7-hydroxyflavylium compound

Fig. 12 Energy level diagram for the species involved in the equilibria of the 4 -hydroxyflavylium compound.1171...

Fig. 22 A write-lock-read-unlock-erase cycle with two memory levels, based on the 4 -hydroxyflavylium compound. ...

Fig. 23 Absorbance oscillations resulting from alternating pH-jump and light excitation in a 3.3 x 10-5 M aqueous solution starting from the AH+ form of the 4 -hydroxyflavylium compound at pH = l. 17 ...

For the 4,-hydroxyflavylium compound in the presence of micelles, 18 starting from Ct at pH 5.0 and taking the formation of the AH+ absorption at 436 or 450 nm as an output, the tmth table for the effect of the three inputs (pH-jump to 1.0, addition of SDS, light excitation) shows a peculiar pattern (Table 3) corresponding to an OR function, which is activated only in the presence of the third input (enabled OR). 

Tab. 2 Truth table for the AND logic behavior of the 4 -hydroxyflavylium compound, starting from Ct at pH = 5.5.

Each anthocyanidin is involved in a series of equilibria giving rise to different forms, which exhibit their own properties including color. One- and two-dimensional NMR have been used to characterize the various forms of malvidin 3,5-diglucoside present in aqueous solution in the pH range 0.3 to 4.5 and to determine their molar fractions as a function of pH. In addition to the flavylium cation, two hemiacetal forms and both the cis and trans forms of chalcone were firmly identified. In a reexamination, the intricate pH-dependent set of chemical reactions involving synthetic flavylium compounds (e.g., 4 -hydroxyflavylium) was confirmed to be basically identical to those of natural anthocyanins (e.g., malvidin 3,5-diglucoside) in... 

In flavylium compounds that bear OH substituents in their 4 - and/or 7-positions, deprotonation of the OH group can result in other forms being obtained, not seen in the case of the 4 -methoxyflavylium compound discussed above. Figure 8 illustrates this for the 4 -hydroxyflavylium ion.1171 The new species are the quinoidal base A, obtained by simple deprotonation of the AH+ flavylium cation, and the dianionic Cc2- and Ct2- forms, obtained by second deprotonations of Cc and Ct. The roles played by these forms depend on the specific compound and the pH conditions. For... 

An intuitive way to describe the interconversion processes in flavylium-type compounds is their description by a hydraulics analogy.1411 By such an analogy, the behavior of aqueous solution of flavylium ions upon a pH-jump from 1.0 to 4.2 can be schematically represented as in Figure 14. In the case of 4 -hydroxyflavylium, Cc... 

The hydraulic analogy can also be used to illustrate the photochemical behavior of these compounds, the light playing the role of a pump. The scheme shown in Figure 15 is appropriate for 4 -hydroxyflavylium. 

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