Synthesis and Crystal Structure of Bis-{N-[2-(6-ethylpyridyl)]-salicylideneiminato} Cobalt(Ⅱ)

1 INTRODUCTION The Schiff bases derived from salicylaldehyde and 2-aminopyridine derivatives have been used as potentially terdentate ligands[1]. Yamada and Yam- anouchi have synthesized the type of ML2nH2O complexes (M = CoⅡ, NiⅡ, CuⅡ, ZnⅡ or PdⅡ)[     

二[1-(2-噻吩基)-4,4,4-三氟丁二酮-1,3]合铜(Ⅱ)及其某些溶剂加合物的热分析研究

Thermoanalysis study has been carried out on the complex of bis[1-(2-thienyl)-4,4,4-trifluoro-butanedione- 1,3]copper(Ⅱ) and its adducts with pyridine, 2,2′-bipyridine, quinoline and dimethyl sulfoxide in a dynamic ni-trogen atmosphere by simultaneous TG-DTG-DSC technique. The experimental results showed that the decomposi-tion modes of the solvent molecules were various according to the different structures of the complex, in general, the decomposition of them was ahead of the decomposition of the ligand 1-(2-thienyl)-4,4,4-triflurobu- tanedione-1,3. Among them the adduct with 2,2-bipyridine showed a quite unique thermal behavior. Several methods have been jointly used to study the kinetics of all the thermal decomposition stages for title compounds, which showed that the evolution of the solvent molecules was controlled mainly by Rn mechanism (or Am mechanism for 2,2-bipyridine adduct) with lower activation energy; while the release of 1-(2-thienyl)-4,4,4-trifluro-butane- dione-1,3 was gove- rned by D2 or D3 mode with higher activation energy.     

Theoretical Investigation on Interaction between Guanine and Luteolin

The interacting patterns of the luteolin and guanine have been investigated by using the density functional theory B3LYP method with 6-31＋G＊ basis set. Eighteen stable structures for the luteolin-guanine complexes have been found respectively. The results indicate that the complexes are mainly stabilized by the hydrogen bonding interactions. Meanwhile, both the number and strength of hydrogen bond play important roles in determining the stability of the complexes which can form two or more hydrogen bonds. Theories of atoms in molecules and natural bond orbital have also been utilized to investigate the hydrogen bonds involved in all the systems. The interaction energies of all the complexes which were corrected by basis set superposition error are 6.04-56.94 kJ/mol. The calculation results indicate that there are strong hydrogen bonding interactions in the luteolin-guanine complexes. We compared the interaction between luteolin and four bases of DNA, and found luteolin-thymine was the strongest and luteolin-adenine was the weakest. The interaction between luteolin and DNA bases are all stronger than luteolin-water.     

Synthesis and Crystal Structure of 1-D Chain Copper（Ⅱ） Complex： [Cu（L）Cl2]n （L=2,5-Di-2-pyridyl-1,3,4-oxodiazole）

INTRODUCTION The design and construction of the coordi- nation polymer with one-dimensional chain, two- dimensional layer or three-dimensional framework structure is of considerable interest and has been developing rapidly in recent years[1]. Relevant to…     

Synthesis and Structural Characterization of Gd（Ⅱ） Coordination Polymer [Gd2（μ-phth）3（b-pd）（H2O）5]n

1 INTRODUCTION The polymeric metal complexes with extended structures are of great interest because of their useful chemical or physical properties[1]. Due to the noti- ceable fact that the aromatic polycarboxylate can provide versatile coordination mode and the non- coplanar structure of carboxylate groups and benze- ne rings, a lot of efforts in this field have been parti- cularly directed to the preparation of aromatic poly- carboxylate (such as phthalate, terephthalate and isophthalat…     

Dioxygen Affinities and Biomimetic Catalytic Oxidation Performance of Transition-metal Complexes with Unsymmetrical Bis-Schiff Bases

Bis-Schiff base complexes as mimetic monooxgenase have been extensively reported1, 2. The bis-Schiff bases transition-metal complexes modified by crown ethers ring or pseudo-macrocylic polyethers have significantly improved dioxygen affinities and biomimetic catalytic performance in comparison with uncrowned analogues3, 4. However, most of them were symmetric and oxacrown ether substituted, the bis-Schiff bases bearing an azacrown ether, with special configuration and possibility to approach…     

Syntheses and Properties of Lanthanide Hydroxy-meso-tetra（p-chlorophenyl） porphyrin Complexes

The syntheses and characterization of porphyrins and metalloporphyrins have been studied extensively. Hemoglobin, myoglobin or cytochrome P450, has been applied as a model compound. Wong C. P. et al. synthesized the first lanthanide porphyrin, acetylacetonate tetraphenylporphyrin europium, in 1974. Since then the study of porphyrin complexes, as a new field, has devel-     

Cuprous Iodide Catalyzed Synthesis of Diaryl Selenide and Telluride from Organoboronic Acids with Diphenyl Diselenide and Ditelluride

Organoselenium and tellurium compounds have received much attention not only as synthetic reagents or intermediates in organic synthesis but also as promising donor molecules for conductive materials.[1] A number of synthetic methods have been reported to prepare organoselenium and tellurium derivatives. A convenient and general method to introduce a selenium or tellurium moiety into organic molecules is the reaction of a metal selenolate or tellurolate with appropriate electrophiles such as organic halides, acyl chlorides, epoxides, and α, β-enones.[2] However, it is difficult to synthesize the unsymmetrical diarylselenides and tellurides through the reaction of selenide anion with organic halides because of the less reactivity of aryl halides. To accomplish this purpose, the reaction (iodobenzene with phenylselenol)was generally carried out in the presence of catalysts, ligands and strong bases. But, the reaction needs longer time to accomplish and form the products in moderate yields.     

Synthesis and Crystal Structure of a New Lanthanum（Ⅲ） 4-Cyanobenzoate Complex

A new dinuclear La（Ⅲ） complex [La2（4-cba）4[H（4-cba）2]2（phen）2（H2O）4] （4-Hcba = 4-cyanobenzoic acid and phen = 1,10-phenanthroline） 1 has been synthesized by solvothermal reaction in an ethanol/water mixed solution at 100 ℃ and structurally characterized by singlecrystal X-ray diffraction. Crystallographic data： C88H58La2N12O20, Mr = 1881.28, triclinic P1, a = 7.518（3）, b = 17.033（6）, c = 17.551（6）A, α = 115.333（4）, β = 92.9910（10）, γ = 99.366（5）°, V = 1985.3（12）A^3, Z = 1, Dc = 1.574 g/cm^3, F（000） = 944 μ = 1.145 mm^–1, the final R = 0.0281 and wR = 0.0686 for 6708 reflections with Ⅰ 〉 2σ（I）. In 1, two nine-coordinated La（Ⅲ） ions are connected by two 4-cba ligands in a syn-syn bidentate coordination mode, and the other six 4-cba ligands terminate the La（Ⅲ） ions, resulting in an isolated dinuclear structure. Two different types of intramolecular hydrogen bonds, asymmetrical O-H…O and symmetrical O…H…O, exist in the crystal. The title complex molecules are connected through hydrogen bonds and weak π-π stacking interactions to generate a 2-D layered network. The thermogravimetric analysis of 1 has also been discussed.     

Molecular Recognition of Bases and Nucleosides by Mono－substituted Mononuclear Complexes of 1,4,7,10－Tetraaza－cyclododecane

The mononuclear macrocyclic polyamine metal complexes 5a-5e have been shown to form stable 1 : 1 complexes with bases and nucleosides. Their binding constants (K) were determined by UV-visible spectrometric titration. The results show that recognition ability of the complexes 5a--5e for uracil, U (Uridine), dT (Thymidine) is higher than that for the other bases or nucleosides (such as Cytidine, Guanosine, Adenosine). The metal ion also plays an important role for the recognition ability of complexes.     

Theoretical Investigation on the Geometries and Properties of Guanine-BX3 （X = F, Cl） Complex

Geometries and binding energies were predicted at the B3LYP/6-311+G* level for the guanine-BX3 (X = F, Cl) systems and four isomers with no imaginary frequencies have been obtained for both guanine-BF3 and guanine-BCl3, respectively. Single energy calculations using much larger basis sets (6-311+G(2df,p) and aug-cc-pVDZ were carried out as well. It was found that the most stable isomer of guanine-BF3 is BF3 connected to N3 of guanine with the stabilization energy of –19.93 kcal/mol (BSSE corrected), while that of guanine-BCl3 is BCl3 connected to O10 of guanine having stabilization energy of –15.02 kcal/mol at the same level. The analyses for the combining interaction between BX3 and guanine with the atom-in-molecules theory (AIM) and natural bond orbital (NBO) methods have been performed. The results indicated that all the isomers are formed with σ-p type interactions between guanine and BX3, in which pyridine-type nitrogen or carbonyl oxygen or nitrogen atom of amino group offers its lone pair electrons to the empty p orbital of boron atom and the concomitance of charge transfer from guanine to BX3 has occurred. Still, one or two hydrogen bonds exist in some isomers of guanine-BX3 system and contribute to the stability of complex systems. Frequency analysis suggested that the stretching vibration of BX3 undergoes a red shift in complexes. Guanine-BF3 complex is more stable than guanine-BCl3 although the B–Y (Y=N, O) bond distance in the latter is shorter.     

Theoretical investigation of adenine–BX3 (X=F,Cl) complex

Geometries and binding energies are predicted at B3LYP/6-311+G* level for the adenine–BX₃ (X=F,Cl) systems and four conformers with no imaginary frequencies have been obtained for both adenine–BF₃ and adenine–BCl₃, respectively, and single energy calculations using much larger basis sets (6-311+G(2df,p)) and aug-cc-pVDZ were carried out as well. The most stable conformer is BF₃ or BCl₃ connected to N₃ of adenine and with the stabilization energy of 22.55 or 20.59 kcal/mol at B3LYP/6-311+G* level (BSSE corrected). The analyses for the combining interaction between BX₃ and adenine with natural bond orbital method (NBO) and the atom-in-molecules theory (AIM) have been performed. The results indicate that all the conformers were formed with σ–p type interactions between adenine and BX₃, in which pyridine-type nitrogen or nitrogen atom of amino group offers its lone pair electron to the empty p orbital of boron atom and the concomitances of charge transference from adenine to BX₃ were occurred. Frequency analysis suggested that the stretching vibration of BX₃ underwent a red shift in complexes. Adenine–BF₃ complex was more stable than adenine–BCl₃ although the distance of B–N is shorter in the later.     

吡啶-BH~3相互作用复合物的理论研究

对吡啶-BH~3复合物分别用MP2/6-31+G^*和B3LYP/6-31+G^*进行理论计算以预测该复合物的构型及解离能，得到四种构型，在MP2优化构型基础上作CCSD/6-31+G^*单点能量计算以验证MP2与B3LYP结果的可靠性，然后用B3LYP作振动频率分析，计算了各构型的垂直电离势，最后用更大基组作单点能量计算和自然键轨道(NBO)分析。结果表明，N-B直接相连的构型最稳定，其解离能为141.50kJ/mol,MP2和B3LYP对N-H接近的构型结果相关较大，另外两种构型稳定性介于二者之间，解离能分别为15.18kJ/mol,14.06kJ/mol(MP2/6-31+G^*)。     

Mechanistic insights into triterpene synthesis from quantum mechanical calculations. Detection of systematic errors in B3LYP cyclization energies

Most quantum mechanical studies of triterpene synthesis have been done on small models. We calculated mPW1PW91/6-311+G(2d,p)//B3LYP/6-31G* energies for many C30H51O+ intermediates to establish the first comprehensive energy profiles for the cationic cyclization of oxidosqualene to lanosterol, lupeol, and hopen-3beta-ol. Differences among these 3 profiles were attributed to ring strain, steric effects, and proton affinity. Modest activation energy barriers and the ample exothermicity of most annulations indicated that the cationic intermediates rarely need enzymatic stabilization. The course of reaction is guided by hyperconjugation of the carbocationic 2p orbital with parallel C-C and C-H bonds. Hyperconjugation for cations with a horizontal 2p orbital (in the plane of the ABCD ring system) leads to annulation and ring expansion. If the 2p orbital becomes vertical, hyperconjugation fosters 1,2-methyl and hydride shifts. Transition states leading to rings D and E were bridged cyclopropane/carbonium ions, which allow ring expansion/annulation to bypass formation of undesirable anti-Markovnikov cations. Similar bridged species are also involved in many cation rearrangements. Our calculations revealed systematic errors in DFT cyclization energies. A spectacular example was the B3LYP/6-311+G(2d,p)//B3LYP/6-31G* prediction of endothermicity for the strongly exothermic cyclization of squalene to hopene. DFT cyclization energies for the 6-311+G(2d,p) basis set ranged from reasonable accuracy (mPW1PW91, TPSSh with 25% HF exchange) to underestimation (B3LYP, HCTH, TPSS, O3LYP) or overestimation (MP2, MPW1K, PBE1PBE). Despite minor inaccuracies, B3LYP/6-31G* geometries usually gave credible mPW1PW91 single-point energies. Nevertheless, DFT energies should be used cautiously until broadly reliable methods are established.     

Theoretical Study on Hydrogen Interaction between 5-Fluorouracil and Glycine

The geometries,electronic structure,IR spectrum and other properties of hydrogen interaction between 5-fluorouracil and glycine were studied at the B3LYP/6-31+G* level.Single point energy calculations were executed at the B3LYP/6-311++G** and B3LYP/aug-cc-pvdz levels,and natural bond orbital (NBO) analysis was carried out at the B3LYP/6-31+G* level.Finally,the hydrogen bonds were discussed via AIM electronic density topology analysis.     

Quantum-Chemical Modeling of B<Subscript>32</Subscript> Complexes with Nitrogen: Endo or Exo?

Computational modeling of borospherene B₃₂ complexes with nitrogen has been performed by the density functional theory method (DFT UB3LYP*/6-311+G(d)). The geometry of isomers of these complexes with a different starting orientation of N has been found, their relative energies have been calculated, and the spin density distribution has been studied. Computation results predict that the structures with a nitrogen atom or ion built into the boron cage are more favorable than the endohedral isomers.     

Intramolecular hydrogen bond in the push–pull CF3-aminoenones: DFT and FTIR study,NBO analysis

Postulated conformers of trifluoromethylated β-aminoenones stabilized by intramolecular NH?O and N?HO bonds were studied by IR and NMR spectroscopy and evaluated with quantum chemical calculations (B3LYP/6-311+G(d,p), MP2/6-311+G(d,p)//B3LYP/6-311+G(d,p) and MP2/6-31G(d,p)) and NBO analysis. The influence of the nature of EWG, substituents at the nitrogen atom and double bond, and of orbital interactions of heteroatoms and double bonds in these structures on the proton affinity of basic and acid centers, strength of hydrogen bonds, and the energy of tautomeric transfers is discussed. The theoretical results agree satisfactorily with the experimental observations.     

DFT法研究3-羟基丙烯醛的双键旋转异构反应机理

利用密度泛函理论(DFT)分别在B3LYP/6-31G**和B3LYP/6-311＋＋G**的计算水平上优化了基态3-羟基丙烯醛分子在双键旋转异构反应过程中的平衡态以及过渡态的几何构型，分析了反应过程中键参数的变化，计算了该反应的内禀反应坐标(IRC)，发现在重排反应途径上存在一个四元环骨架的中间体.通过振动分析对平衡态和过渡态进行了确认，并得到了零点能.计算结果表明，基态3-羟基丙烯醛分子的双键旋转异构反应经过两步完成，第一步反应位垒稍高，第二步反应位垒较低，存在着发生重排反应的可能性.     

胸腺嘧啶-BH3构型与性质的DFT和MP2研究

Geometries and combination energies are predicated at B3LYP / 6-31G（d）and MP2 / 6-31G（d）level for thymine-BH3 complexes and 5 geometries have been obtained. Then single point energy calculations using larger basis sets（6-311 + G（2df）and aug-cc-pVDZ）and vibrational analysis and natural bond orbital analysis are carried out on the 5 optimized conformers. The outcome indicates that the conformers with the boron atom combined with O directly are relatively stable ones,（a）and（b）,with the combination energies of 90. 4 and 88. 0 kJ / mol （B3LYP / 6-31G（d）,BSSE corrected）. The fact is that the nitrogen atom offers electron to the empty atomic orbital of boron which produces the conformers（c）and（d）. Only one conformer is found which is formed because two carbon atoms offer π electron to the empty orbital of boron. The charge transference exists in all the conformers. The combination energies have a good line relation with their charge transference. The calculated results show that when the complex forms their IR spectrum moved to the red side and the frequency shifts are relative to the stabilities of the complexes.     

2,3,7,8-四氯苯并二英分子结构与热力学性质的理论研究

用密度泛函理论(DFT)和从头算(ab initio)方法,在B3LYP/6-31G、 B3LYP/6-31G*、 B3LYP/6-311G*和MP2/6-31G*水平上全优化计算了2,3,7,8-四氯苯并二英(2,3,7,8-TCDD)的几何构型、电子结构和振动频率,并用校正后的频率计算了298～1500 K的标准热力学函数,同时用半经验的PM3 SCF-MO进行了同样的计算,计算结果与实验值及文献值较好地吻合.