is made between QMRC and the corresponding reaction coordinates (BORC) derived by applying the Pauling bond order concept together with the principle of conservation of bond order. Theoretical calculation have shown that sum of the bond orders remains close to constant along the reaction coordinate in agreement with the Pauling postulate. The BORC correlation curves agree very well with theoretical results. The results indicate that the BORC curve gives a good representation of the reaction coordinates (ptoton transfer path) for any X-H---Y aggregate.
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| 19. |
- Olovsson, Ivar
(författare)
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The Role of the Lone Pairs in Hydrogen Bonding
- 2006
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Ingår i: Zeitschrift fur physikalische Chemie (Munchen. 1991). - : Walter de Gruyter GmbH. - 0942-9352. ; 220:7, s. 963-978
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Tidskriftsartikel (refereegranskat)abstract
- The paper discusses some aspects of the electron lone-pairs in H-bonded structures: their role in determining the short-range structure and the effect of the environment on the electron density. In the water molecule the entire non blonded region apperars to be equally accessible for hydrogen bonding and the details of the hydrogen-bond arrangement are mainly determined by simple geometrical and topological requirements. Many examples may be taken to illustrate that it is important to take the whole electron and nuclear distribution into account when discussing the relative arrangement of interacting molecules. The resulting structure of one particular compound is determined by the net balance of many intermolecular interactions and not only by the hydrogen bonding, even if the resulting structure is consistent with hydrogen-bond directionality. From structural data it can be concluded that immediate accptor of a hydrogen bond is some negative charge accumulation, such as in a lone-pair region, but not specifically any individual lone pairs in the traditional, atomic sense.
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| 20. |
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