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In this paper, X-ray diffraction (XRD), differential scanning calorimetry (DSC), broadband dielectric (BDS), and Fourier transform infrared (FTIR) spectroscopy supported by molecular dynamics (MD) simulations and quantum chemical computations were applied to investigate the structural and thermal properties, molecular dynamics, and H-bonding pattern of R -, S -, and RS -flurbiprofen (FLP). Experimental data indicated various spatial molecular arrangements in crystalline forms of examined systems, which seemed to disappear in the liquid state. Surprisingly, deeper analysis of high-pressure dielectric data revealed unexpected variation in the activation volume of pure enantiomers and a racemate. MD simulations showed that it is an effect of the clusterization phenomenon and a higher population of small associates in the former samples. Moreover, theoretical consideration exposed the particular role of unspecific F-Π interactions as a driving force underlying local molecular arrangements of molecules in the liquid and the crystal lattice of R -, S -, and RS -FLP.

In this paper, we propose one-step synthetic strategies for obtaining well-defined linear and star-shaped polyvinylpyrrolidone ( lin PVP and star PVP). The produced macromolecules and a commercial PVP K30 with linear topology were investigated as potential matrices for suppressing metronidazole (MTZ) crystallization. Interestingly, during the formation of binary mixtures (BMs) containing different polymers and MTZ, we found that linear PVPs exhibit maximum miscibility with the drug at a 50:50 weight ratio ( w / w ), while the star-shaped polymer mixes with MTZ even at a 30:70 w / w . To explain these observations, comprehensive studies of MTZ-PVP formulations with various contents of both components were performed using Fourier-transform infrared spectroscopy, differential scanning calorimetry, and X-ray diffraction. The obtained results clearly showed that the polymer's topology plays a significant role in the type of interactions occurring between the matrix and MTZ. Additionally, we established that for MTZ-PVP 50:50 and 75:25 w / w BMs, linear polymers have the most substantial impact on inhibiting the crystallization of API. The star-shaped macromolecule turned out to be the least effective in stabilizing amorphous MTZ at these polymer concentrations. Nevertheless, long-term structural investigations of the MTZ- star PVP 30:70 w / w system (which is not achievable for linear PVPs) demonstrated its complete amorphousness for over one month.

A series of four alcohols, n -propanol and its halogen (Cl, Br, and I) derivatives, were selected to study the effects of variation in polarity and halogen-driven interactions on the hydrogen bonding pattern and supramolecular structure by means of experimental and theoretical methods. It was demonstrated on both grounds that the average strength of H-bonds remains the same but dissociation enthalpy, the size of molecular nanoassemblies, as well as long-range correlations between dipoles vary with the molecular weight of halogen atom. Further molecular dynamics simulations indicated that it is connected to the variation in the molecular order introduced by specific halogen-based hydrogen bonds and halogen-halogen interactions. Our results also provided important experimental evidence supporting the assumption of the transient chain model on the molecular origin of the structural process in self-assembling alcohols.

In this paper, the molecular dynamics at different thermodynamic conditions of hydrogen-bonded (H-bonded) active pharmaceutical ingredient-ticagrelor (TICA) have been investigated. Extensive high-pressure (HP) dielectric studies revealed surprising high sensitivity of the structural (α)-relaxation to compression. They also showed that unexpectedly the shape of the α-peak remains invariable at various temperature (T) and pressure (p) conditions at constant α-relaxation time. Further infrared measurements on the ordinary and pressure densified glasses of the examined compound indicated that the hydrogen-bonding pattern in TICA is unchanged by the applied experimental conditions. Such behavior was in contrast to that observed recently for ritonavir (where the organization of hydrogen bonds varied at high p) and explained the lack of changes in the width of α-dispersion with compression. Moreover, HP dielectric measurements performed in the glassy state of TICA revealed the high sensitivity of the slow secondary (β)-relaxation (Johari-Goldstein type) to pressure and fulfillment of the isochronal superpositioning of α- and JG-β-relaxation times. Additionally, it was found that the activation entropy for the β-process, estimated from the Eyring equation (a high positive value at 0.1 MPa) slightly increases with compression. We suggested that the reason for that are probably small conformational variations of TICA molecules at elevated p., (© 2023. The Author(s).)

In this paper, thermal properties, atomic-scale structure, and molecular dynamics (at ambient and high pressure) of native melatonin (MLT) and its partially-deuterated derivative (MLT-d 2 ) have been investigated. Based on infrared spectroscopy, it was shown that treating MLT with D 2 O causes the replacement of hydrogen atoms attached to the nitrogen by deuterium. The degree of such substitution was very high (> 99%) and the deuterated sample remained stable after exposure to the air as well as during the melting and vitrification processes. Further calorimetric studies revealed the appearance of a peculiar thermal event before the melting of crystalline MLT-d 2 , which was assigned by the X-ray diffraction to a local negative thermal expansion of the unit cell. Finally, the high-pressure dielectric experiments indicated a few interesting findings, including the variation in the shape of the structural relaxation peak during compression, the difference in the pressure evolution of the glass transition temperature, and the temperature dependence of activation volume for both MLT species. The variations in these parameters manifest a different impact of the compression/densification on the dynamics of hydrogen and deuterium bonds in the native and partially-deuterated MLT, respectively., (© 2022. The Author(s).)

In this study, several experimental techniques were applied to probe thermal properties, molecular dynamics, crystallization kinetics and intermolecular interactions in binary mixtures (BMs) composed of flutamide (FL) and various poly( N -vinylpyrrolidone) (PVP) polymers, including a commercial product and, importantly, samples obtained from high-pressure syntheses, which differ in microstructure (defined by the tacticity of the macromolecule) from the commercial PVP. Differential Scanning Calorimetry (DSC) studies revealed a particularly large difference between the glass transition temperature ( T g ) of FL+PVPsynth. mixtures with 10 and 30 wt% of the excipient. In the case of the FL+PVPcomm. system, this effect was significantly lower. Such unexpected findings for the former mixtures were strictly connected to the variation of the microstructure of the polymer. Moreover, combined DSC and dielectric measurements showed that the onset of FL crystallization is significantly suppressed in the BM composed of the synthesized polymers. Further non-isothermal DSC investigations carried out on various FL+10 wt% PVP mixtures revealed a slowing down of FL crystallization in all FL-based systems (the best inhibitor of this process was PVP M n = 190 kg/mol). Our research indicated a significant contribution of the microstructure of the polymer on the physical stability of the pharmaceutical-an issue completely overlooked in the literature.

In this paper, the molecular dynamics, H-bonding pattern and wettability of the primary and secondary monohydroxyalcohols, 2-ethyl-1-hexanol (2E1H), 2-ethyl-1-butanol (2E1B) and 5-methyl-3-heptanol (5M3H) infiltrated into native and functionalized silica and alumina pores having pore diameters, d = 4 nm and d = 10 nm, have been studied with the use of Broadband Dielectric (BDS) and Fourier Transform InfraRed (FTIR) spectroscopies, as well as contact angle measurements. We found significant differences in the behavior of alcohols forming chain- (2E1H, 2E1B) or micelle-like (5M3H) supramolecular structures despite of their similarities in the wettability and interfacial energy. It turned out that nanoassociates as well as H-bonds are more or less affected by the confinement dependently on the chemical structure and alcohol order. Moreover, a peculiar behavior of the self-assemblies at the interface was noted in the latter material (5M3H). Finally, it was found that irrespectively to the sample, type of pores, functionalization, the temperature evolution of Debye relaxation times, τ D , of the confined systems deviates from the bulk behavior always at similar τ D due to vitrification of the interfacial layer. This finding is a clear indication that unexpectedly dynamics (mobility) of the supramolecular structures close to the hydrophilic and hydrophobic surfaces is similar in each system., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

In the crystal structure of the title compound, C4H9NO2, the O-H⋯N hydrogen bonds link the mol-ecules into supra-molecular chains extending along the b-axis direction. The conformation of the NOH group in the nearly planar (r.m.s. deviation = 0.0546 Å) ethyl aceto-hydroximate mol-ecule is trans to N=C.

The Title Compound (systematic Name: 4-oxo-penta-noic acid), C5H8O3, is close to planar (r.m.s. deviation = 0.0762 Å). In the crystal, the mol-ecules inter-act via O-H⋯O hydrogen bonds in which the hy-droxy O atoms act as donors and the ketone O atoms in adjacent mol-ecules as acceptors, forming C(7) chains along [20-1].

Polarized IR spectra of hydrogen-bonded acetone oxime and 3,5-dimethylpyrazole crystals were measured at 293 and 77 K in the ν(X-H) and ν(X-D) band frequency ranges. These crystals contain molecular trimers in their lattices. The individual crystal spectral properties remain in a close relation with the electronic structure of the two different molecular systems. We show that a vibronic coupling mechanism involving the hydrogen-bond protons and the electrons on the π-electronic systems in the molecules determines the way in which the vibrational exciton coupling between the hydrogen bonds in the trimers occurs. A strong coupling in 3,5-dimethylpyrazole trimers prefers a "tail-to-head"-type Davydov coupling widespread via the π-electrons. A weak through-space exciton coupling in acetone oxime trimers involves three adjacent hydrogen bonds in each cycle. The relative contribution of each exciton coupling mechanism in the trimer spectra generation is temperature and the molecular electronic structure-dependent. This explains the observed difference in the temperature-induced evolution of the compared spectra. The mechanism of the H/D isotopic "self-organization" processes in the crystal hydrogen bonds was also analyzed. The two types of the hydrogen-bond trimers exhibit the same way, in which the H/D isotopic recognition mechanism occurs. In acetone oxime and 3,5-dimethylpyrazole trimers, identical hydrogen isotope atoms exist in these entire hydrogen-bond systems.

Polarized IR spectra of hydrogen-bonded 3,5-diphenylpyrazole and of 4-methyl-1,2,4-triazolethione crystals were measured at 293 and 77 K in the νN-H and νN-D band frequency ranges. These crystals contain molecular tetramers in their lattices. The individual crystal spectral properties remain in close relation with the electronic structure of the two different molecular systems. We show that a vibronic coupling mechanism involving the hydrogen bond protons and the electrons on the π-electronic systems in the molecules determines the way in which the vibrational exciton coupling between the hydrogen bonds in the tetramers occurs. A strong coupling in 3,5-diphenylpyrazole tetramers prefers a "tail-to-head"-type Davydov coupling widespread via the π-electrons. A weak through-space exciton coupling in 4-methyl-1,2,4-triazolethione tetramers involves two opposite hydrogen bonds in the cycles. The relative contributions of each exciton coupling mechanism in the tetramer spectra generation are temperature and the molecular electronic structure dependence. This explains the observed difference in the temperature-induced evolution of the compared spectra. The mechanism of the H/D isotopic ''self-organization'' processes in the crystal hydrogen bonds was also analyzed. The two types of hydrogen bond tetramers differ by the way in which the processes occur. In 3,5-diphenylpyrazole tetramers, identical hydrogen isotope atoms exist in the entire hydrogen bond system, whereas in the case of 4-methyl-1,2,4-triazolethione crystals, the H/D isotopic self-organization mechanism involves the opposite hydrogen bonds in a tetramer.

This article focuses on the problem of remarkably strong changes in the fine structure patterns of the ν(N-H) and ν(N-D) bands attributed to the hydrogen and deuterium bonds accompanying the phase transition, which occurs between two polymorphic forms of oxindole. The lattices of these two different crystals contain hydrogen-bonded cyclic dimers differ in their geometry parameters. The source of these differences in the polymorph spectral properties results from the geometry relations concerning the dimers constituting the lattice structural units. In the case of the "alpha" phase, the hydrogen bond lengths of the dimers differ by 0.18 Å. This leads to the "off-resonance exciton coupling" weakly involving the dimer hydrogen bonds. For the "beta" phase, with practically symmetric dimers in the lattice, the spectra become typical for centrosymmetric hydrogen bond systems due to the full resonance of the proton or deuteron vibrations.

The molecule of the title compound (systematic name: 6-chloroindolin-2-one), C(8)H(6)ClNO, is almost planar, with a dihedral angle of 1.13 (9)° between the planes of the constituent pyrrolidine and benzene rings. Centrosymmetric dimers are formed in the crystal structure by N-H···O hydrogen bonds, and these dimers are additionally linked by Cl···Cl and C-H···O interactions. Density functional theory (DFT) calculations at the B3LYP/6-31 G(d,p) level of theory were used to optimize the molecular structure and the geometry was best reproduced by optimization of two interacting molecules. The bond orders in the molecule, estimated using the natural bond orbitals (NBO) formalism, are consistent with the observed bond lengths. In particular, the contribution of the lone pair of electrons on the N atom to the N-C bond in the N-C=O group is revealed. The measured IR spectrum of the compound shows a red shift of the N-H stretching frequency compared with the free molecule, due to the formation of the hydrogen bonds.

This paper presents the investigation results of the polarized IR spectra of the hydrogen bond in crystals of 3- and 4-methylthioacetanilide. The spectra were measured at 293 and 77 K by a transmission method, with the use of polarized light. The main spectral properties of the crystals can be interpreted satisfactorily in terms of the "strong-coupling" theory, on the basis of the hydrogen bond centrosymmetric dimer model. The spectra revealed that the strongest vibrational exciton coupling involved the closely spaced hydrogen bonds, each belonging to a different chain of associated 3- and 4-methylthioacetanilide molecules. A weaker exciton coupling involved the adjacent hydrogen bonds in each individual chain. It was proven that a nonrandom distribution of the protons and deuterons took place in the lattices of isotopically diluted crystalline samples of 3- and 4-methylthioacetanilide. In each case, the H/D isotopic "self-organization" mechanism involved all four hydrogen bonds from each unit cell.

The mononuclear title complex, [MnCl(2)(C(3)H(4)N(2))(2)(H(2)O)(2)], is located on a crystallographic inversion center. The Mn(II) ion is coordinated by two imidazole ligands [Mn-N = 2.2080 (9) A], two Cl atoms [Mn-Cl = 2.5747 (3) A] and two water molecules [Mn-O = 2.2064 (8) A]. These six monodentate ligands define an octahedron with almost ideal angles: the adjacent N-Mn-O, N-Mn-Cl and O-Mn-Cl angles are 90.56 (3), 92.04 (2) and 90.21 (2) degrees , respectively. Hydrogen bonds between the coordinated water molecules and Cl atoms form a two-dimensional network parallel to (100) involving R(4)(2)(8) rings. The two-dimensional networks link into a three-dimensional framework through weaker N-H...Cl interactions. Thermogravimetric analysis results are in accordance with the water-coordinated character of the substance and its dehydration in two successive steps.

The title compound (systematic name: trans-hex-3-enedioic acid), C(6)H(8)O(4), (I), is located on an inversion centre. A less accurate room-temperature structure has been reported previously [Ganis & Martuscelli (1966). Ric. Sci. 36, 439], without the position of the H atom involved in hydrogen bonding. The carboxylic acid groups of (I) link molecules across inversion centres through O-H...O hydrogen-bonded pairs. The result of these interactions is the formation of chains with the graph-set description C(2)(2)(18), which run along the c axis. The significance of this study lies in the analysis of the interactions occurring via hydrogen bonds, as well as in the comparison drawn between the molecular structure of (I) and the structures of several other acid derivatives possessing two carboxylic acid groups.

The crystal structure of the title compound, C(10)H(12)O(4).H(2)O, consists of (3,4-dimethoxyphenyl)acetic acid and water molecules linked by O-H...O hydrogen bonds to form cyclic structures with graph-set motifs R(1)(2)(5) and R(4)(4)(12). These hydrogen-bond patterns result in a three-dimensional network with graph-set motifs R(4)(4)(20) and R(4)(4)(22), and the formation of larger macrocycles, respectively. The C-C bond lengths and the endocyclic angles of the benzene ring show a noticeable asymmetry, which is connected with the charge-transfer interaction of the carboxyl or methoxy groups and the benzene ring. The title compound is one of the simple carboxylic acid systems that form hydrates. Thus, the significance of this study lies in the analysis of the interactions in this structure and the aggregations occurring via hydrogen bonds in two crystalline forms of (3,4-dimethoxyphenyl)acetic acid, namely the present hydrate and the anhydrous form [Chopra, Choudhury & Guru Row (2003). Acta Cryst. E59, o433-o434]. The correlation between the IR spectrum of this compound and its structural data are also discussed.

The title compound, C(10)H(9)NO, contains an acetyl group that is nearly coplanar with the indole ring system, with an angle between the planes of the heterocyclic ring and the acetyl group of 1.75 (17) degrees . The planes of the benzene and pyrrole rings in the indole system make a dihedral angle of 2.05 (11) degrees . Each molecule in the unit cell is linked through N-H...O hydrogen bonds to two other molecules, forming hydrogen-bonded chains in the [101] direction with graph set C(6). The significance of this study lies in the analysis of the interactions occurring via hydrogen bonds in this structure, as well as in the comparison drawn between the molecular structure of the title compound and those of several other indole derivatives possessing a 3-carbonyl group. The correlation between the IR spectrum of this compound and the structural data is also discussed.