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Evstigneev, Maxim P.; Veselkov, D. A.; Djimant, L. N.; Davies, David B.; Veselkov, A. N.

doi:10.1023/a:1017921501011

Cited by 11 publications

(15 citation statements)

References 16 publications

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“…The algebraic and matrix approaches use analytical evaluations of the main equations of hetero-association model and are commonly referred to as 'analytical' approaches; algorithm approach is presented in Refs. [62,68]. All possible molecular complexes are generated by a special computer algorithm, which computes the concentration and contribution to the experimentally observed parameter from every type of complex, thereby ruling out the necessity to deal with analytical expressions.…”

Section: Analytical Approaches To Building Hetero-association Modelsmentioning

confidence: 99%

“…Complete removal of the problem of 'reflected' complexes and 'edge effects' was accomplished with respect to a reaction scheme reduced to no more than two hetero-stacks in all possible hetero-complexes in solution [75,76]. Removal of all these limitations was made possible by an N-component algorithmical model [62,68,77] and later by the two-component algebraic hetero-association model [66]. A step forward in expanding the algebraic approach towards N-component hetero-association was attempted with respect to mass balance equations, although no link to the experimental observable was provided to account for 'edge effects' [78].…”

Section: Evolution Of Non-cooperative Models Of Hetero-associationmentioning

confidence: 99%

“…The model of cooperativity in hetero-association is very specific to the system under study. To the best of our knowledge, there are only a few examples in the literature demonstrating the treatment of hetero-association in terms of the empirical cooperativity parameter, introduced with respect to formation of homo-and hetero-aggregates [59,64,68,80].…”

Section: Evolution Of Non-cooperative Models Of Hetero-associationmentioning

confidence: 99%

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Hetero-association of aromatic molecules in aqueous solution

Evstigneev

2014

International Reviews in Physical Chemistry

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Knowledge of the physical chemistry of small molecules complexation (the hetero-association) in aqueous solution is increasingly important in view of the rapidly emerging branch of supramolecular chemistry dealing with the formation of heterogeneous polymeric structures having specific functional roles. In this paper, the 50-year history of scientific studies of hetero-association of heterocyclic aromatic molecules in aqueous solution has been reviewed. Some important correlations of structural and thermodynamic parameters of complexation have been reported based on large data-set of hetero-association parameters accumulated to date. The fundamental problem of 'energetic composition' of π-stacking is extensively discussed. The review has shown that there are some gaps in our understanding of heteroassociation, which provides a challenge for further studies in this area.

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Section: Analytical Approaches To Building Hetero-association Modelsmentioning

confidence: 99%

Section: Evolution Of Non-cooperative Models Of Hetero-associationmentioning

confidence: 99%

Section: Evolution Of Non-cooperative Models Of Hetero-associationmentioning

confidence: 99%

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Hetero-association of aromatic molecules in aqueous solution

Evstigneev

2014

International Reviews in Physical Chemistry

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“…( 54) actinomycin D, 55) theaflavin, 56) novatrone (mitoxantrone) 57,58) and aromatic drugs [59][60] have been studied by NMR spectroscopy. It has been suggested that the imidazole moiety of caffeine is involved in the interaction with aromatic species.…”

Section: Stability Constants Of Rf-caffeine Complexmentioning

confidence: 99%

Effect of Caffeine Complexation on the Photolysis of Riboflavin in Aqueous Solution: A Kinetic Study

Ahmad

Ahmed

Sheraz

et al. 2009

CHEMICAL & PHARMACEUTICAL BULLETIN

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1363Riboflavin is a highly photosensitive compound and is degraded in aqueous solution by several mechanisms [1][2][3] including intramolecular photoreduction 4,5) and intramolecular photoaddition. [6][7][8][9] These reactions are affected by pH, 4,5,[10][11][12] solvent polarity and viscosity, 13,14) ionic strength, 15) buffer kind and concentration [6][7][8][9]16) and light intensity and wavelengths. [6][7][8][9]17) Various methods including the use of photostabilizers, incorporation into liposomes and cyclodextrin complexation have been used to stabilize riboflavin solutions in the presence of light. [18][19][20][21] Another approach to achieve stabilization of drugs is through complexation with caffeine and other agents. [22][23][24][25][26] Riboflavin is known to form molecular complexes with caffeine [27][28][29][30][31][32] which has been found to influence the rate of its chemical 33) and photochemical degradation.17) Riboflavin-caffeine complexation may improve the bioavailability 34) and therapeutic activity 35) of the vitamin. NMR studies have been conducted to understand the nature of association between caffeine and flavin mononucleotide 36) that may help in the understanding of the mode of riboflavin stabilization. The present work is based on a detailed study of the kinetics of riboflavin photolysis in the presence of caffeine over a wide range of pH using a specific multicomponent spectrophotometric method 12) for the determination of riboflavin and photoproducts. The kinetic data have been used to determine the stability constants for riboflavin-caffeine complex. The quantitative and kinetic evaluation of such interactions may suggest the possibility of achieving the stabilization of photolabile compounds and thus enhance their biological action. The chemical structures of riboflavin, its photoproducts and caffeine are shown in Fig. 1. ExperimentalThe materials and methods used are the same as previously described for a similar study.5) The photolysis of 5ϫ10 Ϫ5 M riboflavin (RF) solutions was carried out in the presence of 0.5-2.5ϫ10Ϫ4 M caffeine using a Philips HPLN 125 W high pressure mercury vapor fluorescent lamp (emission at 405 and 435 nm) 9) as the irradiation source. The spectral measurements on RF and degraded solutions were performed on a Shimadzu UV-1601 recording spectrophotometer using silica cells of 10 mm path length. The intensity of the fluorescent lamp was determined by potassium ferrioxalate actinome- The effect of caffeine complexation with riboflavin on the kinetics of riboflavin photolysis in the pH range 2.0-10.5 has been studied. The photolysis of riboflavin solutions (5؋10 ؊ ؊5 M) was carried out in the presence of caffeine (0.5-2.5؋10 ؊ ؊4 M) using a visible radiation source. A specific multicomponent spectrophotometric method was used for the determination of riboflavin and photoproducts in photolysed solutions. The apparent first-order rate constants (k) for the photolysis reactions range from 2.71؋10 ؊4 to 4.26؋10 ؊2 min Effect of Caffeine Complexation on the Photol...

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“…This result may be explained by the contribution from aliphatic side chain of the molecules which impedes the formation of high order aggregates, and was previously reported for variety aromatic molecules with branched side chains. [10] Another anticooperative contribution to σ may arise due to the loss of degrees of freedom (intrinsic attenuation of K on aggregate growth) upon aggregate formation [6b] . The aggregation parameters calculated using the AK-model taking into account this factor, display slightly better discrepancy as compared with the EK-model (supplementary information), which supports this conclusion.…”

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confidence: 99%

Measuring Self‐Association of Pt Complexes by ¹⁹⁵Pt NMR

et al. 2017

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A highly soluble neutral cyclometallated Pt complex of C N N type was prepared and its self‐aggregation in CDCl3 solution was studied by NMR dilution method. It was shown that 195Pt NMR can be used to quantify aggregation and therefore be potentially applied to many other Pt complexes. Two‐dimensional HMBC 1H‐195Pt technique increases sensitivity of experiment and allowed recording 195Pt chemical shift values at concentration as low as 1 mM and it was observed that opposite to shielding of aromatic protons, Pt nucleus is deshielded upon increase of concentration.

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Cited by 11 publications

References 16 publications

Hetero-association of aromatic molecules in aqueous solution

Hetero-association of aromatic molecules in aqueous solution

Effect of Caffeine Complexation on the Photolysis of Riboflavin in Aqueous Solution: A Kinetic Study

Measuring Self‐Association of Pt Complexes by ¹⁹⁵Pt NMR

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Untitled

Cited by 11 publications

References 16 publications

Hetero-association of aromatic molecules in aqueous solution

Hetero-association of aromatic molecules in aqueous solution

Effect of Caffeine Complexation on the Photolysis of Riboflavin in Aqueous Solution: A Kinetic Study

Measuring Self‐Association of Pt Complexes by 195Pt NMR

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Measuring Self‐Association of Pt Complexes by ¹⁹⁵Pt NMR