Structure of Sulfophthalexons, Chelating Analytical Reagents

Pankratov, A. N.; A, Mustafin

doi:10.1007/s10809-005-0107-9

Cited by 4 publications

(6 citation statements)

References 6 publications

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“…The results presented in Table 4 show that as in the case considered in [23][24][25][26][27], the density distribution of water molecules in the cell approaches that of water in the liquid state, even if we neglect the fact that part of the cell volume is occupied by the molecular system I -IV . Table 1.…”

Section: Resultsmentioning

confidence: 88%

Tautomerism and Regioselectivity of the Protonation of 2-Pyrrolidone. Stereoselectivity of Complexation between Palladium(II), Chloride Ion, and 2-Pyrrolidone

2005

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Palladium(II) complexes with organic ligands are promising as medicines [1] that interact with functional groups of biological systems to give the corresponding coordination entities [2]. In the study of reactions of the palladium ion with bioligands, its interactions with inorganic compounds contained in an organism's fluids should also be considered. It is not improbable that inorganic ligands (H 2 O , Cl -, etc.) competing with biologically active substances for the metal ion can reduce its toxicity. On the other hand, coordination of inorganic ligands by the metal cation can diminish the efficiency of palladium-based medicines; for this reason, mixed-ligand complexes of palladium(II), in which the opposite trends are more or less counterbalanced, are acceptable as medicines.It is expedient to use the chloride ion as an inorganic ligand since it is contained in biological fluids. For instance, blood plasma is simulated by 0.86% (0.147 mol/l) NaCl, while the gastric juice is simulated by 0.1 M HCl [3].2-Pyrrolidone (2-pyrrolidinone, pyrrolidine-2-one, 2-oxopyrrolidine, and γ -butyrolactam) is a promising ligand for the formation of biologically active complexes with platinum metal cations [4]; 2-pyrrolidone can exhibit lactam-lactim tautomerism [5,6]. In sufficiently acidic media, protonation of 2-pyrrolidone (which is possible both at the N and O atoms) can compete with its coordination by metal cations. In[7], dichlorobis(pyrrolin-2-ol)palladium [Pd ( C 4 H 7 NO ) 4 Cl 2 ] was synthesized by the reaction of palladium(II) chloride with 2-pyrrolidone in aqueous acetone and its crystal and molecular structures were determined by X-ray diffraction analysis [8]. The structure consists of an electrically neutral complex and two 2-pyrrolidone molecules attached to it by intermolecular éç ··· é hydrogen bonds [8]. The most important features of the complexation is the lactim (pyrroline-2-ol) structure of the organic ligand, N-coordination, and the cis -structure of dichlorobis(pyrroline-2-ol)palladium [8].Usually, complexation reactions yield trans -isomeric products [9, 10]. However, it is cis -isomers that are of interest as potential antitumor preparations. For this reason, it is important to explain the stereoselectivity of complexation.The goal of this study was to calculate, by quantumchemical methods, the tautomerism and regioselectivity of the protonation of 2-pyrrolidone in the gas phase and an aqueous solution and to justify the stereoselectivity of the complexation between palladium(II), chloride ion, and pyrroline-2-ol. EXPERIMENTALQuantum-chemical calculations for the gas phase were performed by the AM1 [11] and PM3 methods Abstract -According to the AM1, PM3, HF/6-31G(d,p), and MP2/6-31G(d,p)//HF/6-31G(d,p) calculations, it is the lactam tautomer of 2-pyrrolidone that is thermodynamically most stable in both the gas phase and an aqueous solution. Analysis of the PM3 data with consideration of the medium showed that the tautomeric equilibrium of 2-pyrrolidone (pyrroline-2-ol) in aqueous solution is shift...

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Section: Resultsmentioning

confidence: 88%

Tautomerism and Regioselectivity of the Protonation of 2-Pyrrolidone. Stereoselectivity of Complexation between Palladium(II), Chloride Ion, and 2-Pyrrolidone

2005

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“…The first reduction waves were observed at significantly higher overpotentials, and the second reduction waves almost disappeared due to the presence of electron-donating groups (HCCCH 2 O– and HO−). That is, the diazonium cations became less susceptible to the decomposition with the release of nitrogen, as the electron donating properties of para-substituent became more pronounced . The reduction wave was further shifted to a lower potential of 0.06 V for 4-hydroxyphenyl than 0.16 V for 4-propargyloxyphenyl diazonium salt, because the hydroxy group (HO−) is more electron-donating than the propargyloxy group (HCCCH 2 O−) .…”

Section: Resultsmentioning

confidence: 99%

“…In the 4-nitrophenyl diazonium salt, two waves were observed, indicating that the deposition of diazonium salt on the GC substrate was a two-step process. 16 The first wave at 0.58 V was attributed to the irreversible formation of 4nitrophenyl radicals (NO 2 −C 6 H 4 •) and the release of nitrogen, which occurred due to the reduction of the diazonium salt 19,20 and led to the formation of a covalent bond between the glassy carbon electrode and the 4-nitrophenyl group. 21 The second wave at 0.27 V likely corresponds to the relatively slower reduction of diazonium salts through intermolecular binding leading to the arylation.…”

Section: Resultsmentioning

confidence: 99%

Manipulating Electron Transfer between Single-Walled Carbon Nanotubes and Diazonium Salts for High Purity Separation by Electronic Type

et al. 2012

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Diazonium salts preferentially react with metallic single-walled carbon nanotubes (SWNT) over semiconducting SWNT, enabling the separation of SWNT by electronic type. Therefore, the reaction selectivity of diazonium salts for metallic SWNT is crucial for high purity separation of both metallic and semiconducting SWNT. Herein, we developed an efficient method of increasing the reaction selectivity by manipulating the redox potential of diazonium salts. The electron affinity of diazonium salts is effectively lowered when the para-substituent of the diazonium salts is an electron-donating group, (i.e., 4hydroxy and 4-propargyloxy) rather than an electron-withdrawing group (i.e., 4-nitro, 4-carboxy, and 4-cholro). The reduction potential of 4-hydroxyphenyl and 4-propargyloxyphenyl diazonium salt was greater than the oxidation potential of semiconducting SWNT; therefore, the electron transfer reaction between these two reagents was effectively suppressed, leading to a highly selective reaction for metallic SWNT. We confirmed that this highly selective reaction scheme can be used to separate SWNT, and high purity semiconducting SWNT can be obtained via density-induced separation.

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“…Table 3 compares the thermodynamic stability of cations V, IX, and X, on the one hand, and VIII, XI, and XII, on the other hand, according to the PM3 estimates with the aqueous medium explicitly taken into account. To do that, we considered clusters including the above cations and water molecules (similar to [67][68][69][70], the density of the water molecule distribution in the cluster was close to that in liquid water; that is, real aqueous …”

Section: Methodsmentioning

confidence: 99%

“…One can semiquantitatively assess the effect of the aqueous medium on the state of the dissolved molecular systems (M) using the estimated interaction energy of molecule M with an ensemble (m) of water molecules, which has the physical meaning of hydration enthalpy [67][68][69][70] ∆H…”

Section: XVIImentioning

confidence: 99%

Analytical Azo Coupling Reactions: A Quantum-Chemical Consideration

Pankratov

2005

J Anal Chem

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The nitrite ion is a priority environmental toxicant and a precursor of N-nitrosamines, which are carcinogenic and mutagenic agents [1,2]. It interacts with oxyhemoglobin in blood to form methemoglobin, which disturbs cell respiration, and, therefore, the vital functions of the entire organism [3,4]. Nitrites are added to meat foods to improve vendibility. The analytical determination of nitrites and N-nitrosamines in foodstuff and other samples is a topical problem. The simplicity, availability, and satisfactory metrological characteristics of photometry make it one of the most suitable methods for solving this problem [5,6]. The most important photometric reactions for nitrites and N -nitrosamines are the diazotization of primary aromatic amines and the subsequent azo coupling reaction [5,6].In photometric analysis, the following processes in which or N -nitrosamines participate are used: (1) the self-coupling of 1-aminonaphthalene ( I ) through the diazotization of I followed by the coupling of the resulting naphthalene-1-diazonium cation ( II ) with I [5-8] and (2) the analytical Griess reaction involving the diazotization of 4-aminobenzenesulfonic (sulfanilic) acid followed by the azo coupling of the resulting 4-sulfobenzenediazonium with amine I [5,6,9].In an aqueous solution, the former of the processes mentioned above occurs to only a small extent and the product precipitates [7,8]. However, the yield of the analytical form and the stability of the analytical signal over time improve dramatically if the reaction is performed in microreactors [10], such as anionic surfactant (sodium dodecyl sulfate) micelles [7,8]. On the contrary, the Griess reaction is successfully performed in an aqueous medium [5,6], whereas anionic surfactant micelles only slightly enhance the analytical signal NO 2 -(increase the absorbance of the solution of the analytical form) and stabilize it over time [9].Note that the stability of an analytical signal and the thermodynamic stability of molecular systems discussed below are different concepts. The former is characterized by the time in which the maximum intensity of the analytical signal remains virtually constant, whereas the latter is characterized by the enthalpy and the free energy of formation of a certain molecule.In the diazotization-azo coupling tandem, the azo coupling reaction is crucial, because its products are the sources of the analytical signal in the photometric determination of nitrite and N -nitrosamines.According to [11], the self-coupling product of 1-aminonaphthalene I is 4-amino-1,1'-azonaphthalene resulting from the interaction of naphthalene-1-diazonium cation II with I at the 4-position of the amine molecule. At the same time, the possibility is discussed [11] for the formation of 1,1'-diazoaminonaphthalene (triazene) upon the electrophilic attack of the nitrogen atom in molecule I by cation II . The author of [11] reports nothing concerning the detection of 1-amino-2,1'-azonaphthalene (the result of coupling at position 2 of molecule I ).At the same tim...

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Structure of Sulfophthalexons, Chelating Analytical Reagents

Cited by 4 publications

References 6 publications

Tautomerism and Regioselectivity of the Protonation of 2-Pyrrolidone. Stereoselectivity of Complexation between Palladium(II), Chloride Ion, and 2-Pyrrolidone

Tautomerism and Regioselectivity of the Protonation of 2-Pyrrolidone. Stereoselectivity of Complexation between Palladium(II), Chloride Ion, and 2-Pyrrolidone

Manipulating Electron Transfer between Single-Walled Carbon Nanotubes and Diazonium Salts for High Purity Separation by Electronic Type

Analytical Azo Coupling Reactions: A Quantum-Chemical Consideration

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