Short Contacts Research Articles

Synthesis, analysis of mol-ecular and crystal structures, estimation of inter-molecular inter-actions and biological properties of 1-benzyl-6-fluoro-3-[5-(4-methylcyclohexyl)-1,2,4-oxadiazol-3-yl]-7-(piperidin-1-yl)quinolin-4-one.

The title compound, C30H33N4O2F, can be obtained via a two-step synthetic scheme involving 1-benzyl-6-fluoro-4-oxo-7-(piperidin-1-yl)-1,4-di-hydro-quino-line-3-carbo-nitrile as a starting compound that undergoes substitution with hydroxyl-amine and subsequent cyclization with 4-methyl-cyclo-hexane-1-carb-oxy-lic acid. It crystallizes from 2-propanol in the triclinic space group P with a mol-ecule of the title compound and one of 2-propanol in the asymmetric unit. After the mol-ecular structure was clarified using NMR and LC/MS, the mol-ecular and crystalline arrangements were defined with SC-XRD. A Hirshfeld surface analysis was performed for a better understanding of the inter-molecular inter-actions. One strong (O-H⋯O) and three weak [C-H⋯F (intra-molecular) and two C-H⋯O] hydrogen bonds were found. The contributions of short contacts to the Hirshfeld surface were estimated using two-dimensional fingerprint plots showing that O⋯H/H⋯O, C⋯H/H⋯C and C⋯C contacts are the most significant for the title compound and O⋯H for the 2-propanol. The crystal structure appears to have isotropically packed tetra-mers containing two mol-ecules of the title compound and two mol-ecules of 2-propanol as the building unit according to analysis of the distribution of pairwise inter-action energies. A mol-ecular docking study was carried out to evaluate the inter-actions of the title compound with the active centers of macromolecules corresponding to viral targets, namely, anti-hepatitis B activity [HBV, capsid Y132A mutant (VCID 8772) PDB ID: 5E0I] and anti-COVID-19 main protease activity (PDB ID: 6LU7). The data obtained revealed a noticeable affinity towards them that exceeded that of the reference ligands.

Anticooperativity and Competition in Some Cocrystals Featuring Iodine-Nitrogen Halogen Bonds.

Phenomena such as anticooperativity and competition among non-covalent bond donors and acceptors are key considerations when exploring the polymorphic and stoichiomorphic landscapes of binary and higher-order cocrystalline architectures. We describe the preparation of four cocrystals of 1,3,5-trifluoro-2,4,6-triiodobenzene with N-heterocyclic compounds, namely acridine, 3-aminopyridine, 4-methylaminopyridine, and 1,2-di(4-pyridyl)ethane. The cocrystals, which are characterized by single-crystal and powder X-ray diffraction experiments, all show moderately strong and directional iodine⋅⋅⋅nitrogen halogen bonds with reduced distance parameters ranging from 0.79 to 0.92 and carbon-iodine⋅⋅⋅nitrogen bond angles ranging from 165.4(3) to 175.31(7)°. The cocrystal comprising 1,3,5-trifluoro-2,4,6-triiodobenzene and acridine provides a relatively rare example where all three halogen bond donor sites form halogen bonds with three acceptor molecules, overcoming an anticooperative effect. This effect manifests itself through the lengthening of non-halogen-bonded C-I bonds, weakening their potential to form halogen bonds. The effect is only observed once two halogen bonds have been formed to 1,3,5-trifluoro-2,4,6-triiodobenzene; one such bond does not appear to be adequate. Among the four cocrystals studied, competition between the pyridyl nitrogen atoms and the amine nitrogen atoms suggests that the former are the preferred halogen bond acceptors. Analysis by Hirshfeld fingerprint plots and 13 C and 19 F magic-angle spinning solid-state nuclear magnetic resonance (NMR) spectroscopy provides additional insights into the prevalence of various short contacts in the crystal structures and into the spectral response to halogen-bond-induced cocrystallization.

Crystal structures of 4-(2/3-meth-oxy-phen-oxy)phthalo-nitrile.

The syntheses and crystal structures are reported of 4-phen-oxy-substituted phthalo-nitriles with meth-oxy groups in the ortho- and meta-positions of the terminal benzene rings, respectively, namely, 4-(2-meth-oxy-phen-oxy)phthalo-nitrile and 4-(3-meth-oxy-phen-oxy)phthalo-nitrile, both C15H10N2O2. The https://journals.iucr.org/e/issues/2023/03/00/mol-ecular structure was determined using the single-crystal X-ray diffraction method. It is shown that short contacts play a more decisive role in the mol-ecular packing compared to van der Waals inter-actions.

Self-assembly, physico-chemical characterization, biological, virtual screening, and computational approach of novel 2-amino pyridine derivatives

Two novel compounds, [Zn(SCN)4] (C5H7N2)2 (I) and (C5H7N2)NCS (II), were successfully synthesized and grown at room temperature by slow evaporation. The investigation of compound's properties was occurred using various techniques such as IR, thermal analysis, and single X-ray analysis. X-ray diffraction shows that both compounds (I) and (II) crystallizes in the monoclinic system with the space group P 21/c." Compound (I) contains a distorted tetrahedral [Zn(SCN)4] anions. According to crystal packing analysis, the [Zn(NCS)4]2− anions and 2-aminopyridine cations are linked via N–H...S hydrogen bonds. Compound (II) consolidates the stacking of the crystal by forming an intriguing three-dimensional network via N–H...N, C–H...S, C–H...π, and π...π intermolecular interactions between 2-aminopyridinium and NCS. The vibrational modes of the various functional groups contained in both compounds were investigated using FT-IR. Hirshfeld surface analysis was performed to investigate the short contacts and hydrogen bonds in the compounds. To get further insights into the molecular properties, NLO, NBO, electrostatic potential, molecular orbital, and QTAIM analyses were performed. Explorations of impedance spectroscopy on (I) and (II) reveal fascinating electrical behavior. It is a useful material for the development of photonic and non-linear optical devices due to the increased dielectric constant and dielectric loss with frequency variation. In the [273–623 K] ranking, the thermal behavior shows a phase transition and the decomposition of both complexes. Finally, the compound's antioxidant activity was tested to reveal a high chelating power which is confirmed by ESP values around sulfur atoms and the QTAIM and NCI-RDG calculation.

REACTIONS OF ALKYLTRIPHENYLPHOSPHONIUM HALIDES WITH ARENESULFONIC ACID

The reaction of equimolar amounts of alkyltriphenylphosphonium bromides with 1-naphthalenesulfonic, 2,4-dinitrobenzenesulfonic, and sulfosalicylic acids in water leads to the formation of ionic alkyltriphenylphosphonium arenesulfonates [Ph3PR][OSO2Ar], R = CH2OMe, Ar = Naft-1 (I); R = CH=СHPPh3, Ar = C6H3(NO2)2-2,4 (II); R = (CH2)2Br (III), R = C6H11-cyclo (IV), Ar = C6H3(COOH-3)(OH-4). Structures of complexes I‒IV have been established by X-ray diffraction analysis. Complexes I–IV are air-stable transparent crystals, readily soluble in arenes, ethanol, chloroform, acetonitrile, tetrahydrofuran, carbon tetrachloride, diethyl ether, and poorly soluble in water at room temperature. Phosphorus atoms in alkyltriphenylphosphonium cations I–IV have tetrahedral coordination, arenesulfonate anions have the usual geometry with a tetrahedral sulfur atom. Compound II crystallizes as a hydrate. The P–C bond lengths vary in the range 1.240(3)–1.827(3) Å, which is less than the sum of the covalent radii of partner atoms (1.83 Å). CPC bond angles vary within 103.77(9)°−112.80(12)°; S–C distances in sulfonate anions are 1.768(3)‒1.807(3) Å. The S–O bond lengths are close to each other and take the values 1.427(3)‒1.4710(17) Å. The bond angles OSO (111.56(10)°−115.74(18)°) are larger than the OSC angles (103.02(12)°−107.26(9)°). Cations and anions in complexes I‒IV are connected by short contacts of S=O∙∙∙Н(Рh) type [2.350‒2.717 Å] (the sum of Van der Waals partner atoms O···Н is 2.62 Å). In crystal II, short contacts of the N=O∙∙∙H(Ph) type [2.448–2.699 Å] are also observed. Crystal structures of I, III, IV contain CH∙∙∙π interactions (2.658‒2.898 Å). Moreover, the spatial structure of crystals II, III is formed with the participation of π–π interactions. (3.276‒3.359 Å). For citation: Sharutin V.V., Sharutina O.K., Mekhanoshina E.S. Reactions of alkyltriphenylphosphonium halides with arenesulfonic acid. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 3. P. 18-26. DOI: 10.6060/ivkkt.20236603.6724.

Experimental and Theoretical Study of Tetrel Bonding and Noncovalent Interactions in Hemidirected Lead(II) Phosphorodithioates: An Implication on Crystal Engineering

The importance of tetrel bonds (TtBs) in spontaneous self-assembly has been highlighted in two new lead(II) complexes: i.e. Pb[S2P{OC6H4(4-C(CH3)3)}2]2 (1) and Pb[S2P{OC6H4(4-C2H5)}2]2 (2), which were successfully isolated and characterized by FT-IR, UV–vis and multinuclear NMR (31P, 1H and 13C) spectroscopy. The structures of both complexes have been confirmed by single-crystal X-ray diffraction analyses. Interestingly, lead is coordinated by three sulfur atoms in 1 but by four sulfur atoms in 2, due to stereochemically active lone pair electrons, thus leading to trigonal-pyramidal and tetragonal-pyramidal geometries, respectively. Complex 1 is the first example of a lead(II) dithiophosphate wherein the lead(II) center is coordinated to three S atoms. These complexes are stabilized at a lower coordination number and display hemidirected structures that allow forming σ-hole bonds. The lead(II) center establishes short contacts with sulfur atoms to form Pb···S TtBs that contribute to the construction of a self-assembled dimer in 1 but to a supramolecular polymer in 2. The supramolecular assemblies are further stabilized by Pb···π TtB interactions. The attractive nature of TtBs has been studied by DFT calculations and characterized using a combination of Bader’s quantum theory of atoms-in-molecules (QTAIM) and noncovalent interaction plot (NCI plot) index based on a reduced density gradient (NCI-RDG) analysis. A systematic Hirshfeld surface analysis facilitates a comparison of intermolecular interactions such as C–H···π, π···π, Pb···S, and Pb···π in both complexes, which play a crucial role in the crystal engineering.

3 a,6 a-Diaza-1,4-Diphosphapentalenes: Synthesis and Complexation with the Organic π-Acceptor 1,2,4,5-Tetracyanobenzene.

The reaction of PCl3 with diethyl ketazine and 4-phenylcyclohexanone azine results in the formation of 1,4-dichloro-3a,6a-diaza-1,4-diphosphapentalenes which were reduced by magnesium in THF to give corresponding diazadiphosphapentalenes EtMeDDP and PhcHexDDP, containing two-coordinate phosphorus atoms. According to the CVA data, the new diazadiphosphapentalenes are strong electron donors showing oxidation peak potentials at 0.34 and 0.10 V, respectively, (vs. Ag/AgCl). Interaction of 1,2,4,5-tetracyanobenzene (TCNB) with the obtained diazadiphosphapentalenes in any stoichiometry produces sandwich complexes of the composition DDP-TCNB-DDP. Black-purple crystals of π-complexes contain infinite molecular chains with short P⋅⋅⋅P contacts between DDP molecules and short (Csp2 -H⋅⋅⋅N) contacts between TCNB molecules. Calculations showed that each TCNB molecule is an acceptor of ∼0.3e from two DDP molecules. Estimation of the HOMO-LUMO gap from the onset of optical absorption give values of 1.25 eV and 1.31 eV for [(EtMeDDP)2 (TCNB)] and [(PhcHexDDP)2 (TCNB)] respectively.

Observation of Structural Diversity Based on the Cationic Influence in a Series of Zn/Cd Pyridine Carboxylate Coordination Compounds

In this study, we used a 6-methyl-2,3-pyridine dicarboxylate ligand to develop the frameworks. Two novel compounds, [Zn2(L)2(H2O)4] (1) and [Cd(L)(H2O)] (2) (where L = 6-methyl-pyridine-2,3-dicarboxylate) were produced. The compounds were characterized by elemental analysis, powder X-ray diffraction, Fourier-transform infrared spectroscopy and single crystal X-ray crystallography. We successfully tuned the framework dimensionality by varying the size of the metal ions from small Zn to large Cd ions. Single crystal X-ray investigations of compound 1 show a good dimeric motif, while compound 2 shows a 2D network. In compound 1, the dimeric units are further bonded by strong hydrogen bonds and create a 3D network whereas compound 2 produces a 2D layer that in turn connects via short contacts to form a 3D network in the crystallographic space.

Gold Polyiodide Hybrid Perovskite Solar Cells

In this work, we present the ionic liquid (IL) synthesis of two novel pseudo-2D perovskite-type gold(III)polyiodide compounds, [DodMe2S][AuI4][I3] (1) and [Et3S][AuI4][I5] (2), and their application as active layers in monolithic solar cells. The compounds are composed of tetraiodoaurate anions and polyiodide entities, infinite polyiodide chains in 1 and pentaiodides in 2, which display short intermolecular contacts resulting in relatively small electronic bandgaps. This work represents the first demonstration of film deposition of gold iodide/polyiodide compounds onto porous monolithic substrates with subsequent solar cell characterization. The devices show promising photovoltaic performance and could unlock new materials design possibilities, ultimately moving away from lead-based photovoltaic materials. These findings further highlight the use of simple polyiodide entities to increase the structural and electronic dimensionality of gold perovskite-type anions.

Alkali metal⋯methyl short contacts in aluminates: more than agostic interactions.

Knowing the nature and strength of noncovalent interactions is key to enhancing the synthetic methods and catalytic processes in which they are involved. We present herein the synthesis and characterization of a novel aluminium sodium oximate compound, followed by a comprehensive computational study of the sodium⋯methyl interaction that appears in its crystal structure. Our experimental results have been compared to a large set of structural data retrieved from the Cambridge Structural Database in order to assess the main geometrical preferences of these interactions. Moreover, representative model systems have been studied at the DFT level and the topology of their electron density analysed by means of QTAIM. Although alkali metal⋯methyl short contacts have been traditionally considered as agostic interactions, we have demonstrated here that the physical origin of the attraction relies on the electron-rich carbon atom bound to aluminium and its interaction with the cation.

Trans-9,10-Dihydro-9,10-ethanoanthracene-11,12-dicarboxylic Acid: Remarkable Host Selectivities in the Presence of Mixtures of Anisole and Bromoanisole Isomers

In this work, trans-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid (DED), a host compound that formed complexes with anisole (ANI), 2-bromoanisole (2-BA), and 4-bromoanisole (4-BA), was revealed to possess a remarkable affinity (93.1–98.6%) for 4-BA when recrystallized from any mixtures containing this guest species, be these binary (ANI/4-BA, 2-BA/4-BA, or 3-BA/4-BA), ternary (ANI/2-BA/4-BA, ANI/3-BA/4-BA, or 2-BA/3-BA/4-BA), or quaternary (ANI/2-BA/3-BA/4-BA) in nature. Furthermore, this striking host selectivity persisted even in binary solutions containing low concentrations of 4-BA (18–25%); near-complete selectivities in favor of 4-BA were observed here too. Single crystal X-ray diffraction analyses showed that the favored guest species, 4-BA, was the only one to experience short intermolecular contacts, through its phenyl ring, with the host molecule’s carbonyl oxygen atom and the host hydrogen atom on the carbon bearing the second carboxylic acid group. Furthermore, ANI and 2-BA were accommodated in wide open channels, while the guest accommodation type for 4-BA was significantly more constricted. Thermal analyses confirmed that 2(DED)·3(ANI) and DED·2-BA, having the disfavored guests in open channels, were unstable at room temperature, while the preferred guest species, 4-BA, in its decidedly constricted channels, was only released at significantly higher temperatures (116.8 °C). Therefore, by employing host–guest chemistry strategies, DED has the ability to purify and separate any of these 4-BA-containing mixtures, a distinct advantage over fractional distillations which are cumbersome owing to physical property similarities of 2-, 3-, and 4-BA.

Dynamics of ethylene groups and hyperfine interactions between donor and anion molecules in λ -type organic conductors studied by Ga69,71 -NMR spectroscopy

We present the results of $^{69,71}\mathrm{Ga}$-NMR measurements on an organic antiferromagnet $\ensuremath{\lambda}$-(BEDSe-${\mathrm{TTF})}_{2}{\mathrm{GaCl}}_{4}$ [BEDSe-TTF = bis(ethylenediseleno)tetrathiafulvalene], with comparison with reports on $\ensuremath{\lambda}$-(${\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ [BETS = bis(ethylenedithio)tetraselenafulvalene] [T. Kobayashi et al., Phys. Rev. B 102, 235131 (2020)]. We found that the dynamics of two crystallographically independent ethylene groups induce two types of quadrupolar relaxation in the high-temperature region. As the ethylene motion freezes, hyperfine (HF) interactions develop between $\ensuremath{\pi}$ spin and Ga nuclear spin below 100 K, and thereby, magnetic fluctuations of the $\ensuremath{\pi}$-spin system are detected even from the Ga site. The HF interaction in $\ensuremath{\lambda}$-(${\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ was more than twice as large as in $\ensuremath{\lambda}$-(BEDSe-${\mathrm{TTF})}_{2}{\mathrm{GaCl}}_{4}$, implying that the short contacts between Cl atoms and the chalcogens of the fulvalene part are essential for the transferred HF interaction. We propose that NMR using nuclei in anion layers is useful for studying interlayer interactions in organic conductors, which have not been studied experimentally. In addition, because the mechanism of the transferred HF interaction is considered the same as the $\ensuremath{\pi}\text{\ensuremath{-}}d$ interaction in isostructural Fe-containing $\ensuremath{\lambda}$-type salts, our findings aid in the understanding of their physical properties.

Enabling Donor: Acceptor Bicontinuous Networks via Short Contacts in Double‐Cable Polymers with Pendant Rylene Diimides

Double‐cable polymers (DCPs) with donors and acceptors in the same molecular matrix exhibit excellent stability and have great potential in the practical application of organic solar cells (OSCs). However, such chemical structures of DCPs make the morphology and charge transport very complicated. Here, the packing structures and charge transport channels are revealed for the DCPs with pendant acceptors of rylene diimides. Because of strong π–π overlap, the number of neighboring acceptors is limited and the acceptors cannot form a percolation network for electron transport. Importantly, introducing twisted dimeric rylene diimides can significantly increase the number of neighbors and connectivity for the acceptors via short contacts. Moreover, donor:acceptor bicontinuous networks can be achieved by tuning the dimerization ratio. This opens an avenue toward independent, efficient hole, and electron transport for efficient DCP‐based OSCs.

Crystal structure of methylene blue citrate

Abstract The structure of the salt-type methylene blue citrate hydrate, [MB]+[H3Cit]– × 0.18H2O (where [MB]+ represents the methylene blue cation and [H3Cit]– the anion of the mono-deprotonated citric acid), has been determined by single-crystal X-ray diffraction. The [MB]+ cation is planar and stacked in an antiparallel fashion, exhibiting π–π stacking associations at an interplane distance of 3.746(6) Å. The [MB]+ cation forms short contacts of the C–H⋯O type with the citrate anion through methyl groups of the NMe2 substituents. Water molecules are distributed in the voids between stacks of the [MB]+ cations with very low site occupancies (total 0.18) and do not form hydrogen bonds with the citrate anion, but feature hydrogen bonds between the water molecules. In order to visualize the intermolecular interactions in the crystal structure of the title compound, a Hirshfeld surface analysis was carried out.

Three for the Price of One: Concomitant I⋯N, I⋯O, and I⋯π Halogen Bonds in the Same Crystal Structure.

The ditopic molecule 3-(1,3,5-trimethyl-1H-4-pyrazolyl)pentane-2,4-dione (HacacMePz) combines two different Lewis basic sites. It forms a crystalline adduct with the popular halogen bond (XB) donor 2,3,5,6-tetrafluoro-1,4-diiodobenzene (TFDIB) with a HacacMePz:TFDIB ratio of 2:3. In a simplified picture, the topology of the adduct corresponds to a hcb net. In addition to the expected acetylacetone keto O and pyrazole N acceptor sites, a third and less common short contact to a TFDIB iodine is observed: The acceptor site is again the most electron-rich site of the pyrazole π-system. This iminic N atom is thus engaged as the acceptor in two orthogonal halogen bonds. Evaluation of the geometric results and of a single-point calculation agree with respect to the strength of the intermolecular contacts: The conventional N⋯I XB is the shortest (2.909(4) Å) and associated with the highest electron density (0.150 eÅ-3) in the bond critical point (BCP), followed by the O⋯I contact (2.929(3) Å, 0.109 eÅ-3), and the π contact (3.2157(3) Å, 0.075 eÅ-3). If one accepts the idea of deducing interaction energies from energy densities at the BCP, the short contacts also follow this sequence. Two more criteria identify the short N⋯I contact as the most relevant: The associated C-I bond is significantly longer than the database average, and it is the only intermolecular interaction with a negative total energy density in the BCP.

Elaborating on anti CTLA-4 mechanisms of action using an agent-based modeling approach

Anti CTLA-4 therapy is aimed at blocking the Cytotoxic T-lymphocyte antigen-4 (CTLA-4), a key cancer immunity cycle checkpoint. The mechanism of action of CTLA-4 may be described as a dynamic competition for the B7 ligand which, subsequently, interferes with the CD28-B7 costimulatory pathway. Anti CTLA-4 blockade enhances the process of cognate T cell activation and leads to a broadening of the T cell repertoire. In the present work, we used an agent-based modeling (ABM) platform of T cell immune response development, to explore hypothetical modes of anti CTLA-4 action. The model features a selected number of activated T cell clones, calculated based on combined random and chemotactically-driven encounters with antigen-presenting dendritic cells (DCs) and a distribution of individual T cell affinities to the antigen of interest. The proposed model can be used as a quantitative tool to explore various hypotheses on T cell immunity regulation and validate these against experimental data. A comprehensive ABM model analysis of immune response dynamic simulations revealed several putative anti CTLA-4 mechanisms of action, including: (i) an increase in the probability of primary activation of lymphocytes; (ii) T cell activation enhancement via a prolongation of short contacts with dendritic cells; and (iii) an increase in the maximum level of activation signal (or saturation), accumulated through a series of short contacts with DCs. The modeling work further demonstrates that it is only when considering jointly these various modes of anti CTLA-4 effects on the T cell immune response dynamics that a biologically meaningful increase in both the production of activated cells and the expansion of the T cell repertoire is observed. These model-based results are overall consistent with the collective biological knowledge on the functional role of CTLA-4. Furthermore, the ABM presented here may allow to interrogate various mechanistic scenarios underlying adverse events mediated by anti CTLA-4 pharmacologic therapies.

Crystallographic, DFT, Lattice Energy and Hirshfeld Surface Analysis of Some CSD-Based 6-Chloropurines

A comparative crystallographic and detailed computational analysis of four known 6-chloropurine X-ray structures, accessed from the CSD repository, has been reported in this paper. The quantum chemical analysis of each structure, including the optimized geometry, lattice energy, Hirshfeld surface, HOMO-LUMO energies, has been made to account for the properties of this class of biologically important organic materials. The lattice energy contribution in terms of intermolecular interactions, responsible for the packing stability, has been estimated by PIXEL procedure. Three-dimensional Hirshfeld surfaces and the corresponding 2D-fingerprint plots include the analysis of short intermolecular contacts. The π…π interactions and stacking features of molecules in the packing, have been analyzed using shape index and curvedness plots.

A new hydrazide functionalized Schiff’s base derivative: Insights into crystallography, Hirshfeld surface, and energy framework analysis

A new hydrazide functionalized Schiff’s base derivative, N'-(3,4-dichlorobenzylidene)-4-hydroxybenzohydrazide (I), has been synthesized using a solvent-assisted mechano-chemical grinding strategy and structurally characterized using elemental analysis, 1H NMR and crystallographic studies. The single crystal X-ray diffraction study depicts that molecule is puckered with two aromatic rings lying out-of-plane in near anti-configuration across the C=N bond. The weak interactions involved in supramolecular framework formation are Cl···O, Cl···Cl, Cl···H, Cl···N, C···H, and O···H contacts. The intermolecular O···H interaction being stronger than other dispersive interactions such as halogen bonding, interlocks the molecules in a 2D sheet-type packing. All the structure directing interactions involved in developing crystal architecture are addressed with Hirshfeld surface analysis and fingerprint plots. The energy framework analysis shows visualization of 3D topology of short contacts related to molecular packing of compound I which further clarifies the predominance of both Coulombic and dispersive energies in developing supramolecular architecture.

Control of 11-Aza:4-X-SalA Cocrystal Polymorphs Using Heteroseeds That Switch On/Off Halogen Bonding

A family of: 1:1 cocrystals 11-Aza:4-X-SalA have been prepared from the potent anti-malarial compound 11-azaartemisinin with 4-halosalicylic acids. When X = 4-Cl, 4-Br and 4-I, two conformational polymorphs can be isolated in each case. Monoclinic type-I was found previously for parent 11-Aza:SalA (1) and 11-Aza:4-Br-SalA (3a) which have polar 21 stacks of molecular pairs with no short halogen bond contacts between stacks. Orthorhombic type-II is found for 4-Cl (3b) and 4-I (4b) from solution growth. This has a translational stack of molecular pairs involving a conformational change of the acid-lactam hetero-synthon and supramolecular association of stacks via halogen bonds. Notably, phase pure polymorph type-I can be formed for 4-Cl (3a) and 4-I (4a) by hetero-seeding with 11-Aza:SalA, whist conversely phase pure type-II for 4-Br (2b) can be formed using homo-seeding from liquid assisted grinding (LAG) product. This work demonstrates both the viability of engineering polymorphic cocrystal forms using hetero-seeds and the involvement of halogen bonds in helping to discriminate quite different polymorphic types.

Synthesis, structural, spectral and molecular docking of Ni(II) and Pd(II) complexes with isatin moiety and their DNA cleavage activity

New complexes of Ni(II) and Pd(II) with Schiff base ligand derived from 5-nitro isatin with 4-phenyl-3-thiosemicarbazide have been synthesized in absolute ethanol. The isolated solid compounds have been characterized by elemental analyses and spectral (FT-IR, 1 H NMR and UV-Vis.) measurements. The Schiff base ligand has been further characterized by single-crystal XRD. It has been found that the Schiff base ligand behaves as a tridentate ligand forming chelates with 1:2 (metal:ligand) in the case of Ni-complex and 1:1 (metal:ligand) in the case of Pd-complex. Octahedral-geometry has been suggested for the Ni(II) chelate while square-planar geometry has been suggested for the Pd(II) chelate. The supramolecular structure of the thiosemicarbazide is controlled by large number of short intermolecular contacts such as O…H, H…H, C…C, S…C, S…H, S…N, H…C, N…O and C…O interactions where the most dominant contacts are H…H, H…C, C…C, O…H and S…H interactions. The optimized molecular geometry calculated at B3LYP/6-31G(d,p) level agreed very well with the reported X-ray structure. The two bands observed at 434 and 250 nm in the UV-Vis. spectrum of the compound in DMSO as solvent have been calculated using TD-DFT method at 430.9 nm (f = 0.1178) and 257.2 nm (f = 0.387), respectively. These bands have been assigned to HOMO→LUMO (96%) and HOMO→LUMO+2 (90%) excitations which belong to n-π* and π-π* transitions, respectively. All the synthesized compounds have been tested against supercoiled pBR322 DNA. These compounds have been found to promote the cleavage of plasmid DNA in the presence of H 2 O 2 . The molecular docking of the ligand and its metal complexes refer to groove binding toward the DNA with high docking score of Ni(II) complex rather than the corresponding ligand and Pd(II) complex.