Intermolecular Interaction Patterns Research Articles

Photocatalytic Degradation of Ciprofloxacin: A Combined Experimental and Theoretical Study Using Curcumin and Hydrogen Peroxide

Contamination of soil, water, and wastewater by pharmaceuticals, including antibiotics, is a global health problem. This work evaluated the use of a natural compound, curcumin (CUR), as a homogeneous photocatalyst, together with hydrogen peroxide (H2O2) as a benign oxidant, to promote the photodegradation of ciprofloxacin (CIP). Furthermore, we carried out theoretical calculations using density functional theory (DFT) to assess the chemical reactivity of ciprofloxacin. In addition, the intermolecular interaction patterns of two crystalline polymorphs of the antibiotic drug were analyzed through Hirshfeld surfaces. Finally, calculations using the TD-DFT formalism were carried out to understand the effects on the CIP molecule caused by the simultaneous presence of the CUR molecule and ultraviolet-visible light (UV-Vis). A photooxidative effect was observed in the presence of the CUR photocatalyst (CIP + CUR (1:0.5)), resulting in a degradation of CIP of up to 24.4%. However, increasing the concentration of the CUR photocatalyst (ciprofloxacin + curcumin (1:1)) decreased the photodegradation of CIP, which may be caused by competition between the CIP molecule and CUR for ROS generated in situ. Additionally, the calculation results showed that the electronic excitations caused by the associated CIP + CUR structures affect the CIP molecule, resulting in the effects observed experimentally. The results show that CUR, when applied as a photosensitizing catalyst, presents synergistic potential with H2O2 in the photocatalytic degradation of ciprofloxacin. This photocatalytic process can be applied to the environmental remediation of pharmaceutical micropollutants, a subject of ongoing studies.

Preparation of intrinsically fragile bent crystals.

Although molecular crystals have long been considered to be intrinsically brittle, a study of molecular crystals that are capable of plastic or elastic bending upon applying mechanical stress recently attracted significant attention. Malleable molecular crystals often need to meet specific criteria regarding the intermolecular interaction patterns within the crystal structure. Accordingly, examples have been reported where one polymorph shows bending, while other polymorphs of the same compound exhibit fracturing upon exposure to mechanical force. Here, we have succeeded in preparing bent crystals of an intrinsically fragile polymorph. Methylated flufenamic acid (1) can form three different polymorphs, i.e., 1α, 1β, and 1γ, of which 1β is difficult to isolate. Under mechanical force, the crystals of 1α exhibit remarkable plastic deformation, while those of 1γ are readily broken. Similar to the mechanical properties, the emission properties of 1 differ depending on the polymorph, i.e., 1γ exhibits a shorter-wavelength emission maximum and much higher emission quantum yield than 1α. Remarkably, both the unbent and bent forms of the 1α crystals can undergo a phase transition to the 1γ phase upon exposure to ethyl acetate. In this manner, phase transitions of the mechanically bent crystals of polymorph 1α afforded bent crystals of the intrinsically fragile polymorph 1γ. These findings may lead to a potential post-modification method for the preparation of functional flexible materials with enhanced emission properties in order to expand their applications.

Interactions of Nucleosomes with Acidic Patch-Binding Peptides: A Combined Structural Bioinformatics, Molecular Modeling, Fluorescence Polarization, and Single-Molecule FRET Study.

In eukaryotic organisms, genomic DNA associates with histone proteins to form nucleosomes. Nucleosomes provide a basis for genome compaction, epigenetic markup, and mediate interactions of nuclear proteins with their target DNA loci. A negatively charged (acidic) patch located on the H2A-H2B histone dimer is a characteristic feature of the nucleosomal surface. The acidic patch is a common site in the attachment of various chromatin proteins, including viral ones. Acidic patch-binding peptides present perspective compounds that can be used to modulate chromatin functioning by disrupting interactions of nucleosomes with natural proteins or alternatively targeting artificial moieties to the nucleosomes, which may be beneficial for the development of new therapeutics. In this work, we used several computational and experimental techniques to improve our understanding of how peptides may bind to the acidic patch and what are the consequences of their binding. Through extensive analysis of the PDB database, histone sequence analysis, and molecular dynamic simulations, we elucidated common binding patterns and key interactions that stabilize peptide-nucleosome complexes. Through MD simulations and FRET measurements, we characterized changes in nucleosome dynamics conferred by peptide binding. Using fluorescence polarization and gel electrophoresis, we evaluated the affinity and specificity of the LANA1-22 peptide to DNA and nucleosomes. Taken together, our study provides new insights into the different patterns of intermolecular interactions that can be employed by natural and designed peptides to bind to nucleosomes, and the effects of peptide binding on nucleosome dynamics and stability.

Stereochemically Pure Si‐Chiral Aminochlorosilanes

AbstractSilicon‐based compounds with stereochemical information and convertible functional units are valuable building blocks in synthetic chemistry. Si‐stereogenic aminochlorosilanes are built up by Si−N bond formation between an achiral dichlorosilane and a chiral enantiomerically pure primary amine. Both diastereomers could be isolated as stereochemically pure single‐crystals by fractional crystallization and were analyzed by X‐ray crystallography. Defined intermolecular interaction patterns were identified illustrating the role of N−H⋅⋅⋅π, C−H⋅⋅⋅π, and N−H⋅⋅⋅Cl contacts in the molecular crystalline packing arrangements. Stepwise functionalization of the silicon−chlorine and silicon−amine functions was carried out, demonstrating their potential for use as a chiral synthesis precursors. Via optically pure aminomethoxysilanes, enantiomerically enriched methoxysilanols, chloromethoxysilanes, and methoxysilanethiols were synthesized. The stereospecificity of the transformations was monitored. The (R)‐BINOL‐PSSLi method for determining the enantiomeric purity was found to be the tool of choice for acid‐sensitive silanols and silanethiols.

Study on Volumetric, Compressibility and Viscometric Behavior of Cationic Surfactants (CTAB and DTAB) in Aqueous Glycyl Dipeptide: A Thermo-Acoustic Approach

This study aims to understand how glycyl dipeptide affected the compressibility, volumetric behavior and viscometric behavior of the cationic surfactants CTAB (Cetyltrimethylammonium bromide) and DTAB (dodecyltrimethylammonium bromide). Information on solute-solute, solute-solvent, and solvent-solvent interactions has been inferred using the quantification of density (ρ), speed of sound (u) and viscosity in aqueous media containing glycyl dipeptide in the temperature range 293.15-313.15 K at an interval of 5 K. The data from the aforementioned research have been used to enumerate numerous volumetric and compressibility metrics that aid in the collection of information about the interactional behavior of the system under consideration. The study suggests that CTAB interacts strongly compared to DTAB with dipeptide, and it also significantly dehydrates glycyl dipeptide. The difference in water-water interactions caused by the loss of hydrophobic hydration of the surfactant molecules upon the addition of cationic surfactants may be the cause of the variation in determined parameters with surfactant concentration. Consideration of the structural rearrangement of molecules that may occur in the system has been used to explain the results of viscosity and computed factors related to viscosity. The patterns of competitive intermolecular interactions in the ternary (dipeptide + water + surfactant) system have been used to analyze the trends of all the parameters. The study may be helpful to understand the stability and structural changes in protein-surfactant systems mediated through various interactions that may be present in the system.

Solid-liquid equilibrium of 1-[4-(4-hydroxyphenyl)piperazin-1-yl]ethenone in twelve mono-solvents: Solubility determination, Hansen solubility parameter and thermodynamic analysis

The mole fraction solubility of 1-[4-(4-hydroxyphenyl)piperazin-1-yl]ethenone (1-HPE) in twelve mono-solvent systems namely “2-methoxyethanol (2-ME), methanol (MeOH), ethanol (EtOH), butan-1-ol (n-BuOH), 2-propoxyethanol (2-PE), propan-2-ol (i-PrOH), 2-methylpropan-1-ol (i-BuOH), Acetonitrile (MeCN), ethane-1,2-diol (EG), 2-ethoxyethanol (2-EE), propan-1-ol (n-PrOH), 2-butoxyethanol (2-BE)” were determined from 283.15 K to 323.15 K under 0.1 MPa. The experimental solubility order follows: 2-ME > 2-EE > 2-PE > 2-BE > MeOH > EtOH > n-PrOH > i-PrOH ≈ n-BuOH > i-BuOH ≈ MeCN > EG. The UNIQUAC model, modified Apelblat model, NRTL model, Wilson model, Jouyban model and NRTL-SAC model equation were used to correlate of 1-HPE solubility, and the average 104RMSD of them was 0.89, 1.21, 0.94, 4.72, 0.60 and 1.25, respectively. Furthermore, Hansen solubility parameters analysis (HSP) was used to evaluate the miscibility of 1-HPE in the selected solvents. Hirshfeld surface (HS) analysis was performed to discuss the electrostatic features and the patterns of intermolecular interactions of 1-HPE. Thermodynamic properties (ΔmixG, ΔmixS, ΔmixH, ΔdisG, ΔdisS, ΔdisH) were calculated by the UNIQUAC model. The calculated results indicated that the dissolution and mixing process of 1-HPE in the mono-solvents selected in this work was spontaneous and entropy increment.

New Insights on Glutathione's Supramolecular Arrangement and Its In Silico Analysis as an Angiotensin-Converting Enzyme Inhibitor.

Angiotensin-converting enzyme (ACE) inhibitors are one of the most active classes for cardiovascular diseases and hypertension treatment. In this regard, developing active and non-toxic ACE inhibitors is still a continuous challenge. Furthermore, the literature survey shows that oxidative stress plays a significant role in the development of hypertension. Herein, glutathione's molecular structure and supramolecular arrangements are evaluated as a potential ACE inhibitor. The tripeptide molecular modeling by density functional theory, the electronic structure by the frontier molecular orbitals, and the molecular electrostatic potential map to understand the biochemical processes inside the cell were analyzed. The supramolecular arrangements were studied by Hirshfeld surfaces, quantum theory of atoms in molecules, and natural bond orbital analyses. They showed distinct patterns of intermolecular interactions in each polymorph, as well as distinct stabilizations of these. Additionally, the molecular docking study presented the interactions between the active site residues of the ACE and glutathione via seven hydrogen bonds. The pharmacophore design indicated that the hydrogen bond acceptors are necessary for the interaction of this ligand with the binding site. The results provide useful information for the development of GSH analogs with higher ACE inhibitor activity.

Framework robustness in early d-block metal complexes with tripodal polyalcohol ligands

While performing our research on the tetranuclear “star-shaped” complexes formulated as [M3M'(LR)2(dpm)6], where M, M' are first-row d-block metals; H3LR is a tripodal alcohol, RC(CH2OH)3, with R = Et, Me or Ph; and Hdpm = dipivaloylmethane, we isolated a series of binuclear, alkoxide-bridged chelate complexes of titanium and chromium upon spontaneous deprotonation of the polyalcohol. In the titanium system, both [TiIII2Cl4(H2LEt)2]·4thf and [TiIV2Cl4(HLEt)2]·2thf were identified; they present analogous binuclear frameworks but distinct metal oxidation states and polyalcohol deprotonation degrees. Four similar CrIII2 compounds were also isolated, differing in the tripodal R groups and cocrystallized solvent or proligand molecules. The products were characterized by single-crystal X-ray diffraction analysis and spectroscopic, thermogravimetric and magnetic measurements. Cocrystallization influences the nature, strength and pattern of intermolecular interactions. Among the binuclear MIII products, all those containing solvating tetrahydrofuran, [M2Cl4(H2LR)2]·x thf (R = Et, Ph; x = 4 or 5 respectively), lose solvent upon gradual polyalcohol deprotonation, mild heating or vacuum drying. The versatile tripodal skeleton assembles the alkoxide-bridged M2 units (M = TiIII/IV or CrIII) in various experimental conditions, including air or inert atmosphere and non-protic or protic media, and confers remarkable robustness to the final binuclear aggregates.

Theoretical analysis of the effects of counterions on the supramolecular arrangement of sulfamethoxazole.

Active pharmaceutical ingredients are formulated as the salt form, aiming to modulate their physicochemical properties. In this regard, the optimization and choice of the salt former have a strong influence on toxicity, therapeutic efficiency, and bioavailability. Sulfamethoxazole (SMZ) salts with Na+, Cl-, and Br- counterions influence in the supramolecular arrangement as well as in their thermodynamic and kinetic parameters. Herein, we analyzed the interactions of the Na+, Cl-, and Br- counterions on the supramolecular arrangement of the sulfamethoxazole salts by Hirshfeld surfaces, fingerprint plots, and theoretical methods-quantum theory of atoms in molecules and natural bond orbitals. Moreover, we evaluated their electronic structure by density functional theory using calculation of the frontier molecular orbitals. Molecular electrostatic potential maps were also obtained to predict the interactions of the counterions along crystalline arrangements. We observed that the structures of [SMZ]+ and [SMZ]- ions differ slightly from the SMZ. The chemical reactivity indices show that the SMZ is kinetically more stable than its respective ions, while its anion is more polarizable, and its cation has a higher global electrophilicity index. The molecular electrostatic potential maps show high charge density in the sulfonyl group (nucleophilic region) and the heterocyclic amino group (electrophilic region). Although the molecular skeleton is identical among the three SMZ species and the presence of different counterions in the formation of the crystalline structure of the salts results in supramolecular arrangements with different patterns of intermolecular interactions, despite being very similar in terms of intensities.

105 K Wide Room Temperature Spin Transition Memory Due to a Supramolecular Latch Mechanism

Little is known about the mechanisms behind the bistability (memory) of molecular spin transition compounds over broad temperature ranges (>100 K). To address this point, we report on a new discrete FeII neutral complex [FeIIL2]0 (1) based on a novel asymmetric tridentate ligand 2-(5-(3-methoxy-4H-1,2,4-triazol-3-yl)-6-(1H-pyrazol-1-yl))pyridine (L). Due to the asymmetric cone-shaped form, in the lattice, the formed complex molecules stack into a one-dimensional (1D) supramolecular chain. In the case of the rectangular supramolecular arrangement of chains in methanolates 1-A and 1-B (both orthorhombic, Pbcn) differing, respectively, by bent and extended spatial conformations of the 3-methoxy groups (3MeO), a moderate cooperativity is observed. In contrast, the hexagonal-like arrangement of supramolecular chains in polymorph 1-C (monoclinic, P21/c) results in steric coupling of the transforming complex species with the peripheral flipping 3MeO group. The group acts as a supramolecular latch, locking the huge geometric distortion of complex 1 and in turn the trigonal distortion of the central FeII ion in the high-spin state, thereby keeping it from the transition to the low-spin state over a large thermal range. Analysis of the crystal packing of 1-C reveals significantly changing patterns of close intermolecular interactions on going between the phases substantiated by the energy framework analysis. The detected supramolecular mechanism leads to a record-setting robust 105 K wide hysteresis spanning the room temperature region and an atypically large TLIESST relaxation value of 104 K of the photoexcited high-spin state. This work highlights a viable pathway toward a new generation of cleverly designed molecular memory materials.

Amphiphile conformation impacts aggregate morphology and solution structure across multiple lengthscales

Although the self-assembly of amphiphiles is well-studied in aqueous solutions, much less is understood about the fundamental driving forces and structure property relationships in non-polar media. In recent work [Journal of Physical Chemistry B, 2020, 124, 10822.] the authors have studied a series of malonomide-based amphiphiles that are relevant to liquid-liquid extraction. That work demonstrated that aggregation is largely driven by local dipole-dipole interactions between molecules. Here, we build upon this observation to develop a more detailed understanding of how the balance of dipole-dipole interactions (controlled by conformation) and molecular architecture influences the morphology of the aggregates across lengthscales. Using constrained molecular dynamics about key degrees of freedom, we demonstrate that the conformation of N,N-dimethyl,N,N-dioctylhexylethoxy malonamide (DMDOHEMA) and N,N-dimethyl,N,N-dibutyltetradecyl malonamide (DMDBTDMA) has a significant impact upon self-association - where appropriate conformational sampling is essential. To quantify the aggregate morphology, several graph theoretic and persistent homology based properties are determined. The former examines the patterns of intermolecular interactions within clusters, while the latter examines the 3-dimensional spatial distribution. Based upon these analyses, we find that the morphology of aggregates, particularly at higher malonamide concentration, depends on a balance of dipole alignment and alkyl tail sterics. Dipole alignment encourages linear patterns of the intermolecular interactions within aggregates, while the alkyl tail steric interactions between the malonamide result in noticeably less linear aggregates for DMDOHEMA than DMDBTDMA. This is reflected in the spatial distribution, where more holes or voids exist between extractants within the DMDOHEMA that distribute within the solution in more of a “swiss cheese” arrangement as opposed to the more filamentous distribution of DMBDTDMA. This study links conformation and molecular structure to the morphology of amphiphile assemblies, and serves as a basis for ongoing study of multicomponent amphiphile solutions with polar and other solutes, and how these impact aggregation phenomena.

Polyurethane as high-functionality crosslinker for constructing thermally driven dual-crosslinking plant protein adhesion system with integrated strength and ductility

Wood products have gained considerable interest for use in furniture and construction materials; however, adhesives for bonding wood components are mainly formaldehyde-based resins, which release hazardous substances and can cause serious health concerns during service. The development of plant protein adhesives is in high demand to satisfy requirements for green wood-based composites and stringent environmental regulations. However, their practical application is hindered by the trade-off between high mechanical strength and good adhesion toughness. Herein, a biomimetic branched polyurethane is synthesised initially using a blocking agent of dopamine and sodium bisulfite to form a thermally driven dual-functionalised elastomer (PUSD). The prepared PUSD is employed as a novel dual-crosslinker for the improvement of soy protein (SP) adhesives. Because of the deblocking effect of sodium bisulfite under the thermal stimulus during hot pressing, the isocyanate groups are exposed and further cooperates with catechol groups to induce the construction of a thermally responsive dual-crosslinking network within the SP system. These structures not only promote the optimisation of the crosslinking density for a rigid system but also improve the intermolecular interaction patterns, thereby achieving effective energy dissipation. Consequently, the modified SP adhesives exhibit an integrated improvement in adhesive strength, adhesion toughness, and water resistance compared to the untreated adhesive. The outcome of this work enables the utilisation of plant proteins instead of traditional wood adhesives, thus addressing health and environmental concerns.

Bromhexine and its fumarate salt: Crystal structures, Hirshfeld surfaces and dissolution study

Bromhexine is an expectorant drug repurposing as a TMPRSS2 inhibitor, which has also been proposed for potential treatment in COVID-19 infection. Multicomponent crystal strategy has been applied in bromhexine to improve its poor solubility, which limits its bioavailability and efficacy. A new bromhexine crystal and its fumarate salt crystal have been successfully obtained by slow evaporation technique. Both compounds have been characterized by X-ray single-crystal diffraction, TGA and FT-IR spectroscopy. Hirshfeld surface analysis has been carried out to further quantify the patterns of intermolecular interactions. Compared with bromhexine, the multicomponent crystal with pharmaceutically acceptable conformer of fumaric acid shows improved thermal stability and solubility in water.

Ocotea daphnifolia: phytochemical investigation, in vitro dual cholinesterase inhibition, and molecular docking studies

This study aimed to evaluate the anticholinesterase activities of extracts and fractions of Ocotea daphnifolia in vitro and characterize its constituents. The effects of hexane, ethyl acetate, and ethanolic extracts on acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activity were determined with a spectrophotometry assay. All extracts inhibited cholinesterase activity, and the ethanolic extract (2 mg/mL) exhibited the highest inhibition of both enzymes (99.7% for BuChE and 82.4% for AChE). The ethanolic extract was fractionated by column chromatography resulting in 14 fractions that were also screened for their anticholinesterase effects. Fraction 9 (2 mg/mL) showed the highest activity, inhibiting AChE and BuChE by 71.8% and 90.2%, respectively. This fraction was analyzed by high-performance liquid chromatography high-resolution mass spectrometry which allowed the characterization of seven glycosylated flavonoids (containing kaempferol and quercetin nucleus) and one alkaloid (reticuline). In order to better understand the enzyme-inhibitor interaction of the reticuline toward cholinesterase, molecular modeling studies were performed. Reticuline targeted the catalytic activity site of the enzymes. Ocotea daphnifolia exhibits a dual cholinesterase inhibitory activity and displays the same pattern of intermolecular interactions as described in the literature. The alkaloid reticuline can be considered as an important bioactive constituent of this plant.

A Proline-Based Tectons and Supramolecular Synthons for Drug Design 2.0: A Case Study of ACEI.

Proline is a unique, endogenous amino acid, prevalent in proteins and essential for living organisms. It is appreciated as a tecton for the rational design of new bio-active substances. Herein, we present a short overview of the subject. We analyzed 2366 proline-derived structures deposited in the Cambridge Structure Database, with emphasis on the angiotensin-converting enzyme inhibitors. The latter are the first-line antihypertensive and cardiological drugs. Their side effects prompt a search for improved pharmaceuticals. Characterization of tectons (molecular building blocks) and the resulting supramolecular synthons (patterns of intermolecular interactions) involving proline derivatives, as presented in this study, may be useful for in silico molecular docking and macromolecular modeling studies. The DFT, Hirshfeld surface and energy framework methods gave considerable insight into the nature of close inter-contacts and supramolecular topology. Substituents of proline entity are important for the formation and cooperation of synthons. Tectonic subunits contain proline moieties characterized by diverse ionization states: -N and -COOH(-COO−), -N+ and -COOH(-COO−), -NH and -COOH(-COO−), -NH+ and -COOH(-COO−), and -NH2+ and -COOH(-COO−). Furthermore, pharmacological profiles of ACE inhibitors and their impurities were determined via an in silico approach. The above data were used to develop comprehensive classification, which may be useful in further drug design studies.

A competition between hydrophobic and electrostatic interactions in protein-ligand systems. Binding of heterogeneously halogenated benzotriazoles by the catalytic subunit of human protein kinase CK2.

A series of chlorine-substituted benzotriazole derivatives, representing all possible substitution patterns of halogen atoms attached to the benzotriazole benzene ring, were synthetized as potential inhibitors of human protein kinase CK2. Basic ADME parameters for the free solutes (hydrophobicity, electronic properties) together with their binding affinity to the catalytic subunit of protein kinase CK2 were determined with reverse-phase HPLC, spectrophotometric titration, and Thermal Shift Assay Method, respectively. The analysis of position-dependent thermodynamic contribution of a chlorine atom attached to the benzotriazole ring confirmed the previous observation for brominated benzotriazoles, in which substitution at positions 5 and 6 with bromine was found crucial for ligand binding. In all tested halogenated benzotriazoles the replacement of Br with Cl decreases the hydrophobicity, while the electronic properties remain virtually unaffected. Supramolecular architecture identified in the just resolved crystal structures of three of the four possible dichloro-benzotriazoles shows how substitution distant from the triazole ring affects the pattern of intermolecular interactions. Summarizing, the benzotriazole benzene ring substitution pattern has been identified as the main driver of ligand binding, predominating the non-specific hydrophobic effect.

Facile strategy for obtaining luminescent polymorphs based on the chirality of a boron-fused azomethine complex.

A chloro-substituted boron-fused azomethine complex (BAmCl) having a stereogenic boron center was synthesized for obtaining a luminescent chiral crystal. We succeeded in isolating the (R)- and (S)-enantiomers of BAmCl and preparing the homochiral polymorphic crystal, while we obtained the racemic crystal with rac-BAmCl. Single crystal X-ray diffraction analyses suggest that a variety of intermolecular interaction patterns and intrinsic flexibility of the molecular framework should play a significant role in stabilizing the homochiral crystal. We found the difference in molecular arrangements between the racemic and the homochiral crystals, and we observed distinctly different emission colors. In particular, we observed heat-initiated homogeneous racemization without the need for a solvent or catalyst in the molten state of the homochiral crystal (R)-BAmCl. Our results mean that chiral resolution of a flexible fused-skeleton having a stereogenic boron center can be a platform for creating luminescent polymorphic materials.

Case Study of the Correlation between Metallogelation Ability and Crystal Packing

In the present paper, in order to find the correlation between the molecular structure and the intermolecular interaction patterns in the crystalline state and the corresponding gelating or nongela...

Polymorphism of the dinuclear CoIII-Schiff base complex [Co2(o-van-en)3]·4CH3CN (o-van-en is a salen-type ligand).

Reactions of Co(OH)2 with the Schiff base bis(2-hydroxy-3-methoxybenzylidene)ethylenediamine, denoted H2(o-van-en), under different conditions yielded the previously reported complex aqua[bis(3-methoxy-2-oxidobenzylidene)ethylenediamine]cobalt(II), [Co(C18H18N2O4)(H2O)], 1, under anaerobic conditions and two polymorphs of [μ-bis(3-methoxy-2-oxidobenzylidene)ethylenediamine]bis{[bis(3-methoxy-2-oxidobenzylidene)ethylenediamine]cobalt(III)} acetonitrile tetrasolvate, [Co2(C18H18N2O4)3]·4CH3CN, i.e. monoclinic 2 and triclinic 3, in the presence of air. Both novel polymorphs were chemically and spectroscopically characterized. Their crystal structures are built up of centrosymmetric dinuclear [Co2(o-van-en)3] complex molecules, in which each CoIII atom is coordinated by one tetradentate dianionic o-van-en ligand in an uncommon bent fashion. The pseudo-octahedral coordination of the CoIII atom is completed by one phenolate O and one amidic N atom of the same arm of the bridging o-van-en ligand. In addition, the asymmetric units of both polymorphs contain two acetonitrile solvent molecules. The polymorphs differ in the packing orders of the dinuclear [Co2(o-van-en)3] complex molecules, i.e. alternating ABABAB in 2 and AAA in 3. In addition, differences in the conformations, the positions of the acetonitrile solvent molecules and the pattern of intermolecular interactions were observed. Hirshfeld surface analysis permits a qualitative inspection of the differences in the intermolecular space in the two polymorphs. A knowledge-based study employing Full Interaction Maps was used to elucidate possible reasons for the polymorphism.

Substituent Effects on the Patterns of Intermolecular Interactions of 3-Alkyl and 3-Cycloalkyl Derivatives of Phenytoin: A Crystallographic and Quantum-Chemical Study

A series of five derivatives of the anticonvulsant drug phenytoin was synthesized, and their crystal structures were determined. The relationship between the molecular and crystal structure of the investigated compounds was rationalized in the context of contribution of intermolecular interactions and supramolecular structural motifs. The conformational preferences were analyzed by comparing the rotational freedom of the phenyl groups in the investigated compounds with 5,5-diphenylhydantoins from the Cambridge Structural Database. With the exception of compound 3 bearing the cyclopropyl group, the crystal packing of the investigated compounds contains centrosymmetric dimers linked by paired N–H···O hydrogen bonds, which further self-organize through pairs of C–H···O interactions and a parallel interaction of two phenyl rings at a large offset into chains running along the c-axis. The principal feature of the crystal structure of compound 3 is formation of the chains by N–H···O hydrogen bonds and C–H···O and C–H···π interactions. The coordination of phenytoin enables more rotational freedom for the phenyl groups. An emphasis was placed on docking of the investigated compounds into the voltage-gated ion channel in the open and closed state. The obtained results indicate that hydrogen bonding and hydrophobic interactions are dominant in stabilizing energetically favored orientations of the investigated compounds bound to the protein.