Classical Hydrogen Bonds Research Articles

Benzilic acid: a monoclinic polymorph

The title compound, C14H12O3, is an α-hydroxycarboxylic acid whose orthorhombic polymorph has been reported earlier [Qiu et al. (2007). Inorg. Chim. Acta, 360, 1819–1824]. The asymmetric unit contains two complete molecules. Classical hydrogen bonds, as well as C—H...O contacts, connect the molecules to infinite chains along the crystallographic c-axis direction.

X-ray structures, thermal stabilities and kinetics of guest desolvation of complexes of three fluorenone-derived host compounds with the polar aprotic guest solvent, tetramethylurea

The wheel-and-axle host compounds 9,9′-(1,4-phenylene)bis(fluoren-9-ol) (H1), 9,9′-(ethyne-1,2-diyl)bis(fluoren-9-ol) (H2) and 9,9′-(biphenyl-4,4′-diyl)bis(fluoren-9-ol) (H3) each formed complexes with tetramethylurea (TMU), a polar aprotic organic solvent, with host: guest ratios of 1:2. Single crystal X-ray diffraction revealed that these complexes crystallized in the monoclinic space group P21/c, their analyses being performed in P21/c for H1⋅2(TMU) and in the alternative setting P21/n for both H2·2(TMU) and H3·2(TMU). Furthermore, these inclusion compounds are stabilized by both classical and non-classical hydrogen bonds between the host and guest molecules. Hirshfeld surface analyses demonstrated that the percentage of interatomic (host)H···O(guest) interactions ranged between 7.8 and 10.3%, while thermal analyses showed that the relative thermal stabilities of these complexes were high, with the onset temperatures for the guest release event, Ton, being 83.1 (H1·2(TMU)), 81.1 (H2·2(TMU)) and 90.3 °C (H3·2(TMU)). Moreover, the calculated mass loss percentages, after heating each complex in a controlled manner to release the guest species, correlated closely with those expected for these 1:2 host: guest inclusion complexes. Finally, determination of the activation energies for complex desolvation yielded 148.7 ± 5.4, 128.6 ± 10.8 and 149.4 ± 0.8 kJ·mol‒1 for H1·2(TMU), H2·2(TMU) and H3·2(TMU) respectively. A single guest desolvation mechanism was at work in the first and last of these complexes, while this mechanism in H2·2(TMU) changed during this process. The H1·2(TMU) inclusion complex has been reported previously, and the results obtained in that work are also compared with those from the present investigation.

Polymorphism of 3-hydroxy-2-naphthoic acid: crystal structures, Hirshfeld surface analysis and properties

Polymorphs play an important role in mediating the physical properties of compounds. Therefore, a set of polymorphs based on 3‑hydroxy-2-naphthoic acid (HA), namely, α-HA (1), β-HA (2) and γ-HA·DMF (3) (DMF = N,N-dimethylformamide), were obtained by slow evaporation method, which were the solution of HA in ethanol, acetone and DMF, respectively. These crystal morphologies of HA have been characterized by single–crystal X–ray diffraction, IR and UV–Vis, and powder X-ray diffraction. In these polymorphism, classical hydrogen bonds of O–H∙∙∙O can be obviously observed, through which a supramolecular architecture will be generated. Apart from the classical hydrogen bonds, the hydrogen bonds of C–H⋯O can be only found in form γ-HA. The luminescent maximal are 497, 504 and 510 nm for α-HA,β-HA andγ-HA·DMF, respectively. The order of the maximal peaks is listed as the following: 3 > 2 > 1. Single-crystal X-ray diffraction analysis results reveal that the order of the distances between the aromatic rings is 3 > 2 > 1. The Hirshfeld analysis further confirm that there exists the largest contribution of the H∙∙∙H and H∙∙∙O close contacts in compound 3, which is in a good agreement with of the luminescent maxima in compound 3.

Copper (II) halide compounds with cationic N-donor ligands: Design, synthesis, structure and magnetism

Copper (II) complexes of the cationic ligands 1-(4′-pyridyl)-pyridinium (L1) and 1-(4′-pyridyl)-pyridin-4-ol (L2) have been prepared and characterized by single crystal X-ray diffraction and variable temperature magnetic susceptibility measurements: [Cu(L1)2X2]X2 [where X = Cl (1), Br (2)], and [Cu(L2)2X2]X2 [where X = Cl (3), Br (4)]. The complexes are fundamentally square planar with L2X2 coordination planes and long, semi-coordinate bonds to the additional halide ions. All compounds crystallize in monoclinic systems with 1 and 2 in the P21/n space group and 3 and 4 in the P21/c space group. The crystal structures are stabilized by both non-classical (in the case of 1 and 2) and classical (3 and 4) hydrogen bonds. EPR data for 1–4 support a rhombohedral structure, in good agreement with the local geometry as seen in the crystal structures. Magnetic susceptibility measurements show the presence of very weak antiferromagnetic interactions. In addition, the syntheses and magnetic properties of two neutral complexes, [Cu(L3)2X2]·2H2O [L3 = 1-(4′-pyridino)-4-pyridone; X = Cl (5), Br (6)] are reported. Magnetic susceptibility data indicate the presence of moderate antiferromagnetic exchange interactions [J ∼ 28 K (5), 60 K (6)] which were well modeled by the S = 1/2 Heisenberg uniform chain model.

Unravelling the hydrogen bonding patterns in telomeric G-quadruplexes: from structure to function*

In this work, we investigate the molecular basis of the telomere model of ageing. Its key trait is the hydrogen (H–) bonding patterns of G-tetrads that serve a top of G-quadruplexes composing telomeres. We show that these patterns demonstrate a variety of bonding characters – from classic hydrogen bonds to so-called ‘over-coordinated oxygen (OCO)’ bifurcated H-bonds that thus result in non-rigidity of G-tetrad structures. This work has implications for the functionality of G-quadruplexes and, in turn, for the quadruplex-based telomere model of ageing.

Theoretical description of hydride-hydride interactions in selected hydrogen storage materials.

The high content of hydride-hydride contacts Hδ-···δ-H in hydrogen storage materials appears to be relevant for hydrogen formation. At present time there is no consensus whether these contacts are attractive or repulsive. Accordingly, the main goal of this article is to shed light on physical factors which constitute homopolar hydride-hydride interactions Hδ-···δ-H in selected transition metal complexes i.e. HCoL4, L = CO,PPh3,PH3. In order to achieve this goal, the charge and energy decomposition ETS-NOCV approach along with the Interacting Quantum Atoms (IQA) and reduced density gradient (NCI) are applied for the bonded adducts L4CoH···HCoL4. Based on DFT and correlated methods it has been shown, that hydride-hydride interactions might be attractive and even far stronger than classical hydrogen bonds. The stability of the adducts is increased by phosphine ligand installation: overall Hδ-···δ-H bonding energy changes in the order: CO << PPh3 ~ PH3. It has been revealed that depending on monomer's conformations Hδ-···δ-H bonds are dominated by charge delocalization or London dispersion forces and the electrostatic term is also relevant. It is finally determined by IQA energy decomposition, that diatomic hydride-hydride interaction CoH···HCo is chameleon-like, namely, it is attractive in CO4CoH···HCoCO4, whereas the repulsion is unveiled in (CO)3(PPh3)CoH···HCo(CO)3(PPh3).

Polymorphism in 5-methylsalicylic acid: Insights into relative thermal behavior, luminescent properties, crystal structure, and Hirshfeld surface analysis

Polymorphs play an important role in mediating the physical and chemical properties of compounds. Three polymorphs were obtained from different solvents used in crystallization. A new polymorph of 5-methylsalicylic acid (γ-MSA) were obtained from acetic acid. The polymorphs α-MSA and β-MSA crystallized from water, and the mixed solvent containing methanol and water, respectively. The novel morphology of γ-MSA has been characterized by single–crystal X–ray diffraction, IR spectroscopy data, and powder X-ray diffraction. Single-crystal X-ray diffraction analysis shows that γ-MSA belongs to the monoclinic system with the P21/c space group. The parameters are listed as the following: a = 7.2795(5) Å, b = 15.2560(7) Å, c = 6.7170(4) Å, β=100.834(7)°, V = 762.83(8) Å3. In the novel polymorphic structure, classical hydrogen bonds of O–H···O can be obviously observed, through which a supramolecular architecture will be generated. Apart from the classical hydrogen bonds, the weak hydrogen bonds of C–H⋯O can be only found in form γ-MSA. The luminescent maximal are 394, 398 and 406 nm for α-MSA,β-MSA and γ-MSA, respectively. The order of the luminescent maximal peaks is listed as the following: α<β<γ. Single-crystal X-ray diffraction analysis results reveal that the order of the stacking interactions and the dihedral angles occurred between the carboxylic group and phenyl ring presents the following: α<β<γ. The Hirshfeld analysis further confirms that there exists the same sequence of the C···H intercontacts in α-, β- and γ-polymorphs. The contribution of the H···O/O···H close contacts in γ-MSA is the largest among these polymorphs, being confirmed by differential scanning calorimeter (DSC) data, which is in a good agreement with that of melting point. On the basis of analysis of DSC data and the fusion rules, the enthalpies (ΔH) and entropies (ΔS) can be estimated to be 29.5 kJ mol-1 and 69.4 J K-1 mol-1 for α; 31.1 kJ mol-1 and 72.8 J K-1 mol-1 for β, and 35.4 kJ mol-1 and 74.5 J K-1 mol-1 for γ), and these polymorphs are monotropically related. The sequences of melting point, enthalpies and entropies can be proposed: α<β<γ.

Crystal structures of four thio-glycosides involving carbamimido-thio-ate groups.

The compounds 2',3',4',6'-tetra-O-acetyl-β-d-gluco-pyranosyl N'-cyano-N-phenyl-carbamimido-thio-ate (C22H25N3O9S, 5a), 2',3',4',6'-tetra-O-acetyl-β-d-galacto-pyranosyl N'-cyano-N-phenyl-carbamimido-thio-ate, (C22H25N3O9S, 5b), 2',3',4',6'-tetra-O-acetyl-β-d-galacto-pyranosyl N'-cyano-N-methyl-carbamimido-thio-ate (C17H23N3O9S, 5c), and 2',3',4',6'-tetra-O-acetyl-β-d-galacto-pyranosyl N'-cyano-N-p-tolyl-carbamimido-thio-ate (C23H27N3O9S, 5d) all crystallize in P212121 with Z = 4. For all four structures, the configuration across the central (formal) C=N(CN) double bond of the carbamimido-thio-ate group is Z. The torsion angles C5-O1-C1-S (standard sugar numbering) are all close to 180°, confirming the β position of the substituent. Compound 5b involves an intra-molecular hydrogen bond N-H⋯O1; in 5c this contact is the weaker branch of a three-centre inter-action, whereas in 5a and 5d the H⋯O distances are much longer and do not represent significant inter-actions. The C-N bond lengths at the central carbon atom of the carbamimido-thio-ate group are almost equal. All C-O-C=O torsion angles of the acetyl groups correspond to a synperiplanar geometry, but otherwise all four mol-ecules display a high degree of conformational flexibility, with many widely differing torsion angles for equivalent groups. In the crystal packing, 5a, 5c and 5d form layer structures involving the classical hydrogen bond N-H⋯Ncyano and a variety of 'weak' hydrogen bonds C-H⋯O or C-H⋯S. The packing of 5b is almost featureless and involves a large number of borderline 'weak' hydrogen bonds. In an appendix, a potted history of wavelength preferences for structure determination is presented and it is recommended that, even for small organic crystals in non-centrosymmetric space groups, the use of Mo radiation should be considered.

Self-associates of 1,2,4-triazole: FTIR studies, quantum chemical calculations and topological analysis

The Fourier Transform Infrared (FTIR) spectroscopic technique has been employed to study the self-associates of 1,2,4-triazole (Htrz) in solid phase. The self-associates have been identified using density functional theory (DFT) calculations carried out on various multimers of Htrz under B3LYP/6–311++ G(d, p) level. Comparison of the experimental and theoretical frequencies of N−H andC−Hstretching absorptional bands indicate that Htrz exists as multimers upto hexamer. The Occupancy of the anti-bonding orbitals of the proton donors, Natural bond Orbital (NBO), Frontier Molecular Orbital (FMO), Electrostatic potential surface (ESP), reduced density gradient (RDG) analyses have also been executed. In addition, topological parameters have also been analysed to characterize the hydrogen bonds and proton donating covalent bonds. The analyses show that pentamer is the most stable among all the H-bonded associates and the dimer 3 in which classical and non-classical H-bond interaction coexists is the least stable. The topological parameter values suggest that the N−H bonds of dimer1/pentamer are with the highest/smallest covalent character. The criteria proposed in literature to describe the covalent nature of bonds, in particular proton donor bonds, appears to fails in the Htrz dimer in which classical and non-classical hydrogen bonds coexist.

Crystallization experiments of the wheel-and-axle host compound, 1,4-phenylene-bis(di-p-tolylmethanol), from pyridine and methylpyridine mixtures

1,4-Phenylene-bis(di-p-tolylmethanol) (H), a host compound with the wheel-and-axle design, formed complexes with organic guest solvents pyridine (PYR) and 2-, 3- and 4-methylpyridine (2MP, 3MP and 4MP). The host: guest (H: G) ratios were 1:3, 1:2, 1:2 and 1:1, respectively. Host crystallization experiments from mixed guests demonstrated H to prefer both PYR and 4MP; however, it was established that these difficult-to-separate (by fractional distillations) guest mixtures cannot be purified/separated by means of H through supramolecular chemistry strategies owing to these selectivities for PYR and 4MP being less than optimal. Single crystal X-ray diffraction experiments showed that each guest compound was held in its complex by means of a classical hydrogen bond with H, and that one of the preferred guests, PYR, experienced a significantly shorter contact of this type than the other guests. Hirshfeld surface analyses demonstrated that PYR was also involved in a greater percentage of (guest)N···H(host) interactions compared with the other guest molecules. Thermal analyses, on the other hand, revealed that 4MP (also a favoured guest species) formed the most stable complex of the four in this investigation. These results with H were compared to those obtained when employing a closely related host compound from a previous report, 1,4-bis(diphenylhydroxymethyl)benzene: while both host species preferred the same guests (PYR and 4MP), the extent of the selectivity of that host compound compared with H in the present work was significantly more enhanced. Thus, minor modifications may deleteriously affect the selectivity behaviour of closely related host compounds.

Crystal structures of tri-chlorido-(4-methyl-piperidine)gold(III) and two polymorphs of tri-bromido(4-methyl-piperidine)-gold(III).

Tri-chlorido-(4-methyl-piperidine)-gold(III), [AuCl3(C6H13N)], 1, crystallizes in Pbca with Z = 8. Tri-bromido-(4-methyl-piperidine)-gold(III), [AuBr3(C6H13N)], 2, crystallizes as two polymorphs, 2a in Pnma with Z = 4 (imposed mirror symmetry) and 2b, which is isotypic to 1. The Au-N bonds trans to Cl are somewhat shorter than those trans to Br, and the Au-Cl bonds trans to N are longer than those cis to N, whereas the Au-Br bonds trans to N are slightly shorter than the cis bonds. The methyl and AuX 3 groups (X = halogen) occupy equatorial positions at the six-membered ring. The packing of all three structures involves chains of mol-ecules with offset stacking of the AuX 3 moieties associated with short Au⋯X contacts; for 1 and 2b these are reinforced by N-H⋯X hydrogen bonds, whereas for 2a there are no classical hydrogen bonds and the chains are inter-connected by Br⋯Br contacts.

Crystal structure of 2,4-di-amino-5-(4-hy-droxy-3-meth-oxy-phen-yl)-8,8-dimethyl-6-oxo-6,7,8,9-tetra-hydro-5H-chromeno[2,3-b]pyridine-3-carbo-nitrile-di-methyl-formamide-water (1/1/1).

In the structure of the title compound, C22H22N4O4·C3H7NO·H2O, the entire tricyclic system is approximately planar except for the carbon atom bearing the two methyl groups; the meth-oxy-phenyl ring is approximately perpendicular to the tricycle. All seven potential hydrogen-bond donors take part in classical hydrogen bonds. The main mol-ecule and the DMF combine to form broad ribbons parallel to the a axis and roughly parallel to the ab plane; the water mol-ecules connect the residues in the third dimension.

New Aspects of Alcohol-Alcohol and Alcohol-Water Interactions: Crystallographic and Quantum Chemical Studies of Antiparallel O-H/O-H Interactions.

New modes of interaction, antiparallel O-H/O-H interactions of alcohol-alcohol dimers and alcohol-water dimers, were studied by analyzing data in the Cambridge Structural Database (CSD) and by calculating potential energy surfaces at a very accurate quantum chemical CCSD(T)/CBS level. The data reveal the existence of antiparallel interactions in crystal structures and significant interaction energies. Data from the CSD for alcohol-alcohol dimers show 49.2% of contacts with classical hydrogen bonds and 10.1% of contacts with antiparallel interactions, while for alcohol-water dimers, 59.4% of contacts are classical hydrogen bonds and only 0.6% of contacts are antiparallel interactions. The calculations were performed on methanol, ethanol, and n-propanol dimers. Classical hydrogen-bonded alcohol-alcohol and alcohol-water dimers have interaction energies of up to -6.2 kcal/mol and up to -5.5 kcal/mol, respectively. Antiparallel interactions in alcohol-alcohol and alcohol-water dimers have interaction energies of up to -4.7 kcal/mol and up to -4.4 kcal/mol, respectively. Symmetry-adapted perturbation theory analysis for antiparallel interactions shows their electrostatic nature.

An unexpected tautomer: synthesis and crystal structure of N-[6-amino-4-(methylsulfanyl)-1,2-dihydro-1,3,5-triazin-2-ylidene]benzenesulfonamide

The title compound, C10H11N5O2S2, consists of an unexpected tautomer with a protonated nitrogen atom in the triazine ring and a formal exocyclic double bond C=N to the sulfonamide moiety. The ring angles at the unsubstituted nitrogen atoms are narrow, at 115.57 (12) and 115.19 (12)°, respectively, whereas the angle at the carbon atom between these N atoms is very wide, 127.97 (13)°. The interplanar angle between the two rings is 79.56 (5)°. The molecules are linked by three classical hydrogen bonds, forming a ribbon structure. There are also unusual linkages involving three short contacts (&lt; 3 Å) from a sulfonamide oxygen atom to the C—NH—C part of a triazine ring.

Supramolecular motifs formed by CH3/Cl-substituted arene groups: evidence for structural differences in thiophosphoramides and similarities in their complexes.

Differences/similarities of supramolecular motifs are discussed in two new thiophosphoramide structures and their Ni molecular complexes: (C2H5O)2P(S)(NHC(S)NHCH2C6H4X) and [{(C2H5O)2P(S)(NC(S)NHCH2C6H4X)}2Ni] (X = Cl/CH3I/II and III/IV). The structures have equal numbers of donor/acceptor sites contributing to classical hydrogen bonds (PS/CS and 2 × NH in ligands and 2 × PS and 2 × NH in the complexes). However, these donor and acceptor sites contribute to inter/intramolecular hydrogen bonding in ligands and intramolecular hydrogen bonding in complexes. In the supramolecular assemblies of the ligands, the classic hydrogen bonds (N-H⋯S[double bond, length as m-dash]C) are restricted in dimer synthons, and the weaker interactions (formed by Cl/CH3 substituents) compete against each other. In the complexes, despite the lack of classic intermolecular hydrogen bond, numerous weak interactions, e.g., C-H⋯Y (Y = S, O, Ni, N, and π), contribute to the molecular assemblies, which do not include the participation of Cl/CH3. Thus, different packing features of ligands, but similar in complexes are observed. Each ligand and the associated complex show nearly equal supramolecular motifs in the slice of the substituted benzyl groups, related to the formation of C-H⋯Cl/π⋯π for the 4-Cl-C6H4CH2 groups in I/III and C-H⋯π for the 4-CH3-C6H4CH2 groups in II/IV. The repeatabilities of the motifs made by 4-Cl-C6H4CH2/4-CH3-C6H4CH2 were checked by surveying 142/844 structures with 178/1482 segments in the CSD, which show that 17% and 12% of the structures exhibited similarities with the title structures. The methods X-ray crystallography, 2D fingerprint plots, electrostatic potential surfaces, QTAIM, and energy framework calculations were applied to present the discussion.

Self-assembled Supramolecular Frameworks and Interaction Energy Studies of Acridine and Dihydroxynaphthalene based Cocrystals

Three cocrystals of acridine with 2,7-dihydroxynaphthalene (Ia and Ib) in two different polymorphs and 1,5-dihydroxynaphthalene (II) have been synthesized and characterized by single crystal x-ray diffraction method. Two polymorphs of acridine,2,7-dihydroxynaphthalene cocrystal crystallizes in same sapcegroup P-1 with different unit-cell parameters. In (Ia) the O‒H group form a syn-anti conformation whereas in (Ib) the O‒H group form an anti-anti conformation leads to the polymorphic structure of acridine, 2,7-dihydroxynaphthalene. This study reveals that the influence of π…π and C‒H…π interactions in the formation of one-, two-, and three-dimensional supramolecular frameworks when the classical hydrogen bonds such as O‒H…N and C‒H…O are limited to discrete motifs. The acridine molecules form continuous π…π stacking in the crystal structure of (Ia) and discrete π…π stacking in the crystal structure of (Ib) and (II). The conformational flexibility of the substituted hydroxy group has an influence in the supramolecular frameworks of the three-dimensional crystal structure. The intermolecular interaction energy calculation between the molecular pairs has been carried out to study the strength of the interaction and its dependence on the geometrical parameters.

Crystal structure of 2-[(5-amino-1-tosyl-1H-pyrazol-3-yl)-oxy]-1-(4-meth-oxy-phen-yl)ethan-1-one 1,4-dioxane monosolvate.

In the structure of the title compound, C19H19N3O5S·C4H8O2, the two independent dioxane mol-ecules each display inversion symmetry. The pyrazole ring is approximately parallel to the aromatic ring of the oxy-ethanone group and approximately perpendicular to the tolyl ring of the sulfonyl substituent. An extensive system of classical and 'weak' hydrogen bonds connects the residues to form a layer structure parallel to (201), within which dimeric subunits are conspicuous; neighbouring layers are connected by classical hydrogen bonds to dioxanes and by 'weak' hydrogen bonds from Htol-yl donors.

Crystal structures of the isotypic complexes bis-(morpholine)-gold(I) chloride and bis-(morpholine)-gold(I) bromide.

The compounds bis-(morpholine-κN)gold(I) chloride, [Au(C4H9NO)2]Cl, 1, and bis-(morpholine-κN)gold(I) bromide, [Au(C4H9NO)2]Br, 2, crystallize isotypically in space group C2/c with Z = 4. The gold atoms, which are axially positioned at the morpholine rings, lie on inversion centres (so that the N-Au-N coordination is exactly linear) and the halide anions on twofold axes. The residues are connected by a classical hydrogen bond N-H⋯halide and by a short gold⋯halide contact to form a layer structure parallel to the bc plane. The morpholine oxygen atom is not involved in classical hydrogen bonding.

Crystal structures and thermal analyses of three new high-energy hydrazinium hydro-closo-borates

New hydrazinium hydro-closo-borates with [BnHn]2– anions (n = 10 and 12) were obtained by direct reaction of the free acids (H3O)2[BnHn] with hydrazinium hydrate (N2H4 · x H2O) in aqueous solution. The three new compounds (N2H5)2[B10H10], (N2H5)2[B10H10] · 2 N2H4 and (N2H5)2[B12H12] · 2 N2H4 crystallize in the space groups P21/c, C2/c and P1‾, respectively. They contain up to 11 wt-% hydrogen. Two main kinds of bonding were observed in all crystal structures, classical hydrogen bonds (Nδ––Hδ+⋯Nδ–) and dihydrogen bonding between the negatively polarized hydrogen of the boron clusters and positively polarized hydrogen in hydrazinium cations (Bδ+–Hδ–⋯Hδ+–Nδ–). Thermal decomposition analyses of these compounds show that they absorb energy first, and then release a huge amount of energy upon decomposition and collapse of the structure. Due to the differently polarized hydrogen atoms in these compounds, hydrogen molecules (H2) are generated during the decomposition, which can be used as hydrogen fuel.

Applicability of transferable multipole pseudo-atoms for restoring inner-crystal electronic force density fields. Chemical bonding and binding features in the crystal and dimer of 1,3-bis(2-hydroxyethyl)-6-methyluracil.

We considered it timely to test the applicability of transferable multipole pseudo-atoms for restoring inner-crystal electronic force density fields. The procedure was carried out on the crystal of 1,3-bis(2-hydroxyethyl)-6-methyluracil, and some derived properties of the scalar potential and vector force fields were compared with those obtained from the experimental multipole model and from the aspherical pseudo-atom model with parameters fitted to the calculated structure factors. The procedure was shown to accurately replicate the general vector-field behavior, the peculiarities of the quantum potentials and the characteristics of the force-field pseudoatoms, such as charge, shape and volume, as well as to reproduce the relative arrangement of atomic and pseudoatomic zero-flux surfaces along internuclear regions. It was found that, in addition to the quantum-topological atoms, the force-field pseudoatoms are spatially reproduced within a single structural fragment and similar environment. In addition, the classical and nonclassical hydrogen bonds in the uracil derivative crystal, as well as the H...O, N...O and N...C interactions in the free π-stacked dimer of the uracil derivative molecules, were studied using the potential and force fields within the concepts of interatomic charge transfer and electron lone pair donation-acceptance. Remarkably, the nitrogen atoms in the N...O and N...C interactions behave rather like a Lewis base and an electron contributor. At the same time, the hydrogen atom in the H...O interaction, being a Lewis acid, also participates in the interatomic electron transfer by acting as a contributor. Thus, it has been argued that, when describing polar interatomic interactions within orbital-free considerations, it makes more physical sense to identify electronegative (electron occupier) and electropositive (electron contributor) atoms or subatomic fragments rather than nucleophilic and electrophilic sites.