Dominant Intermolecular Interactions Research Articles

High-pressure phase transitions of series of catenated nitrogen energetic crystals Nx (x = 4, 8, 10): A comparative DFT-D study.

High-pressure chemistry has advantages in exploring novel energetic materials and is the key to the development of new high-energy materials. The complexity and danger of experimental processes require a deeper understanding by advanced simulation techniques. Therefore, a high-precision comparative DFT-D study was performed to investigate the effect of pressure on series of catenated nitrogen energetic crystals. The results show that there exist phase transitions for N4, N8, and N10 at 4 GPa, 3 GPa, and 2 GPa respectively, which are embodied in various properties of these crystals. Studies on band gap and DOS indicate pressure-induced improvement on the ability for electrons transition from occupied orbitals to empty ones. Hirshfeld surface analysis qualitatively suggests that hydrogen bonding interactions are becoming dominant inter-molecular interactions. The topological analysis quantitatively reveals that pressure is beneficial to enhancing the inter-molecular hydrogen bonding energy, thereby playing an important role in the stability of high-pressure phases. The discussions on mechanical properties imply that pressure can improve the rigidity of these energetic systems and enhance their mechanical properties. Our findings evidence the high-pressure phase transitions for catenated nitrogen energetic crystals, which lay the theoretical foundation for the development of novel energetic materials. Series of catenated nitrogen energetic crystals N4, N8 and N10 were obtained from experiments. Optimizations were performed by GGA/PBE functional and G06 dispersion correction within the framework of CASTEP code, and the cutoff energies of the plane waves were set to 700 eV. The particular moiety in the crystals was extracted by Multiwfn 3.6 and subsequent analysis was conducted by Gaussian 09W package.

Investigation of intermolecular interactions in binary mixtures of N,N-dimethyl benzyl amine with higher alkanols (N,N-dimethyl benzyl amine with 1-octanol, 1-nonanol, 1-decanol)

ABSTRACT Measurements of densities (ρ), speeds of sound (u), and viscosities (η) for binary mixtures of N,N-dimethyl benzyl amine (DMBA) with 1-octanol (D1), 1-nonanol (D2), and 1-decanol (D3) were performed across temperatures from 303.15 K to 313.15 K under atmospheric pressure, covering all composition ranges. These experimental results were utilised to calculate the excess molar volume, excess isentropic compressibility, viscosity deviation, and the excess Gibbs free energy of activation for viscous flow. Calculations for partial molar properties and infinite dilution partial molar properties were also carried out for each binary mixture. The dominant intermolecular interactions within these mixtures were analysed using the PFP theory. Additionally, the Jouyban−Acree model was applied to predict the thermo physical properties such as density, speed of sound, and viscosity. The model’s accuracy was evaluated by comparing predicted values with experimental data through mean relative deviations (MRDs) and individual relative deviations (IRDs).

Triadic Halobenzene Processing Additive Combined Advantages of Both Solvent and Solid Types for Efficient and Stable Organic Solar Cells.

Solvent additives with a high boiling point (BP) and low vapor pressure (VP) have formed a key handle for improving the performance of organic solar cells (OSCs). However, it is not always clear whether they remain in the active-layer film after deposition, which can negatively affect the reproducibility and stability of OSCs. In this study, an easily removable solvent additive (4-chloro-2-fluoroiodobenzene (CFIB)) with a low BP and high VP is introduced, behaving like volatile solid additives that can be completely removed during the device fabrication process. In-depth studies of CFIB addition into the D18-Cl donor and N3 acceptor validate its dominant non-covalent intermolecular interactions with N3 through effective electrostatic interactions. Such phenomena improve charge dynamics and kinetics by optimizing the morphology, leading to enhanced performance of D18-Cl:N3-based devices with a power conversion efficiency of 18.54%. The CFIB-treated device exhibits exceptional thermal stability (T80 lifetime = 120h) at 85°C compared with the CFIB-free device, because of its morphological robustness by evolving no residual CFIB in the film. The CFIB features a combination of advantages of solvent (easy application) and solid (high volatility) additives, demonstrating its great potential use in the commercial mass production of OSCs.

Thin Film Formation of HSA in the Presence of CTAB-Capped Gold Nanorods through Phase Separation.

Phase behavior in protein-nanoparticle systems in light of protein corona formation has been investigated. We report the formation of HSA thin films following the addition of a solid protein to a solution of CTAB-capped gold nanorods (AuNRs) via phase separation. The phase separation behavior was observed through UV-vis spectroscopy, turbidity assays, and DLS studies. UV-vis spectra for the protein-AuNR solution indicated a possible self-assembly formation by CTAB-HSA complexes and AuNR-HSA conjugates. The turbidity was found to increase linearly up to 30-50% v/v for each component. The growth phase slope is proportional to the concentration of the components, AuNRs, and HSA, with no lag phase. Dynamic light scattering (DLS) shows the formation of larger aggregates with time, implying a segregated phase of AuNR-HSA and a CTAB-HSA-AuNR network. ζ-potential values confirm surface modification, implying protein corona formation on nanorods. The thin films were also characterized using SEM, AFM, SAXS, XPS, FTIR, and TGA studies. SEM images show a smooth surface with a reduced number of pores, indicating the compactness of the deposited structure. AFM shows two different structural pattern formations with the deposition, indicating possible self-assembly of the protein-conjugated nanoparticles. FTIR studies indicate a change in the hydrogen bonding network and confirm the CTAB-HSA-AuNR complex network formation. The XPS studies indicate Au-S bond formation, along with Au-S-S-Au interactions. SAXS studies indicate the formation of aggregates (oligomers), as well as the presence of dominant attractive intermolecular interactions in the thin films.

Understanding leaching of amylopectin from cellulose/amylopectin/[Bmim][Cl] blends during regeneration from water and aqueous ethanol using molecular dynamic simulations

The difference in amylopectin leaching from cellulose/amylopectin/1-butyl-3-methylimidazolium chloride ([Bmim][Cl]) blends during regeneration in water and aqueous ethanol has been observed in experimental studies. To fully understand the above phenomenon, molecular dynamic simulation was adopted to illustrate the regeneration mechanism after dissolution to understand interactions responsible for the elution/leaching of amylopectin starch. Molecular dynamics (MD) simulations reveal that amylopectin dissolution in [Bmim][Cl] is similar to cellulose in ionic liquids (ILs). Strong hydroxyl-Cl- hydrogen bonding drives dissolution, with [Bmim]+ ions playing a stabilizing role through van der Waals interactions. Amylopectin regeneration in water and aqueous ethanol occurs through the initial disruption of weak hydroxyl-Cl- bridging bonds followed by the disruption of strong non-bridging hydrogen bonds. The water network intercalates amylopectin chains, forming a few “short-lived” interchain HBs. This leaves a very weak electrostatic interaction as the dominant intermolecular interaction between water-regenerated amylopectin chains. Water solvates and elutes low molecular weight amylopectin oligomers, with only 47.29 % amylopectin retained in the blend. In contrast, ethanol-water hydrophobic-hydrogen interactions disrupt the water network, create an ethanol-rich environment, shorten the intermolecular distance between chains, decrease diffusivity, increase hydrogen bonding lifetime between amylopectin, and regenerate amylopectin in aqueous ethanol. The regenerated amylopectin chains interact through improved but weak electrostatic interaction. Improved interaction between chains limits the erosion of low-molecular-weight amylopectin from films retaining 83.11 % amylopectin, approximately two times that in water. At a molecular level, we established that a very weak electrostatic interaction among amylopectin is responsible for leaching in water during regeneration. Ethanol enhances electrostatic interaction among amylopectin chains to limit amylopectin leaching in aqueous ethanol. These observations could apply to other polysaccharide blended materials prepared by the dissolution-regeneration method.

Homogeneous and Heterogeneous Self‐Assembly of Luminescent Pyromellitic Dianhydride‐Based Charge‐Transfer Complexes

AbstractUsing easily hydrolyzable brominated pyromellitic dianhydride (PMDA) as an electron acceptor, a wide variety of structurally stable binary organic charge‐transfer (CT) microcrystals that are stabilized by dominant intermolecular CT interactions is achieved. By varying the electron‐donating abilities of π‐electron compounds, the resulting single crystalline CT assemblies display tailorable fluorescence emissions spanning from green to near‐infrared. Upon implantation of a π‐electron donor anthracene (An) into fluoranthene‐PMDA (Fl‐PMDA), red and NIR emissions of ternary alloyed assemblies are substantially enhanced due to efficient energy transfer from Fl‐PMDA to An‐PMDA as well as structural complementarity between two CT complexes. Depending on the well‐matched epitaxial relationship, seeded growth of phenanthrene‐PMDA (Ph‐PMDA) onto the pre‐existing An‐PMDA microcrystals is also achieved, leading to core‐shell heterostructures with full and partial coverage. Such an epitaxial growth strategy is also applicable to the construction of microscale heterostructures of diverse CT complex combinations. The ternary Fl1−xAnx‐PMDA alloyed assemblies display composition‐dependent tailorable optical waveguiding behaviors. While An‐PMDA@Ph‐PMDA core‐shell microrods present wavelength‐dependent two‐photon excited fluorescence performances. The rational creation of these homogeneous and heterogeneous CT‐assembled architectures provides us a deep insight to investigate multicomponent functional organic cocrystals.

Molecular simulations of understanding the structure and separation thermodynamics of 5-Hydroxymethylfurfural from 1-Butyl-3-Methyl imidazolium tetrafluoroborate

The furfural-based compounds derived from biomass is proven to be reducing greenhouse gas emissions for sustainable chemical processes. 5-hydroxymethylfurfural (5-HMF) is a bio-renewable material that can serve as a significant platform chemical to produce biofuels, green polymers, solvents, etc. Ionic liquids (ILs) have shown promising reaction media to produce 5-HMF from glucose and fructose. However, there is a substantial challenge in separating the 5-HMF from the ILs. In this paper, we use an organic solvent tetrahydrofuran (THF) to understand the molecular level properties of 5-HMF from 1-butyl-3-methyl imidazolium tetra-fluoroborate [BMIM]+[BF4]− using all-atom molecular dynamics simulations. We have analyzed various intermolecular structures, and dynamic and separation thermodynamic properties. Our results show that with an increase in 5-HMF concentration, we observe a favorable intermolecular interaction between 5-HMF and THF compared to the interactions between 5-HMF and [BMIM]+. The 5-HMF presents the dominant intermolecular interactions with cations compared to the anions. The self-diffusion coefficient of 5-HMF shows a decrease in THF and an increase in [BMIM]+[BF4]− with the rise in 5-HMF concentration. The solvation free energy (ΔGsolv) values of 5-HMF in both IL and THF show less negative value with an increase in 5-HMF concentration. The transfer free energy (ΔGtransfer) of 5-HMF (from IL to THF) shows less positive values with an increase in 5-HMF concentration. Overall results presented in this work are promising for understanding the complex interactions between furfural-based compounds and ILs.

Synthesis, structural elucidation, Hirshfeld surface analysis and cytotoxicity studies of homometallic dinuclear Cu(II), Ni(II) and Zn(II) Schiff base complexes derived from m-phenylenediamine

A polydentate Schiff base ligand, L was synthesized via condensation reaction between o-vanillin (OVan) and trimethyl-m-phenylenediamine [(Me)MPD]. Its Cu(II), Ni(II), and Zn(II) dinuclear complexes were prepared through complexation with corresponding acetate salts. The compounds were characterized via CHN elemental analyzer, molar conductivity, magnetic susceptibility, TGA, IR, 1H and 13C NMR. The crystal structure of the ligand, L and zinc(II) complex, Zn2L2 were elucidated by using single crystal x-ray diffraction. The crystal structure of Zn2L2 showed that the two Zn(II) metal atoms serve as bridges between the two units of the ligand through ONNO donor atoms leading to the formation of a centrosymmetric cyclic dinuclear complex. Based on the single x-ray crystallography, the zinc atoms exhibit a distorted tetrahedral geometry. Hirshfeld surface analysis was performed to determine the intermolecular interactions in the crystal structures. From this analysis, it revealed that H···H interaction for L (55%) and Zn2L2 (62.7%) was the dominant intermolecular interaction in the total area of Hirshfeld surface. The ν(CN) and ν(CO) peaks in IR spectra of the ligand L appeared at 1615 cm−1 and 1255 cm−1, respectively. The peaks shifted to lower and higher frequency by Δν of 4–12 cm−1 in the complexes. The new peaks assignable to ν(MN) and ν(MO) were observed at 514–562 cm−1 and 422–436 cm−1, respectively, indicating the coordination of the metal centers to the azomethine N and phenolic O. The Cu(II) and Ni(II) complexes are paramagnetic with μeff of 1.90 and 2.89 B.M., respectively. The thermal gravimetric analysis revealed the presence of three lattice water molecules in Cu(II) complex. The cytotoxicity studies of all compounds were carried out against colon cancer cell lines (HCT116). The parent ligand was found to be less cytotoxic than its metal complexes. Cu(II) showed the highest activity with IC50 of 0.73 ± 0.21 μM, better than the standard 5-FU.

Synthesis of a Novel Hydrazone of Thieno[2,3-d]pyrimidine Clubbed with Ninhydrin: X-ray Crystal Structure and Computational Investigations

The novel hydrazone-containing thieno[2,3-d]pyrimidine, namely, N′-(1,3-dioxo-1,3-dihydro-2H-inden-2-ylidene)-2-(4-oxo-5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidin-3(4H)-yl)acetohydrazide 4 was synthesized in a very good yield from the reaction of the triketoester 1 or ninhydrin 2 with the exocyclic acetohydrazide 3 in methanol. Good-quality crystals of 4 were obtained by recrystallization of the compound from the DMF/MeOH solvent mixture. The target product 4 crystallized in the triclinic crystal system and P-1 space group. The topology analysis of molecular packing indicated that the H…H (30.4%), O…H (22.0%) and H…C (17.0%) contacts are the most dominant intermolecular interactions in the crystal of 4, while the O…H, N…H, H…C, N…C, O…C, C…C and O…O are the only contacts which have shorter interaction distances than the vdWs radii sum of the interacting atoms. The structure of 4 is optimized and the calculated structure showed good agreement with the experimental one. Additionally, MEP, HOMO, LUMO and the reactivity descriptors were calculated.

Understanding the agglomerate crystallisation of hexamine through X-ray microscopy and crystallographic modelling

The detailed molecular-scale mechanism of the growth of organic crystals underpins a diversity of phenomena, such as the isolation and purification of high-quality materials for the pharmaceutical and fine chemical sectors. Recent advances in X-ray Microscopy (XRM) and complementary diffraction contrast tomography (DCT) have enabled the detailed characterisation of the micro-structure of hexamine agglomerates. Detailed XRM analysis of the growth history and micro-structure of such agglomerates reveals a highly orientated epitaxial inter-relationship between their constituent micro-crystallites. This is found to be consistent with a secondary nucleation growth mechanism associated with re-growth at the 3-fold corner sites within the crystals’ dominant {110} dodecahedral morphology. The agglomeration appears to heal upon further growth as the aligned agglomerated micro-crystals connect and fuse together but, in doing so, pockets of inter-crystallite mother liquor become trapped forming a symmetric pattern of solvent inclusions. The mechanistic origin of this phenomenon is rationalised with respect to historical data together with an analysis of the solid-state chemistry of the compound through the development of a ‘snow flake’ model. The latter draws upon hexamine’s propensity for edge growth instabilities with increasing crystal size as well as its tendency for unstable growth at the facet corners along the 〈111〉 directions, a situation compounded by the lack of growth-promoting dislocations at the centers of the {110} habit surfaces. The agglomerative mechanism presented here could apply to other high symmetry crystal systems, particularly those whose crystal structures involve centred Bravais lattices and where the dominant inter-molecular interactions are angled towards the facet edges.

The combination of terahertz spectroscopy and density functional theory for vibrational modes and weak interactions analysis of vanillin derivatives

Three vanillin derivatives, including methyl vanillin, ethyl vanillin, and vanillyl alcohol were investigated in the range of 0.4–2.0 THz by terahertz time-domain spectroscopy (THz-TDS) and density functional theory (DFT). Vibrational mode automatic relevance determination (VMARD) method was introduced to assign the absorption peaks to the contribution ratio of corresponding vibrational modes, and VMARD revealed the dihedral angle torsion was the primary vibrational mode. Simultaneously, through independent gradient model based on Hirshfeld partition of molecular density (IGMH) method, van der Waals interaction was ascertained to be dominant weak noncovalent intermolecular interaction. This research, combining THz-TDS and the above-mentioned methods, elucidates the principle of material performance differences with structural analogs in the terahertz frequency band.

Host-aided intermolecular proton transfer in the inclusion complexes of imidazole ⊂ p-sulfonatocalix[4]arene

ABSTRACT Structural analysis of two multi-component complexes comprising p-sulfonatocalix[4]arene penta-anion as the host molecule and 1-methylimidazolium or 1-butylimidazolium monocation as the guest species, aquated gadolinium(III) ion along with tetraphenylphosphonium cation, is reported. An interesting process during the formation of these inclusion complexes was seen, in which a proton transfer from p-sulfonatocalix[4]arene to the neutral guest molecules took place via acid-base reaction. 1H NMR experiment confirms the formation of the host–guest complexes and the proton transfer between the calixarene and imidazolium species in solution. Careful analysis aided by CrystalExplorer, the dominant intermolecular interactions that contribute to the stabilisation of the host–guest complex formation were readily identified. Bilayer arrangement prevails in the extended structure for both complexes regardless of the type of guest species.

How Different Electrolytes Can Influence the Aqueous Solution Behavior of 1-Ethyl-3-Methylimidazolium Chloride: A Volumetric, Viscometric, and Infrared Spectroscopy Approach.

The density, sound velocity, and viscosity of 1-ethyl-3-methylimidazolium chloride [C2mim]Cl in pure water and aqueous solutions of some electrolytes such as potassium chloride, potassium carbonate, and potassium phosphate (weight fraction of salt fixed at ws = 0. 11) have been measured over a wide range of temperatures from 298.15 to 318.15 K. The obtained experimental data have been used to compute various volumetric, compressibility, and viscometric parameters, e.g., apparent molar properties, limiting apparent molar and transfer properties. The co-sphere overlap model was employed to describe the dominant intermolecular interactions in the ternary solutions. Additionally, the structure making/breaking nature of the [C2mim]Cl in the ternary solutions has been discussed in terms of Hepler's constant and the temperature derivative of viscosity B-coefficient (dB/dT). The activation free energy of solvent and solute, activation enthalpy, and activation entropy have been calculated by the application of transition state theory. The calculated parameters have been interpreted in the sense of solvent–solute and solute–solute interactions. The Fourier transform infrared (FTIR) studies also have been done for the studied systems. Volumetric, acoustic, viscometric, and spectroscopic studies can render some evidence and help to understand the aqueous solution behavior of ionic liquids.

Prediction of Solid Solution Formation among Chemically Similar Molecules Using Calculation of Lattice and Intermolecular Interaction Energy

Several 2-substituted 4-nitrobenzoic acid (NBA) derivatives such as 2-chloro-4-nitrobenzoic acid (2C4NBA), 2-methyl-4-nitrobenzoic acid (2CH34NBA) and 2-hydroxy-4-nitrobenzoic acid (2OH4NBA) were selected as model compounds because of their availability and chemically similar structures, in which the different group/atom (R) does not significantly affect the dominant intermolecular interactions – hydrogen bonds formed by the carboxylic group [1]. Quantum chemical calculations of lattice and intermolecular interaction energy were carried out to identify possible factors, which could be, used in prediction of the formation of solid solutions (SS) in binary systems of chemically similar molecules, in this case - various nitrobenzoic acid derivatives. Meanwhile, crystallization experiments were used to determine the experimental information about formation of solid solutions. The obtained crystalline phases were characterized by combined use of powder X-ray diffraction (XRPD) and differential scanning calorimetry/thermogravimetry (DSC/TG) [2].

Combining computational calculations with Raman spectroscopy to identify intermolecular interactions between SCN− and C6F5Br in solution

Raman spectra that reflect the actual interactions of molecular complexes in solution can be obtained in situ, and the dominant intermolecular interactions can be determined via comparison with the calculated Raman spectra of all the possible configurations of the molecular complexes. In this study, we investigated the intermolecular interactions between C6F5Br and SCN− in solution using this method. The dominant intermolecular interaction in this di-molecular complex is identified as anion-π interaction, rather than halogen bonding. This method may find further applications in many fields, especially in biology.

Combining photoinduced linkage isomerism and nonlinear optical properties in ruthenium nitrosyl complexes.

The complex trans-[RuNO(NH3)4F]SiF6 was synthesized in quantitative yield and the structure was characterized by X-ray diffraction and spectroscopic methods. The complex crystallizes in the non-centrosymmetric space group Pn. Hirshfeld surface analysis revealed that the dominant intermolecular interactions are of types H...F and F...O, which are likely to be responsible for the packing of the molecules in a non-centrosymmetric structure. Irradiation with blue light leads to the formation of Ru-ON (metastable state MS1) and Ru-η2-(NO) (metastable state MS2) bond isomers, as shown by IR and UV-Vis spectroscopy. The structural features of the MS1 isomer were elucidated by photocrystallography. The complex exhibits exceptionally good thermal stability of the metastable state MS1, such that it can be populated by light at 290-300 K, which is important for potential applications. The second harmonic (SH) emission can be generated by femtosecond-pulsed irradiation of the complex. The generated SH is rather efficient and stable under long-term exposure. Finally, since both metastable states and harmonic generation can be generated at room temperature, an attempt to drive the SH response by photoisomerization of the nitrosyl ligand was made and is discussed.

Quantifying the influence of surface chemical composition on surface energy during powder flow

In this study, the dominant intermolecular interactions at powder surfaces were investigated using inverse gas chromatography. Silica beads coated with molasses, corn starch, butter, or wheat gluten were used as model powders to emulate the interactions of surface components present in common food powders. The flow properties of the powders were analyzed using a rotational shear cell device at ambient conditions (25 °C and 40% relative humidity). A positive correlation (r = 0.72, p < 0.05) between the acid-base ratio (accounting for the ratio between the number of electron acceptor to electron donor surface sites) and the flow factor (flowability indicator, ffc at 1 kPa pre-shear stress) was observed for all the size ranges of surface-modified silica beads and industry-grade powders (modified corn starch and palm oil powders). The results depict the importance of acid-base surface components in understanding the mechanistic influence of pre-load molecular dynamics on the bulk flowability.

Influence of ligand coordination, solvent, and non-covalent interaction on the structural outcomes in coordination polymers with direct Cd(II)-alkanesulfonate bonds: A combined experimental and computational study

One-pot three-component Arbuzov-type reaction, involving anhydrous cadmium acetate, dimethyl sulfite, and tetraethylammonium iodide, has produced the cadmate salt, [Et4N]2 [Cd(OMs)4] (1) revealing weakly-coordinating methanesulfonate (OMs) ligands inside the metal-coordination sphere. The ‘ate’ salt 1 was found useful as a precursor in the preparation of coordination polymers with compositions, [Cd(OMs)2 (MeOH)]n (2) and [Cd(OMs)2(H2O)2]n (3), when subjected to crystallization in a methanol/chloroform mixture, in dry and ambient conditions, respectively. Compounds 1–3 were characterized by spectroscopic [1H, 13C NMR, FT-IR] techniques, and elemental and thermogravimetric analysis, while the structural attributes of 2 and 3 were investigated using single-crystal X-ray diffraction. The composition of 1 was further scrutinized by electrospray-ionization mass-spectrometry (ESI-MS). The crystal structure of 2 exhibits formation of a two-dimensional (2-D) layer facilitated by the bidentate (μ2) and tridentate (μ3) modes of coordination of sulfonate ligands around the metal center. The structure of 3 demonstrates the formation of 1-D linear chains, comprising of eight-membered cyclic [−Cd–O–S–O−] rings, owing to the bridging bidentate (μ2) mode of coordination of the sulfonate ligands. The involvement of hydrogen-bond interactions in 2 and 3 further perpetuates the assemblies into 2-D and 3-D supramolecular coordination polymers, respectively. This paper reports noticeable features such as, (a) cadmate dianion was afforded by the in situ generation of methanesulfonate ligands and subsequent complexation to the Cd(II) atom; (b) ability of alkanesulfonate ligand to display flexible coordinating behaviour [(μ2 and uncommon (μ3)] and prolific H-bond acceptor; (c) competitive ligation between strong coordinating solvents (MeOH and H2O) and weakly-coordinating methanesulfonate ligands; (d) effect of types and number of solvent molecules around the metal center with their participation in non-covalent interactions in bringing variation in the structural outcome; (e) the values of distances of Cd–O bonds in 1 and 2 fall in the range of 2.24 Å to 2.29 Å, suggesting the presence of direct metal-sulfonate interactions. The dispersion-corrected density functional theory (DFT-D) and Bader’s quantum theory of atoms in molecule (QTAIM) (primary and secondary) studies explored the structures, electronics, and non-covalent interactions of compounds 2 and 3. Additionally, among different involved non-covalent interactions, Hirshfeld surface analysis emphasized the presence of O⋯H/H⋯O contacts as the dominant intermolecular non-covalent interactions as the consolidating factor in crystal packing, in both compounds.

Cobalt Cubane Clusters Based on Schiff Base: Synthesis, Characterization, Magnetic Properties and Hirshfeld Surface Analysis

Three cobalt cubane clusters with the composition of [Co4(L)4], (1, H2L is 1-{3-[(3,5-dibromo-2-hydroxy-benzylidene)-amino]-2-hydroxy-phenyl}-ethanone (H2DBHBA); 2, H2L is 1-{3-[(5-bromo-2-hydroxy-benzylidene)-amino]-2-hydroxy-phenyl}-ethanone (H2BHBA); 3, H2L is 1-{3-[(3,5-dichloro-2-hydroxy-benzylidene)-amino]-2-hydroxy-phenyl}-ethanone (H2DCHBA)), were prepared by the reaction of cobalt nitrate hexahydrate with 2-hydroxy-benzaldehyde ramification under solvothermal conditions. All the complexes were characterized by elemental analysis, infrared spectroscopy, and X-ray single-crystal diffraction. Complexes 1–3 have tetranuclear clusters with a cubane topology in which the metal ions and the oxygen atoms from the L ligands occupying the alternate vertices of the cubane. The {Co4O4} cores display dominant anitferromagnetic interactions owing to the μ3-O bridged binding modes. Hirshfeld surface analysis revealed that H···H, and C···X (X = Br or Cl) interactions were the dominant intermolecular interactions.

Tetrahydroberberine pharmaceutical salts/cocrystals with dicarboxylic acids: Charge-assisted hydrogen bond recognitions and solubility regulation

With our consistent aim to further expand the solid-state landscape via molecular recognition and regulate solubility of tetrahydroberberine (THB), charge-assisted hydrogen bond (CAHB) recognitions and solubility regulation of pharmaceutical salts/cocrystals of THB are comprehensively investigated through exploring four pharmaceutical salts/cocrystals of THB. Four pharmaceutical salts/cocrystals of THB with oxalic acid, malonic acid, maleic acid and fumaric acid were obtained with solution evaporation approach. Comprehensive crystal structures and Hirshfeld surface analyses reveal CAHB recognitions between THBs and coformers are dominant intermolecular interactions to stabilize crystal packing. As expected, solubilities of four pharmaceutical salts/cocrystals of THB have been improved by dicarboxylic acids. Importantly, the dicarboxylic acid with higher solubility can modulate solubility of THB to become higher. The enthalpy of hydration for four pharmaceutical salts/cocrystals is greater than that for neutral pure THB when CAHBs (with electrostatic interactions) exist, which effectively improve solubility of THB. Solvent molecules can disrupt interactions of pharmaceutical salts/cocrystals by solvent···solute interactions when dicarboxylic acids are highly soluble thereby leading to enhancement of dissolution. Research results inspirationally enlightens that the solubility of insoluble APIs could be effectively regulated by utilizing gradient solubility coformers with simultaneously forming CAHBs between active pharmaceutical ingredients and coformers.