Temperature dependent absorption spectroscopy of some tautomeric azo dyes and Schiff bases

Joshi, H. C.; Kamounah, Fadhil S.; Zwan, Gert van der; Gooijer, C.; Antonov, Liudmil

doi:10.1039/b106241g

Cited by 69 publications

(63 citation statements)

References 18 publications

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“…2). 24,43 According to the calculations, shown in Figure 2, the implementation of an aza-15-crown-5 moiety could lead to stabilization of the enol form through hydrogen bonding between the OH group and the macrocyclic nitrogen. The complexation could fully reverse the equilibrium towards the keto form.…”

Section: Resultsmentioning

confidence: 99%

Tautocrowns: a concept for a sensing molecule with an active side-arm

et al. 2010

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A new sensing molecule containing aza-15-crown-5 as a receptor and 4-(phenyldiazenyl)naphthalen-1-ol as a signal converter has been synthesized. In the free ligand, the hydrogen bonding between the tautomeric OH group and the nitrogen atom from the macrocycle fully shifts the tautomeric equilibrium towards the enol form. The complexation reverses the equilibrium as a result of the strong interaction between the metal ion captured in the macrocyclic moiety and the tautomeric carbonyl group. The complex formation is accompanied by strong bathochromic (between 60 and 100 nm) and hyperchromic effects on the absorption spectra. Obviously, the tautomeric OH/C]O groups play the role of an active side-arm in the complexation, supporting it via formation of a 3D cavity and giving possibility for ejection of the guest compound under stimuli to shift the tautomeric process back.

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Section: Resultsmentioning

confidence: 99%

Tautocrowns: a concept for a sensing molecule with an active side-arm

et al. 2010

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“…In quantitative terms the relative stability is defined by the tautomeric constant and the corresponding ΔG value at room temperature. In the case of 1 the Gibbs free energy has been determined in three non-polar solvents: cyclohexane (1.42 kcal mol À1 ) [5], methylcyclohexane/toluene (1.26 kcal mol À1 ) [5] and in Fig. 5.…”

Section: The Tautomeric Equilibrium In Solutionmentioning

confidence: 99%

“…, is very sensitive to the solvent environment and the temperature [4,5]. In spite of the intensive spectral and theoretical investigations many questions about the effects influencing the tautomerism in azonaphthols remained unanswered, due to the impossibility to isolate the individual tautomers by switching of the equilibrium [6,7].…”

Section: Introductionmentioning

confidence: 99%

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Tautomerism in 1-phenylazo-4-naphthols: Experimental results vs quantum-chemical predictions

et al. 2012

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The reliability in the description of the tautomerism of 1-phenylazo-4-naphthol by using of HF and MP2 ab initio levels of theory and DFT methods with variety of pure GGA (OLYP), hybrid (B3LYP and B3PW91), long range corrected (LC-BLYP) and double-hybrid (B2PLYP and mPW2PLYP) functionals with large number of basis sets was estimated. In this evaluation three criteria were used: reproduction of the bond lengths in the structures of the individual tautomers, description of the non-planarity of the enol tautomer and prediction of the position of the tautomeric equilibrium (ΔG value) at 298 K. The results show that in substantial number of cases HF reasonably covers all requirements. The tested pure (OLYP) and hybrid functionals (B3LYP and B3PW91) fail in the prediction of the position of the equilibrium independent on the basis set. The situation is slightly better at the long range corrected functional (LC-BLYP), which give predominance of the enol tautomer at 6-31þG** and D95þþ**. The double hybrid functionals give very good description with D95þþ** basis set, but at substantial computational costs.

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“…2-Hydroxy Schiff base ligands are of interest mainly due to the existence of (O-H···N and N-H···O) type hydrogen bonds and tautomerism between the enol-imine and keto-enamine forms (Scheme 1). Tautomerism in 2-hydroxy Schiff bases both in solution and in the solid state was investigated using different spectroscopic techniques [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. In the spectra of solutions of these compounds different Schiff bases have been studied in both polar and non-polar solvents [5,6,8,9,11,13,16,20].…”

Section: Introductionmentioning

confidence: 99%