Lithium bond structures of HnY （n=2, 3; Y=O,S, N）…LiNH2 and the abnormal blue shift of N-Li bond

The optimized geometries of the complexes between HnY （n=2, 3; Y=O, S, N） and LiNH2 have been calculated at the B3LYP/6-311＋＋G^＊＊ and MP2/6-311＋＋G^＊＊ levels. Three stable complexes were obtained. Frequency analysis showed that the enlarged 2N-4Li presents the abnormal blue shift in three complexes. The calculated binding energy with basis set super-position error （BSSE） and zero-point vibrational energy （ZPE） corrections of complex Ⅰ-Ⅲ is -58.65, -31.66 and -69.59 kJ·mol^-1 （MP2）, respectively. Natural bond orbital theory （NBO） analysis has been performed, and the results revealed that the H2O…LiNH2 （complex I） and H3N…LiNH2 （complex Ⅲ） are formed with coexisting σ-s and n-s type lithium bond interactions, complex Ⅱ is formed with ττ-s type lithium bond interaction between HnY （n=2,3; Y=O, N） and LiNH2, and H2S…LiNH2 （complex Ⅱ） is formed with n-s type lithium bond interaction between H2S and LiNH2. Natural resonance theory （NRT） and atom in molecule （AIM） theory have also been studied to investigate the bond order and topological properties of the lithium bond structures.     

Theoretical study on the lithium bond interaction of furan homologues C_4H_4Y (Y=O, S) with LiCH_3 via DFT and MP2

The optimizations geometries and interaction energy corrected by BSSE of the complexes between C4H4Y (Y=O, S) and CH3Li have been calculated at the B3LYP/6-311 G** and MP2/6-311 G** levels. Three complexes were obtained. Abnormally, the calculations showed that all the C10—Li14 bond lengths increased obviously but the blue-shift of C10—Li14 stretching frequency occurred after formed complexes. The calculated binding energy with basis set super-position error (BSSE) and zero-point vibrational energy corrections of complexes I―III is ?45.757, ?35.700 and ?39.107 kJ·mol?1, respectively. The analyses on the combining interaction with the atom-in-molecules theory (AIM) also showed that a relatively strong lithium bond interaction presented in furan homologues C4H4Y---LiCH3 systems. Natural bond orbital theory (NBO) analysis has been performed, and the results revealed that the com- plex I is formed with n-σ type lithium bond interaction between C4H4O and LiCH3, complex II is formed with π-s type lithium bond interaction between C4H4O and LiCH3, and complex III is formed with π-s and n-s type lithium bond interactions between C4H4S and LiCH3, respectively.     

Theoretical study on the lithium bond interaction of furan homologues C4H4Y （Y=O,S） with LiCH3 via DFT and MP2

The optimizations geometries and interaction energy corrected by BSSE of the complexes between C4H4Y （Y=O, S） and CHiLi have been calculated at the B3LYP/6-311＋＋G^＊＊ and MP2/6-311＋＋G^＊＊ levels. Three complexes were obtained. Abnormally, the calculations showed that all the C10--Li14 bond lengths increased obviously but the blue-shift of C10-Li14 stretching frequency occurred after formed complexes. The calculated binding energy with basis set super-position error （BSSE） and zero-point vibrational energy corrections of complexes I-III is -45.757, -35.700 and -39.107 kJ·mol^-1, respectively. The analyses on the combining interaction with the atom-in-molecules theory （AIM） also showed that a relatively strong lithium bond interaction presented in furan homologues C4H4Y-LiCH3 systems. Natural bond orbital theory （NBO） analysis has been performed, and the results revealed that the complex I is formed with n-σ type lithium bond interaction between C4H40 and LiCH3, complex II is formed with TT-s type lithium bond interaction between C4H4O and LiCH3, and complex III is formed with TT-s and n-s type lithium bond interactions between C4H4S and LiCH3, respectively.     

Theoretical study of N(C)―H…H―B multi-dihydrogen bonds

The optimized geometries, frequencies and interaction energy corrected with basis set superposition error (BSSE) of the multi-dihydrogen bond complexes C₄H₄NH…BH₄^–. and CH≡CH…BH₄^–. have been calculated at both the B3LYP/6-311++G** and the MP2/6-311++G** levels. The calculations were per-formed to study the nature of the N―H…H3―B and C―H…H2―B red shift multi dihydrogen bond in complex C4H4NH…BH^–₄ and CH≡CH…BH4–. The BSSE-corrected multi-dihydrogen bond interaction en-ergy of complex I (C₄H₄NH…BH₄^–.) and complexⅡ(CH≡CH…BH₄^–.) is -76.62 and -33.79 kJ/mol (MP2/6- 311++G**), respectively. From the natural bond orbital（NBO）analysis, we detailedly discussed the orbital interactions, electron density transfers, rehybridizations and the essential of the correlative bond length changes in the two complexes. In addition, solvent effect on the geometric structures, vibration frequencies and interaction energy of the monomer and complexes was studied in detail. It is relevant to the relatively dielectric constants (ε).     

Binding energies and interaction origins between nonclassical single-electron hydrogen,sodium and lithium bonds and neutral boron-containing radicals: a theoretical investigation

Nonclassical single electron hydrogen,sodium and lithium bonds(SEHBs,SENaBs and SELiBs)between single electron acceptors X–A(A=H,Na,Li;X=CN,HCC,HO,NC,CF3)and neutral radicals BY2(Y=H,OH,CH3)and have been systematically investigated by high level theoretical methods,such as second-order Mφller-Plesset perturbation theory(MP2),spin-component-scaled MφllerPlesset theory(SCS-MP2),the coupled cluster method with perturbative triples(CCSD(T)),and the correlation consistent composite approach(ccCA).Binding energies have been corrected for zero-point vibrational effects and(when applicable)basis set superposition error.The quantum theory of atoms in molecules(AIM)and natural bond orbital(NBO)analyses were also employed to qualitatively characterize the single electron bond interactions.The stabilization energy was partitioned via the localized molecular orbital energy decomposition analysis(LMOEDA)method,and both electrostatic and exchange interactions were seen to be major driving forces for the complex stabilization.Interestingly,the sum of the energy contributors of exchange(EEX),repulsion(EREP),polarization(EPOL),dispersion(EDIS)is close to zero and the changes in the interaction energy follow the trend of the electrostatic energy(EES).We observe several linear relationships among the optimized intermolecular parameters and the interaction energies of the various complexes.     

Synthesis,Structural Characterization,and Electrochemical Properties of Binuclear Copper(Ⅱ) Complexes Containing Tetradentate Schiff Base Ligand

Two binuclear copper(Ⅱ) complexes, [Cu2(saloph)2 (μ-O)2]-2(DMF)[H2saloph=N,N′-o-phenylenebis(salicylideneaminato)] (a) and [Cu2(salen)2(μ-O)2] [H2salen=N,N′-bis(salicylic-deneaminato) ethylene] (b)were synthesized and characterized by X-ray crystallography. Both of them have distorted rectangular pyramidal geometry around Cu(Ⅱ). The complete series of complexes show bridging phenoxo groups between the copper centers, together with hydroxo-bridges in these complexes. The complexes have also been characterized by elemental analysis, IR, TG-DTA, and electrochemical results.     

Unexpected carbon-oxygen bond cleavage of THF promoted by guanidinate titanium complex/lithium diisopropylamide： Synthesis and crystal structure

An unexpected carbon-oxygen bond cleavage of THF （THF = tetrahydrofuran） promoted by guanidinate titanium complex was described. Guanidinate lithium [Pr2 ^1NC（NCy）2]Li （Cy = cyclohexyl） formed in situ reacted with TiCl4（THF）2 in a 2：1 molar ratio to produce the guanidinate titanium chloride [Pr2 ^1NC（NCy）2]2TiCl2 （1） in good yield. The reaction of [Pr2 ^1NC（NCy）2]2TiCl2 with lithium diisopropylamide in THF afforded an unexpected [Pr2 ^1NC（NCy）2]2Ti（OBu^n）2 （2）, which was formed by the cleavage of carbon-oxygen bond of THF. Complexes 1 and 2 were fully characterized by elemental analysis, NMR and IR spectroscopies, and X-ray crystal structure determination for complex 2.     

Theoretical characterization of single-electron iodine-bond weak interactions in CH3…I-Y（Y=BH2,H,CH3,C2H3,C2H,CN,NC）systems

Iodine-involved single-electron halogen bonds (SEXBs) weak interactions in the systems of CH3···I-Y(Y = BH2, H, CH3, CH==CH2, C≡CH, CN, NC) were investigated for the first time using B3LYP/6-311++G(d,p) and MP2/aug-cc-pVTZ computational levels (the relativistic effective core potential basis set of Lanl2dz was used on iodine atom). The interaction energies between two moieties with basis set super-position error corrections for the seven complexes are -0.57, -1.36, -3.80, -2.17, -4.49,-6.33 and -8.64 kJ mol-1 (MP2/aug-cc-pVTZ ), respectively, which shows that SEXBs interactions are all weak. Natural bond orbital theory analysis revealed that charges flow from CH3 to the I-Y moiety. The total amount of natural bond orbital charge transfer (ΔNC) from the CH3 radical to I-Y increases in the order CH3…IBH2 < CH3…IH ≈ CH3…ICH3 ≈ CH3···IC2H3 < CH3…ICCH< CH3…ICN< CH3…INC. Atoms-in-molecules theory was used to investigate the topological properties of the bond critical points in the seven SEXB structures.     

Synthesis of [(C5H5Y (η2-PzMe2)(η-PzMe2)]2 and [Y(η2-PzMe2)2(η-PzMe2)(η-THF)]2 and the insertion of Me2SiO into the Y-N bond

3,5-Dimethylpyrazole (HPzMe2) reacted with (C5H5)3Y in THF to yield dinuclear complexes [(C5H5)Y-(η2-PzMe2)(μ-PzMe2)]2 (I) and [Y(η 2-PzMe2)2(μ-PzMe2)-(μ-THF)]2 (II), revealing a new method for synthesizing tris(pyrazolate) complexes of lanthanide metals. The X-ray crystallographic analysis showed that complex II crystallizes in space group P 1 , with unit cell dimensions a = 1.0798(1), b = 1.0818(1), c = 1.1313(1) nm, α= 76.914(2)°, β= 68.940(2)°, (R= 60.510(2)°, V = 1.0715(2) nm3, Z = 1. The final R factor is 0.0445. The investigation results showed that Me2SiO can only be inserted into the Y-N (bridging) bond of complex I to form [(C5H5)Y(η 2-PzMe2)(μ-OSiMe2 PzMe2)]2 (Ⅲ), but cannot be inserted into the Y-N (bridging) bond of complex Ⅱ due to the bulky crowding of the tetraple bridge structure.     

First-principle study of interaction of H2 and H2O molecules with (ZnO)n(n=3?6) ring clusters

A density functional calculation was performed to investigate the impact of hydrogen and water molecules on zinc oxide clusters (ZnO)n=3–6 ··· X, where X=H2 and H2O. The calculated binding energies were corrected for the basis set superposition error (BSSE). The structural parameters and chemical hardness were calculated for the complexes of zinc oxide clusters and guest molecules. The strength values of the interaction between the clusters and the guest molecules were analyzed based on the topological properties of atoms in molecules (AIM) theory of Bade r. The stereo electronic interact ions inside the ZnO clusters were analyzed in detail using the natural bond orbital (NBO) analysis.     

Theoretical characterization of electronic structures and properties of C-F···H-C pseudohydrogen bonds

The weak intermolecular interactions between 2-F-tetrahydrofuran and imidazole, pyrimidine, adenine, and guanine were studied theoretically using density functional B3LYP/6-311++G** and HF/6-311++G** methods. The results showed that both conven- tional N···H hydrogen bond and C-F···H-C pseudohydrogen bond (PHB) structures coexist in the four complexes. The weak intermolecular interaction energies indicate that the relative stabilities of the four complexes are in the order guanine···F > imidazole···F > adenine···F > pyrimidine···F. The characteristics of the four PHBs were determined using geometry optimizations, stretching vibrational frequencies, and natural bond orbital and electron density topological properties calculations. The most important result is that the F group of 2-F-tetrahydrofuran can activate the C-H to accept electrons from another molecule, and C-F···H-C PHB formation is relatively favorable.     

Synthesis, structure and superoxide dismutase activity of two self-assembly transition metal complexes containing a tridentate amino-Schiff base deviating from salicylaldehyde with glycine

Two new transition metal （Cu, Ni） complexes with amino-Schiff base ligand, （CgH7NO3）Cu（C14H12N2）.H2O （1） and （C9HTNO3）Ni（C3H4N2）3.H2O （2）, have been designed and synthesized in ethanol solution at room temperature. Both of the complexes have been characterized by elemental analysis, IR spectra, UV-vis spectroscopy and X-ray single crystal diffraction. For complex 1, the coordination environment of the central copper atom is a distorted square pyramid, and one-dimensional chain is formed through the inter-molecular hydrogen bonds （O4-H2W…O3, O4…H2W…O3#1 （#1： -x＋1, y, -z＋3/2）） and weak interactions （∏-∏ stacking interaction） between the phenyl rings. For complex 2, the nickel atom is 6-coordinated and in a distorted octahedral environment, and a discrete hydrogen-bond cluster （four molecules are connected by hydrogen bonds into a group） is formed via two types of intra-molecular hydrogen bonds （O-H...O, N-H...O） and inter-molecular hydrogen bonds （O-H...O, N-H...O）.     

Weak interaction between CH3SO and HOCl: Hydrogen bond, chlorine bond and oxygen bond

B3lyp/6-311＋＋g＊＊ and mp2/6-311＋＋g＊＊ calculations were used to analyze the interaction between CH3SO and HOCl. Nine （complex A： S1A-S9A） and five （complex B： S4B-S7B and S10B） minima were localized on the potential energy surface of CH3SO…HOCl complexes at b3lyp/6-311＋＋g＊＊ and mp2/ 6-311＋＋g＊＊ computational levels, respectively. The AIM and NBO theories were also applied to explain the nature of the complexes. Bonding energy of complexes A and B corrected with BSSE falls in the ranges of -0.4―-41.4 kJ·mol-1 and -6.9―-35.8 kJ·mol-1 at mp2/6-311＋＋g＊＊ level, respectively. The re- sults show that a novel oxygen bond complex （S6） exists in the system, besides hydrogen bond and chlorine bond. Especially, S6B-F, S6B-Br and S7B are blue shifted complexes compared with red shifted S6A, because the electron transfer occurs between LP1（S8） and σ＊（O5-Cl7）, resulting in the increase of O5-Cl7 and the decrease of vibrational frequency. The complex of S10B has characteristics of both red shift and blue shift.     

Synthesis,structure and catalytic behavior of yttrium complexes bearing a diaminobis（phenolate） ligand

Yttrium complexes stabilized by a diaminobis（phenolate） ligand were synthesized and their catalytic behavior was explored. Reaction of YCI3 with 1 equiv of LNa2 [L= Me2NCH2CH2N{CH2-（2-O-C6H2-^1Bu2-3,5）}2] gave the yttrium chloride LYCI（THF） （1） in 92% yield. Complex I can be used as starting material to prepare the yttrium amido derivative. Complex 1 reacted with 1 equiv of LiNPh2 in THF to afford the expected yttrium amido complex LYNPh2 （2） in high yield. Both of complexes 1 and 2 have been well detected by elemental analysis, NMR spectra and single-crystal X-ray analysis. It was found that complex 2 can efficiently initiate the ring-opening polymerization of L-lactide and ε-caprolactone, and a controlled manner is observed in the former case.     

Analysis of active sites for N2 and H^＋ reduction on FeMo-cofactor of nitrogenase

Dinitrogen (N2) and proton (H ),which act as physiological substrates of nitrogenase,are reduced on FeMo-co of the MoFe protein. However,researchers have different opinions about their exact reduction sites. Nitrogenases were purified from the wild type (WT) and five mutants of Azotobacter vinelandii (Av),including Qα191K,Hα195Q,nifV-,Qα191K/nifV- and Hα195Q/nifV-; and the activities of these en-zymes for N2 and H reduction were analyzed. Our results suggest that the Fe2 and Fe6,atoms closed to the central sulfur atom (S2B) within FeMo-co,are sites for N2 binding and reduction and the Mo atom of FeMo-co is the site for H reduction. Combining these data with further bioinformatical analysis,we propose that two parallel electron channels may exist between the 8Fe7S cluster and FeMo-co.     

Synthesis and Characterization of Quaternary Complexes [Ln(CH_2=C(CH_3)-COO)_2(NO_3)(phen)]_2

Many trinary lanthanide complexes have been studied. However, few mixed anion complexes with bidentate heterocyclic amines were synthesized. Mixed anion complexes [Ln (CH2=C(CH3)-COO)2(NO3)(phen)]2 was synthesized and its properties were determined by elemental analyses, IR and TGA. The IR spectra analysis indicate that NO3- , CH2=C(CH3)-COO- and Phen are coordinated with Ln. And the fluorescent spectra of [Eu(CH2=C(CH3)-COO)2(NO3)(phen)]2 and 1H NMR spectra of [La(CH2=C(CH3)-COO)2 (NO3)(phen)]2 was determined respectively.     

Investigation of adsorption of surfactant at the air-water interface with quantum chemistry method

Density functional theory （DFT） of quantum chemistry was used to optimize the configuration of the anionic surfactant complexes CH3（CH2）7OSO3^- （H2O）n （n=0-6） and calculate their molecular frequencies at the B3LYP/6-311＋G^＊ level. The interaction of CH3（CH2）7OSO3^- with 1 to 6 water molecules was investigated at the air-water interface with DFT. The results revealed that the hydration shell was formed in the form of H-bond between the hydrophilic group of CH3（CH2）7OSO3^- and 6 waters. The strength of H-bonds belongs to medium. Binding free energy revealed that the hydration shell was stable. The increase of the number of water molecules will cause increases of the total charge of hydrophilic group and S10-O9-C8 bond angle, but decreases of the alkyl chain length and the bond lengths of S10-O11, S10-O12 as well as S10-O13, respectively.     

Synthesis of L-cystine bridged bis(p-cyclodextrin) and its cooperative binding toward guest molecules

A novel p-cyclodextrin derivative, L-cystine bridged bis(β-cyclodextrin) 1 has been synthesized and characterized by 1H NMR, 13C NMR, IR, Raman and combustion analyses. Spectrofluorometric titrations have been performed in aqueous phosphate buffer solution (pH=7.20) at 25℃ to give the complex stability constants (Ks) and Gibbs free energy changes (-△G°) for the stoichiometric 1 : 1 inclusion complexation of 1 with four dyes. The binding abilities and molecular selectivities are discussed from the viewpoint of size/shape-fit and electrostatic interactions between hosts and guests. 2D ROESY investigation for the complexation between host and guest further confirms the cooperative binding of bridged cyclodextrin 1 with guest.     

Permeation of vanadium(III,IV,V)-dipicolinate complexes across MDCK cell monolayer and comparison with Caco-2 cells

In resent years, great attention has been paid to the in-sulin-mimetic property of various vanadium compounds. Although the mechanism of the hypoglycemic effect of vanadium compounds has not been elucidated, the major problems limiting further clinical applications for inor-ganic vanadium compounds include low oral absorption (<10%)[1] and gastrointestinal stress[2―5]. Hence, a series of vanadium complexes with organic ligands have been syn-thesized, such as bis(maltolato) oxovanadium(IV) (V…     

Synthesis of L-cystine bridgedbis（β-cyclodextrin） and its cooperative binding toward guest molecules

A novel p-cyclodextrin derivative, L-cystine bridged bis(β-cyclodextrin) 1 has been synthesized and characterized by 1H NMR, 13C NMR, IR, Raman and combustion analyses. Spectrofluorometric titrations have been performed in aqueous phosphate buffer solution (pH=7.20) at 25℃ to give the complex stability constants (Ks) and Gibbs free energy changes (-△G°) for the stoichiometric 1 : 1 inclusion complexation of 1 with four dyes. The binding abilities and molecular selectivities are discussed from the viewpoint of size/shape-fit and electrostatic interactions between hosts and guests. 2D ROESY investigation for the complexation between host and guest further confirms the cooperative binding of bridged cyclodextrin 1 with guest.