Extra Coordination of Zn-Tetraphenylporphine with Pyridine, Quinoline, and Acridine N-Oxides

Andreev, V.; Nizhnik, Ya. P.; Bezruchko, D. G.; Morozov, A. K.

doi:10.1007/s11176-005-0416-6

Cited by 14 publications

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References 26 publications

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“…According to our data [35], on complex formation of Zn-TPP with N-oxides of pyridines there was a certain deviation from the linear relationships logK -and -(where K is the stability constant of the complex in chloroform, is the displacement of the absorption bands of metalloporphyrin (MP) in the electronic spectra on interaction with ligand) in the case of the N-oxide of 3-methyl-4-nitropyridine, which is also explained by "wresting" the nitro group and as a result of this by a reduction of its conjugation with the aromatic system of the N-oxide. In reality, according to data of X-ray structural analysis, the angle between the planes passing through the atoms of the nitro group and the pyridine ring in the N-oxide of 3-methyl-4-nitropyridine was 14.68 o [43] (31.98 o in the case of its complex with ZnBr 2 [44]).…”

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confidence: 80%

“…Electronic spectra were taken on a SF 2000-02 instrument. The stability constants of Zn-TPP with pyridines in chloroform were determined as described in [35].…”

Section: Methodsmentioning

confidence: 99%

“…the introduction of two methyl groups possessing a +I effect leads to reversal of the relative basicity of the two donor centers. Special mention is made of the N-oxide of 4-(4-dimethylaminostyryl)pyridine, which contains two potential coordination centers (the N O group (pKa 1.46) and NMe 2 (pKa 4.30) separated by the styryl fragment [35]). In organic solvents it interacts with Bronsted-Lowry and Lewis acids at the oxygen atom of the N-oxide group, but in water it is protonated at the amino group [36].…”

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confidence: 99%

“…It is evident that the methyl group shows only an electronic effect on the reactivity of this compound. On the basis of the value of K = 269 ± 20 obtained by us for the complex of Zn-TPP with the N-oxide of 2-methyl-4-nitropyridine in chloroform we calculated PyO for the methyl group in position 2 from the equation logK = -0.71 PyO + 3.03 [35]. This value (-0.35) proved to be far greater in absolute value than for a methyl group in position 4 (-0.24) and especially in position 3 (-0.139) of the pyridine ring and agreed with that calculated by us on the basis of the pKa in water for the N-oxide of 2-methyl-4-nitropyridine.…”

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The effect of electronic factors on the reactivity of heteroaromatic N-oxides

Andreev

2010

Chem Heterocycl Comp

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On the basis of an analysis of the reasons for the multiplicity of constants for substituents it has been concluded that they are variables, the absolute value and sign of which depend on the nature of the compounds being considered (in particular other substituents), the partner with which reaction occurs, and the medium (the aggregate state of participants of the interaction). The use of modifications of the Hammett equation is caused by the impossibility in principle of only varying the values and sign of to describe universally linear functions of the dependence of rate (or equilibrium) constants of chemical processes from the algebraic sum of the electronic, steric, and other factors, which differ in their nature.At the present time empirical equations of the Hammett and Taft type (log(k/k 0 ) = ) are widely used in organic chemistry in spite of the fact that the multiplicity of constants requires greater care in choosing them for making correlations, and the use for interpreting the structure of a transition state interferes with certain other resistant concepts [1-6]. Thus the Hammett equation is used for assessing the structure of a transition state (according to the size of ) among similar compounds by the variation of substituents and consequently by the change in reactivity. It is therefore assumed that is a constant (but is dependent on the nature of the second reactant and the reaction conditions), i.e. the nature ( ) of a substituent does not affect the structure of the transition state. However according to the Hammond postulate [5] in rapid reactions the transition state is more like the reactants, but in slow reactions it is more like the reaction products, i.e. on changing the reaction rate the structure of the transition state must also be changed.In the monograph [4] V. A. Palm notes that the problem of constructing a precise scale even for induction constants of substituents of the type of functional groups or containing functional groups has no solution. The assumption of even O. A. Reutov, A. L. Kurts, and K. P. Butin [5, Vol. 1, p. 288], that " and are not independent parameters, as suggested, but are linked to one another, while a parameter linking and is reduced in their product", does not only not clarify the situation, but also remains as an additional problem as to the nature of this parameter.

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confidence: 80%

“…Electronic spectra were taken on a SF 2000-02 instrument. The stability constants of Zn-TPP with pyridines in chloroform were determined as described in [35].…”

Section: Methodsmentioning

confidence: 99%

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confidence: 99%

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The effect of electronic factors on the reactivity of heteroaromatic N-oxides

Andreev

2010

Chem Heterocycl Comp

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“…We previously showed [1][2][3] that shifts of absorption maxima (Δλ) in the electronic spectra of Zn-TPP in chloroform upon reaction with 3-and 4-substituted pyridines, as well as with pyridine, quinoline, and acridine N-oxides, are linearly related to logarithms of the stability constants (K) of the complexes, pK a of ligands (L) in water and other solvents, and Hammett constants σ of substituent in the heteroring.…”

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Quantitative relations holding in coordination of (Tetraphenylporphyrinato)zinc(II) and nucleophilic substitution with anilines

2012

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Thermodynamic parameters (ΔG°, ΔS°) of quasi-isoenthalpic coordination of (tetraphenylporphyrinato)zinc(II) with anilines (except for 4-halo derivatives) in chloroform at 273-313 K in the absence of steric factors are linearly related to shifts of their absorption bands in the electronic spectra in reactions with anilines, as well as with logarithms of the stability constants of the complexes, pK a values of the ligands in water, and Hammett substituent constants σ + . Linear relations were also found between thermodynamic and kinetic parameters of some nucleophilic substitution reactions and complex formation of (tetraphenylporphyrinato)zinc(II) with anilines.The present article continues our studies on quantitative relations between the stability constants of complexes formed by (tetraphenylporphyrinato)zinc(II) (Zn-TPP) with various organic compounds, rate constant of nucleophilic substitution, and physicochemical parameters characterizing these processes. We previously showed [1-3] that shifts of absorption maxima (Δλ) in the electronic spectra of Zn-TPP in chloroform upon reaction with 3-and 4-substituted pyridines, as well as with pyridine, quinoline, and acridine N-oxides, are linearly related to logarithms of the stability constants (K) of the complexes, pK a of ligands (L) in water and other solvents, and Hammett constants σ of substituent in the heteroring.Using the extended Taft equation (1), modified by Litvinenko et al. [4] for amines, we succeeded [5] in obtaining correlation (2) between log K in benzene (determined by calorimetry), Σσ*, E N , and log k for the reaction of phenacyl bromide with amines in benzene at 25°C.Here, k is the rate constant, the term ρ* Σσ* describes the inductive effect of all substituents on the nitrogen atom, and δE N characterizes steric factor (δE s in the Taft equation). log(K/k) = 2.77 + 2.73 Σσ* -0.94 E N ; r = 0.983. (2) The goal of the present work was to analyze kinetic and thermodynamic parameters of coordination of Zn-TPP with substituted anilines Ia-Iv in chloroform. R 2 = X = H, R 1 = Me (p), Et (q); Ph (r); R 1 = R 2 = Et, X = H (s);We found that shifts of the absorption maxima (Δ λ) in the electronic spectra observed in reactions of Zn-TPP with anilines in chloroform are linearly related (r = 0.95-0.98) to logarithms of the stability constants of the complexes (Δ λ II = 3.26 log K + 6.85), pK a values of the ligands in water (Δ λ II = 1.11 pK a + 9.15), and Hammett constants σ of substituents in the benzene ring of anilines (Δ λ II = 2.92 σ + 14.12) provided that steric factors are lacking (see table).The experimental stability constants (K) of the Zn-TPP complexes with aniline derivatives in chloro-

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