Search Results (111)

The metallogelation process has been successfully achieved by utilizing a crystal engineering approach to generate a new metallogel. While the coordination of metal ions to ligands plays a very important role for building the primary structure, the stabilization and morphology of metallogels are heavily dependent on various intra-molecular interactions and non-covalent interactions, with hydrogen bonding (HB) often playing a dominant and structurally organizing role. In the present study, gelation experiments were achieved successfully by reacting vanadium acetylacetonate with a hydrazone ligand using different solvents. The metallogel shows excellent gelation ability with 1.7 wt% minimum gelator concentrations and the gel–sol dissociation temperature, T_gel is 55 °C (water/methanol). The structural properties of the metallogel were studied using single-crystal X-ray crystallography. The crystal structure analysis of the metallogel shows the presence of various interactions such as hydrogen bonding, pi–pi interactions, pnictogen bonding, and other weak non-covalent interactions. These molecular interactions play a very important role in the gelation process and also affect the gel’s properties like swelling behavior, viscosity, and elasticity. Full article

The water thermodynamics is characterized by polydispersity, which determines its structural and dynamic properties. This is due to the specifics of its characteristic bond: the hydrogen bond (HB). The isobars of the two fundamental thermodynamic functions, the isothermal compressibility ($K_T(P.T)$) and the isobaric expansivity (${\alpha }_P(P,T)$), show the presence of a temperature $T^{*}\simeq 315\pm 5$ K where both have a singular behavior. In this work, by carefully considering the thermal properties of the isobars of density $\rho$, specific heat $C_P$ and the self-diffusion $D_S$, we suggest the universality characteristics of this temperature. In addition, by analyzing the average intermolecular distance $d_{OO}$, in the same area of the P-T phase diagram, we demonstrate that such realities are due in the supercooled liquid state to the ratio between its two characteristic phases: the low-density liquid (LDL due to HB) and the HDL (which entirely characterizes the remaining parts of the phase diagram). Full article

Crystal molecular structure of 3-(anthracen-2′-yl)-ortho-carborane was determined by single crystal X-ray diffraction study at 100 K. The asymmetric cell unit contains two enantiomeric pairs of molecules, in one of which the intramolecular dihydrogen bond CH...HB is formed with the participation of the C(1)H hydrogen of the anthracene substituent, and in the other with the participation of the C(3)H hydrogen. In all molecules, the polycyclic aromatic and carborane fragments are rotated relative to each other in such a way that the C-C bond of the ortho-carborane cage is approximately parallel to the plane of the aromatic substituent. According to quantum chemical calculations, the minimum energy corresponds to the formation of an intramolecular dihydrogen bond C(1)H...HB(4/7), whereas the C(3)H...HB(4/7) bond is formed rather as a result of intermolecular interactions in the crystal lattice. Full article

A new method is presented for the estimation of contributions to solvation free energy from dispersion, polar, and hydrogen-bonding (HB) intermolecular interactions. COSMO-type quantum chemical solvation calculations are used for the development of four new molecular descriptors of solutes for their electrostatic interactions. The new model needs one to three solvent-specific parameters for the prediction of solvation free energies. The widely used Abraham’s LSER model is used for providing the reference solvation free energy data for the determination of the solvent-specific parameters. Extensive calculations in 80 solvent systems have verified the good performance of the model. The very same molecular descriptors are used for the calculation of solvation enthalpies. The advantages of the present model over Abraham’s LSER model are discussed along with the complementary character of the two models. Enthalpy and free-energy solvation information for pure solvents is translated into partial solvation parameters (PSP) analogous to the widely used Hansen solubility parameters and enlarge significantly their range of applications. The potential and the perspectives of the new approach for further molecular thermodynamic developments are discussed. Full article

The interaction between DNA and two-dimensional materials, such as graphene oxide (GO), has aroused significant research interest due to its potential applications, including biosensors, drug delivery, and gene therapy. However, the difference in interaction between DNA and oxygen functional groups on GO remains unclear, and direct observation at the experimental level is still challenging. In this work, we investigated the adsorption process of a single-stranded DNA (ssDNA) onto GO exhibiting a series of oxidation degrees by molecular dynamics simulations. We found that the ssDNA preferentially binds to hydroxyl groups (-OH) over epoxy groups (-O-) on the GO surface. This preferential adsorption feature may be attributed to the stronger tendency of ssDNA to form hydrogen bonds (HBs) with hydroxyl groups compared to epoxy groups in aqueous solutions. Further analysis indicates that the affinity interaction between ssDNA and hydroxyl groups presumably increases the oxidation degree of GO, thus suggesting a better binding between ssDNA and GO. This work is not only expected to provide the underlying mechanism of ssDNA onto graphene-based interfaces but also offers a deeper understanding of the structures of DNA-two-dimensional complexes, which may potentially contribute to designing new molecular structures for bio-sensing-related nano-devices and nanostructures. Full article

The cocrystallization of trans-[PtI₂(NCR)₂] (R = NMe₂1, NEt₂2, Ph 3, o-ClC₆H₄4) with iodine and iodoform gave the crystalline adducts 1∙4I₂, 2∙2CHI₃, 3∙2CHI₃, and 4∙4I₂, whose structures were studied by single-crystal X-ray diffractometry (XRD). In the structures, apart from the rather predictable C–H⋯I hydrogen bonds (HBs) and I–I⋯I or C–I⋯I halogen bonds (XBs) with the iodide ligands, we identified bifurcated I–I⋯(I–Pt) and C–I⋯(I–Pt) metal-involving XBs, where the platinum center and iodide ligands function as simultaneous XB acceptors toward σ-holes of I atoms in I₂ or CHI₃. Appropriate density functional theory (DFT) calculations (PBE-D3/jorge-DZP-DKH with plane waves in the GAPW method) performed with periodic boundary conditions confirmed the existence of the bifurcated metal-involving I–I⋯(I–Pt) and C–I⋯(I–Pt) interactions and their noncovalent nature. Full article

The present work deals with polymer blends produced from poly(3-hydroxybutyrate), P3HB and polyurethane. Linear polyurethane (PU) was here synthesized by reacting polypropylene glycol with 4,4′-diphenylmethane diisocyanate, and was used in amounts of 5, 10 and 15 wt. %. The polymers were melt-mixed using a twin-screw extruder after prior premixing. The obtained blends were tested by differential scanning calorimetry analysis (DSC), Fourier transformation infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX). Their thermal and mechanical properties, including impact resistance, hardness, tensile and flexural properties, were also determined, and the surface topography and roughness were analyzed. FTIR analysis of the prepared blends confirmed the interactions of PU with the P3HB matrix via hydrogen bonding. Analysis of the surface topography of the samples showed that the higher the PU content, the greater the regularity and homogeneity of the surface structure. The roughness of the P3HB blend containing 5 wt. % PU was the greatest. SEM images of the fracture surfaces of the blend samples explain the mechanism of the improvement of their mechanical properties. The obtained polymer blends were characterized by significantly lower hardness, and better impact strength and relative elongation at break compared to native P3HB. The DSC results confirm a decrease in the glass transition, melting and crystallization temperatures with increasing amounts of PU in the blends. The lower melting temperature and the higher degradation temperature of the resulted blends than native P3HB make the processing conditions easier, and prevent the degradation of the material. The best mechanical and thermal properties were shown by blends containing 10 wt. % of PU. Full article

This work is a continuation of our recent work on the prediction of hydrogen-bonding (HB) interaction enthalpies. In the present work, a simple method is proposed for the prediction of the HB interaction free energies. Quantum chemical (QC) calculations are combined with the Linear Solvation Energy Relationship (LSER) approach for the determination of novel QC-LSER molecular descriptors and the development of the method. Each hydrogen-bonded molecule is characterized by an acidity or proton donor capacity, ${\alpha }_G$, and/or a basicity or proton acceptor capacity, ${\beta }_G$. These descriptors suffice for the prediction of HB interaction free energy when the interacting molecules possess one acidic and or one basic site. In this case of two interacting molecules, 1 and 2, their overall HB interaction free energy is $c\left({\alpha }_{G1}{\beta }_{G2}+{\beta }_{G1}{\alpha }_{G2}\right)$, where c is a universal constant equal to (ln10)RT = 5.71 kJ/mol at 25 °C. This holds true over the full composition range, that is, regardless of which molecule is solute and which solvent. In the case of complex multi-sited molecules possessing more than one distant acidic site and/or more than one type of distant basic sites, two sets of ${\alpha }_G$ and ${\beta }_G$ descriptors are needed, one for the molecule as solute in any solvent and one for the same molecule as the solvent of any solute. Descriptors ${\alpha }_G$ and ${\beta }_G$ are reported for a number of common hydrogen-bonded molecules but they may be obtained for any other hydrogen-bonded molecule of interest from its molecular surface charge distribution already available or easily obtained via relatively cheap DFT/basis-set QC calculations. The new predictive scheme is validated against corresponding estimations of the widely used Abraham’s LSER model. The developments in the present work and the previous one are useful for solvation studies in chemical and biochemical systems and, particularly, for equation-of-state developments in molecular thermodynamics. The strengths and limitations of the new predictive method are critically discussed. Full article

Background: Diosgenin, a powerful compound found in fenugreek and Dioscorea villosa, has diverse pharmacological effects. This study examines the anticancer potential of diosgenin nanoparticles (Dio-NPs) against DMBA-induced breast cancer in mice in combination with tamoxifen. Methods: In the current investigation, characterization of Dio-NPs was performed, including their size, shape, zeta potential, UV-vis, and FT-IR spectra. Dio-NPs (120 mg/kg) and tamoxifen (2 mg/kg) were given to mice with DMBA-induced breast cancer, either alone or in combination, over 4 weeks. We measured inflammatory and oxidative stress markers, as well as gene expressions related to apoptosis, using ELISA and qRT-PCR. Additionally, molecular docking studies were conducted to assess the binding affinity of diosgenin with specific proteins. Molecular dynamics simulations were conducted on CDK4, AKT, and CDK6 proteins with diosgenin using GROMACS. The systems were solved, neutralized, and equilibrated under NVT and NPT ensembles. Simulations ran for 100 ns, and trajectories were analyzed for RMSD, RMSF, RG, SASA, and hydrogen bonds. Results: The IC₅₀ of Dio-NPs against MCF-7 cells was 47.96 ± 1.48 µg/mL. Dio-NPs had a zeta potential of −21.8 ± 0.6 mV and a size of 56.85 ± 3.19 nm and were uniform and spherical. The LD₅₀ of Dio-NPs was 2400 mg/kg. DMBA exposure increased WBCs, inflammatory markers, oxidative stress, and gene expression of CDK2, CDK4, CDK6, and Akt, while reducing Hb%, RBCs, PLTs, GSH, superoxide dismutase, and catalase levels. Dio-NPs and tamoxifen, both alone and combined, significantly reduced these effects. The combination treatment was more effective than individual treatments. Histological analyses supported these findings. Molecular docking showed diosgenin had a stronger binding affinity with the target proteins compared to tamoxifen. The simulations revealed that diosgenin effectively binds to CDK4, AKT, and CDK6, maintaining their stability and structural integrity. CDK4, AKT, and CDK6 showed consistent RMSD, RG, and SASA values, with moderate flexibility and stable hydrogen bonding patterns, suggesting their potential as therapeutic targets. Conclusions: Combining diosgenin and tamoxifen effectively inhibits breast cancer progression in DMBA-treated mice. This is primarily due to the reduction in expression of CDK2, CDK4, CDK6, and Akt proteins, which enhances the sensitivity of resistant breast cancer cells to tamoxifen. Full article

We report the topochemical solid-state polymerization of different series of symmetrical diacetylenes (DAs) and asymmetrical chlorodiacetylenes (ClDAs), whose members differ in their alkyl spacing lengths of one to four methylene units (n = 1, 2, 3, 4) between the diyne and carbamate functionalities. Structure determination by single-crystal X-Ray diffraction (SCXRD) confirms that in each of these series, at least 50% of the analyses show monomers with a particular stacking pattern presenting two potential directions of polymerization simultaneously. An organization of a crystalline polydiacetylene (PDA) with an oblique chain orientation with respect to the network of cooperatives hydrogen bonds is rather rare in the literature (only two cases), and here we have obtained two more examples of this type of structural motif (supported by SCXRD analysis of the polymer). Orientation control is essential to optimize the performance of conjugated polymers, and a spacer length modification strategy presents a potential way to achieve this in the case of PDA. Full article

Two new Co(II) coordination compounds viz. [Co(H₂O)(bz)₂(μ-3-Ampy)₂]_n (1) and [Co(4-Mebz)₂(2-Ampy)₂] (2) (wherebz = benzoate, 4-Mebz = 4-Methylbenzoate and Ampy = Aminopyridine) were synthesized and characterized via elemental (CHN), electronic spectroscopy, FT-IR spectroscopy, and thermogravimetric analysis (TGA). The molecular structures were determined by single-crystal X-ray diffraction analysis, inferring that compound 1 crystallizes as a 3-Ampy bridged Co(II) coordination polymer, whereas compound 2 crystallizes as a mononuclear Co(II) compound. Compound 1 unfolds the presence of N–H⋯O, C–H⋯O, O–H⋯O, C–H⋯N and aromatic π⋯π interactions, while for compound 2, N–H⋯O, C–H⋯O, C–H⋯C and C–H⋯π interactions are observed. Both the compounds showcase scarcely reported chelate ring interactions involving the benzoate moiety (chelate ring⋯π in 1 and N–H⋯chelate ring in 2). We also conducted theoretical evaluations comprising of combined QTAIM/NCI plot analysis, DFT energy calculation and MEP surface analysis to analyze the supramolecular interactions present in the crystal structures. As per QTAIM parameters, the predominance of π-stacking interactions over hydrogen bonds in stabilizing the assembly in compound 1 is affirmed. Likewise, in compound 2, both hydrogen bonding (HBs) and C–H⋯π interactions are deemed pivotal in stabilizing the dimeric assemblies. The in vitro antiproliferative activities of compounds 1 and 2 were performed against Dalton’s lymphoma (DL) cancer cell lines through cytotoxicity and apoptosis assays, showcasing higher cytotoxicity of compound 1 (IC₅₀ = 28 μM) over compound 2 (IC₅₀ = 34 μM). Additionally, a molecular docking study investigated the structure–activity relationship of these compounds and allowed an understanding of the molecular behaviour after treatment. Full article

The benzimidazole core (BI) plays a central role in biologically active molecules. The BI nucleus is widely used as a building block to generate a variety of bioactive heterocyclic compounds to be used as antihelmintics, antiprotozoal, antimalarials, anti-inflammatories, antivirals, antimicrobials, antiparasitics, and antimycobacterials. A versatile BI derivative is the 2-guanidinobenzimidazole (2GBI), which, together with its derivatives, is a very interesting poly-functional planar molecule having a delocalised 10 π electrons system conjugated with the guanidine group. The 2GBI molecule has five nitrogen atoms containing five labile N–H bonds, which interact with the out-ward-facing channel entrance, forming a labile complex with the biological receptor sites. In this work, 2GBI and their derivatives were analyzed as ligands to form host–guest, coordination and organometallic complexes. Synthesis methodology, metal geometries, hydrogen bonding (HB) interactions, and the biological activities of the complexes were discussed. Full article

Herein, β-glucan (BG) was extracted from different colored varieties of highland barley (HB, Hordeum vulgare), defined as BBG, WBG, and LBG depending on the colors of black, white, and blue and their molecular structure and physicochemical properties were investigated through a series of technical methods. The high-performance anion-exchange chromatography (HPAEC) results indicated the extracted BBG, LBG, and WBG mainly comprised glucose regardless of color. The molecular weight (M_w) of BBG, LBG, and WBG were 55.87 kDa, 65.19 kDa, and 81.59 kDa, respectively. 4-Glc(p), 3-Glc(p), and t-Glc(p) accounted for a larger proportion (>90%) of the total methylated residues according to gas chromatography–mass spectrometry (GC-MS) analysis. Additionally, Fourier transform infrared (FT-IR) spectroscopy revealed that the β-linkage of LBG had a greater capacity to develop stronger hydrogen bonds, due to the absence of 3,4-Glc(p). Among them, LBG had a low particle size distribution and a high shear viscosity, showing obvious round aggregates on its surface. Meanwhile, BBG presented a high peak viscosity (PV) and thermal stability. Based on the differences in their molecular structure, it could be concluded that there were different physicochemical properties among BBG, LBG, and WBG. Full article

This publication reports a facile and convenient preparation of tri-O-acetyl-glucopyranoses, derived from the corresponding 2-deoxyaminosugar, where the vicinal anomeric and C2 positions are decorated by azido and (thio)ureido groups, respectively. This double functionalization leads to an inherently chiral core incorporating the versatile azido and (thio)ureido linkages prone to further manipulation. The latter also provides a structural element for hydrogen-bonded donor-acceptor (HB-DA) sites, which are of immense value in organocatalytic pursuits. A computation-aided conformational analysis unveils the landscape of available conformers and their relative stability. N-aryl (thio)ureas bearing substituents at ortho positions exist as mixtures of M- and P-atropisomeric conformers. Full article

Ammonium oxathioamidate (1) was synthesised by the reaction between O-ethyl-thioxamate (oxalic acid-1-amide-2-O-ethyl ester) and ammonium hydrogen carbonate in water solution. Compound 1 was fully characterised by both microanalytical (elemental analysis, melting point determination) and spectroscopic means (FT-IR and NMR spectroscopy). Crystals suitable for single-crystal X-ray diffraction were isolated by slow evaporation of an ethanol solution of the compound. The analysis of the crystal packing reveals the prominent role exerted by intermolecular hydrogen bonding (HB) and chalcogen bonding (ChB) interactions. Full article