New description of the substituent effect on electronic spectra by means of substituent constants—IV. Charge transfer spectra of EDA complexes of tetracyanoethylene with meta-disubstituted benzenes

Charge transfer spectra of EDA complexes composed of TCNE and various kinds of m-disubstituted benzenes are discussed on the basis of a general equation, theoretically derived to express the substituent effect on electronic spectra. Molecular orbital calculation shows that the HOMO of the substituted benzenes is divided into two groups. One has a₂-like character and the other b₂-like, so that the substituent effect on the CT spectra has been also classified into two groups, since the CT spectral character is different in the two. This viewpoint is supported by the application of the general equation to the CT spectra. Also, we have applied the equation successfully to the other typical π-π or n-σ type EDA complexes.     

Electronic spectra of o-, m- and p-tolunitrile—substituent effect on internal rotation of the methyl group

The S₁ ← S₀ fluorescence excitation spectra and the S₁→S₀ dispersed fluorescence spectra of o-, m-and p-tolunitrile were measured in supersonic jets. Low-frequency bands due to internal rotation of the methyl group were observed in m- and p-tolunitrile. Observed band positions and relative intensities of the internal rotational bands were reproduced by a calculation using a free rotor basis set. From the analysis, the potential curve of the internal rotation was determined in both S₁ and S₀. It was found that the barrier height increases in going from S₀ to S₁ in m-tolunitrile, while it decreases in p-tolunitrile. In contrast, no low-frequency band was found in o-tolunitrile. It is concluded that the potential curve in o-tolunitrile does not change in going from S₀ to S₁. The change of the barrier height by electronic excitation in tolunitriles differs greatly from that observed in other toluene derivatives. It is suggested that the electronic properties of a substituent are important for the methyl rotation in the excited state.     

Charge-transfer spectra of organometallic complexes—VII. Electron—donor—acceptor complexation of trialkyltinisothiocyanates with iodine and tetracyanoethylene

An ultraviolet-visible study of the charge-transfer interaction between R₃ SnNCS (R  Me, Et, iPr and nBu) and iodine, respectively, tetracyanoethylene has revealed that the HOMO with dominant lone pair character located on S is the preferred donor site in the electron—donor—acceptor (EDA) complexes. Formation constants of the complexes were calculated using a non-linear regression analysis of the u.v.-vis. data.     

Charge transfer spectra of organometallic complexes—IX. Evaluation of solvent effects on the electron donor—acceptor interactions between trimethyltinisothiocyanate and iodine

Charge transfer energies of trimethyltinisothiocyanate—iodine complexes in solution are found to depend on the nature of the solvent. The relationship of these solvent shifts with various solvent properties, and is discussed. Stabilization energies of the excited states in the different solvents are determined using the Onsager theory of dielectrics.     

Reductive demetalation of manganese corroles： The substituent effect

The reductive demetalation of manganese corroles was investigated in CH2Cl2/HCl （aqueous） solvent by using SnCl2 as reducing agent. It was found that the demetalation yields depend on the substituents of corrole macrocycle significantly. Electron- rich manganese corrole undergoes reductive demetalation more easily than electron-deficient ones. The isolated reductive demetalation yield of manganese 5,10,15-tris（phenyl）corrole in present system is moderate （46%）. As for electron-deficient Mn（Ⅲ） 5,10,15-tris（pentafluorophenyl）corrole, the acid-induced demetalation in HOAc-HESO4 （V/V = 3：1） is preferable with an isolated yield of 67%.     

Accurate prediction of cation-π interaction energy using substituent effects

Substituent effects on cation-π interactions have been quantified using a variety of Φ-X···M(+) complexes where Φ, X, and M(+) are the π-system, substituent, and cation, respectively. The cation-π interaction energy, E(M(+)), showed a strong linear correlation with the molecular electrostatic potential (MESP) based measure of the substituent effect, ΔV(min) (the difference between the MESP minimum (V(min)) on the π-region of a substituted system and the corresponding unsubstituted system). This linear relationship is E(M(+)) = C(M(+))(ΔV(min)) + E(M(+))' where C(M(+)) is the reaction constant and E(M(+))' is the cation-π interaction energy of the unsubstituted complex. This relationship is similar to the Hammett equation and its first term yields the substituent contribution of the cation-π interaction energy. Further, a linear correlation between C(M(+))() and E(M(+))()' has been established, which facilitates the prediction of C(M(+)) for unknown cations. Thus, a prediction of E(M(+)) for any Φ-X···M(+) complex is achieved by knowing the values of E(M(+))' and ΔV(min). The generality of the equation is tested for a variety of cations (Li(+), Na(+), K(+), Mg(+), BeCl(+), MgCl(+), CaCl(+), TiCl(3)(+), CrCl(2)(+), NiCl(+), Cu(+), ZnCl(+), NH(4)(+), CH(3)NH(3)(+), N(CH(3))(4)(+), C(NH(2))(3)(+)), substituents (N(CH(3))(2), NH(2), OCH(3), CH(3), OH, H, SCH(3), SH, CCH, F, Cl, COOH, CHO, CF(3), CN, NO(2)), and a large number of π-systems. The tested systems also include multiple substituted π-systems, viz. ethylene, acetylene, hexa-1,3,5-triene, benzene, naphthalene, indole, pyrrole, phenylalanine, tryptophan, tyrosine, azulene, pyrene, [6]-cyclacene, and corannulene and found that E(M)(+) follows the additivity of substituent effects. Further, the substituent effects on cationic sandwich complexes of the type C(6)H(6)···M(+)···C(6)H(5)X have been assessed and found that E(M(+)) can be predicted with 97.7% accuracy using the values of E(M(+))' and ΔV(min). All the Φ-X···M(+) systems showed good agreement between the calculated and predicted E(M(+))() values, suggesting that the ΔV(min) approach to substituent effect is accurate and useful for predicting the interactive behavior of substituted π-systems with cations.     

On the extraction of spectra of components from spectra of mixtures. A development in factor theory—II

The theory of factor analysis developed in Part I [A. Muller and D. Steele, Spectrochim. Acta 46A, 817 (1990) [1] is extended to cases where m > 3, m being the number of factors. The effect of increasing the number of independent parameters by m(m-1) for T′ and the subsequent changes produced in the transformed eigenspectra, are investigated. Applications to actual spectra of mixtures of: (A) butan-2-one, ethyl ethanoate, cyclohexane and oct-1-ene (B) butan-2-one, ethyl ethanoate, cyclohexane and 2-methylpentane and (C) oct-1-ene, butan-2-one, ethyl ethanoate, cyclohexane and 2-methyl-pentane are presented. Using standard target techniques, an alternative approach is developed for the m> 3 case. This is based on transformation of the leading three eigenspectra, followed by identification and elimination of a component in a repetitive manner, until completion. The problems associated with the implementation of the Beer-Lambert Law are explored the need for accurate determination of a suitable wavenumber block to ensure the removal of the correct amount of each component, is examined. The ability to recognize at least one of the m component spectra per programme cycle is demonstrated.     

On the extraction of spectra of components from spectra of mixtures. A development in factor theory—I

The theory of factor analysis is extended to permit the computer based extraction of the spectra of pure components from spectra of mixtures. A simultaneous linear, non-orthogonal transformation of the eigenspectra and eigenvectors is used to generate all positive absorbances and concentrations within noise level. Applications to actual spectra of mixtures of: (A) ethyl ethanoate, butan-2-one and oct-1-ene; (B) ethyl ethanoate, butan-2-one and cyclohexane; and (C) butan-2-one, cyclohexane and 2-methylpentane are presented. The effects of changes in signs of the constrained diagonal elements of the transformation matrix is investigated. To explore the ability of the software to cope with component spectra in which there are no wavenumbers at which one component dominates an artificial set of mixtures is examined. Recognizable spectra are extracted. It appears that, even when there are no wavenumbers at which one component dominates, the condition of finding “the sum of squares of negative absorbances/concentrations” near zero is adequate to yield useful spectra for library searches.     

Effects of substituent and solvent on the Sonogashira coupling reaction of β-bromoporphyrin

A series of experiments were designed to understand the effects of substituent and solvent on the Sonogashira coupling reaction of β-bromoporphyrin using a Pd₂(dba)₃/AsPh₃ system as the catalyst. Electron-efficient groups and aprotic solvents are conducive to the reaction. A possible explanation was given. A new family of β-pyrrole substituted porphyrins was also synthesized during the study.     

μSR-study of reactivity of substituent ions and point-like defects in quartz monocrystals

SR-method has been used for studying reactions of muonium as an analogue of a light hydrogen isotope with impurity atoms and point-like defects. The relaxation rate of muonium polarization _Mu was measured for 11 samples with different concentrations of impurity atoms and defects. The rate constants of reactions of muonium with Fe, Al, Li, Ba, Cu, Mn, Ti and Pb atoms in quartz were defined.     

Quantum-chemical study of germanium—substituent bonds in tricoordinated germanium compounds

The spatial and electronic structures of molecules with three substituents at the germanium atom (tricoordinated germanium) were calculated by the DFT method (Gaussian-98 program package, B3LYP functional, 6-311G(d,p) basis set). The main characteristics of Ge-X bonds in these molecules were determined by NBO and AIM procedures. It is shown that Ge-X are weak, “intermediate” type bonds. The bond energies were calculated.     

Effects of substituent and catalyst on the intramolecular Povarov reaction—synthesis of chromenonaphthyridines

2-(N-Alkenyl-N-aryl)aminochromone-3-carbaldehyde undergoes intramolecular Povarov reaction with aromatic amines in the presence of Ph₃P·HClO₄ to produce chromenonaphthyridine. The effects of substituent and catalyst have been studied. The substituent on the alkenyl part of aminochromone controls the mode of reaction as well as the stereochemistry of the product.     

Direct introduction of a benzoyloxy substituent at the C-4 position of β-lactams

The copper-promoted reaction of β-lactams with t-butyl perbenzoate results in benzoyloxylation of the azetidin-2-one ring at the C-4 position. There is no competing reaction at the C-3 position, but reaction at exocyclic carbon α to nitrogen competes with ring substitution.     

Polarographic immunoassay coupled with catalysis of non-radioactive multiple iodine label

A now polarographic immunoassay was developed In this assay,human serum albumin (HSA) as the model antigen was covalently labeled with organic compound erythrosin B(EB) containing four non-radioactive iodides through Ⅰ step chemical reaction The labeling procedure is simple and the conditions needed are moderate.The molar labeling ratio of KB HSA was 12 Ⅰ The content of iodine in the conjugate obtained by the proposed procedure is ninth higher than that by the other existing methods.A heterogeneous competitive immunoassay was established by compling the catalysis of the conjugate to substrate As(Ⅲ)-Ce(Ⅳ) reaction with the linear-sweep polarographic detec-tion of As(Ⅲ) amount HSA can be determined in the HSA concentration range from 1 to 200μg/mL,with the de-tection hum of 0 66μg/ml.     

Characteristics of mass spectra of dichlorocarbene derivatives of isomeric dodecen-1-ols

The m/z of characteristic ion of the mass spectra of the dichlorocarbene derivatives of dodecen-1-ols was used as a parameter to locate the position of double bond in these isomers by a new formula.     

Ultrasound-assisted rapid synthesis of β-cyanoepoxides using hypervalent iodine reagents

An elegant approach for the rapid synthesis of β-cyanoepoxides 3 by the epoxidation of β-cyanostyrenes 1 with PIDA 2a is described. The epoxidation of β-cyanostyrenes 1 was performed with 1.2 equiv. of PIDA 2a in MeCN-H₂O (1:1) at room temperature in ultrasonic bath. The epoxidation reactions were completed in short reaction time and β-cyanoepoxides 3 were isolated in 69–94% yields.