Equilibrium studies of the diorganotin(IV) complexes with some amino acids and related compounds

The interaction of dimethyltin(IV) and diethyltin(IV) cations with water and some amino acids and related compounds was investigated at 25 degrees C and ionic strength 0.1 M NaNO(3) using a potentiometric technique. The results showed the formation of 11 and 12 (organotin:ligand) complexes and the corresponding stability constants were determined. The participation of different ligand functional groups in binding to organotin is discussed. The effect of the pK(a) value of the respective ligand on the stability constant of its complex species was elucidated. The concentration distribution of the complexes in solution was evaluated.     

Solvent effects on charge-transfer intensities and heats of formation of chloranil complexes with aromatic hydrocarbons

The spectrophotometric and thermodynamic properties of the charge-transfer complexes of chloranil with aromatic hydrocarbons such as benzene, toluene, xylenes (o-, m- and p-) and mesitylene have been studied in n-heptane solvent to make a correlation between the charge-transfer intensities and the heats of formation of the complexes. The results disagree with Mulliken's prediction—the charge-transfer intensities decrease with increase of heats of formation. An attempt has been made to calculate the thermodynamic as well as spectrophotometric properties of these complexes free from the influence of chloranil—solvent interaction and the results thus obtained show a good correlation between the charge-transfer intensities and the heats of formation of the complexes.     

Spectrophotometric determination of microgram amounts of amino acids with chloranil

Amino acids form molecular complexes with chloranil at pH 9.0 having apparent molar absorptivities at 350 nm ranging from 4,000 to 28,000. A spectrophotometric method for the determination of μg amounts of amino acids is described, based on such complex formation. There is no interference from urea and only a weak interference from ammonium ions.     

Mechanistic appraisal of the charge-transfer complexes of promethazine with chloranil: a modelling approach.

Various mechanisms are often used to explain the interaction between electron donors and acceptors. Commonly proposed mechanisms are those in which the acceptor interacts with the aromatic pi-systems in the donor molecule or the acceptor forms a weak interaction of the Lewis acid with Lewis base type. In this study, the above mechanisms were examined as well as other possible mechanisms. Promethazine was chosen as the model drug containing aromatic systems capable of pi-pi interaction as well as N-methyl group capable of forming a complex with the weak Lewis acid, p-chloranil. Our modelling studies revealed that the situation where the p-chloranil interacts with a protonated N-methyl group is the most significant mechanism of interaction, based on the calculated energies for the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), the Tripos force field energy terms and also the stability of the complexes during molecular dynamics simulations.     

Spectroscopic investigation of the charge-transfer interactions between 1,4,7-trimethyl-1,4,7-triazacyclononane and the acceptors iodine, TCNE, TCNQ and chloranil

The interaction of the interesting polynitrogen cyclic base 1,4,7-trimethyl-1,4,7-triazacyclononane (TMTACN) with the sigma-acceptor iodine and pi-acceptors tetracyanoethylene (TCNE), 7,7,8,8-tetracyanoquinodimethane (TCNQ) and tetrachloro-p-benzoquinone (chloranil) have been studied spectrophotometrically and cyclic voltametrically in chloroform at 20 degrees C. Based on the obtained data, the formed charge-transfer complexes were formulated as [(TMTACN)I](+).I(3)(-), [(TMTACN)(TCNE)(5)], [(TMTACN)(TCNQ)(3)] and [(TMTACN)(chloranil)(3)] where the stoichiometry of the reactions, donor:acceptor molar ratios, were shown to equal 1:2 for iodine complex, 1:3 for chloranil and TCNQ complexes and 1:5 for TCNE complex.     

Charge-transfer complexes of chloranil with trialkylsilylmethyl esters of α-phenylbutyric and N-substituted aminoacetic acids

Conclusions ELectronic spectral data for charge-transfer complexes of choranil with trialkylsilyl-methyl esters of -phenylbutyric and N-substituted aminoacetic acids indicate that the CH₂CO₂CH₂SiAlk₃ group has an electron-donor effect, leading to an increase in electron density of the aromatic ring and arylamino group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1670–1671, July, 1986.     

表面活性剂增敏荷移反应紫外分光光度法测定三聚氰胺

在pH =7.55的Tris-HC1缓冲溶液中,以十六烷基三甲基溴化铵( CTMAB)为增敏剂,三聚氰胺与四氯对苯醌之间发生荷移反应,研究了其反应产物的紫外光谱性质,据此建立了荷移反应紫外分光光度法测定三聚氰胺的方法.三聚氰胺的线性范围为8.61×10-8 ～2.60×10 -6mol/L,r=0.9995,检出限为2...     

Spectroscopic studies and X-ray crystal structures of charge-transfer complexes of 1,4,7-trithiacyclononane with diiodine

1,4,7-Trithiacyclononane ([9]aneS₃) reacts with molecular diiodine in CH₂Cl₂ to form a 1:1 adduct. The formation constant and the thermodynamic parameters of this adduct have been determined by UV-visible spectra of several solutions at the temperatures of 15, 20, 25, 30, and 35°C. The ¹³C NMR spectra show that adducts with higher ligand/diiodine molar ratios are formed. Two neutral charge-transfer molecular compounds having formula 2[9]aneS₃ · 4I₂ ( I ) and [9]aneS₃ · 3I₂ · ( II ) have been obtained as crystals. The crystals of I are triclinic (a = 8.498(2) Å, b = 13.984(4) Å, c = 14.898(6) Å, α = 65.57(2)°, γ = 89.19(2)°, γ = 81.26(2)°, Z = 2, space group P1; R = 0.025) and contain units formed by two [9]aneS₃ molecules connected by a diiodine molecule; one [9]aneS₃ binds two other diiodine molecules, while the second binds only one other diiodine molecule. The crystals of II are monoclinic (a = 13.810(2) Å, b = 9.829(4) Å, c = 16.198(6) Å, β = 113.41(2)°, Z = 4, space group P2₁/c; R = 0.019) and contain molecules of [9]aneS₃ binding three diiodine molecules. FT-Raman spectra in the characteristic v(I–I) region, carried out on the solid adducts, are discussed in comparison with the structural parameters.     

Spectroscopic study of germanium-containing compounds

Conclusions The values of C=0 in the IR spectra and the position of the band from the n ^* electronic transition in the UV spectra of the amides R¹CONR²R³ vary linearly with the inductive effect of the R¹ substituent (for R²=R³=H, Alk). This may indicate the absence of the intramolecular coordination Ge 0, where or. The substituent R¹=Ge(C₂H₅)₂ exhibits electron-acceptor properties besides a +I-effect.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 349–352, February, 1984.     

含氨基酸Schiff碱-金属手性配合物的合成及其相关反应进展

本文综述了"含氨基酸Schiff碱-金属"手性配合物的合成及其结构。同时还讨论了"含氨基酸Schiff碱-金属"手性配合物不对称反应, 如: 烷基化反应、缩合反应、Michael加成反应、溴化反应等。这些反应为氨基酸拆分及非蛋白质类氨基酸合成提供了新方法。     

氨基酸和核苷的五配位磷化合物

五配位磷化合物在生物化学中起着重要作用。磷所参与的绝大多数生命化学过程,包括酶活性调节过程中蛋白质的磷酰化与去磷酰化,信息传导过程中蛋白质的磷酰化与去磷酰化,ATP的能量转移,RNA的自体切割等,其化学本质都是磷酰基转移反应。生物化学家们的研究表明,这些磷酰基转移反应都是通过五配位中间体来完成的。因此,对生物化学中五配位磷化合物的研究具有重要意义。     

Theoretical study on the structure and UV–visible spectrum of pyridine–chloranil charge-transfer complex

The ground-state structure of the charge-transfer complex formed by pyridine (Py) as electron donor and chloranil (CA) as acceptor has been studied by full geometry optimization at the MP2 and DFT levels of theory. Binding energies were calculated and counterpoise corrections were used to correct the BSSE. Both MP2 and DFT indicate that the pyridine binds with chloranil to form an inclined T-shape structure, with the pyridine plane perpendicular to the chloranil. The CP and ZPE corrected binding energies were calculated to be 14.21 kJ/mol by PBEPBE/6-31G(d) and 23.21 kJ/mol by MP2/6-31G(d). The charge distribution of the ground state Py–CA complex was evaluated with the natural population analysis, showing a net charge transfer from Py to CA. Analysis of the frontier molecular orbitals reveals a σ–π interaction between CA and Py, and the binding is reinforced by the attraction of the O₇ atom of CA with the H₂₃ atom of Py. TD-DFT calculations have been performed to analyze the UV–visible spectrum of Py–CA complex, revealing both the charge transfer transitions and the weak symmetry-relieved chloranil π–π^* transition in the UV–visible region.     

硝基芴酮与N-乙基咔唑电荷转移复合物的研究——-用X射线光电子能谱确定复合物的电荷转移量

Mulliken等从理论上指出电荷转移式复合物必伴有电子从给体原子或分子向受体原子或分子间的电荷转移.而用X射线光电子能谱(XPS)测定的某给定原子内壳电子结合能位移(即XPS化学位移)正是该原子周围环境电荷分布变化的反映.因此XPS技术是确定形成电荷转移复合物和提供电荷转移量信息的有效手段之一.为此,我们用XPS技术研究了2-硝基芴酮(2-MNF);2,7-二硝基芴酮(2,7-DNF);2,4,7-三硝基芴酮(2,4,7-TNF);     

Spectroscopic characterization of oxidized nanocellulose grafted with fluorescent amino acids

A hardwood bleached kraft pulp was oxidized by sodium hypochlorite using 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and sodium bromide in water as catalysts to produce oxidized fibers. These oxidized fibers were mechanically disintegrated into oxidized nano-elements which were separated from the coarse components by centrifugation to obtain oxidized nanocellulose (ONC). The ONC was then coupled with fluorescent amino acids using a two step coupling procedure. First, the ONC was activated by N-ethyl-N′-(3-dimethylaminopropyl) carbodiimide hydrochloride, forming a stable active ester in the presence of N-hydroxysuccinimide. Second, the active ester was reacted with the amino groups on the amino acids, forming an amide bond between the ONC and amino acids. The products (ONC-amino acids) were characterized by transmission electron microscopy and by different spectroscopic techniques such as absorption, emission, FTIR and XPS.     

Spectroscopic studies of isonicotinoyl-, nicotinoyl-, and piconoylhydrazines with chloranil

Isonicotinoyl-, nicotinoyl-, and piconoylhydrazines form molecular complexes with chloranil at pH 9. The composition and stability of these complexes have been studied spectrophotometrically. The results indicate that all complexes were of the 1:1 type and their stabilities depend on the position of the substituent group in the pyridine ring. The method of complexation was used to determine parts per million amounts of INH, NH, PH, and isoniazid tablets in solution spectrophotometrically.