Search Results (180)

The present work reports the synthesis and structural design of three novel Zn(II) complexes [Zn(L¹)(CH₃COO)(H₂O)] (1), [Zn(L²)₂] (2), and [Zn(L³)₂] (3) with carbazate ligands, 2-acetylpyridine-methylcarbazate (HL¹), 2-acetylpyridine-ethylcarbazate (HL²), and 2-acetylpyridine-benzylcarbazate (HL³). All compounds were characterized by spectroscopic methods, and the crystal structures of the complexes were elucidated by single-crystal X-ray. Based on the analysis, distorted square pyramid geometry is suggested for complex (1) and an octahedral geometry is suggested for complexes (2) and (3) with the ligands exhibiting an NNO-donor system. The 3D Hirshfeld surface and the 2D fingerprint plot were used to study the non-covalent interactions in the crystal structures. The in vitro antibacterial investigation of the free ligands and their complexes was performed against different strains of periodontopathogen bacteria. The Zn(II) complexes showed more potent antibacterial activity than the free ligand. Molecular docking studies showed the metal complexes as promising candidates for further therapeutic exploration, particularly in targeting the ATP-binding cassette transporter with peptidase domain of the cariogenic bacteria S. mutans (PDB code 5XE9) and the prolyl tripeptidyl aminopeptidase from P. gingivalis anaerobic bacteria (PDB code 2EEP) inhibition. Full article

The substituent effects on crystal stacking topology and stability of the 5,5-dinitro-2H,2H-3,3-bi-1,2,4-triazole (DNBT) and its three energetic cocrystals with 1,3,5-trinitrobenzene (TNB), 2,4,6-trinitrotoluene (TNT), and picric acid (PA) were systematically investigated through combined density functional theory (DFT) calculations and classical molecular dynamics (MD) simulations. The interaction mechanism and detonation performance of the three energetic cocrystals were implemented to the electrostatic potential (ESP), Hirshfeld surface analysis, radial distribution function (RDF), binding energy, and detonation parameters. In contrast to N-H⋯O interactions in DNBT, three cocrystals exhibited more distinctly weak C-H⋯O intermolecular hydrogen bonds and NO₂-π stacking interactions to stabilize the lattice. Notably, the highest binding energy of PA/DNBT shows the largest stability and lowest impact sensitivity is related to the more intermolecular interactions. Although the introduction of substituents slightly affects the crystal density of DNBT crystals, it significantly reduces the impact sensitivity. Moreover, the balanced detonation performance and impact sensitivity of DNBT-based cocrystals make it a candidate to expand the applications of DNBT crystals. These findings contribute to a broadened understanding of construction and design strategies for the energy release mechanisms of energetic compounds with the azoles ring family. Full article

We present a comprehensive structural and thermomechanical investigation of N-salicylideneaniline, a Schiff base derivative that exhibits remarkable thermosalient phase transition behavior. By combining variable-temperature X-ray powder diffraction (VT-XRPD), differential scanning calorimetry (DSC), hot-stage microscopy, and Hirshfeld surface analysis, we reveal two distinct thermosalient mechanisms operating in different polymorphic forms. Form I displays pronounced anisotropic thermal expansion with negative strain along a principal axis, culminating in a sudden and explosive phase transition into Form IV. In contrast, Form III transforms more gradually through a microstrain accumulation mechanism. Fingerprint plots and contact evolution from Hirshfeld surface analysis further support this dual-mechanism model. These insights highlight the importance of integrating macro- and microscale structural descriptors to fully capture the mechanical behavior of responsive molecular solids. The findings not only enhance the fundamental understanding of thermosalience but also inform the rational design of functional materials for actuating and sensing applications. Full article

The coordination chemistry, structural characterization, and biomolecular interactions of europium(III) and iron(III) complexes with the pyridoxal-semicarbazone (PLSC) ligand were thoroughly examined using experimental and computational approaches. Single-crystal X-ray diffraction revealed that the europium complex exhibits a nine-coordinate geometry with one protonated and one deprotonated PLSC ligand and nitrato and aqua ligands. In contrast, the iron complex adopts a six-coordinate structure featuring a monoprotonated PLSC, two chlorido, and an aqua ligand. Hirshfeld surface analysis confirmed the significance of intermolecular contacts in stabilizing the crystal lattice. Theoretical geometry optimizations using DFT methods demonstrated excellent agreement with experimental bond lengths and angles, thereby validating the reliability of the chosen computational levels for subsequent quantum chemical analyses. Quantum Theory of Atoms in Molecules (QTAIM) analysis was employed to investigate the nature of metal–ligand interactions, with variations based on the identity of the donor atom and the ligand’s protonation state. The biological potential of the complexes was evaluated through spectrofluorimetric titration and molecular docking. Eu-PLSC displayed stronger binding to human serum albumin (HSA), while Fe-PLSC showed higher affinity for calf thymus DNA (CT-DNA), driven by intercalation. Thermodynamic data confirmed spontaneous and enthalpy-driven interactions. These findings support using PLSC-based metal complexes as promising candidates for future biomedical applications, particularly in drug delivery and DNA targeting. Full article

This article discloses the synthesis of four new positional isomeric zwitterionic ligands exhibiting semi-flexible and flexible characteristics—n-pyridinium-1,2,3-triazole-4-carboxy-5-Acetate (n-PTCA), and n-methylpyridinium-1,2,3-triazole-4-carboxy-5-Acetate (n-MPTCA; where n = 3, 4)—which were derived from an aqueous solution of the corresponding sodium salts in an acidic medium (HCl). These compounds are successfully synthesized and characterized with FT-IR and multinuclear NMR spectroscopy; likewise, proper single crystals are obtained for each compound. All compounds adopt zwitterionic forms in the solid state, which are stabilized via intermolecular proton transfer processes involving HCl and solvent molecules. A single-crystal X-ray analysis revealed how positional isomerism and molecular flexibility influence the supramolecular topology. Specifically, 3-PTCA and 4-PTCA exhibit isomorphic hydrogen bond networks, while 3-MPTCA and 4-MPTCA display distinct packing motifs, attributed to the presence of a methylene spacer between the pyridinium and triazole rings. The Hirshfeld surface analysis quantitatively confirmed the dominance of O···H/H···O and N···H/H···N interactions in the solid-state architecture. These strong hydrogen-bonding networks are indicative of the potential proton-conductive behavior in the crystalline state, positioning these compounds as promising candidates for applications in proton-conducting materials. The structural insights gained underscore the pivotal role of molecular topology in tailoring crystal packing, with implications for the rational design of zwitterionic ligands in functional materials, including MOFs and coordination polymers. The calculated HOMO-LUMO energy gaps reveal a significant electronic variability among the ligands, influenced primarily by the positional isomerism and structural flexibility introduced by the methylene spacer. Full article

Representatives of the hexasubstituted benzene derivatives, also known as hexa-hosts, have been the subject of extensive studies in solution and in the solid state, including the investigation of their ability to act as artificial receptors for various substrates, as well as detailed conformational analyses. In this paper, we describe the X-ray crystal structure of hexakis(acetoxymethyl)benzene (1), a member of the above class of compounds. The molecules of 1 adopt an aaabbb conformation, in which three side-arms point to the same face of the central benzene ring, while the other three point in the opposite direction. As the compound lacks strong hydrogen bond donors, C–H···O hydrogen bonds connect the molecules to a three-dimensional supramolecular network. According to the Hirshfeld surface analysis, the H∙∙∙O/O∙∙∙H interactions represent the major contribution of the molecular Hirshfeld surface. Full article

A series of three 1,3-phenylene bis-oxamides 3a–c, structurally related to the GPR35 receptor-agonist drug lodoxamide, has been synthesized by reacting the 1,3-phenylene bis-oxalamates 2a and 2b with amines. The obtained compounds were characterized by ¹H and ¹³C NMR, and IR spectroscopy, they showed characteristic signals for the aromatic, N―H, and C=O groups. Molecular structure was determined using single-crystal X-ray diffraction. The supramolecular architecture is driven by N―H···O=C, N―H···N, C—H···π, and O=C···O=C interactions depicting a supramolecular helix (3a) and tapes (3b–c). Intermolecular interactions were studied using Hirshfeld surface analysis, where N―H∙∙∙X (X = N, O) hydrogen bonding represents 30.2% to the surface of 3a and 17.8–18.8% to the surface of 3b–c. The most energetic interactions involve the amide N—H∙∙∙O hydrogen bonding, contributing in the −113.9 to −97.0 kJ mol⁻¹ range to the crystal energy, being more dispersive than electrostatic in nature. The molecular docking study was performed to evaluate the binding ability of 3a–c compounds to the GPR35 receptor, showing a favorable binding in a similar way to lodoxamide. Full article

The polymorphism of the ultraviolet luminescent security ink Orlyum White 520T (N-(2-(4-oxo-4H-benzo[d][3,1]-oxazin-2-yl)phenyl)naphthalene-2-sulfonamide) is revealed, obtaining two new polymorphic forms with enhanced stability. Beyond the known form (lit. mp. 184.8–185.2 °C, Form III, YOCTAO), we succeeded in gaining two new polymorphic forms, Form II and Form I, with higher melting points of 195–196 and 197–198 °C, respectively. Their elemental composition, ¹H and ¹³C NMR spectra have been found to be identical, while their powder XRD patterns and FT-IR spectra are significantly different. Based on the single-crystal structure determination of Form II and redetermination of Form III, we uncover the similarities and differences in their packing arrangement and in their secondary interaction systems, all of which affect the molecular conformations in their crystals. In order to explain their significantly distinguishable melting points, Hirshfeld surface analysis and lattice energy calculations have also been carried out. We have made efforts toward revealing the reproducible conditions under which certain polymorphs are formed. It seems that the solvents or other probable organic contaminations are more likely responsible for the formation, nucleation and growth of crystals of various polymorphic forms, traced by thermogravimetric evolved gas analysis (TG/DTA-EGA-MS). Full article

The selective adsorption and separation of benzene from structurally similar six-membered hydrocarbons and fluorocarbons remain a significant challenge due to their comparable physical properties. In this study, we investigated the molecular recognition and separation properties of a perfluorinated triketonate Cu(II) complex (1) as a Nonporous Adaptive Crystal (NAC). In addition to the previously reported benzene (2)-encapsulated crystal of 1•(2)₃, we report here the crystal structures of guest-free 1 and cyclohexene (3)-encapsulated 1•(O)₂•3, where (O)₂ represents two water molecules. Single-crystal analysis demonstrated that 1 selectively encapsulates 2 while excluding other hydrocarbons, including 3, cyclohexane (4), trifluorobenzene (5), and hexafluorobenzene (6). Gas adsorption experiments confirmed this high affinity for 2, as reflected in its preferential adsorption behavior in mixed solvent and vapor environments. The molecular selectivity of 1 was attributed to strong π-hole···π and metal···π interactions, which favor electron-rich aromatic guests. Additionally, crystallization experiments in competitive solvent systems consistently led to the formation of 1•(2)₃, reinforcing the high selectivity of 1 for 2. These findings highlight the unique molecular recognition capabilities of NACs, providing valuable insights into the rational design of advanced molecular separation materials for industrial applications involving aromatic hydrocarbons. Hirshfeld surface analysis revealed that the contribution of F···F interactions to crystal packing decreased upon guest recognition (48.8% in 1, 34.2% in 1•(O)₂•3, and 22.2% in 1•(2)₃), while the contribution of F···H/H···F interactions increased (8.6% in 1, 22.2% in 1•(O)₂•3, and 35.4% in 1•(2)₃). Regarding Cu interactions, the self-assembled columnar structure of 1 results in close contacts at the coordination sites, including Cu···Cu (0.1%), Cu···O (0.7%), and Cu···C (1.3%). However, in the guest-incorporated structures 1•(O)₂•3 and 1•(2)₃, the Cu···Cu contribution disappears; instead, 1•(O)₂•3 exhibits a significant increase in Cu···O interactions (1.2%), corresponding to water coordination, while 1•(2)₃ shows an increase in Cu···C interactions (1.5%), indicative of the metal···π interactions of benzene. Full article

Herein, nine square planar trans-arylbis(triphenylphosphine)palladium halides (PdX(PPh₃)₂Ar) were synthesized and fully characterized. The molecular structure of two complexes (1 and 2) have been determined by both X-ray diffraction and described thanks to Hirshfeld surface analysis. Investigation of the antioxidant activities showed that most of the complexes exhibit a strong dose-dependent radical scavenging activity towards DPPH radical as well as in the ABTS radical scavenging test. Complexes 1 [PdI(PPh₃)₂(4-MeOC₆H₄)] and 3 [PdCl(PPh₃)₂(4-MeOC₆H₄)] showed the highest activity in the DPPH assay with EC₅₀ values of 1.14 ± 0.90 and 1.9 ± 0.87 µM, respectively. In contrast, for the ABTS assay, quercetin (5.56 ± 0.97 µM) was slightly more efficient than the three complexes 1 (5.78 ± 0.98 µM), 2 (7.01 ± 0.98 µM), and 3 (11.12 ± 0.94 µM). The use of kinetic studies as a powerful parameter shows that complexes 1, 2, and 3 displayed the best antioxidant efficiency. The antioxidant effect of the nine palladium complexes has been also evaluated on the enzyme-catalyzed oxidation of the L012 probe (using HRP/H₂O₂) by using a chemiluminescence technique. As with the last model, complexes 1, 2, and 3 showed the best activity, with EC50 values of 3.56 ± 1.87, 148 0.71, and 5.8 ± 2.60 µM, respectively. Interestingly, those complexes (1, 2, and 3) even exhibited a higher dose-dependent activity than the quercetin (7.06 ± 2.56 µM) used as a standard. Taken together, the combined results reveal that the antiradical and enzyme (HRP) inhibitory activity of complexes decrease following the ligand order of p-OMePh > p-OAcPh >> Ph. Full article

Ribavirin, 1-(β-D-Ribofuranosyl)-1H-1,2,4-triazole-3-carboxamide, which is included in the list of drugs recommended in the guidelines for the diagnosis and treatment of SARS-CoV-2 infection, has been the subject of experimental and theoretical investigation. The most thermodynamically stable polymorphic form was studied using ¹H-¹⁴N NQR cross-relaxation, periodic DFT/QTAIM/RDS/3D Hirshfeld surfaces, and molecular docking. For the first time, a ¹H-¹⁴N cross-relaxation spectrum of ribavirin was recorded and interpreted. Twelve resonance frequencies were assigned to four inequivalent nitrogen positions in the molecule using combined experimental techniques and solid-state quantum chemical calculations. The influence of the structural alteration on the NQR parameters was modeled using GGA/RPBE. The differences in the binding pattern of ribavirin, acadesine, inosine, guanosine, and favipiravir-ribofuranosyl in the solid state and the protein-ligand complex were assessed to elucidate the differences in the binding mechanism at the molecular level due to aglycone modification. The replacement of the carbon adjacent to the ribose with nitrogen, in conjunction with the absence of oxygen at the 2-position of the ring, resulted in an increased flexibility of the RBV structure in comparison to the favipiravir-ribofuranosyl structure. The present study identified the intramolecular hydrogen bond NH···N in RBV as playing a crucial role in the formation of a quasi-five-membered ring. However, this bond was proven to be too weak to force positioning of the amide group in the ring plane. The ribofuranosyl in RBV inhibits tautomerism and freezes the conformation of the amide group. The results of the molecular dynamics simulations demonstrated that RBV and favipiravir-ribofuranosyl incorporated into the RNA primer exhibited comparable stability within the protein binding region. The titular anti-butterfly (inverted butterfly) effect is associated with the consequences of both the changes in aglycone moiety and the neighborhood alteration. Seven structure-binding strength indices and six novel quadrupolar indices defined in this study have been proven to facilitate the evaluation of the similarity of binding motifs in the solid state and protein-ligand complex. Full article

Due to the emergence of drug resistance, many antimicrobial medications are becoming less effective, complicating the treatment of infections. Therefore, it is crucial to develop new active agents. This article aims to explore the ruthenium(IV) complexes with the following formulas: (Hdma)₂(HL)₂[Ru^IVCl₆]·2Cl·2H₂O (1), where Hdma is protonated dimethylamine and L is 2-hydroxymethylbenzimidazole, and [Ru^IVCl₄(AN)₂]·H₂O (2), where AN is acetonitrile. This paper delves into the physicochemical characteristics and crystal structures of these complexes, employing various techniques such as spectroscopy (IR, UV–Vis), electrochemistry (CV, DPV), and X-ray crystallography. Hirshfeld surface analysis was also performed to visualize intermolecular interactions. Furthermore, the potential antibiofilm activity of the complexes against Pseudomonas aeruginosa PAO1 was investigated and the effect of the compounds on the production of pyoverdine, one of the virulence factors of the Pseudomonas strain, was assessed. The results show that particularly complex 1 reduces biofilm formation and pyoverdine production. Additionally, the bioavailability of these complexes in biological systems (by fluorescence quenching of human serum albumin (HSA) and molecular docking studies) is discussed, assessing how their chemical properties influence their interactions with biological molecules and their potential therapeutic applications. Full article

The introduction of functional groups, such as graphene oxide, can improve the reactivity between molecules, increasing the potential for their use in many fields such as gas sensing and adsorption. It was reported that that graphene materials are actively utilized in toxic gas sensor materials by modifying the surface with their chemical and structural stability. In order to understand the mechanisms of graphene and graphene oxides for adsorbing the hazardous gases, we classified the four gases (H₂S, NH₃, HF and COS) with their phases (two asymmetric and two linear), and conducted density functional theory calculations to determine the adsorption affinity, which represents the binding energy, bond distance, energy charge (Mulliken and Hirshfeld methods) and band gap between the HOMO (Highest Occupied Molecular Orbital) and the LUMO (Lowest Unoccupied Molecular Orbital). The results showed that introducing a functional group enhanced the binding energy with a narrowed band gap in asymmetric gas adsorption (H₂S and NH₃), while the results of the linear gases (HF and COS) showed lowered binding energy with a narrowed band gap. It is judged that the oxygen functional groups can narrow the band gap by introducing localized states between the valence and conduction bands or by forming new hybrid states through interactions with all the gases. However, from the differences in the phases, the linear gases stably interacted with a defect-free, porous and flat structure like with π–π interactions. In short, the theoretical findings confirm that the oxidation functional groups narrowed the band gap with a local interaction; however, linear gases showed enhanced binding energies with pristine graphene, which highlights the importance of surface material selection dependent on the target gases. Full article

In this paper, a novel mixed Tutton salt (K_0.86Na_0.14)₂Ni(SO₄)₂(H₂O)₆ was successfully synthesized as a single crystal and evaluated as a thermochemical heat storage material. Its thermal and thermochemical properties were correlated with the structure, which was determined by powder X-ray diffraction using the Le Bail and Rietveld methods. The elemental ratio between the K⁺ and Na⁺ monovalent cations was established by energy-dispersive X-ray spectroscopy. Similar compounds such as Na₂Ni(SO₄)₂(H₂O)₄ and K₂Ni(SO₄)₂(H₂O)₆ were also synthesized and used for structural comparisons. The (K_0.86Na_0.14)₂Ni(SO₄)₂(H₂O)₆ salt crystallizes in monoclinic symmetry with the P2₁/c-space group, typical of hexahydrate crystals from the Tutton salt family. The lattice parameters closely resemble those of K₂Ni(SO₄)₂(H₂O)₆. A comprehensive analysis of the intermolecular contacts, based on Hirshfeld surfaces and 2D fingerprint mappings, revealed that the primary interactions are hydrogen bonds (H···O/O···H) and ion-dipole interactions (K/Na···O/O···Na/K). The unit cell exhibits minimal void space, accounting for only 0.2%, indicative of strong atomic packing. The intermolecular molecular and atomic packing are important factors influencing crystal lattice stabilization and thermal energy supplied to release crystallographic H₂O. The thermal stability of mixed Tutton salt ranges from 300 K to 365 K. Under the dehydration of its six H₂O molecules, the dehydration reaction enthalpy reaches 349.8 kJ/mol, yielding a thermochemical energy storage density of 1.79 GJ/m³. With an H₂O desorption temperature ≤393 K and a high energy storage density ≥1.3 GJ/m³ (criteria established for applications at the domestic level), the (K_0.86Na_0.14)₂Ni(SO₄)₂(H₂O)₆ shows potential as a thermochemical material for small-sized heat batteries. Full article

Copper–semicarbazone ligands have been extensively investigated for several medicinal applications. In this contribution, a novel copper(II) complex with a pyridoxal–semicarbazone ligand, [Cu(PLSC)Cl(H₂O)](NO₃)(H₂O), was synthesized and characterized by X-ray crystallography, elemental analysis, UV-VIS, and FTIR spectroscopies. The stabilization interactions within the structure were assessed using the Hirshfeld surface analysis. The crystallographic structure was optimized at the B3LYP/6-311++G(d,p)(H,C,N,O)/LanL2DZ(Cu) level of theory. A comparison between the experimental and theoretical bond lengths and angles was undertaken to verify the applicability of the selected level of theory. The obtained high correlation coefficients and low mean absolute errors confirmed that the optimized structure is suitable for further investigating the interactions between donor atoms and copper, along with the interactions between species in a neutral complex, using the Quantum Theory of Atoms in Molecules approach. The electrostatic potential surface map was used to reveal distinct charge distributions. The experimental and calculated FTIR spectra were compared, and the most prominent bands were assigned. The interactions with human serum albumin (HSA) were assessed by spectrofluorometric titration. The spontaneity of the process was proven, and the thermodynamic parameters of binding were calculated. Molecular docking analysis identified the most probable binding site, providing additional insight into the nature of the interactions. Full article