Nature Of Intermolecular Interactions Research Articles

Five Novel Polymorphs of Cardarine/GW501516 and Their Characterization by X-ray Diffraction, Computational Methods, Thermal Analysis and a Pharmaceutical Perspective.

GW501516, also known by the name of cardarine, is a synthetic peroxisome-proliferator-activated receptor delta (PPR-δ) agonist agent developed for applications in the treatment of metabolic disorders and cardiovascular diseases. A broad polymorph screening in various solvents and mixtures was completed in order to explore its capabilities to grow polymorphs. The crystal structures of four polymorphs were elucidated using single-crystal X-ray diffraction, while one structure was solved via a powder X-ray diffraction method. The solid state features (nature of intermolecular interactions) were investigated by computational methods. The polymorphs were further investigated by thermal DSC analysis and X-ray diffraction on powders. From a pharmaceutical perspective, the stability and solubility of the polymorphs were analyzed as well.

Modeling the Interaction between the Isoniazid Anti-Tuberculosis Drug and Functionalized Carbon Nanotubes for Medical Applications: A Quantum Chemical Study

Introduction: The purpose of using nano-carriers for drugs delivery, such as nanotubes, was slow release of drug and reducing side effects of drugs. Drugs are very active due to their many functional groups. Therefore, reactivity of drug is reduced by being in nanotube field due to electronic resonance of drug with nanotube and it stays longer in body. The present study aimed to investigate the interaction of isoniazid with functionalized single-walled carbon nanotubes.
 Methods: In the present theoretical study, considering the importance of isoniazid as the first line of treatment for tuberculosis disease, the performance of carbon nanostructures for adsorption of isoniazid was evaluated using quantum computation. Using density functional theory at theoretical level of B3LYP/6-31G** structure of drug and f-SWCNT and nano-drug complexes were optimized.
 Results: Effect of adsorption on the electronic properties and stability of the nanotube was also examined. In this regard, for different configurations, the strength and nature of intermolecular interactions were evaluated by energy parameters and molecular orbitals. Based on the obtained results, a specific configuration displayed the most negative adsorption energy and enthalpy, establishing itself as the most stable structure among the various configurations.
 Conclusion: Results showed that the electron density of the HOMO (Highest Occupied Molecular Orbital) was localized on the nanotube, while the electron density of the LUMO (Lowest Unoccupied Molecular Orbital) was situated on the drug molecule. The energy gap between two molecular orbitals increased due to the adsorption process; changes lead to an increase in the electrical conductivity of the complex following adsorption. According to the natural bond orbitals, results, the isoniazid molecule and functionalized single-walled carbon nanotube act as both electron donor and acceptor in the complex. Analysis of the results obtained from quantum theory of atoms in molecules, showed the intermolecular interaction between the drug and the functional group of the nanotube has been established, the most important of which is the hydrogen bond. Finally, the findings showed that functionalized SWCNTs can be acted as a drug carrier for isoniazid anti-tuberculosis drug.

Investigation of intermolecular interactions in butyl acetate using vibrational spectroscopy and non-empirical calculations

In this work, on the example of butyl acetate, the nature of intermolecular interactions was studied using vibrational spectroscopy (Raman and FTIR) and non-empirical calculations. The geometric structures of the most stable dimer and trimer aggregates of butyl acetate were optimized using the Density Functional Theory (DFT) method based on the B3LYP/6-311++G(d,p) basis set. Molecular aggregations in liquid butyl acetate were shown to be formed by dipole-dipole interactions and weak C-H…O hydrogen bonds. A potential energy distribution (PED) analysis was performed for the butyl acetate molecule, and experimental and calculated frequencies were found to be in good agreement. Frontier molecular orbitals such as the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the butyl acetate molecule were analyzed.

Volumetric Behaviour of Binary Mixture of Dual Purpose Kerosene (DPK) and Automotive Gas Oil (AGO) at 303K

The study of volume changes in binary mixtures is attracting considerable interest from researchers due to the degree of molecular interaction between the mixed solvent molecules and their importance in many chemical industries and engineering disciplines. The experimental values of densities (ρ) and viscosities (η) of pure and binary mixtures of dual-purpose kerosene (DPK) and automotive gas oil (AGO) were obtained over the whole range of mixture composition at a temperature of 303 K. The experimental data obtained were employed to determine the excess molar volume (V_m^E), excess viscosity (VE), and excess Gibb’s free energy of activation (ΔGE) based on the molecular interactions arising due to the structural effect of the mixture. The measured viscosity values were correlated with Grunberg and Nissan, Kendel and Monroe, and Frenkel’s semi-empirical models to evaluate the best fit for the system. The results acquired were explained according to their structural differences, strength, and nature of intermolecular interactions in the binary mixture. The experimental result revealed that the binary mixture of DPK and AGO shows positive excess molar volume and negative excess viscosity. Weak, specific interactions were responsible for the dispersion force in the binary mixtures.

Topological analysis and reactivity study of monomeric and dimeric forms of 2-methyl-4(1H)-quinolone: a computational study.

Quinolone derivatives have gathered major attention largely due to their wonderful biological activities. Quinolones are a class of molecules that are derived from quinolines and also extracted from natural sources. Most of these quinolones have significant medicinal properties ranging from antiallergenic and anticancer to antimicrobial activities. Some bacteria produce several 2-alkyl-4(1H)-quinolones. In past years, a variety of methods have been reported for the synthesis of quinolone derivatives. In this present work, structural, wave functional, and electronic properties of monomeric and dimeric forms of 2-methyl-4(1H)-quinolone are investigated. From the calculated binding energies, it was found that the formation of dimers is thermodynamically favorable. The analysis of reactivity parameters confirms that the keto form is more reactive than the enol form and keto-keto dimer is more reactive than compared to all monomeric and dimeric forms of our studied compound. Geometry optimizations of monomers and dimers of studied molecules were carried out using the B3LYP-D3(BJ)/ma-def2-TZVPP level of theory. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies were calculated using the B3LYP/def2-TZVP level of theory. All DFT calculations were done with the ORCA 5.0.3 program. The reactivity parameters such as ionization potential, electron affinity, global hardness, global softness, electronegativity, chemical potential, and electrophilicity index were calculated. The nature of intermolecular interactions within the dimers was studied using topological analysis such as atoms in molecule (AIM) and reduced density gradient (RDG) surface analyses. To visualize the electron delocalization in the dimer electron localization function (ELF) and localized orbital locator (LOL) studies were also performed. The analyses such as AIM, RDG, ELF, and LOL were carried out by the multifunctional wavefunction analysis program Multiwfn 3.8.

Facile fabrication of a Cu(II) 1D zig–zag coordination polymer demonstrating affinity toward DNA molecules

A Cu(II) compound [Cu2(5-nip)2(3-brpy)2·(H2O)2·(DMF)2] (1) was synthesized using 5-nitroisophthalic acid (H25-nip) and 3-bromopyridine (3-brpy) employing slow diffusion technique. Visibly distinct blue-colored crystals of compound 1 were obtained. Single crystal X-ray analysis discloses that compound 1 crystallizes in the triclinic system, having space group P1¯ with cell dimensions a = 12.4491(14) Å, b = 13.6238(15) Å, c = 14.3315(15) Å; α = 68.027(3)°, β = 69.914(3)°, γ = 87.173(3)°and V = 2108.3(4)Å3. The compound contains core metal atom Cu(II) that is hexa-coordinated to 5-nip, 3-brpy, dimethylformamide (DMF), and aqua molecule resulting in one- dimensional coordination polymer (1D CP), propagated via strands of 5-nip bridges. The pyridine-based ligand and aqua ligands are decorated as arms on both sides of Cu(II) centers. The prominence of hydrogen bonding interactions in compound 1 was found which leads to the formation of 1D double-chain strand. The combination of 5-nip and 3-brpy ligands is responsible for the strong affinity towards DNA molecules for compound1. Docking studies have been employed to examine DNA binding affinity. Hirshfeld surface analysis was carried out in order to check out the nature of intermolecular interactions and packing modes of compound 1 in the crystalline state.

Thermodynamic Study of Properties in Certain Binary Liquid Mixtures Containing Anisole with 2-Butoxyethanol at Different Temperatures (303.15K to 318.15K)

Comprehensive experimental investigations were carried out on density (ρ), viscosity (η), and ultrasonic velocity (u) for binary mixtures comprising Anisole and 2-Butoxyethanol within the temperature range of 303.15K to 318.15K, covering the complete range of mole fractions. These parameters were measured at intervals of 5K. Derived excess parameters, including acoustic impedance (ZE), intermolecular free length (LEf), molar volume (VEm), excess ultrasonic velocity (uE), and excess viscosity (ηE), were calculated to probe the molecular interactions present in the mixture. These excess parameters were correlated with temperature and mole fraction, revealing the complexity and nature of intermolecular interactions. Notably, the Arrhenius, Bingham, Eyring, Grunberg, Kurata, Nissan, and Tamura models were utilized to theoretically validate the acquired empirical data. This study aims to offer invaluable insights into the thermodynamics and molecular dynamics that govern these binary liquid mixtures.

Volumetric, transport and acoustic properties of binary mixtures containing alkanol at 298.15–318.15 K

The measurement of density (ρ), viscosity (η) and ultrasonic speed (u) have been conducted at T = 298.15 K–318.15 K and at 0.1 MPa to study the intermolecular interactions between p–chlorotoluene with alkanol (C1–C2). These data were utilized to derive the excess properties like excess molar volume (VmE), deviation in viscosity (Δη), excess free energy of activation (ΔG*E), deviation in ultrasonic speed (Δu), and excess isentropic compressibility (κsE) for binary mixtures. Utilizing the VmE values, partial molar volume and excess partial molar volume were calculated. The Δη and κsE were investigated using theoretical models such as the Singh model and ab initio approach, which yielded interactional parameters that not only indicate the extent of unlike interactions and depolymerization of self–associated alkanol but also predicts the Δη and κsE for these systems. The conclusions of the ab initio approach were further validated by the Singh model for viscosity. The u data were further interpreted by various correlations and theories. Regarding correlation, Nomoto’s correlation demonstrated high predictive power for ultrasonic speed data, respectively, compared to other correlations. The resulting excess properties were fitted to Redlich–Kister polynomial equations. The VmE values were observed to be negative for p–chlorotoluene + alkanol systems at all temperatures. The study of the binary mixtures is significant because it sheds light on the nature of intermolecular interactions which has practical implications in areas such as chemical synthesis, solvent selection, and understanding the effects of solvents on reaction rates and product yields.

ONO-pincer Zn(II) & Cd(II) complexes: Synthesis, structural characterization, Hirshfeld surface analysis and CT-DNA interactions

Four new ONO pincer complexes of type Na2[Cd(L′)(OAc)2] (2a), Na2[Zn(L)(OAc)2] (3a), [Zn(LMe)(OAc)2] (4a) and [Cd(LMe)(OAc)2] (4b), where L′ = N,N'-bis(4-methylpyridin-2-yl)pyridine-2,6-dicarboximidate, L = N,N'-di(pyridin-2-yl)pyridine-2,6-dicarboximidate and LMe=N,N'-bis(1-methylpyridinium-2-yl)pyridine-2,6-dicarboximidate, were synthesized. The ligands were generated during complex formation reaction by the in situ deprotonation of their respective pro-ligands; H2L′ (2), H2L (3) and H2LMe (OTf)2 (4). The newly synthesized metal complexes were characterized by elemental analysis, FT-IR, NMR (1H and 13C), and single crystal X-ray diffraction techniques. The single crystal analysis of 4b disclosed that the central Cd(II) ion is adopting capped trigonal prism geometry. The nature of intermolecular interactions within the crystal structure, fingerprint plots, and molecular surface contours have been studied using Hirshfeld surface analysis. The DNA binding assay was conducted by molecular absorption spectroscopy, viscosity measurement and molecular modeling simulations. DNA-interaction measurements show that the compounds have a high propensity for binding with DNA as a groove binder.

Hirshfeld surface analyses, NCI–RDG and effect of surfactant on the size of Co3O4 nanostructures obtained from cobalt(II) nano-complex

Nanostructures of the compound [Co(O2CCH3)2(2-apy)2] (1) (2-apy = 2-Aminopyridine) have been synthesized by a sonochemical process at different of concentrations cobalt acetate tetrahydrate and 2-aminopyridine ligand. The smallest nanostructures of compound 1 are produced in low concentrations of initial reagents. Co3O4 nanoparticles were prepared from thermal decomposition in oleic acid as a surfactant and direct calcination of compound 1 at different temperatures. The effect of calcination temperature and oleic acid, as a surfactant, was investigated on the particle size distribution of the products. The compounds were studied by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), UV–vis, FT-IR spectroscopy, thermal analyses (TGA and DTA) and elemental analyses. Hirshfeld surface analyses and Noncovalent interaction reduced density gradient (NCI-RDG) calculations of compound 1 were illustrated and discussed in order to quantify the order and nature of intermolecular interactions in the crystal network. Hirshfeld surface analysis indicated that there are other types of intermolecular contacts in Crystal, including H…H, H…O, C…H, H…N, C…C and C…N interactions, and the contributions of these interactions are 55.4%, 19.7%, 19.2%, 4.1%, 1.4% and 0.2%, respectively.

Fabrication of a pyridyl appended linear Co(II) based coordination polymer: Structural insights and molecular docking

A Co(II) compound [Co2(ip)2(4-phpy)4·(H2O)2] (1); (H2ip = isophthalic acid and 4-phpy = 4-phenylpyridine) has been synthesized employing slow diffusion technique. Single crystal X-ray analysis reveals that compound 1 crystallizes in the triclinic system, space group P1¯ with a = 10.7041(3) Å, b = 14.2959(4) Å, c = 18.3474(5) Å; α = 73.3930(10)°, β = 76.0190(10)°, γ = 88.4780(10)° with V = 2608.06(13) Å3. The compound 1 forms based one-dimensional coordination polymer (1D CP) constructed by distorted octahedral Co(II) centres, which are interconnected via strands of isophthalate bridges resulting in a 1D chain polymer. The pyridine-based ligands are decorated as arms on both sides of Co(II) centers. The unique coordinating characteristics of isophthalate and pyridine ligands are accounted for the strong affinity towards DNA molecules for compound1. The binding affinities of compound 1 with DNA have been investigated via docking studies. Hirshfeld surface analysis was performed in order to check out the nature of intermolecular interactions and packing modes of compound 1 in the crystalline state.

2D isostructural Ln(III)-based coordination polymer derived from Imidazole carboxylic acid: Synthesis, structure and magnetic behavior

Three new lanthanide-based two-dimensional network like coordination polymers with formula, {[Ln(L)(H2O)2]·2H2O}n (Ln = Ce (1), Gd (2), Sm (3), H3L = 2-(4-carboxy-phenyl)-1H-imidazole-4,5-dicarboxylic acid) have been synthesized hydrothermally and characterized by microanalyses, FT-IR and in case of 1 using single crystal X-ray diffraction. Further, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA) have been performed to assess the phase purity and thermal stabilities of all three polymers. Structural analysis showed that adjacent Ce(III) ions in 1 are intra-connected to form infinite metal-carboxylate oxygen 1D alternating chain-shaped building blocks. The nature of intermolecular interactions in 1 have been analyzed using Hirshfeld surface analysis. In addition, the magnetic properties of all three polymers indicate large magnetic anisotropy for 1 and 3, and ferromagnetic interaction for 2.

Energy decomposition analysis methods for intermolecular interactions with excited states.

Intermolecular interactions with excited states play important roles in various photochemical and photophysical processes. In this work, an energy decomposition analysis (EDA) method of intermolecular interactions for systems in which one monomer is in a singly excited state while others are in their ground states, called GKS-EDA(TD), is proposed. Based on the computational results of time-dependent density functional theory (TD-DFT), GKS-EDA(TD) divides the total interaction energy with excited states into electrostatic, exchange-repulsion, polarization, correlation and dispersion. The nature of intermolecular interactions in test examples with their low-lying singly excited states is investigated, which shows that GKS-EDA(TD) can be used for various intermolecular interactions with different excitation modes. Furthermore, GKS-EDA(TD) is employed to explore the non-covalent interactions in a series of C60⋯ nucleic acid base complexes with the decomposition of excitation energy contribution.

Preparation and computational investigation of molecular imprinted polymers for Clidinium Bromide

Molecular imprinted polymers (MIPs) are polymers that possess recognition sites specific for a predetermined target molecule (Template). Inspired by the idea of biological natural receptors, they behave like synthetic molecular recognition elements. They have been developed into a promising tool in several crucial applications, including analytical methods, drug delivery, and catalysis. The non-covalent imprinting is more commonly used approach in the preparation of MIPs because of its simplicity. In this approach, intermolecular interactions between the template molecule (T) and the functional monomer (FM) are the forces that govern the performance of the resulting MIP. Hence, studying these interactions is very important to elucidate and understand the imprinting mechanism. This paper focuses on preparation of two MIPs for a Clidinium Bromide (CB), using two different types of FMs. These MIPs are characterized by using IR and SEM techniques. Adsorption isotherm properties to CB are assayed for them. Then the structures of the pre-polymerization complexes of prepared MIPs were investigated using Density Functional Theory (DFT) calculations at B3LYP/6-31G level in a vacuum and other media. Finally, Bader's Quantum Theory of Atoms in Molecules (QTAIM) was used to prove the existence and nature of intermolecular interactions between CB and FM. The theoretical results were in complete agreement with experiments and indicated that the use of AM as FM is preferred over MA in the MIP preparation for CB.

Preferred conformations of osmium cluster in terms of electron density

In this article, we propose to use AlteQ quantum free orbital method to determine preferred conformers of osmium-containing complexes. The study is based on the conformational analysis of a triosmium cluster with a morpholine fragment [(μ-H)(μ-Cl)Os3{η1-C(CH3)N(CH2CH2)2O}(CO)9]. 3D electron density maps were computed for each conformer of the cluster along with its environment in the crystal. The “cluster-environment” complementarity was assessed for each conformer based on the determination of relationships between the parameters of the electronic structures, which in turn are determined by the nature of intermolecular interactions. Free versions of the AlteQ for Windows and Linux are available at https://www.chemosophia.com.

Formation of 2D Self-Assembled Layers of Allyl Cyanide on Pd(111)

We present a mechanistic study on the interaction of allyl cyanide (AC) with Pd(111) resulting in the formation of different types of self-organized 2D layers. We employ a combination of scanning tunneling microscopy with infrared reflection absorption spectroscopy to obtain complementary information on the real space distribution of AC molecules in the self-organized 2D layers and on their chemical structure as a function of surface temperature. Specifically in the temperature range of 230–250 K, AC was found to form a self-organized 2D layer involving two different types of surface species adsorbed in trans and cis configurations. Each of these species forms identical individual (8 × 5) sublattices, which are shifted with respect to each other by three Pd atoms. Both functional groups of AC─the CN and C═C bonds─are oriented nearly parallel with respect to the metal surface. With decreasing temperature, strong changes in the layer structure were observed: the AC species agglomerate in irregular concave nonagons comprising nine molecules with the nearest AC–AC distance of three Pd atoms. These individual concave nonagons form a self-assembled 2D layer with the (13 × 10) overstructure on the extended areas of Pd(111). Below 210 K, the degree of order in the AC overlayer drastically decreases and only little structured features can be found. They comprise mainly hexagons embedded into a disordered 2D layer and some parallel rows. The nearest AC–AC distance is close to three Pd atoms in these structures. For all observed AC layers, we provide detailed atomistic-level models and accurate distances between the individual species, which were found to strongly depend on the surface temperature. With the increasing surface temperature, a noticeable increase in the characteristic distances between the interacting neighboring species was observed, which we refer to as changes in the nature of intermolecular interactions.

Phenol-cyclohexanol eutectic mixtures: Phase diagram and microscopic structure by experimental and computational studies

• Non ionic eutectic solvents: phenol-cyclohexanol mixture. • SLE phase diagram by DSC experiment. • Microscopic structure and hydrogen bonding by IR spectroscopy, X-ray diffraction and theoretical calculations. Non ionic deep eutectic solvents (type V) have been recently proposed as innovative and alternative solvents. Prepared by mixing the starting components, their mixtures show strong deviations from thermodynamic ideality. An example of deep eutectic solvent is the 1:1 thymol-menthol mixture: deviations from ideality are originated from the strength of the hydrogen bond between different components. With the aim to investigate the role of hydrogen bonding in the non-ideality of mixtures of phenolic and alcoholic compounds, we studied the phase diagram and the structural properties of cyclohexanol and phenol mixtures coupling experimental and computational techniques. The phase diagram was measured by differential scanning calorimetry (DSC) providing a lowest melting point at about -35°C . The microscopic structure of eutectic composition was characterized by infrared spectroscopy (FT-IR), DFT and classical molecular dynamic simulations. The X-ray pattern was compared with MD results with the aim to describe the intermolecular interactions between phenol and cyclohexanol. The deviations from ideal mixing seem to be smaller than those observed for the 1:1 thymol-menthol mixture. The nature of intermolecular interactions in the phenol-cyclohexanol system has been compared with that of the thymol-menthol system by quantum chemistry calculations. In both the systems heteroassociation is energetically preferred to homoassociation because hydrogen bonding is stronger between different components, however van der Waals contributions involving alkyl groups can play an additional and significant role in the intermolecular association of the thymol-menthol system.

Nonlinear Optical Behavior Due to Charge Transfer within Selected Heterocyclic Anthracenyl Chalcones under Continuous Wave Laser Excitation

Three new heterocyclic-chalcone (HC) derivatives consisting of the π-conjugated system attached to anthracene moiety were proposed for nonlinear optical properties and optical limiting application. The NLO behavior is confirmed through obtained χ3 by Z-scan method. The closed aperture z-scan showed the HC possesses a self-defocusing effect with a negative nonlinear refractive index, n 2 ∼ 10−8 cm/W, with a magnitude of real part of the third-order nonlinear optical susceptibilities, Re χ( 3 ) of the order of 10−7 esu. Open Z-scan results showed that the HC samples demonstrate a reverse saturable absorption (RSA), β ∼ 10−4 cm/W, corresponding to large imaginary parts, Im χ( 3 ) in the order of 10−6 esu. Overall, the Z-scan analysis unveils an excellent value of χ3 in order of 10−6 which indicates good nonlinear material under 532 nm continuous wave laser. The optical limiting study reveals that AC exhibit a strong limiting behavior with action beginning from 0.8 KW/cm2, and seems to be promising optical limiting candidates for future optoelectronic applications. Through B3LYP/6-311G++d,p level of theory Density Functional Theory (DFT), Global Reactivity, Natural Bond Orbital (NBO), and Natural Population were calculated and investigated. Delocalization and hyperconjugation interactions, intramolecular charge transfers, and stabilization energies were discovered using NBO and NPA. The comprehensive studies of Hirshfeld surface (HS) and fingerprint plots (FP) calculations were done in order to evaluate the nature of intermolecular interactions in the compounds. The inclusion of a strong donor and the π-conjugated system improved charge transfer, chemical stability, and optoelectronic properties of the anthracene-heterocyclic chalcone derivatives. As a result, the present work realizes the potential of designed derivatives that can be used in NLO applications.

Synthesis, crystal structure, hirshfeld surface analysis, molecular docking and molecular dynamics studies of novel olanzapinium 2,5-dihydroxybenzoate as potential and active antipsychotic compound

The antipsychotic drug Olanzapine was crystallized with aromatic acid, 2,5-dihydroxybenzoic acid in isopropyl alcohol by slow evaporation which led to the formation of olanzapinium 2,5-dihydroxybenzoate crystalline salt. The structure of the compound was characterized by 1H-NMR, 13C-NMR, and single-crystal X-ray diffraction analysis. The Hirshfeld analyses were performed to quantify the order and nature of intermolecular interactions in the crystal network. Employing computational approaches, the compound was tested for its affinity against antipsychotic activity by molecular docking and molecular dynamic simulation to attest the conformational stability over time step of 100 ns. Besides, bioactivity and ADMET properties were also predicted to ratify the result. The compound asserted neither carcinogenic nor mutagenic activity and has high oral bioavailability. Hence, this synthesized novel compound Olanzapinium 2,5-dihydroxybenzoate recognized in the study possesses high potential as an effective antipsychotic compound, and can further be examined for its efficiency by in vivo studies. The synthesized compound was submitted to NCBI PubChem database using accession substance ID: 441329256. The crystal structure was submitted to CCDC (Cambridge Crystallographic Data Centre) with submission ID: 2010899.

FUNDAMENTAL ASPECTS OF THE COORDINATION CHEMISTRY OF TRANSITION METALS WITH FUNCTIONALLY SUBSTITUTED THIOAMIDES (PART 1)

The influence of competitive coordination, a tautomeric form of functionally substituted thioamides, conditions of synthesis and nature of the metal on the course of the reaction and structure of mono-, bi, and polynuclear complexes of 3d, 4d-metals is considered based on results obtained in the Department of "Chemistry of Complex Compounds" of the V.I. Vernadsky Institute of General and Inorganic Chemistry NAS of Ukraine, together with the staff of the Department of “Chemistry of Heterocyclic Compounds” of the Institute of Organic Chemistry NAS of Ukraine.
 The influence of ligand denticity, as well as conditions of complex formation on the structure of obtained complexes and their polymorphic modifications, was studied based on the reaction of d-metals with functionally substituted N, S- and O, N, S-containing thioamides. In addition, it is proved the influence of tautomeric forms of thioamides on the stereochemistry of coordination polyhedra: it is found that the thionic tautomeric form promotes the transposition of thioureas, while the thiol form promotes its cis-position in the square-planar of a polyhedron of 3d, 4d-metals in the structure of complexes. However, it was found that the thion tautomeric form leads to the formation of octahedral, while the thiol form to the square-planar of coordination nodes in complexes of Cu(II) and Ni(II), which are characterized by a change in coordination polyhedra (from square-planar and tetrahedron to octahedron) that depending on the strength of the ligand field. It is obvious that this effect of tautomeric forms of thioamides is associated with the formation of a conjugate system of double bonds in their molecules. In this case, the transition of thioamide to thiol form depends on the pH and the nature of the organic solvent: in a weakly alkaline medium or polar organic solvent (pyridine, chloroform) there is a shift of equilibrium towards to the dominance of thiol tautomeric form.
 It was found that the thionic tautomeric form of thioamides (depending on pH and substituent composition) reacts with metal salts mainly in neutral form or in the monoanionic form, forming complexes of molecular or ionic nature, while thiol form reacts in the form of dianion, forming complexes preferably anionic type. Ionic compounds are usually soluble or sparingly soluble in water in low concentrations (10-3–10-5 mol/l), while compounds of the molecular type are soluble only in DMSO and DMF.
 It is shown that the stereoselective synthesis of various ligand complexes is carried out mainly in three ways: 1) by the interaction of the initial components in the corresponding stoichiometry. In this case, the vacancy in the metal environment is occupied by either the anions of the starting metal salt (Hal-, SO42-, NO3-, CH3COO-, etc.) or other organic molecules (triphenylphosphine, pyridine, etc.); 2) carrying out parallel reactions (hydrolysis and oxidation of thioureas), which lead to participation in the coordination of by-products of the reaction; 3) carrying out reactions with intraligand rearrangements, which leads to the cyclization of organic ligands and coordination of the products of their transformation to the central metal ion. However, it was found that hydrolysis / oxidation or intraligand cyclization of substituted polydentate thioamides can occur both under the action of synthesis conditions and under the action of complexing metals as promoters of organic reactions.
 It was found that depending on the temperature and time of interaction of the starting reagents, different polymorphic modifications of complexes (triclinic or monoclinic) are formed, which differ in packing density and the nature of intermolecular interactions. As a result, such polymorphic modifications have different solubilities in water, which is important for the controlled synthesis of appropriate structures and their practical application.