Nonvalent Interactions Research Articles

Carbometallic derivatives of C 1v and C 5v boranes: Enumeration and identification of substitution isomers and the calculation scheme of the properties of C 5v based on pascal’s triangle numbers

Combinatorial analysis methods are employed to solve the problem of determining the number and form of X-substituted (X, XY, … are some substituents) of carbometallic derivatives of boranes (C5H5)Co(C2B9H11) C1v and (C5H5)Co(C5B6H11) C5v (over vertices) based on Polya’s theorem. formulas of Z symmetry and generating functions of the number of chiral and achiral substitution stereoisomers are determined. Family distributions of the isomers depending on the form and number of substituents and depending on the number m of possible substitution sites are found. Mono-, di-, and tri-X-substituted (X = CH3, F, …) isomers of (C5H5)Co(C5B6H11) C5v are identified. Based on the partition of simple (n) and triangular numbers (K3) of Pascal’s triangle, additive schemes are obtained which take into account valence and non-valence pair interactions of atoms in the polyhedron framework and contain 2, 6, and 23 parameters for the calculation of properties of X-substituted borane (C5H5)Co(C5B6H11) C5v.

Structure and spectral properties of triphenylamine dye functionalized with 3,4-propylenedioxythiophene

Based on the density functional theory with the B3LYP, BMK, and PBE1PBE hybrid functionals and 6–31G(d) atomic-orbital basis set, the structure and electronic-spectral properties of a triphenylamine dye sensitizer for photoelectric converters that is functionalized with 3,4-propylenedioxythiophene have been studied. The nature of an intense color of the sensitizer is elucidated. The relation of the orbital structure of the first excited state to the mechanism by which the intensity and polarization of the visible absorption band are formed, as well as the electron injection efficiency into the conduction band of titanium oxide, are explained. In terms of the Bader theory, a complete analysis of the electron density distribution in the dye molecule under study has been performed and the role played by nonvalent interactions in its stabilization has been determined.

The construction of graph models for calculations of the properties of substitution isomers of basis structures on the basis of additivity of energy contributions

A method for the construction of additive models for calculations of the properties of substitution isomers of basis structures is described for the example of a series of X-substituted methylsilanes CH3 − k X k -SiH3 − l X l (where X = CH3, F, Cl, …, k, l = 0, 1, 2, 3). The method is based on similarity of subgraphs in graphs of several molecules and the arrangement of polygonal numbers (triangular, tetrahedral) of the Pascal triangle. Parameters taking into account multiple nonvalence interactions (-C-Si C-Si<, …) through two atoms along the molecular chain of an X-substituted methylsilane (X = CH3) were for the first time explicitly included in the calculation scheme. Taking these interactions into account allows us to completely differentiate all the structural isomers of certain molecules and obtain numerical parameter values for predicting properties P under consideration in various approximations. Numerical calculations of Δf H g,298 K o were performed for 16 alkylsilanes (as X-substituted methylsilanes), including 7 compounds not studied experimentally.

New criterion for conformational polymorphism

An analysis of nonvalent interactions in 29 crystal structures of compounds that have the CaHbNcOd composition (salicylaldoxime, glycine, and 2,4,6,8,10,12-hexaazaisowurzitane) and form polymorphic modifications is performed using molecular Voronoi-Dirichlet polyhedra. It is found that each conformational polymorph is characterized by a unique combination of the types of intramolecular and intermolecular nonvalent interactions. It is shown that a criterion which takes into account the total number of intramolecular nonvalent contacts and their distribution depending on the nature of neighboring atoms and the rank of faces of molecular Voronoi-Dirichlet polyhedra can be used to reveal conformational polymorphs.

Synthesis and crystal structure of [UO2(OH)(CO(NH2)2)3]2(ClO4)2

The complex [UO2(OH)(CO(NH2)2)3]2(ClO4)2 (I) was synthesized. A single crystal X-ray diffraction study showed that compound I crystallizes in the triclinic system with the unit cell parameters a = 7.1410(2), b = 10.1097(2), c = 11.0240(4) A, α = 104.648(1)°, β = 103.088(1)°, γ = 108.549(1)°, space group \(P\bar 1\), Z = 1, R = 0.0193. The uranium-containing structural units of the crystals are binuclear groups [UO2(OH)· (CO(NH2)2)3]22+ belonging to crystal-chemical group AM2M31 [A = UO22+, M2 = OH−, M1 = CO(NH2)2] of uranyl complexes. The crystal-chemical analysis of nonvalent interactions using the method of molecular Voronoi-Dirichlet polyhedra was performed, and the IR spectra of crystals of I were analyzed.

Effect of structural features of molecules (Cl3PNZ)2 (Z = CH3 and CH2CH2Cl) on the position exchange of chlorine atoms in the P-Cl fragments

Based on the analysis of structural parameters of molecules (Cl3PNCH3)2 (I) and (Cl3PNCH2CH2Cl)2 (II) by the quantum-chemical nonempirical calculations the following was revealed. The structure of I and II dimers has geometric features, which have a decisive influence on the degree of inhibition of positional exchange of the chlorine atoms in the P-Cl fragments known for the chlorine derivatives of pentacoordinated phosphorus atom. The obstacles to this dynamic process in the mentioned intramolecular dimers is shown to result from the spatial nonvalent interactions due to the short contacts of the chlorine and hydrogen atoms.

Analysis of nonvalent interactions in the crystals of conformational polymorphs of the composition C a H b N c O d S e by means of molecular voronoi-dirichlet polyhedra

Nonvalent interactions in crystals of compounds of the composition C a H b N c O d S e that exhibit conformational polymorphism and have no fewer than four structurally characterized modifications are analyzed using molecular Voronoi-Dirichlet polyhedrals. A unique combination of the types of occurring intra- and intermolecular nonvalent contacts is shown to correspond to each conformational polymorph. Nonvalent interactions involving hydrogen atoms are found to occur most often in crystal structures, and least often those involving S, N, and O atoms.

Structure of complexes of sulphuretted tetraphenylporphine with poly-N-vinylpyrrolidone according to the data of small-angle neutron scattering

Aqueous solutions of poly-N-vinylpirrolidone (PVP), a typical polymer for medical purposes, containing sulphuretted tetraphenylporphirine dihydrochloride (H2TPPS4(HCl)2 or TPPS) having antiviral and therapeutic properties were studied. The association of PVP chains due to their nonvalent interactions with TPPS molecules playing the role of interchain and intrachain bonds was observed in complex solution over the temperature range from 20 to 90°C. The character of conformation changes of the polymer was determined; parameters of PVP binding with TPPS were calculated. The TPPS molecules were shown to be associated with PVP ones by means of hydrogen bonds between porphyrin sulfonic groups and polarized water molecules in the polymer hydration shell.

Novel P,N-Containing Cyclophane with a Chiral Hydrophobic Cavity

Macrocycles containing aromatic or heterocyclic units within the macrocyclic core draw an increasing attention for the last few decades.[1] The aromatic units, being rigid building blocks, allow the design and synthesis of molecular cavities with defined spatial characteristics, and also serve as binding sites for hosts capable of interacting with their π-electron systems.[1b-d] On the other side heterocyclic rings are also of special interest for the construction of cyclophane-type molecules[2] because the presence of donor heteroatoms provides means for the incorporation of a binding site for transition metals within the macrocyclic structure. Macrocycles formed both by the aromatic and the heterocyclic units with three-coordinated phosphorus atoms as donors[3] are able to provide a variety of the donoracceptor and the non-valent interactions so they are of interest both for supramolecular chemistry (in particular as selective sensors[4]) and as unusual ligands for transition metal catalyzed reactions in organic synthesis,[5] as the geometry and well-defined position of the complexing donor centers could lead to specific catalytically active complexes.[6] However, the chemistry of cyclophane ligands containing phosphine groups as donor centers within the macrocyclic skeleton is less developed than that of their oxygen or nitrogen analogues.[3] This fact has been mainly attributed to the air sensitivity of these compounds and the poor yields obtained in their preparations by high-dilution[3,7] or template methods,[3] although the high-yield synthesis of a few types of phosphamacrocycles has been reported. [3,8] To the best of our knowledge there are no examples of P-containg cyclophanes with chiral intramolecular cavity. But we are sure that if P-containing cyclophanes, especially chiral, with a unique shape, distinct architecture, and set of functional groups become easily available from natural or synthetic sources, they would start to inspire the imagination of supramolecular chemists to devise and synthesize novel sophisticated receptors, machines, and devices,[1-3,6,8] as well as new types of molecular reactors.[9] Recently, a highly effective self-assembly process giving macrocyclic tetraphosphines with a relatively large hydrophobic prismatic or helical twisted cavities by condensation of the three-component system diamine/ formaldehyde/phosphine was discovered.[10] In the present work diamines possessing inherent chirality, namely N-alkyl-2,6-diamino-9,10-dihydro-9,10-ethanoanthracenecis-11,12-dicarboximide 2-4,[11] were used as spatially divided diamine component of the self-assembling system to prepare a novel type of P,N-containing cyclophanes with chiral intramolecular cavity.

Bond energies and the enthalpies of formation of mono- and polyradicals in nitroakanes 3. Nitroalkanes C4–C7

Based on the experimentally determined values and published data, the enthalpies of formation of nitroalkanes C4–C7 in the standard state and in the gas phase were recommended. The dissociation energies of bonds in these compounds were determined taking into account the enthalpies of atomization and the energies of nonvalent interactions of nitro groups with one another. The calculated values were compared with the available thermal decomposition kinetic data. The dissociation energies of bonds in C4–C7 nitroalkane radicals were also calculated using the enthalpies of atomization and the energies of nonvalent interactions of nitro groups. Regularities of changes in the bond dissociation energies of nitroalkanes C1–C7 and their radicals are established.

Analysis of the conformational polymorph crystal structures by means of molecular Voronoi-Dirichlet polyhedra

The nonvalent interactions in the crystal structures of 16 conformational polymorphs of the CaHbNcOdSe composition (a, b, c, d, and e are stoichiometric indices), including 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile (“ROY”) (which has seven different modifications), have been analyzed using the characteristics of molecular Voronoi-Dirichlet polyhedra. It is established that a unique combination of implementable types of intra- and intermolecular nonvalent contacts corresponds to each conformational polymorph.

Simulation of polymers by the Monte Carlo method using the Wang-Landau algorithm

Studies of several models of polymers with the use of a version of the Monte Carlo method—entropy sampling combined with the Wang-Landau algorithm—are presented. This approach allows derivation of the energy distribution function over a broad energy range. On the basis of this distribution various thermal characteristics of the systems are calculated in a wide temperature range: internal energy, free energy, heat capacity, average gyration radius, and mean end-to-end distance. For simple continuum and lattice models of free chains and rings we consider the athermal case, with eliminated overlaps, and the thermal case, when nonvalence interactions between units at finite distances are accounted for. In the framework of the proposed approaches, the models of alkanes and the simplest polypeptide, polyglycine, and the lattice model of flexible polyelectrolyte are investigated.

Bond energies and the enthalpies of formation of mono- and polyradicals in nitroalkanes 2. Nitro derivatives of ethane and propane

Based on the experimental results and the published data, the enthalpies of formation of ethane and propane nitro derivatives were obtained for both the standard state and gas phase. The bond dissociation energies of the ethane and propane nitro derivatives were calculated using the enthalpies of atomization and the energies of nonvalent interactions of nitro groups. The calculated values were compared with the kinetic data on thermal decomposition. The bond dissociation energies in radicals of the ethane and propane nitro derivatives were also calculated using the enthalpies of atomization and the energies of nonvalent interactions of nitro groups. Regularities of changes in the bond dissociation energies of the ethane and propane nitro derivatives and their radicals were established.

Influence of aminopyrimidyl derivatives on the supramolecular architectures and abundant nonvalent interactions of silver 5-nitroisophthalate coordination polymers

Two 5-nitroisophthalate silver(I) coordination polymers with 2-aminopyrimidyl derivatives, namely [Ag 2(apym) 1.5(nipa)·H 2O] n ( 1) and [Ag 2(dmapym) 2(nipa)] n ( 2) were synthesized and characterized by single-crystal X-ray analysis (apym = 2-aminopyrimidine, dmapym = 2-amino-4,6-dimethylprimidine, H 2nipa = 5-nitroisophthalic acid). Complex 1 possesses a one-dimensional (1D) structure built from rhombic [Ag 4(apym) 2(nipa) 2] second building units (SBUs). The uncoordinated O nitro is involved in the significant lone-pair (lp)⋯π interaction with the benzene ring of nipa. Complex 2 possesses a two-dimensional (2D) structure in which dmapym ligands show two different coordination modes, monodentate and bidentate, respectively. Moreover, 2 shows abundant nonvalent interactions, such as lp(O carboxyl)⋯π, π⋯π, C–H⋯π interactions and hydrogen-bonding simultaneously. 1 and 2 also exhibit diverse structure motifs due to the effects of substituent methyl groups. The photoluminescence properties of these complexes also were examined.

Coordination of gold(III) in the chemisorption by cadmium diisobutyldithiocarbamate: Structure and thermal properties of the polynuclear gold-cadmium complex [Au“S2CN(iso-C4H9)2”2]2n [CdCl4] n

Gold(III) is coordinated by binuclear cadmium diisobutyldithiocarbamate (Dtc) via chemisorption to give a heteropolynuclear Au(III)-Cd complex of the formula [Au“S2CN(iso-C4H9)2”2]2n [CdCl4] n (I). According to X-ray diffraction data, structure I contains three structurally nonequivalent complex cations [Au“S2CN(iso-C4H9)2”2]+. These cations are conformers. Relatively weak nonvalence interactions produce zigzag polymer chains of the type (...C...A...B...A...) n with alternating nonequivalent cations A, B, and C in a ratio of 2: 1: 1. The anions [CdCl4]2− are localized at the side. The calculated theoretical chemisorption capacity of cadmium Dtc with respect to [AuCl4]− is 378.0 mg of Au3+ per gram of the sorbent. To optimize the conditions for isolation of sorbed gold, the thermal properties of complex I were studied by simultaneous thermal analysis. The two-step thermolysis of complex I involves (1) thermal decomposition of the dithiocarbamate part and [CdCl4]2− with liberation of metallic gold and cadmium dichloride and (2) evaporation of CdCl2. The final thermolysis product of complex I is reduced metallic gold.

Thermodynamic stability of 2,4,6-tris(nitromethyl)-1,3,5-triazine: an experimental and theoretical study

The molecular geometries and electronic structures of 2,4,6-tris(nitromethyl)-1,3,5-triazine isomers were investigated by the density functional method DFT/B3LYP/6-311++G** to elucidate the structural factors responsible for the stability of these systems. It was shown that a characteristic feature of the nitromethyl tautomer (1) of 2,4,6-tris (nitromethyl)-1,3,5-triazine consists in nonvalence interactions between an oxygen atom of nitro group and a carbon atom of triazine ring, which are probably due to Coulomb attraction between them. The tautomer with the 2,4,6-tris (nitromethylene)-hexahyrdo-1,3,5-triazine structure (2) is stabilized trough direct polar conjugation between the amino and nitro groups at the double bond. Structural strain of the molecule with the 2,4,6-tris(aci-nitromethyl)-1,3,5-triazine structure (3) is the reason for its thermodynamic instability. X-ray data indicate that the compound under study exists in the triazine tautomeric form 1 and the distances between oxygen atoms of nitro group and carbon atom of the triazine ring are shortened. NMR data suggest the existence of triazine in the nitromethyl form 1 in acetonitrile and acetone and a tautomeric equilibrium between the nitromethyl and nitromethylene forms in a more polar solvent (DMSO). The results obtained suggest a Coulomb-type stabilization of the 2,4,6-tris(nitromethyl)-1,3,5-triazine molecule in the gas phase, in the crystal, and in nonpolar solvents.

Bond energies and formation enthalpies of mono- and polyradicals in nitroalkanes 1. Nitromethanes

The enthalpies of formation of nitromethane derivatives were obtained on the basis of experimental and literature data. The procedure for the calculation of the bond dissociation energies in nitromethanes from the atomization enthalpies and energies of nonvalent interactions of nitro groups was proposed. The calculated values were compared with the data on the thermal decomposition kinetics. The atomization enthalpies and energies of nonvalent interactions of nitro groups were also used for the calculation of the bond dissociation energies in radicals.

X-ray and quantum-topological studies of intermolecular interactions in partially fluorinated quinoline crystals

An X-ray study of the crystals of bicyclic compounds containing fluorinated aromatic and nonfluorinated heteroaromatic rings, 5,6,7,8-tetrafluoroquinoline, 5,6,8-trifluoroquinoline, 5,7-difluoroquinoline, 5,7,8-trifluoro-2-phenylquinoline, and 5,7,8-trifluoro-6-trifluoromethylquinoline, was carried out. The basic supramolecular motifs and the underlying intermolecular interactions that control the lattice structure of these compounds were investigated. B3LYP DFT quantum-chemical calculations (6-311G(d,p) basis set) and the topological analysis of the electron density distribution in terms of Bader’s QTAIM theory were performed for the compounds. It is shown that the intermolecular interactions in question, traditionally regarded as nonvalent interactions, are related, to a definite extent, to the formation of very weak covalent chemical bonds in the intermolecular space due to the overlap of the “tails” of the molecular wave functions.

Non-valent interactions and structural features of monomeric guanidinate complexes of rare earth metals: analyses and predictions based on the ligand solid angle

Analysis of steric saturation of rare earth metal centers in monomeric guanidinate coordination complexes with the use of ligand solid angles indicates that the observed optimal metal shielding is 85(3)%. Non-valent ligand–ligand interactions in the metal coordination sphere affect the shielding of the metal and can facilitate or preclude formation of agostic interactions. Analysis of all structurally characterized to date guanidinate complexes of Ln is presented and general and unique features of such complexes are identified.

Structural features of the phosphorus heterocumulene ylides (sp-ylides)

The features in phosphorus heterocumulene yilides Ph3PCCX [X = NPh, NC(O)Ph, C(CN)CO · (OMe), O, S] with the ylide carbon geometry close to sp-hybridization are studied using ab initio methods. Estimation of structural parameters of a new member in the Ph3PCα=Cβ=NC(O)Ph series on the B3LYP/6-31G(d,p) level and together with experimental data for related ylide (X = NPh) gave the following values: r(PCα) 1.665 A, r(Cα=Cβ) 1.237 A, ω(PCαCβ) 145.2°. Nonvalent interactions of spλ orbital of the ylide carbon atom bearing extra negative charge with coplanar π-electrons of the nearest Cβ=N bond are found close to those of nitrogen lone pair with the Cα=Cβ bond and leading to up to 10° nonlinearity of Cα-Cβ=N triad of the phosphorus iminoketene ylides. Chemical nonequivalence of the PCipso bonds in the triphenylphosphonium fragment, relation of \(^1 J_{PC^\alpha } \) spin-spin coupling and antisymmetric bonding vibration νas(C=C=X) to the structure of the carbanion, and inductive hyperconjugative influence of atom (or group) X on the ylide carbon geometry are discussed.