Hydration of the flavylium ion

McClelland, Robert A.; Gedge, Sherrin

doi:10.1021/ja00538a024

Cited by 167 publications

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“…For several flavylium compounds the rates of the as seven species can be involved (Scheme 1). McClelland thermal cis-trans isomerization reactions [Equation (4)] are and Gedge [5] investigated the thermal reactions of the flavy-much slower than the rates of the reactions involved in the lium cation in acidic and neutral aqueous solutions and other equilibria. In such a case, a pseudo-equilibrium can identified the five species connected by the following equili-be attained and Equations (10) to (13) can be used to evalubria:…”

Section: Equilibria In the Darkmentioning

confidence: 99%

“…[8] tistate/multifunctional compounds potentially useful for the design of molecular-level system for information proPrevious studies [7Ϫ10] have clearly shown that substitucessing. [11Ϫ13] ents in the 4Ј-or 7-positions have a strong influence in deSystematic investigations [5] [6] have shown that in acidic termining the thermal and photochemical reactivity of the and neutral aqueous solution flavylium ions can undergo different forms originating from synthetic flavylium ions. In order to extend the knowledge of the reversible transform- [a] Departamento de Química, ation processes that take place in this family of compounds, Centro de Química Fina e Biotecnologia, we have performed an investigation on the behaviour of the Universidade Nova de Lisboa, P-2825 Monte de Caparica, Portugal unsubstituted flavylium cation.…”

Section: Introductionmentioning

confidence: 99%

“…The thermal reactions of E-mail: fjp@dq.fct.unl.pt this compound in acidic and neutral solutions had already [b] Dipartimento di Chimica "G. Ciamician", been investigated by McClelland and Gedge. [5] By using the served transformations. In this work, we have (i) reexam-the sum of the concentrations of B 2 , C c , and C t and molar fraction given by Equation (8): [15a] ined the thermal reactions of the unsubstituted flavylium cation in acidic and neutral solution, (ii) extended the study to basic solutions, and (iii) investigated the effect of continuous and pulsed photoexcitation.…”

Section: Introductionmentioning

confidence: 99%

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Photo- and pH-Induced Transformations of Flavylium Cation: “Write–Lock–Read–Unlock-Erase” Cycles

et al. 1999

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Section: Equilibria In the Darkmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Photo- and pH-Induced Transformations of Flavylium Cation: “Write–Lock–Read–Unlock-Erase” Cycles

et al. 1999

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“…1,2 Interest in the anthocyanins stems from the fact that they are omnipresent in our diet, exhibit unusual chemical and photochemical properties, [3][4][5][6][7][8][9] and have potential for application as food dyes 1 and antioxidant additives. 10,11 The basic chromophore of anthocyanins is the 7-hydroxyflavylium ion ( Figure 1).…”

Section: Introductionmentioning

confidence: 99%

“…25 The complexity of the pH-dependent chemistry of anthocyanins makes it difficult to quantify experimentally many of the important properties of anthocyanins and of synthetic flavylium ions in aqueous solution. Thus, measurement of the acidity constant, pK a , of the ground state of AH + often requires the use of fast reaction techniques 5 (stopped flow) due to the rapidity of the competitive hydration reaction of AH + . The fact that hydration leads to the formation of the hemiacetal (B) and the isomeric chalcones (C E and C Z ) complicates the determination of the electronic spectra of the quinonoidal base (A).…”

Section: Introductionmentioning

confidence: 99%

A computational study of substituted flavylium salts and their quinonoidal conjugate-bases: S0 -> S1 electronic transition, absolute pKa and reduction potential calculations by DFT and semiempirical methods

Freitas¹,

Shimizu²,

Dias³

et al. 2007

J. Braz. Chem. Soc.

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As transições eletrônicas para os cátions flavílio e bases quinonoidais de dezessete sais deste cátion foram estudadas nos níveis semiempírico e DFT (teoria do funcional da densidade). O efeito do solvente nos espectros eletrônicos foi incluído pelo Modelo Contínuo Polarizado, PCM. As transições eletrônicas de menor energia foram assinaladas como transições HOMO→LUMO. Ambos os níveis de teoria forneceram bons resultados para as transições eletrônicas dos cátions flavílio, enquanto apenas os cálculos por TDDFT-PCM puderam ser empregados para as transições das bases quinonoidais. Foram feitos cálculos de pK a absoluto para nove sais de flavílio em nível DFT. Os valores de pK a calculados pela nossa parametrização do PCM forneceram resultados excelentes, com um desvio médio absoluto de menos de meia unidade de pK a . Foram calculados por DFT potenciais de redução para cinco cátions flavílio. Os resultados teóricos encontrados ficaram em boa concordância com os resultados experimentais após a correção de um desvio sistemático.The electronic transitions for flavylium cations and quinonoidal bases of 17 substituted flavylium salts have been studied at semiempirical and DFT (density functional theory) levels. Solvent effect on electronic spectra was included by Polarizable Continuum Model, PCM. We assigned longest-wavelength absorption maxima to HOMO→LUMO transition. Both levels of theory gave good results for electronic transitions of flavylium cations whereas only TDDFT-PCM calculations could be used for electronic transitions of their quinonoidal bases. We also performed absolute pK a calculations of nine flavylium salts at DFT level. The pK a calculated values by our PCM parameterization gave excellent results with mean absolute deviation less than a half of one pK a unit. One-electron reduction potentials were carried out for 5 flavylium cations at DFT level. The theoretical results found were in good agreement with experimental values after adjustment for a systematic deviation.Keywords: flavylium salts, anthocyanins, quinonoidal base, pK a calculation, time dependent-DFT IntroductionAnthocyanins constitute the major red and purple pigments in plants and can be found in fruits, flowers and leaves. 1,2 Interest in the anthocyanins stems from the fact that they are omnipresent in our diet, exhibit unusual chemical and photochemical properties, [3][4][5][6][7][8][9] and have potential for application as food dyes 1 and antioxidant additives. 10,11 The basic chromophore of anthocyanins is the 7-hydroxyflavylium ion (Figure 1). In nature, the flavylium ion typically has hydroxyl substituents at positions 3 (always glycosylated) and 5 (occasionally glycosylated) and the phenyl or B-ring has one or more hydroxyl or methoxy substituents. 1 The colors of natural and synthetic anthocyanins range from yellow to purple, depending on the degree of substitution of the 7-hydroxyflavylium ion chromophore. Rationalization of the chemical and photochemical properties of anthocyanins is complicated by the fact that, in aqueous solu...

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Multistate/Multifunctional Molecular-Level Systems: Light and pH Switching between the Various Forms of a Synthetic Flavylium Salt

et al. 1998

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The photochromic properties of the 4'-hydroxyflavylium ion (AH ) have been investigated in aqueous solution. This system can be interconverted between as many as ten different forms by light excitation and/or pH changes. In neutral or moderately acidic solution the thermodynamically stable form of this compound is trans-2,4'-dihydroxychalcone (Ct). Light excitation of Ct in acidic or neutral solution gives rise to cis-chalcone Cc (F 0.04 at 365 nm), which undergoes slow equilibration with three other forms, namely hemiacetal B, flavylium cation AH , and quinoidal base A. The relative amounts of the photoproducts depend on pH. At pH3 the only product is the colored AH . In neutral and moderately acidic solutions, the four photoproducts revert back to Ct by a slow thermal reaction (k 4.0 Â 10 À5 s À1, half-life 27 hours at 25 8C, pH 3), whose rate can be accelerated by increasing the temperature (k 1.8 Â 10À2 s À1 at 75 8C, pH 3), and by exploiting the photochemical conversion of Cc to Ct (F b 0.16 at 313 nm). At pH`1, AH is the thermodynamically stable form of the system. A pH jump from 1 to 12 causes the complete conversion of AH to the Cc 2À dianion. This species is relatively stable (half-life 400 hours at pH 12 and 25 8C). Its thermal and photochemical reactions (F 0.17 at 313 nm) lead to Ct 2À , which is the thermodynamically stable form of the system in basic solution. Ct 2À does not undergo any photochemical reaction. All the observed processes are fully reversible and accompanied by large changes in the absorption and emission spectra. The flavylium salt investigated represents a multistate/multifunctional molecular-level system. It has properties required by optical memory devices with multiple storage in two different memory levels and nondestructive readout capacity through a write ± lock ± read ± unlock ± erase cycle. Its light-and/or pH-induced transformations can be taken as a basis for simple logic operations and create an intricate network of chemical processes.

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Hydration of the flavylium ion

Cited by 167 publications

References 0 publications

Photo- and pH-Induced Transformations of Flavylium Cation: “Write–Lock–Read–Unlock-Erase” Cycles

Photo- and pH-Induced Transformations of Flavylium Cation: “Write–Lock–Read–Unlock-Erase” Cycles

A computational study of substituted flavylium salts and their quinonoidal conjugate-bases: S0 -> S1 electronic transition, absolute pKa and reduction potential calculations by DFT and semiempirical methods

Multistate/Multifunctional Molecular-Level Systems: Light and pH Switching between the Various Forms of a Synthetic Flavylium Salt

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