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1.
Two new supramolecular complexes,[Cu(H_2dhbd)(3-pyOH)(H_2O)]_2·3-pyOH·2H_2O(1)and[Cu_2(dhbd)(dpa)_2-(H_2O)]·6H_2O(2)(H_4dhbd=2,3-dihydroxybutanedioic acid,3-pyOH=3-hydroxypyddine,dpa=2,2'-dipyridylamine),have been synthesized in aqueous solution and characterized by single-crystal X-ray diffraction,elemental analyses,UV-Vis and IR spectra,and TGA analysis.X-ray structural analysis revealed that,through four pairs of strong O…H—O hydrogen bonds,the cyclic dinuclear units in 1 together with four adjacent neighbors are connected into a 2Dhoneycomb network encapsulating free 3-pyOH ligands.Unexpectedly,the water-dimers are fixed in interlayers of2D honeycomb network and act as hydrogen-bond bridging to further extend these 2D networks into 3D hydro-gen-bonded framework.Complex 2 includes interesting 2D grids constructed from chiral dinuclear units throughstrong O…H—O and O…H—N hydrogen bonding,which are extended through other crystallization water mole-cules into three dimension with channels.Variable-temperature magnetic susceptibility measurements for bothcomplexes indicate the presence of weak antiferromagnetic exchange interactions between adjacent copper(Ⅱ)ions.  相似文献   

2.
The 1,3,5-triazine-water hydrogen bonding interactions have been investigated using the density functional theory B3LYP method and 6-31 ++G^** basis, obtaining one, two and seven energy minima of the ground states for the 1,3,5-triazine-water, 1,3,5-triazine-(water)2 and 1,3,5-triazine-(water)3 complexes respectively. The fully optimized geometries and binding energies were reported for the various stationary points. The global minima of 1,3,5-triazine-(water)2 and 1,3,5-triazine-(water)3 complexes have a hydrogen bond N…H-O and a chain of water molecules, terminated by a hydrogen bond O…H-C. The binding energies are 13.38, 39.52 and 67.79 kJ/mol for the most stable 1,3,5-triazine-water, 1,3,5-triazine-(water)2 and 1,3,5-triazine-(water)3 complexes respectively, after the basis set superposition error and zero point energy corrections. The H-O symmetric stretching modes of water in the complexes are red-shifted relative to those of the monomer water. In addition, the NBO analysis indicates that inter-molecule charge transfer is 0.02145 e, 0.02501 e and 0.02777 e for the most stable 1 : 1, 1 : 2 and 1 : 3 complexes between 1,3,5-triazine and water, respectively.  相似文献   

3.
In the series of diaminoenones, large high‐frequency shifts of the 1H NMR of the N? H group in the cis‐position relative to the carbonyl group suggests strong N? H···O intramolecular hydrogen bonding comprising a six‐membered chelate ring. The N? H···O hydrogen bond causes an increase of the 1J(N,H) coupling constant by 2–4 Hz and high‐frequency shift of the 15N signal by 9–10 ppm despite of the lengthening of the relevant N? H bond. These experimental trends are substantiated by gauge‐independent atomic orbital and density functional theory calculations of the shielding and coupling constants in the 3,3‐bis(isopropylamino)‐1‐(aryl)prop‐2‐en‐1‐one (12) for conformations with the Z‐ and E‐orientations of the carbonyl group relative to the N? H group. The effects of the N? H···O hydrogen‐bond on the NMR parameters are analyzed with the atoms‐in‐molecules (AIM) and natural bond orbital (NBO) methods. The AIM method indicates a weakening of the N? H···O hydrogen bond as compared with that of 1,1‐di(pyrrol‐2‐yl)‐2‐formylethene (13) where N? H···O hydrogen bridge establishes a seven‐membered chelate ring, and the corresponding 1J(N,H) coupling constant decreases. The NBO method reveals that the LP(O) →σ*N? H hyperconjugative interaction is weakened on going from the six‐membered chelate ring to the seven‐membered one due to a more bent hydrogen bond in the former case. A dominating effect of the N? H bond rehybridization, owing to an electrostatic term in the hydrogen bonding, seems to provide an increase of the 1J(N,H) value as a consequence of the N? H···O hydrogen bonding in the studied diaminoenones. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

4.
The nature of the interactions of cyanide with lithium and hydrogen halides was investigated using ab initio calculations and topological analysis of electron density. The computed properties of the lithium‐bonded complexes RCN···LiX (R = H, F, Cl, Br, C?CH, CH?CH2, CH3, C2H5; X = Cl, Br) were compared with those of corresponding hydrogen‐bonded complexes RCN···HX. The results show that both types of intermolecular interactions are “closed‐shell” noncovalent interactions. The effect of substitution on the interaction energy and electron density at the bond critical points of the lithium and hydrogen bonding interactions is similar. In comparison, the interaction energies of lithium‐bonded complexes are more negative than those of hydrogen‐bonded counterparts. The electrostatic interaction plays a more important role in the lithium bond than in the hydrogen bond. On complex formation, the net charge and energy of the Li atom decrease and the atomic volume increases, while the net charge and energy of the H atom increase and the atomic volume decreases. © 2013 Wiley Periodicals, Inc.  相似文献   

5.
In this work, the geometry optimizations in the ground state and electronic excitation energies and corresponding oscillation strengths of the low‐lying electronically excited states for the isolated fluorenone (FN) and FN‐based molecular monomers, the relatively hydrogen‐bonded dimers, and doubly hydrogen‐bonded trimers, are calculated by the density functional theory and time‐dependent density functional theory methods, respectively. We find the intermolecular hydrogen bond CO···H O is strengthened in some of the electronically excited states of the hydrogen‐bonded dimers and doubly hydrogen‐bonded trimers, because the excitation energy in a related excited state decrease and electronic spectral redshift are induced. Similarly, the hydrogen bond CO···H O is weakened in other excited states. On this basis, owing to the important difference of electronegativity, heteroatoms S, Se, and Te that substitute for the O atom in the carbonyl group of the FN molecule have a significant effect on the strength of the hydrogen bond and the spectral shift. It is observed that the hydrogen bond CTe···H O is too weak to be formed. When the CS and CSe substitute for CO, the strength of the hydrogen bonds and electronic spectra frequency shift are significantly changed in the electronic excited state due to the electron transition type transformation from the ππ* feature to σπ* feature. © 2013 Wiley Periodicals, Inc. Heteroatom Chem 24:153–162, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21075  相似文献   

6.
In this study, the seGVB method was implemented for the N H bonding system, specifically for hydrogen‐bonded ammonia complexes, and the model well reproduces the MP2 geometries and energetics. A comparison between the ammonia dimer and water dimer is given from the viewpoint of valance‐bond structures in terms of the calculated bond energies and pair–pair interactions. The linear hydrogen bond is found to be stronger than the bent bonds in both cases, with the difference in energy between the linear and cyclic structures being comparable in both cases although the NH bonds are generally weaker. The energy decomposition clearly demonstrates that the changes in electronic energy are quite different in the two cases due to the presence of an additional lone pair on the water molecule, and it is this effect which leads to the net stabilization of the cyclic structure for the ammonia dimer. Proton‐transfer profiles for hydrogen‐bonded ammonia complexes [NH2 H NH2] and [NH3 H NH3]+ were calculated. The barrier for proton transfer in [NH3 H NH3]+ is larger than that in [NH2 H NH2], but smaller than that in the protonated water dimer. The different bonding structures substantially affect the barrier to proton transfer, even though they are isoelectronic systems. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 73: 357–367, 1999  相似文献   

7.
The cooperative enhancement of water binding to the antiparallel β‐sheet models has been studied by quantum chemical calculations at the MP2/6‐311++G**//MP2/6‐31G* level. The binding energies of the two antiparallel β‐sheet models consisting of two strands of diglypeptide are calculated by supermolecular approach. Then water molecules are gradually bonded to the diglypeptide by N? H···OH2 and C?O···HOH hydrogen bonds. Our calculation results indicated that the hydrogen bond length and the atom charge distribution are affected by the addition of H2O molecules. The binding energy of antiparallel diglypeptide β‐sheet models has a great improvement by the increasing of the hydrogen bond cooperativity and the more H2O molecules added the more cooperativity enhancement can be found. The orbital interactions are calculated by natural bond orbital analysis, and the results indicate that the cooperative enhancement is closely related to the orbital interaction. © 2012 Wiley Periodicals, Inc.  相似文献   

8.
Series of typical π‐type and pseudo‐π‐type halogen‐bonded complexes B ··· ClY and B ··· BrY and hydrogen‐bonded complex B ··· HY (B = C2H4, C2H2, and C3H6; Y = F, Cl, and Br) have been investigated using the MP2/aug‐cc‐pVDZ method. A striking parallelism was found in the geometries, vibrational frequencies, binding energies, and topological properties between B ··· XY and B ··· HY (X = Cl and Br). It has been found that the lengths of the weak bond d(X ··· π)/d(H ··· π), the frequencies of the weak bond ν(X ··· π)/ν(H ··· π), the frequency shifts Δν(X? Y)/Δν(H? Y), the electron densities at the bond critical point of the weak bonds ρc(X ··· π)/ρc(H ··· π), and the electron density changes Δρc(X? Y)/Δρc(H? Y) could be used as measures of the strengths of typical π‐type and pseudo‐π‐type halogen/hydrogen bonds. The typical π‐type and pseudo‐π‐type halogen bond and hydrogen bond are noncovalent interactions. For the same Y, the halogen bond strengths are in the order B ··· ClY < B ··· BrY. For the same X, the halogen bond strength decreases according to the sequence F > Cl > Br that is in agreement with the hydrogen bond strengths B ··· HF > B ··· HCl > B ··· HBr. All of these typical π‐type and pseudo‐π‐type hydrogen‐bonded and halogen‐bonded complexes have the “conflict‐type” structure. Contour maps of the Laplacian of π electron density indicate that the formation of B ··· XY halogen‐bonded complex and B ··· HY hydrogen‐bonded complex is very similar. Charge transfer is observed from B to XY/HY and both the dipolar polarization and the volume of the halogen atom or hydrogen atom decrease on B ··· XY/B ··· HY complex formation. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011  相似文献   

9.
DFT calculations were conducted to pursue deeper understandings on the mechanism and the explicit role of trace water in the DBU‐catalyzed β‐amination of NBS to chalcone. Being different from previously proposed by Liang et al., a cooperative participation of both DBU and water is noticed in the preferred mechanism. The preferential mechanistic scenario assisted by water undergoes three major steps: the formation of succinimide and HBrO, concerted nucleophilic addition and H‐shift, and keto‐enol tautomerization. Moreover, we found that DBU‐HBrO is unnecessary in the third step and three‐water‐cluster assisted keto‐enol tautomerization is the most advantageous case. It is further noted that the catalytic position of the third water molecule and the proton shift orientation to some extent affect step 3 via O···H O and O H···π interactions, which is confirmed by AIM analysis. The computational results suggest that water molecules play pivotal roles as reactant, catalyst, and stabilizer to promote the reaction of chalcone and NBS. The origin of the more stable transition state structure in the rate‐determining step of DBU‐water catalyzed mechanism is ascribed to noncovalent interactions, halogen bond, and electrostatic interactions than DBU only ones. © 2017 Wiley Periodicals, Inc.  相似文献   

10.
The time‐dependent density functional theory (TDDFT) method has been carried out to investigate the excited‐state hydrogen‐bonding dynamics of 4‐aminophthalimide (4AP) in hydrogen‐donating water solvent. The infrared spectra of the hydrogen‐bonded solute?solvent complexes in electronically excited state have been calculated using the TDDFT method. We have demonstrated that the intermolecular hydrogen bond C? O···H? O and N? H···O? H in the hydrogen‐bonded 4AP?(H2O)2 trimer are significantly strengthened in the electronically excited state by theoretically monitoring the changes of the bond lengths of hydrogen bonds and hydrogen‐bonding groups in different electronic states. The hydrogen bonds strengthening in the electronically excited state are confirmed because the calculated stretching vibrational modes of the hydrogen bonding C?O, amino N? H, and H? O groups are markedly red‐shifted upon photoexcitation. The calculated results are consistent with the mechanism of the hydrogen bond strengthening in the electronically excited state, while contrast with mechanism of hydrogen bond cleavage. Furthermore, we believe that the transient hydrogen bond strengthening behavior in electroniclly excited state of chromophores in hydrogen‐donating solvents exists in many other systems in solution. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010  相似文献   

11.
12.
The nature of the complexes PhTH3 H3ZO and PhSiF3 H3ZO (T = Si, Ge, and Sn; Z = N, P, and As) has been investigated at the MP2/aug’‐cc‐pVTZ(PP) level. These complexes are primarily stabilized by one T···O tetrel bond. Interaction energies of these complexes vary from 11 to 220 kJ/mol, and T···O separations from 1.89 to 3.09 Å. Charge transfer from the O lone pair into the C T and T H σ* antibonding orbitals leads to the stabilization of these complexes. The T···O tetrel bond between PhTH3/PhSiF3 and H3NO exhibits a significant degree of covalence, characterized by the large interaction energy, negative energy density, and large charge transfer. Furthermore, a pentacoordinate silicon (IV) complex is formed in PhSiF3 H3NO with the Si···O distance almost close to the length of Si O bond. This indicates that the oxygen atom in N‐oxides shows a strong affinity to the silicon atom in organosilicon compounds.  相似文献   

13.
A computational study at CCSD(T) theoretical level has been carried out on radical cation [(PH2X)2]·+ homodimers. Four stable minima configurations have been found for seven substituted phosphine derivatives, X = H, CH3, CCH, NC, OH, F and Cl. The most stable minimum presents an intermolecular two-center three-electron P···P bond except for X = CCH. The other three minima correspond to an alternative P···P pnicogen bonded complex, to a P···X contact and the last one to the complex resulting from a proton transfer, PH3X+:PHX·. The complexes obtained have been compared with those of the corresponding neutral ones, (PH2X)2, and the analogous protonated ones, PH3X+:PH2X, recently described in the literature. The spin and charge densities of the complexes have been examined. The electronic characteristics of the complexes have been analyzed with the NBO and AIM methods. The results obtained for the spin density, charge and NBO are coherent for all the complexes.  相似文献   

14.
The title complex, 2C5H7N2+·C4H2O42−·C4H4O4, contains cyclic eight‐membered hydrogen‐bonded rings involving 2‐­aminopyridinium and fumarate ions. The fumaric acid mol­ecules and fumarate ions lie on inversion centers and are linked into zigzag chains by O—H⋯O hydrogen bonds. The dihedral angle between the pyridinium ring and the hydrogen‐bonded fumarate ion is 7.60 (4)°. The fumarate anion is linked to the pyridinium cations by intermolecular N—H⋯O hydrogen bonds. The heterocycle is fully protonated, thus enabling amine–imine tautomerization.  相似文献   

15.
A series of new 3‐(arylhydrazono)pentane‐2, 4‐diones ( 1 ‐ 6 ) synthesized from pentane‐2, 4‐dione and diazonium salts of respective anilines using the procedure of Japp‐Klingemann are described. Complexes with CuII and NiII salts are prepared ( 7 ‐ 10 , respectively). Spectroscopic properties of these compounds have been studied and X‐ray crystal structures of selected hydrazones ( 3 , 4 , 6 ) and of the hydrazone complexes ( 7 ‐ 10 ) are reported. The structures of the uncomplexed hydrazones feature an intramolecular N‐H···O interaction to yield a six‐membered H‐bond ring reflecting preference of the hydrazone tautomeric structure. All the complexes are mononuclear 2:1 (L:M) structures of six‐membered chelate type involving N2O2 binding sites that are quadratic arranged but differ in the entire coordination environment dependent on the metal and the ligand substitution including distorted octahedral and quadratic pyramidal coordination geometries in the CuII complexes 7 and 8 or nearly regular square planar coordination geometry in the NiII complexes 9 and 10 , respectively. In the crystal packings, strong and weak H‐bond interactions cause supramolecular network structures.  相似文献   

16.
The energies, geometries and harmonic vibrational frequencies of 1:1 5‐hydroxytryptamine‐water (5‐HT‐H2O) complexes are studied at the MP2/6‐311++G(d,p) level. Natural bond orbital (NBO), quantum theory of atoms in molecules (QTAIM) analyses and the localized molecular orbital energy decomposition analysis (LMO‐EDA) were performed to explore the nature of the hydrogen‐bonding interactions in these complexes. Various types of hydrogen bonds (H‐bonds) are formed in these 5‐HT‐H2O complexes. The intermolecular C4H55‐HT···Ow H‐bond in HTW3 is strengthened due to the cooperativity, whereas no such cooperativity is found in the other 5‐HT‐H2O complexes. H‐bond in which nitrogen atom of amino in 5‐HT acted as proton donors was stronger than other H‐bonds. Our researches show that the hydrogen bonding interaction plays a vital role on the relative stabilities of 5‐HT‐H2O complexes.  相似文献   

17.
The theoretical study of the dehydrogenation of 2,5‐dihydro‐[furan ( 1 ), thiophene ( 2 ), and selenophene ( 3 )] was carried out using ab initio molecular orbital (MO) and density functional theory (DFT) methods at the B3LYP/6‐311G**//B3LYP/6‐311G** and MP2/6‐311G**//B3LYP/6‐311G** levels of theory. Among the used methods in this study, the obtained results show that B3LYP/6‐311G** method is in good agreement with the available experimental values. Based on the optimized ground state geometries using B3LYP/6‐311G** method, the natural bond orbital (NBO) analysis of donor‐acceptor (bond‐antibond) interactions revealed that the stabilization energies associated with the electronic delocalization from non‐bonding lone‐pair orbitals [LP(e)X3] to δ*C(1)  H(2) antibonding orbital, decrease from compounds 1 to 3 . The LP(e)X3→δ*C(1)  H(2) resonance energies for compounds 1 – 3 are 23.37, 16.05 and 12.46 kJ/mol, respectively. Also, the LP(e)X3→δ*C(1)  H(2) delocalizations could fairly explain the decrease of occupancies of LP(e)X3 non‐bonding orbitals in ring of compounds 1 – 3 ( 3 > 2 > 1 ). The electronic delocalization from LP(e)X3 non‐bonding orbitals to δ*C(1)  H(2) antibonding orbital increases the ground state structure stability, Therefore, the decrease of LP(e)X3→δ*C(1)  H(2) delocalizations could fairly explain the kinetic of the dehydrogenation reactions of compounds 1 – 3 (k 1 >k 2 >k 3 ). Also, the donor‐acceptor interactions, as obtained from NBO analysis, revealed that the (C(4)C(7)→δ*C(1)  H(2) resonance energies decrease from compounds 1 to 3 . Further, the results showed that the energy gaps between (C(4)C(7) bonding and δ*C(1)  H(2) antibonding orbitals decrease from compounds 1 to 3 . The results suggest also that in compounds 1 – 3 , the hydrogen eliminations are controlled by LP(e)→δ* resonance energies. Analysis of bond order, natural bond orbital charges, bond indexes, synchronicity parameters, and IRC calculations indicate that these reactions are occurring through a concerted and synchronous six‐membered cyclic transition state type of mechanism.  相似文献   

18.
Theoretical studies have been carried out on the halogen bonding interaction between para substituted chlorobenzene (Y C6H4Cl, Y = H, NH2, CH3, F, CN, NO2) and N(CH3)3 using ab initio MP2/aug‐cc‐pVDZ and DFT based wB97XD/6‐311++G(d,p) methods. The positive electrostatic potential (VS,max) on the Cl atom and the heterolytic bond breaking enthalpy of the C Cl bond have been calculated and their role on halogen bonding is discussed. The heterolytic bond breaking enthalpy of the C Cl bond is proposed as a measure of the strength of the σ‐hole on Cl atom. The binding strength of the complexes ranging between −6.13 kJ mol−1 and −9.29 kJ mol−1 are linearly related to the VS,max of the Cl atom and the bond breaking enthalpy of the C Cl bond. In addition, energy decomposition analysis was performed on the halogen bonded complexes via symmetry adapted perturbation theory (SAPT) to predict the dominant energy component and the nature of the N···Cl interaction.  相似文献   

19.
The complexes of XH2NH2···HNO(X = B, Al, Ga) are characterized as head to tail with hydrogen bonding interactions. The structural characteristics can be confirmed by atoms in molecules (AIM) analysis, which also provide comparisons of hydrogen bonds strengths. The calculated interaction energies at G2MP2 level show that stability of complexes decrease as BH2NH2···HNO > AlH2NH2···HNO > GaH2NH2···HNO. On the basis of the vibrational frequencies calculations, there are red‐shifts for ν(X1? H) and blue‐shifts for ν(N? H) in the complexes on dihydrogen bonding formations (X1? H···H? N). On hydrogen bonding formations (N? H···O), there are red‐shifts for ν(N? H) compared to the monomers. Natural bond orbital (NBO) analysis is used to discuss the reasons for the ν(X1? H) and ν(N? H) stretching vibrational shifts by hyperconjugation, electron density redistribution, and rehybridization. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008  相似文献   

20.
Quantum chemical calculations have been performed to gauge the effect of substituents on concerted interactions of pnicogen, chalcogen, and halogen bonds in the X–TAZ···Y complexes (X = CN, F, Cl, Br, H, CH3, OH, and NH2, where TAZ and Y denote s-triazine ring and P, S, and Cl atoms, respectively) at the M06-2X/aug-cc-pVDZ level. The mutual interplay of these interactions is also investigated. The results indicate that diminutive effects are observed when the three kinds of noncovalent interactions pnicogen, chalcogen, and halogen bonds are coexisted in the complexes. These effects are studied in terms of energetic and geometric features of the complexes. In addition, Bader’s theory of “atoms in molecules” is used to analyze their strength of varying electron density at bond critical points. Natural bond orbital (NBO) theory is used to characterize the orbital interactions. The results indicate that the electron-withdrawing/donating substituents decrease/increase the magnitude of the binding energies compared to the unsubstituted X–TAZ···Y (X = H) complex. Good correlations among binding energies, Hammett constants, geometrical, atoms in molecular and NBO parameters are established in X–TAZ···Y complexes. By taking advantage of all the aforementioned computational methods, this study examines how these interactions mutually influence each other.  相似文献   

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