Synthesis,Crystal Structure,Optical, Magnetic,and Thermal Properties of the New Heteroleptic Chromium Complex [Ph4P][Cr(en)(S5)2]

The new heteroleptic chromium complex [Ph₄P][Cr(en)(S₅)₂] has been synthesised under mild solvothermal conditions by the reaction of chromium trichloride, sulfur, and tetraphenylphosphoniumbromide in a solution of ethylendiamine ( en ) in water. The crystal structure consists of isolated tetraphenylphosphonium cations and [Cr(en)(S₅)₂]^– anions. The Cr³⁺ cations are in an octahedral coordination of two bidentate S₅^2– polysulfide anions and one bidentate en ligand. The N atoms of the en ligand and the terminal S atoms of the S₅^2– anions bonded to the Cr³⁺ ions are in a cis-position. The six-membered CrS₅ rings are in a chair conformation. The three dimensional arrangement of the cations and anions is achieved via intermolecular hydrogen bonds. Investigations with differential thermal analysis (DTA) combined with thermogravimetry (TG) show a stepwise decomposition. In the first step the en ligand is removed completely followed by the emission of a part of the tetraphenylphosphonium cations and the sulfur atoms in the second step. The temperature dependence of the magnetic susceptibility exhibits a Curie-Weiss behaviour with an effective magnetic moment typical for a Cr³⁺ (d³) ion and a value for the Weiss constant of 1.3(2) K. Fourier transform infrared spectroscopy (FTIR) was also performed to characterise the optical properties.     

Structures of Sb(OC(6)H(3)Me(2)-2,6)(3) and Sb(OEt)(5) x NH(3): the first authenticated monomeric Sb(OR)(n) (n = 3, 5)

The first monomeric antimony alkoxides, Sb(OC(6)H(3)Me(2))(3) (1) and Sb(OEt)(5) x NH(3) (2), have been crystallographically characterized. The former adopts a trigonal pyramidal geometry, while the latter is octahedral about antimony; hydrogen bonding between NH(3) and SbOEt groups in Sb(OEt)(5) small middle dotNH(3) creates a one-dimensional lattice arrangement. Reaction of pyridine with SbCl(5) in EtOH/hexane yields the salt [Hpy(+)](9)[Sb(2)Cl(11)(5)(-)][Cl(-)](4) (3), which has also been crystallographically characterized. Crystallographic data: 1, C(24)H(27)O(3)Sb, a = 10.9080(2), b = 11.9660(2), c = 17.7260(4) A, alpha = 109.740(1) degrees, monoclinic P2(1)/c (unique axis a), Z = 4; 2, C(10)H(28)NO(5)Sb, a = 7.7220(1), b = 19.0700(2), c = 21.6800(3) A, beta = 93.4960(7) degrees, monoclinic P2(1)/c, Z = 8; 3, C(45)H(54)Cl(15)N(9)Sb(2), a = 13.4300(2), b = 14.4180(2), c = 17.4180(3) A, alpha = 82.7650(7), beta = 77.5570(7), gamma = 70.7670(7) degrees, triclinic P1, Z = 2.     

(TMOPP)Er[P(=O)(Oet)2]3Co(η5-C5H5)配合物的电化学行为的研究

研究了Er, Co-卟啉配合物((TMOPP)Er[P(=O)(OEt)2]3Co(η5-C5H5))的电化学行为, 并比较了它与相应的单核配合物电化学行为的差异.该配合物在 CH2Cl2 溶液中有四对氧化还原峰, 其氧化还原过程分别与配合物的中心离子和配体有关.而当该配合物修饰的玻碳电极于NaClO4溶液中时, 同样出现四对氧化还原峰, 但是峰的位置、形状、大小与前者比较发生了很大的变化.进一步实验又表明, 溶液的电解质浓度、酸碱性、种类以及膜的厚度等对修饰电极的反应行为都产生影响.     

Spectroscopic Properties of Lumiflavin: A Quantum Chemical Study

In this work, the electronic structure and spectroscopic properties of lumiflavin are calculated using various quantum chemical methods. The excitation energies for ten singlet and triplet states as well as the analysis of the electron density difference are assessed using various wave function‐based methods and density functionals. The relative order of singlet and triplet excited states is established on the basis of the coupled cluster method CC2. We find that at least seven singlet excited states are required to assign all peaks in the UV/Vis spectrum. In addition, we have studied the solvatochromic effect on the excitation energies and found differential effects except for the first bright excited state. Vibrational frequencies as well as IR, Raman and resonance Raman intensities are simulated and compared to their experimental counterparts. We have assigned peaks, assessed the effect of anharmonicity, and confirmed the previous assignments in case of the most intense transitions. Finally, we have studied the NMR shieldings and established the effect of the solvent polarity. The present study provides data for lumiflavin in the gas phase and in implicit solvent model that can be used as a reference for the protein‐embedded flavin simulations and assignment of experimental spectra.     

Theoretical Analysis of Solvent Polarity Effect on the Electronic and Spectroscopic Properties (IR and UV) of the Ni(CO)2(NHC)2 Complex (NHC = 1H-Imidazol-2-ylidene)

Russian Journal of Physical Chemistry A - In this study, using the wB97XD functional, quantum chemical calculations were used to analyze the solvent effect on the structural, electronic and...     

N—亚硝基二甲胺化学电离的量子化学研究

用质谱化学电离和量子化学方法研究了致癌物质N-亚硝基二甲胺(NDMA)的结构及性质,优化了化学电离质谱中主要离子的构型;探讨了NDMA的质子化合物的形成途径,经NDMA及其质子化合物的静电势计算,阐述了NDMA的可能致癌机理。     

Molecular Dynamics Study of the Photodissociation of ICN in Ethanol: Effect of Solvent Polarity

Journal of Solution Chemistry - In this work the photodissociation process for ICN in ethanol, a moderately polar solvent, was simulated using semi-classical molecular dynamics. Comparisons of the...     

取代基对3(5)-(9-蒽基)吡唑光学性质的影响

使用密度泛函理论(DFT)B3LYP/6-31G(d)方法优化得到了3(5)-(9-蒽基)吡唑及其衍生物的基态(S₀)分子结构, 使用单激发组态相互作用(CIS)/6-31G(d)方法优化得到这些分子的第一单重激发态(S₁)的几何结构, 并使用含时密度泛函理论(TD-DFT)B3LYP/6-311++G(d,p)方法计算了它们的吸收和发射光谱. 计算结果表明, 与3(5)-(9-蒽基)吡唑相比, 无论取代基是吸电子基团还是供电子基团, 衍生物的吸收和发射峰均发生红移, 并且当取代基―R=―BH₂, ―CCl₃, ―CHO, ―NH₂时衍生物有较长的吸收波长和发射波长.     

A Quantum Chemical Study of Germanium-Substituent Bonding in Complex Compounds of Germanium

Spatial and electronic structures of six-coordinated germanium compounds are calculated within МР2 and AIM methods using PC GAMESS-Firefly, MORPHY, and AIMALL software packages. Main topological characteristics of germanium-substituent bonds are determined in these molecules.     

Exchange interactions and electron delocalization in the mixed-valence cluster V(4)(IV)V(2)(V)O(7)(OC(2)H(5))(12)

The mixed-valence cluster compound V4IVV2VO7(OC2H5)12 was studied by X-band electron paramagnetic resonance (EPR) in the temperature range of 4.2-293 K. According to X-ray diffraction study, the crystal structure of the compound was described by a R3m space group at 295 K (four d1 electrons are equally delocalized on all vanadium ions) and changed to a P21/n space group on cooling the crystals to 173 K (the electrons are preferably localized on the four equatorial vanadium ions). The EPR spectra originate from the S = 1 total spin states with the fine structure averaged to a single Lorentzian line and from the S = 2 total spin states with fine structure partly averaged in the temperature range of 295-200 K and well averaged below 45-50 K. The states of S = 1 and S = 2 of comparable energy (DeltaE approximately 2 cm(-1); ES=1 < ES=2) were shown to be the lowest ones. The VIV <--> VV unpaired electron transfers together with isotropic Heisenberg exchange were shown to determine the total spin states composition and the intracluster dynamics of the compound. Two types of electron transfers were assumed: the single-jump transfer leading to the averaged configurations of the V4IVV2V <--> V3IVVV VIVVV type and to the splitting of the total spin states by intervals comparable in magnitude with the isotropic exchange parameter J approximately 100 cm-1 and the double-jump transfer resulting in dynamics. Temperature dependence of the transition rates nutr was observed. In the range of 295-210 K, the value of nutr = (0.5-0.6) x 10(10) s(-1) is sufficient for averaging the fine structure of the S = 1 states, and below 45 K the value of nutr approximately 1.5 x 10(10) s(-1) also averages the fine structure of the S = 2 state. A change in the localization plane of the VIV ions in the temperature range of 40-50 K was discovered.     

溶剂浮选三元缔合物光度法测定痕量锰的研究

在 p H=9.5碱性条件下 Mn( )能与 1 ,1 0 -二氮杂菲 ( Phen)形成配位阳离子 [Mn( Phen) 3 ]2 + ,该阳离子易与四碘荧光素 ( TIF)形成缔合物。缔合物在苯中稳定 ,据此建立了用 N2 浮选三元缔合物于苯中的光度法测定锰的新体系 ,本法灵敏度高 ( ε=9.6× 1 0 5L·mol- 1·cm- 1)。实测了天然水和酒中 Mn( ) ,结果令人满意     

The reaction of TiF4 with Li(OC(CF3)2Ph): direct synthetic route to the lithium-titanium heterometallic fluoride bridged complex {Li(THF)2TiF3(OC(CF3)2Ph)2}2 and Ti(OC(CF3)2Ph)4 alkoxide

Reaction of TiF4 and LiORf (Rf = C(CF3)2Ph) in the donor solvent-THF lead to the isolation of the heterometallic lithium-titanium complex (THF)2Li(mu-F)2Ti(ORf)2(mu-F)2Ti(ORf)(2)(mu-F)2Li(THF)2 (1) and Ti(ORf)4 alkoxide (2). Interaction of TiF4 and LiORf in the non-coordinating and low polar toluene yielded only Ti(ORf)4 (2). Compounds 1 and 2 were characterized by X-ray single-crystal analysis, IR, NMR and mass spectrometry. Compound 1 is a centrosymmetric fluorine bridged dimer and contains the Li(mu-F)2Ti(mu-F)2Ti(mu-F)2Li cage. Complex 2 containing four bulky ligands is monomeric. NMR evidence is presented that the TiF4 and LiORf in THF solution gave lithium-titanium heterometallic complexes containing Li-(mu-F)-Ti and the Ti-(mu-F)-Ti bonds.     

Quantum Chemical Study of the Mechanism of Action of Vitamin K Carboxylase in Solvent

We investigate the post-translational generation of Gla (γ-carboxy glutamic acid) from Glu (glutamic acid) by vitamin K carboxylase (VKC) in solvent. VKC is thought to convert vitamin K, in the vitamin K cycle, to an alkoxide-epoxide form, which then reacts with CO(2) to generate an essential ingredient in blood coagulation, γ-carboxyglutamic acid (Gla). The generation of Gla from Glu is found to be exergenic (-15 kcal/mol) in aqueous solution with the SM6 method. We also produced the free energy profile for this model biochemical process with other solvent methods (polarizable continuum model, dielectric polarizable continuum model) and different dielectric constants. The biological implications are discussed.     

C_(60)RuH_2(CO)(PPh_3)配合物的合成和氧化还原性能研究

自从１９８５年Ｋｒｏｔｏ等人１发现Ｃ６０等碳原子簇以来在化学、物理以及材料科学掀起了富勒烯的研究热潮２。目前富勒烯配合物的制备及其性质的研究是富勒烯化学最为活跃的研究领域之一３～５人们正致力于探索富勒烯各类衍生物的结构与性质之间的依赖关系以期合成出具有特殊性能的富勒烯配合物为富勒烯的实际开发应用奠定基础。本文合成表征了Ｃ６０ＲｕＨ２ＣＯＰＰｈ３配合物研究了其氧化还原特性。１实验部分１．１Ｃ６０ＲｕＨ２ＣＯＰＰｈ３的合成合成按下列反应进行ＲｕＣｌ３＋３ＰＰｈ３＋ＨＣＨＯＲｕＨ２ＣＯＰＰｈ３３ＲｕＨ…     

Solvent effects on the spectroscopic and photophysical properties of the trans-(1,4,8,11-tetraazacyclotetradecane)diisothiocyanatochromium(III) ion, trans-[Cr(cyclam)(NCS)(2)]+

The spectroscopy and photophysics of trans-[Cr(cyclam)(NCS)2]+ (where cyclam is 1,4,8,11-tetraazacyclotetradecane) were studied in a range of solvents. The cyclam NH stretching vibration [nu(NH)] wavenumber correlates with the Gutmann donor number, whereas the thiocyanate CN stretching vibration [nu(CN)] wavenumber correlates with the Snyder solvent strength (P') scale. These results signify that there is a difference in the solvent interactions with the two types of ligands. The energy of the ligand-to-metal charge transfer absorption maximum between 310 and 320 nm and the energy of the spin-forbidden (doublet-quartet) absorption and emission bands above 700 nm correlate with the nu(CN) wavenumber. This establishes the dominant role of solvent effects at the NCS- ligand in "tuning" the energy of these spectroscopic features. Quantum yields phirx for photosubstitution are <0.02 at 54 degrees C and <0.002 at 22 degrees C, demonstrating that photochemical reaction is a very minor pathway. The effects of solvent and temperature on the nonradiative decay of the doublet excited-state were investigated by observing the time-resolved phosphorescence between 700 and 750 nm. Below 30 degrees C, the lifetimes are relatively temperature-independent, whereas at higher temperatures, a strong Arrhenius-type dependence is observed. Values for the preexponential factor (A) and the activation energy (Ea) are solvent-dependent and follow a Barclay-Butler-type correlation. These observations are consistent with a dominant back-intersystem crossing pathway for nonradiative decay in the higher-temperature region. From trends observed between ln(A) and the nu(CN) frequency, it appears that solvent effects at the thiocyanate ligand play a dominant role in influencing the rate of nonradiative decay in the high-temperature region.     

运用NMR和DFT研究Michael加成反应的动力学行为及反应机理：(CO)5W=C(OEt)C2Ph作为底物

利用核磁共振方法研究了取代吡唑对炔基Fischer卡宾化合物的Michael加成的动力学行为，该反应为典型的二级反应。当吡唑的3，5-位由较大基团取代时，反应速率常数变小，而活化焓和活化熵明显增大。利用密度泛函理论研究了炔基钨卡宾为底物的Michael加成反应机理，发现吡唑上取代基团的增大可以导致第三步反应的活化能大于第一步，从而使反应的决速步骤由原来的第一步转变为第三步。