Homonuclear chalcogen–chalcogen bond interactions in complexes pairing YO3 and YHX molecules (Y = S,Se; X = H,Cl, Br,CCH, NC,OH, OCH3): Influence of substitution and cooperativity

MP2/aug‐cc‐pVTZ calculations are performed on complexes of YO₃ (Y = S, Se) with a series of electron‐donating chalcogen bases YHX (X = H, Cl, Br, CCH, NC, OH, OCH₃). These complexes are formed through the interaction of a positive electrostatic potential region (π‐hole) on the YO₃ molecule with the negative region in YHX. Interaction energies of the binary O₃Y???YHX complexes are in the range of ?4.37 to ?12.09 kcal/mol. The quantum theory of atoms in molecules and the natural bond orbital analysis were applied to characterize the nature of interactions. It was found that the formation and stability of these binary complexes are ruled mainly by electrostatic effects, although the electron charge transfer from YHX to YO₃ unit also seems to play an important role. In addition, mutual influence between the Y???N and Y???Y interactions is studied in the ternary HCN???O₃Y???YHX complexes. The results indicate that the formation of a Y???N interaction tends to weaken Y???Y bond in the ternary systems. Although the Y???Y interaction is weaker than the Y???N one, however, both types of interactions seem to compete with each other in the HCN???O₃Y???YHX complexes. © 2016 Wiley Periodicals, Inc.     

Synthesis,characterization and theoretical and fluorescence emission microscopy studies of new Pd/Pt–cyclopropa[60]fullerene complexes: Application of Taguchi method for optimization of parameters in Suzuki–Miyaura reaction

The reactions of unsymmetric phosphorus ylides of the type [Ph₂P(CH₂)_nPPh₂?C(H)C(O)C₆H₄‐p‐CN] (n = 1 (Y¹); n = 2 (Y²)) with C₆₀ and M(dba)₂ (M = Pd or Pt; dba = dibenzylideneacetone) are reported. Based on the various coordination modes of these ylides in complexation, the following new Pd/Pt–cyclopropa[60]fullerene complexes were obtained: P,C‐coordinated [(η²‐C₆₀)Pd(κ²‐Y¹)] ( 1 ) and [(η²‐C₆₀)Pt(κ²‐Y¹)] ( 2 ) complexes and P‐coordinated [(η²‐C₆₀)Pd(Y²)₂] ( 3 ) and [(η²‐C₆₀)Pt(Y²)₂] ( 4 ) complexes. These compounds were characterized using Fourier transform infrared, UV–visible and NMR (¹H, ¹³C and ³¹P) spectroscopies and scanning electron microscopy. Furthermore, cytotoxicity studies showed that nanoparticles of these complexes can be used as non‐toxic labels for cellular imaging application. Also energy decomposition analysis results revealed that the percentage contribution of ΔE_elec in total interaction energy is considerably larger than that of ΔE_orb. Thus, in all complexes the (η²‐C₆₀)M? (Y¹) bond is considerably more electrostatic in nature than the (η²‐C₆₀)? M(Y¹) bond. Finally, by application of the Taguchi method for optimization of parameters in Suzuki–Miyaura reaction, the catalytic activity of Pd complexes 1 and 3 was investigated in the cross‐coupling reaction of various aryl chlorides with phenylboronic acid. According to analysis of variance results, solvent has the highest F value and it has high contribution percentage (36.75%) to the yield of Suzuki–Miyaura reaction.     

Dimers of N‐Heterocyclic Carbene Copper,Silver, and Gold Halides: Probing Metallophilic Interactions through Electron Density Based Concepts

Homobimetallic metallophilic interactions between copper, silver, and gold‐based [(NHC)MX]‐type complexes (NHC=N‐heterocyclic carbene, i.e, 1,3,4‐trimethyl‐4,5‐dihydro‐1H‐1,2,4‐triazol‐5‐ylidene; X=F, Cl, Br, I) were investigated by means of ab initio interaction energies, Ziegler–Rauk‐type energy‐decomposition analysis, the natural orbital for chemical valence (NOCV) framework, and the noncovalent interaction (NCI) index. It was found that the dimers of these complexes predominantly adopt a head‐to‐tail arrangement with typical M ??? M distance of 3.04–3.64 Å, in good agreement with the experimental X‐ray structure determined for [{(NHC)AuCl}₂], which has an Au ??? Au distance of 3.33 Å. The interaction energies between silver‐ and gold‐based monomers are calculated to be about ?25 kcal mol^?1, whereas that for the Cu congener is significantly lower (?19.7 kcal mol^?1). With the inclusion of thermal and solvent contributions, both of which are destabilizing, by about 15 and 8 kcal mol^?1, respectively, an equilibrium process is predicted for the formation of dimer complexes. Energy‐decomposition analysis revealed a dominant electrostatic contribution to the interaction energy, besides significantly stabilizing dispersion and orbital interactions. This electrostatic contribution is rationalized by NHC(δ⁺) ??? halogen(δ^?) interactions between monomers, as demonstrated by electrostatic potentials and derived charges. The dominant NOCV orbital indicates weakening of the π backdonation in the monomers on dimer formation, whereas the second most dominant NOCV represents an electron‐density deformation according to the formation of a very weak M ??? M bond. One of the characteristic signals found in the reduced density gradient versus electron density diagram corresponds to the noncovalent interactions between the metal centers of the monomers in the NCI plots, which is the manifestation of metallophilic interaction.     

Interplay between Cation–π and Coinage‐Metal–Oxygen Interactions: An Ab Initio Study and Cambridge Structural Database Survey

The interplay between cation–π and coinage‐metal–oxygen interactions are investigated in the ternary systems N???PhCCM???O (N=Li⁺, Na⁺, Mg²⁺; M=Ag, Au; O=water, methanol, ethanol). A synergetic effect is observed when cation–π and coinage‐metal–oxygen interactions coexist in the same complex. The cation–π interaction in most triads has a greater enhancing effect on the coinage‐metal–oxygen interaction. This effect is analyzed in terms of the binding distance, interaction energy, and electrostatic potential in the complexes. Furthermore, the formation, strength, and nature of both the cation–π and coinage‐metal–oxygen interactions can be understood in terms of electrostatic potential and energy decomposition. In addition, experimental evidence for the coexistence of both interactions is obtained from the Cambridge Structural Database (CSD).     

Theoretical study on the interactions of halogen‐bonds and pnicogen‐bonds in phosphine derivatives with Br2, BrCl,and BrF

The MP2 ab initio quantum chemistry methods were utilized to study the halogen‐bond and pnicogen‐bond system formed between PH₂X (X = Br, CH₃, OH, CN, NO₂, CF₃) and BrY (Y = Br, Cl, F). Calculated results show that all substituent can form halogen‐bond complexes while part substituent can form pnicogen‐bond complexes. Traditional, chlorine‐shared and ion‐pair halogen‐bonds complexes have been found with the different substituent X and Y. The halogen‐bonds are stronger than the related pnicogen‐bonds. For halogen‐bonds, strongly electronegative substituents which are connected to the Lewis acid can strengthen the bonds and significantly influenced the structures and properties of the compounds. In contrast, the substituents which connected to the Lewis bases can produce opposite effects. The interaction energies of halogen‐bonds are 2.56 to 32.06 kcal·mol^?1; The strongest halogen‐bond was found in the complex of PH₂OH???BrF. The interaction energies of pnicogen‐bonds are in the range 1.20 to 2.28 kcal·mol^?1; the strongest pnicogen‐bond was found in PH₂Br???Br₂ complex. The charge transfer of lp(P) ? σ*(Br? Y), lp(F) ? σ*(Br? P), and lp(Br) ? σ*(X? P) play important roles in the formation of the halogen‐bonds and pnicogen‐bonds, which lead to polarization of the monomers. The polarization caused by the halogen‐bond is more obvious than that by the pnicogen‐bond, resulting in that some halogen‐bonds having little covalent character. The symmetry adapted perturbation theory (SAPT) energy decomposition analysis showes that the halogen‐bond and pnicogen‐bond interactions are predominantly electrostatic and dispersion, respectively.     

Theoretical study of the interaction between LiNH2 and HMgH

The lithium bond between HMgH and LiNH₂ has been predicted and characterized with quantum chemical calculations at the MP2/6‐311++G(d,p) level. Upon formation of the lithium bond, both the Mg? H and Li? N bonds are stretched. The Li? N bond undergoes a red shift, whereas the Mg? H bond exhibits a blue shift. The lithium‐bonded complex is controlled mainly by electrostatic and polarization interactions. The binding energy of HMgH with LiNH₂ is computed to be 12.47 kcal/mol. The binding of the two molecules is enhanced by the substitution with the methyl group in the Li acceptor, whereas it is weakened by the replacement with whether the electron‐withdrawing group such as F, Cl, CN, NC, or the electron‐donating group (OH and HN₂). A negative cooperativity is present in the ternary system of 2LiNH₂ and HMgH. The polarization interaction plays an important role in the negative cooperativity. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Cooperativity between the Halogen Bond and the Hydrogen Bond in H3N⋅⋅⋅XY⋅⋅⋅HF Complexes (X,Y=F,Cl, Br)

Ab initio calculations are used to provide information on H₃N???XY???HF triads (X, Y=F, Cl, Br) each having a halogen bond and a hydrogen bond. The investigated triads include H₃N???Br₂‐HF, H₃N???Cl₂???HF, H₃N???BrCI???HF, H₃N???BrF???HF, and H₃N???ClF???HF. To understand the properties of the systems better, the corresponding dyads are also investigated. Molecular geometries, binding energies, and infrared spectra of monomers, dyads, and triads are studied at the MP2 level of theory with the 6‐311++G(d,p) basis set. Because the primary aim of this study is to examine cooperative effects, particular attention is given to parameters such as cooperative energies, many‐body interaction energies, and cooperativity factors. The cooperative energy ranges from ?1.45 to ?4.64 kcal mol^?1, the three‐body interaction energy from ?2.17 to ?6.71 kcal mol^?1, and the cooperativity factor from 1.27 to 4.35. These results indicate significant cooperativity between the halogen and hydrogen bonds in these complexes. This cooperativity is much greater than that between hydrogen bonds. The effect of a halogen bond on a hydrogen bond is more pronounced than that of a hydrogen bond on a halogen bond.     

Intermolecular interactions in uracil–nitrous acid complexes: structures,binding energy,topological properties,and nuclear magnetic resonance study

Molecular interactions between uracil and nitrous acid (U–NA) [C₄N₂O₂H₄? NO₂H] have been studied using B3LYP, B3PW91, and MP2 methods with different basis sets. The optimized geometries, harmonic vibrational frequencies, charge transfer, topological properties of electron density, nucleus‐independent chemical shift (NICS), and nuclear magnetic resonance one‐ and two‐bonds spin–spin coupling constants were calculated for U–NA complexes. In interaction between U and NA, eight cyclic complexes were obtained with two intermolecular hydrogen bonds N(C)HU…N(O) and OH_NA…O_U. In these complexes, uracil (U) simultaneously acts as proton acceptor and proton donor. The most stable complexes labeled, UNA1 and UNA2, are formed via NH bond of U with highest acidity and CO group of U with lowest proton affinity. There is a relationship between hydrogen bond distances and the corresponding frequency shifts. The solvent effect on complexes stability was examined using B3LYP method with the aug‐cc‐pVDZ basis set by applying the polarizable continuum model (PCM). The binding energies in the gas phase have also been compared with solvation energies computed using the PCM. Natural bond orbital analysis shows that in all complexes, the charge transfer takes place from U to NA. The results predict that the Lone Pair (LP)(O)_U → σ*(O? H) and LP(N(O)_NA → σ*(N(C)? H)_U donor–acceptor interactions are most important interactions in these complexes. Atom in molecule analysis confirms that hydrogen bond contacts are electrostatic in nature and covalent nature of proton donor groups decreases upon complexation. The relationship between spin–spin coupling constant (^1hJ_H…_Y and ^2hJ_H…_Y) with interaction energy and electronic density at corresponding hydrogen bond critical points and H‐bonds distances are investigated. NICS used for indicating of aromaticity of U ring upon complexation. © 2013 Wiley Periodicals, Inc.     

Synthesis,Structure, and Bonding of d3 Molybdenum–Oxo Complexes

Reduction of d² metal–oxo ions of the form [MO(PP)₂Cl]⁺ (M=Mo, W; PP=chelating diphosphine) produces d³ MO(PP)₂Cl complexes, which include the first isolated examples in group 6. The stability and reactivity of the MO(PP)₂Cl compounds are found to depend upon the steric bulk of the phosphine ligands: derivatives with bulky phosphines that shield the oxo ligand are stable enough to be isolated, whereas those with phosphines that leave the oxo ligand exposed are more reactive and observed transiently. Magnetic measurements and DFT calculations on MoO(dppe)₂Cl indicate the d³ compounds are low spin with a ²[(d_xy)²(π*(MoO))¹] configuration. X‐ray crystallographic and vibrational‐spectroscopic studies on d² and d³ [MoO(dppe)₂Cl]^0/+ establish that the d³ compound possesses a reduced M?O bond order and significantly longer Mo?O bond, accounting for its greater reactivity. These results indicate that the oxo‐centered reactivity of d³ complexes may be controlled through ligand variation.     

Titanium and Zirconium Complexes with Non‐Salicylaldimine‐Type Imine–Phenoxy Chelate Ligands: Syntheses,Structures, and Ethylene‐Polymerization Behavior

New Ti and Zr complexes that bear imine–phenoxy chelate ligands, [{2,4‐di‐tBu‐6‐(RCH=N)‐C₆H₄O}₂MCl₂] ( 1 : M=Ti, R=Ph; 2 : M=Ti, R=C₆F₅; 3 : M=Zr, R=Ph; 4 : M=Zr, R=C₆F₅), were synthesized and investigated as precatalysts for ethylene polymerization. ¹H NMR spectroscopy suggests that these complexes exist as mixtures of structural isomers. X‐ray crystallographic analysis of the adduct 1 ?HCl reveals that it exists as a zwitterionic complex in which H and Cl are situated in close proximity to one of the imine nitrogen atoms and the central metal, respectively. The X‐ray molecular structure also indicates that one imine phenoxy group with the syn C?N configuration functions as a bidentate ligand, whereas the other, of the anti C?N form, acts as a monodentate phenoxy ligand. Although Zr complexes 3 and 4 with methylaluminoxane (MAO) or [Ph₃C]⁺[B(C₆F₅)₄]^?/AliBu₃ displayed moderate activity, the Ti congeners 1 and 2 , in association with an appropriate activator, catalyzed ethylene polymerization with high efficiency. Upon activation with MAO at 25 °C, 2 displayed a very high activity of 19900 (kg PE) (mol Ti)^?1 h^?1, which is comparable to that for [Cp₂TiCl₂] and [Cp₂ZrCl₂], although increasing the polymerization temperature did result in a marked decrease in activity. Complex 2 contains a C₆F₅ group on the imine nitrogen atom and mediated nonliving‐type polymerization, unlike the corresponding salicylaldimine‐type complex. Conversely, with [Ph₃C]⁺[B(C₆F₅)₄]^?/AliBu₃ activation, 1 exhibited enhanced activity as the temperature was increased (25–75 °C) and maintained very high activity for 60 min at 75 °C (18740 (kg PE) (mol Ti)^?1 h^?1). ¹H NMR spectroscopic studies of the reaction suggest that this thermally robust catalyst system generates an amine–phenoxy complex as the catalytically active species. The combinations 1 /[Ph₃C]⁺[B(C₆F₅)₄]^?/AliBu₃ and 2 /MAO also worked as high‐activity catalysts for the copolymerization of ethylene and propylene.     

Interaction between ligands in ternary complexes of cadmium(II) with phenanthroline and phenylalkylmalonates in solution

The formation and stability of the ternary complexes of cadmium(II) with phenanthroline and malonate, phenylmalonate, benzylmalonate, 2-phenylethylmalonate, and 3-phenylpropylmalonate are studied by the potentiometric pH-titration technique in 40% (v/v) dioxane-water at 25°C and 0.1 mol/l ionic strength (NaNO₃). In all systems, there are stable ternary complexes. The complexes possess enhanced stability relative to their statistical values. The possible reasons that lead to these results are discussed in terms of π-electron back donation from metal ions to ligands and the intramolecular ligand-ligand aromatic ring stacking interaction. ¹H NMR measurements are used to demonstrate the aromatic ring-stacking interaction. The relative contribution of each interactions to the enhanced stability is also estimated. The results show that there are two weak interactions simultaneously observed in these ternary complexes. The interaction strength of aromatic ring stacking in the ternary complexes increases in the phenylalkylmalonate ligand order: L⁰ < L¹ < L² ≈ L³ (L⁰ = phenylmalonate, L¹ = benzylmalonate, L² = 2-phenylethylmalonate, L³ = 3-phenylpropylmalonate). The text was submitted by the autors in English.     

Boron as an Electron‐Pair Donor for B⋅⋅⋅Cl Halogen Bonds

MP2/aug′‐cc‐pVTZ calculations were performed to investigate boron as an electron‐pair donor in halogen‐bonded complexes (CO)₂(HB):ClX and (N₂)₂(HB):ClX, for X=F, Cl, OH, NC, CN, CCH, CH₃, and H. Equilibrium halogen‐bonded complexes with boron as the electron‐pair donor are found on all of the potential surfaces, except for (CO)₂(HB):ClCH₃ and (N₂)₂(HB):ClF. The majority of these complexes are stabilized by traditional halogen bonds, except for (CO)₂(HB):ClF, (CO)₂(HB):ClCl, (N₂)₂(HB):ClCl, and (N₂)₂(HB):ClOH, which are stabilized by chlorine‐shared halogen bonds. These complexes have increased binding energies and shorter B?Cl distances. Charge transfer stabilizes all complexes and occurs from the B lone pair to the σ* Cl?A orbital of ClX, in which A is the atom of X directly bonded to Cl. A second reduced charge‐transfer interaction occurs in (CO)₂(HB):ClX complexes from the Cl lone pair to the π* C≡O orbitals. Equation‐of‐motion coupled cluster singles and doubles (EOM‐CCSD) spin–spin coupling constants, ^1xJ(B‐Cl), across the halogen bonds are also indicative of the changing nature of this bond. ^1xJ(B‐Cl) values for both series of complexes are positive at long distances, increase as the distance decreases, and then decrease as the halogen bonds change from traditional to chlorine‐shared bonds, and begin to approach the values for the covalent bonds in the corresponding ions [(CO)₂(HB)?Cl]⁺ and [(N₂)₂(HB)?Cl]⁺. Changes in ¹¹B chemical shieldings upon complexation correlate with changes in the charges on B.     

The dual role of halogen,chalcogen, and pnictogen atoms as Lewis acid and base: Triangular XBr:SHX:PH2X complexes (X = F,Cl, Br,CN, NC,OH, NH2, and OCH3)

Using ab initio calculations, we have investigated the possibility of formation of triangular XBr:SHX:PH₂X complexes, where X = F, Cl, Br, CN, NC, OH, NH₂, and OCH₃. These complexes are formed through the interaction of a positive electrostatic potential region (σ‐hole) on a molecule with the negative region in another one. The results show that the combined halogen, chalcogen, and pnictogen interactions can give rise to stable cyclic structures. The interaction energies of these complexes span over a wide range, from ?3.55 to ?24.93 kcal/mol. Nice quadratic correlations are found between the interaction energies and binding distances in the trimers. To understand the nature of the interactions in these complexes, molecular electrostatic potential and quantum theory of atoms in molecule analyses are performed. © 2015 Wiley Periodicals, Inc.     

MP2, DFT‐D,and PCM study of the HMB–TCNE complex: Thermodynamics,electric properties,and solvent effects

Geometry, thermodynamic, and electric properties of the π‐EDA complex between hexamethylbenzene (HMB) and tetracyanoethylene (TCNE) are investigated at the MP2/6‐31G* and, partly, DFT‐D/6‐31G* levels. Solvent effects on the properties are evaluated using the PCM model. Fully optimized HMB–TCNE geometry in gas phase is a stacking complex with an interplanar distance 2.87 × 10^?10 m and the corresponding BSSE corrected interaction energy is ?51.3 kJ mol^?1. As expected, the interplanar distance is much shorter in comparison with HF and DFT results. However the crystal structures of both (HMB)₂–TCNE and HMB–TCNE complexes have interplanar distances somewhat larger (3.18 and 3.28 × 10^?10 m, respectively) than our MP2 gas phase value. Our estimate of the distance in CCl₄ on the basis of PCM solvent effect study is also larger (3.06–3.16 × 10^?10 m). The calculated enthalpy, entropy, Gibbs energy, and equilibrium constant of HMB–TCNE complex formation in gas phase are: ΔH⁰ = ?61.59 kJ mol^?1, ΔS = ?143 J mol^?1 K^?1, ΔG⁰ = ?18.97 kJ mol^?1, and K = 2,100 dm³ mol^?1. Experimental data, however, measured in CCl₄ are significantly lower: ΔH⁰ = ?34 kJ mol^?1, ΔS = ?70.4 J mol^?1 K^?1, ΔG⁰ = ?13.01 kJ mol^?1, and K = 190 dm³ mol^?1. The differences are caused by solvation effects which stabilize more the isolated components than the complex. The total solvent destabilization of Gibbs energy of the complex relatively to that of components is equal to 5.9 kJ mol^?1 which is very close to our PCM value 6.5 kJ mol^?1. MP2/6‐31G* dipole moment and polarizabilities are in reasonable agreement with experiment (3.56 D versus 2.8 D for dipole moment). The difference here is due to solvent effect which enlarges interplanar distance and thus decreases dipole moment value. The MP2/6‐31G* study supplemented by DFT‐D parameterization for enthalpy calculation, and by the PCM approach to include solvent effect seems to be proper tools to elucidate the properties of π‐EDA complexes. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Strong N−X⋅⋅⋅O−N Halogen Bonds: A Comprehensive Study on N‐Halosaccharin Pyridine N‐Oxide Complexes

A study of the strong N?X???^?O?N⁺ (X=I, Br) halogen bonding interactions reports 2×27 donor×acceptor complexes of N‐halosaccharins and pyridine N‐oxides (PyNO). DFT calculations were used to investigate the X???O halogen bond (XB) interaction energies in 54 complexes. A simplified computationally fast electrostatic model was developed for predicting the X???O XBs. The XB interaction energies vary from ?47.5 to ?120.3 kJ mol^?1; the strongest N?I???^?O?N⁺ XBs approaching those of 3‐center‐4‐electron [N?I?N]⁺ halogen‐bonded systems (ca. 160 kJ mol^?1). ¹H NMR association constants (K_XB) determined in CDCl₃ and [D₆]acetone vary from 2.0×10⁰ to >10⁸ m ^?1 and correlate well with the calculated donor×acceptor complexation enthalpies found between ?38.4 and ?77.5 kJ mol^?1. In X‐ray crystal structures, the N‐iodosaccharin‐PyNO complexes manifest short interaction ratios (R_XB) between 0.65–0.67 for the N?I???^?O?N⁺ halogen bond.     

Using (FH)2 and (FH)3 to Bridge the σ‐Hole and the Lone Pair at P in Complexes with H2XP,for X=CH3, OH,H, CCH,F, Cl,NC, and CN

Ab initio MP2/aug′‐cc‐pVTZ calculations are used to investigate the binary complexes H₂XP:HF, the ternary complexes H₂XP:(FH)₂, and the quaternary complexes H₂XP:(FH)₃, for X=CH₃, OH, H, CCH, F, Cl, NC, and CN. Hydrogen‐bonded (HB) binary complexes are formed between all H₂XP molecules and FH, but only H₂FP, H₂ClP, and H₂(NC)P form pnicogen‐bonded (ZB) complexes with FH. Ternary complexes with (FH)₂ are stabilized by F?H???P and F?H???F hydrogen bonds and F???P pnicogen bonds, except for H₂(CH₃)P:(FH)₂ and H₃P:(FH)₂, which do not have pnicogen bonds. All quaternary complexes H₂XP:(FH)₃ are stabilized by both F?H???P and F?H???F hydrogen bonds and P???F pnicogen bonds. Thus, (FH)₂ with two exceptions, and (FH)₃ can bridge the σ‐hole and the lone pair at P in these complexes. The binding energies of H₂XP:(FH)₃ complexes are significantly greater than the binding energies of H₂XP:(FH)₂ complexes, and nonadditivities are synergistic in both series. Charge transfer occurs across all intermolecular bonds from the lone‐pair donor atom to an antibonding σ* orbital of the acceptor molecule, and stabilizes these complexes. Charge‐transfer energies across the pnicogen bond correlate with the intermolecular P?F distance, while charge‐transfer energies across F?H???P and F?H???F hydrogen bonds correlate with the distance between the lone‐pair donor atom and the hydrogen‐bonded H atom. In binary and quaternary complexes, charge transfer energies also correlate with the distance between the electron‐donor atom and the hydrogen‐bonded F atom. EOM‐CCSD spin‐spin coupling constants ^2hJ(F–P) across F?H???P hydrogen bonds, and ^1pJ(P–F) across pnicogen bonds in binary, ternary, and quaternary complexes exhibit strong correlations with the corresponding intermolecular distances. Hydrogen bonds are better transmitters of F–P coupling data than pnicogen bonds, despite the longer F???P distances in F?H???P hydrogen bonds compared to P???F pnicogen bonds. There is a correlation between the two bond coupling constants ^2hJ(F–F) in the quaternary complexes and the corresponding intermolecular distances, but not in the ternary complexes, a reflection of the distorted geometries of the bridging dimers in ternary complexes.     

Chromium‐metformin ternary complexes: Thermal,DNA interaction and Docking studies

Three chromium ternary complexes with metformin (met) as a primary ligand and bipyridine (bipy) or ortho‐phenylenediamine (opda) or ortho‐phenanthroline (phen) as secondary ligand were synthesized. These complexes [Cr (Cl)₂(Hmet)(bipy)]‐( 1 ), [Cr (Cl)₂(Hmet)(opda)]‐( 2 ) and [Cr (Cl)₂(Hmet)(phen)]‐( 3 ) were characterized by LC–MS, elemental analysis, molar conductance, thermal analysis, infrared spectroscopy, electronic spectroscopy. The geometrical structures have been found to be octahedral. Degradation pattern of the compounds is shown by thermal studies. The Kinetic parameters‐ energy of activation (E_a), enthalpy (ΔH), entropy (ΔS) and free energy changes (ΔG) have been determined by thermogravimetric data. Coats‐Redfern integration method with thirteen kinetic models was used to calculate the kinetic and thermodynamic parameters for the degradation of all the complexes. The stabilities of the complexes were obtained from their molecular orbital structures from which the quantum chemical parameters were calculated using the HOMO‐LUMO energies. UV–Visible absorption, fluorescence, and viscosity measurements have been conducted to assess the interaction of the complexes with CT DNA. The complexes showed absorption hyperchromism in its UV–Vis spectrum with DNA. The binding constants K_b from UV–Vis absorption studies were 3.1x10⁴, 4.4x10⁴, 5x10⁴ M^?1 for 1, 2, 3 respectively and Stern–Volmer quenching constants (K_sq) from fluorescence studies were 0.137, 0.532, 0.631 for 1, 2, 3 respectively. Finally, viscosity measurements revealed that the binding of the complexes with CT‐DNA could be surface binding, mainly due to groove binding. The activity of complexes towards DNA cleavage decrease in the order of 3 > 2 > 1.The light switching properties of the complexes were also evaluated. The complexes were docked in to B‐DNA sequence, 5′(D*AP*CP*CP*GP*AP*CP*GP*TP*CP*GP*GP*T)‐3′ retrieved from protein data bank (PDB ID: 423D), using Discovery Studio 2.1 software.     

Hydrogen bond and σ‐hole interaction in M2C=S···HCN (M = H,F, Cl,Br, HO,H3C,H2N) complex: Dual roles of C=S group and substitution effect

An ab initio computational study of the dual functions of C?S group in the M₂C?S ··· HCN (M = H, F, Cl, Br, HO, H₃C, H₂N) complex has been performed at the MP2(Full)/aug‐cc‐pVTZ level. The C?S group can act as both the electron donor and acceptor, thus two minima complexes were found for each molecular pairs. The interaction energy of hydrogen bond in the F, Cl, or Br substituted complexes is less negative than that in the corresponding H₂CS one, while the interaction energy of the σ‐hole interaction is more negative. The OH substitution weakens the hydrogen bond, whereas the H₃C and H₂N substitution strengthens it. The σ‐hole interaction in the HO, H₃C, and H₂N complexes is very weak. The substitution effect has been understood with electrostatic induction and conjugation effects. The energy decomposition analysis has been performed for the halogen‐substituted complexes. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012.     

1‐(2,6‐dibenzhydryl‐4‐fluorophenylimino)‐2‐aryliminoacenaphthylylnickel halides highly polymerizing ethylene for the polyethylenes with high branches and molecular weights

A series of 1‐(2,6‐dibenzhydryl‐4‐fluorophenylimino)‐ 2‐aryliminoacenaphthylene derivatives ( L1–L5 ) and their halonickel complexes LNiX₂ (X = Br, Ni1–Ni5 ; X = Cl, Ni6–Ni10 ) are synthesized and well characterized. The molecular structures of representative complexes Ni2 and Ni4 are confirmed as the distorted tetrahedron geometry around nickel atom by the single crystal X‐ray diffraction. Upon activation with methylaluminoxane, all nickel complexes show high activities up to 1.49 × 10⁷ g of PE (mol of Ni)^?1 h^?1 toward ethylene polymerization, producing polyethylenes with high branches and molecular weights up to 1.62 × 10⁶ g mol^?1 as well as narrow polydispersity. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1369–1378     

Hoop‐Shaped Condensed Aromatic Systems: Synthesis and Structure of Iron– and Ruthenium–Hepta(organo)[60]fullerene Complexes

Potassium reduction of iron– and ruthenium–penta(organo)[60]fullerene complexes, [M(η⁵‐C₆₀R₅)(η⁵‐Cp)] ( 1 a : M=Fe, R=Ph; 1 b : M=Fe, R=Me; 1 c : M=Ru, R=Ph; 1 d : M=Ru, R=Me; Cp=C₅H₅) gave mono‐ and dianions of these complexes. Treatment of the dianion 1 a with α‐bromodiphenylmethane gave three different iron–hepta(organo)[60]fullerenes, [Fe{η⁵‐C₆₀Ph₅(CHPh₂)₂}(η⁵‐Cp)], as a mixture of regioisomers. All three compounds were fully characterized by physical methods, including X‐ray crystallography and electrochemical measurements. One of the three compounds contains a new hoop‐shaped condensed aromatic system.