New basicity/nucleophilicity scale on the basis of parameters of formation of axial n,ν-complexes derived from tetraphenylporphyrinatozinc(II) and base/nucleophile as ligand

Andreev, V.; Nizhnik, Ya. P.; Lebedevа, N. Sh.

doi:10.1134/s1070428008060213

Cited by 12 publications

(15 citation statements)

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“…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. log k = log k 0 + ρ* Σσ* + δ E N ,…”

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“…Taking into account similarity in the structures of Zn-TPP complexes with anilines and transition states in nucleophilic substitution reactions [5] with the latter as nucleophiles, we made an attempt to reveal quantitative relations between the parameters characterizing these processes. It was found that the rate constants k for nucleophilic substitution by anilines in methanolacetonitrile mixtures (50-100%) at 35°C [17] [Eq.…”

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confidence: 99%

“…Diphenylamine (Ir) (pK a 0.78 [15]), like 2,6-dimethyl-4-nitropyridine N-oxide (pK a -0.86 [5]) and 2,6-dichloropyridine (pK a -2.57 [16]), even in a saturated solution did not produce appreciable variations in the electronic absorption spectra of Zn-TPP, in contrast to such even weaker bases as 4-nitro-(pK a -1.7), 3-methyl-4-nitro-(pK a -0.97), and 2-methyl-4-nitropyridine N-oxides (pK a -0.967) [5]. This may be due to joint effect of electronic and especially steric factors which sharply reduce nucleophilicity of the nitrogen atom and hamper bond formation with the metal ion.…”

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

2012

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“…Donor-acceptor interactions of the types mentioned with ligands are similar in many cases and enable the principles of coordination chemistry to be used for explaining kinetic and thermodynamic data of classic chemical reactions investigated in organic chemistry. The expediency and originality of such an approach is also caused by the fact that we have proposed a new scale of nucleophilicity/basicity based on parameters characterizing the formation of axial (n, -type) complexes of the Zn-TPP with ligands (bases/nucleophiles) [7], on using which the values of the stability constants of complexes, and the displacements of the maxima of the absorption bands of the metalloporphyrin in the electronic spectra, conform to the Hammett equation and correlate linearly with the rate constants of chemical reactions.…”

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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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“…As model process [4] for investigation of the nucleophilicity of the reagents, we proposed to use their complex formation with Zn-TPP in chloroform, and as a parameter of the nucleophilicity, which depends on the basicity of the ligand, on the polarizability of the nucleophilic center and the molecule as a whole, and on the electronic and spatial factors operating in the reagent, we proposed to use the stability constant K of the 1:1 Zn-TPP·L molecular complex and the ∆λ value. The aim of the present paper is to investigate the possibility of using these data to predict the kinetic and thermodynamic parameters of coordination processes with other MPs.…”

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Complex formation of zinc-containing metalloporphyrins and nucleophilic substitution reactions involving pyridines

Andreev

Sobolev

Larkina

et al. 2012

Chem Heterocycl Comp

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Linear correlations were found between the thermodynamic and kinetic parameters for the nucleophilic substitution and coordination of metalloporphyrins in various solvents with the participation of pyridines. Complex formation of zinc(II) tetraphenylporphyrin with n-donor ligands in chloroform at 25°C is proposed for use as a model system in the electronic spectroscopic investigation of the nucleophilicity and basicity of compounds capable of forming complexes of the n,ν type.The present paper is a continuation of research of the quantitative relationships between the stability constants of the complexes of zinc(II) tetraphenylporphin (Zn-TPP) and other metalloporphyrins (MP) with various types of organic compounds, the rate constants for the nucleophilic substitution reactions, and the physicochemical parameters characterizing these processes.Earlier we showed [1-3] that the shifts (∆λ) of the absorption bands (λ Soret 418.5 nm; λ II 546.3 nm; λ I 585 nm) of Zn-TPP complexes in chloroform during reaction with 3-and 4-substituted pyridines and also with the N-oxides of pyridines, quinolines, and acridines correlate linearly with the logarithms of the stability constants K of the complexes, the pK a values of the ligands (L) in water and other solvents, and the Hammett σ-constants of substituents in the heterocycle. In addition, linear correlations are observed between the kinetic and thermodynamic parameters of the Zn-TPP coordination process and certain nucleophilic substitution reactions involving pyridines.As model process [4] for investigation of the nucleophilicity of the reagents, we proposed to use their complex formation with Zn-TPP in chloroform, and as a parameter of the nucleophilicity, which depends on the basicity of the ligand, on the polarizability of the nucleophilic center and the molecule as a whole, and on the electronic and spatial factors operating in the reagent, we proposed to use the stability constant K of the 1:1 Zn-TPP·L molecular complex and the ∆λ value. The aim of the present paper is to investigate the possibility of using these data to predict the kinetic and thermodynamic parameters of coordination processes with other MPs.

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New basicity/nucleophilicity scale on the basis of parameters of formation of axial n,ν-complexes derived from tetraphenylporphyrinatozinc(II) and base/nucleophile as ligand

Cited by 12 publications

References 15 publications

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

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

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

Complex formation of zinc-containing metalloporphyrins and nucleophilic substitution reactions involving pyridines

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