Spectral properties of protonated naphthylpyridine in the presence of cyclodexrinsстатья
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Дата последнего поиска статьи во внешних источниках: 2 октября 2014 г.
Аннотация:Electronic absorption and fluorescence spectroscopy showed that the addition of 2-hydroxypropyl cyclodextrin derivatives (HP-a-CD, HP-b-CD, and HP-g-CD) to an aqueous solution
of 4-(2-naphthyl)pyridinium perchlorate (2) results in its partial deprotonation and formation
of an inclusion complex of 4-(2-naphthyl)pyridine (1) with the cavitand. The stoichiometry
and stability of the inclusion complexes of compounds 1 and 2 and 1-methyl-4-(2-naphthyl)
pyridinium perchlorate (3) with cyclodextrins and their hydroxypropyl derivatives (logK =
= 1.5—2.7) were studied by 1H NMR titration. Cyclodextrins with the neutral form 1 form
more stable complexes than with ionic compounds 2 and 3. The protonation of the nitrogen
atom of compound 2 in aqueous solutions can occur in both the ground and excited states, and
the fluorescence spectrum exhibits only the band of the protonated form. Quantum chemical
simulation of the deprotonation/protonation processes in an aqueous solution of compound 2
in the absence and presence of HP-b-CD was performed. A tendency for shifting the acid—base
equilibrium towards the formation of deprotonated form 1 is observed upon the addition of
2-hydroxypropyl cyclodextrin derivatives to the solution.