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Synthesis of Pyridyl and N‐Methylpyridinium Analogues of Rosamines: Relevance of Solvent and Charge on Their Photophysical Properties

Leite, Andreia ; Cunha‐Silva, Luís ; Silva, Daniel ; Lobo Ferreira, Ana I. M. C. ; Santos, Luís M. N. B. F. ; Cardoso, Inês C. S. ; Silva, Vera L. M. ; Rangel, Maria ; Silva, Ana M. G.

Chemistry : a European journal, 2019-11, Vol.25 (66), p.15073-15082 [Periódico revisado por pares]

Germany: Wiley Subscription Services, Inc

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  • Título:
    Synthesis of Pyridyl and N‐Methylpyridinium Analogues of Rosamines: Relevance of Solvent and Charge on Their Photophysical Properties
  • Autor: Leite, Andreia ; Cunha‐Silva, Luís ; Silva, Daniel ; Lobo Ferreira, Ana I. M. C. ; Santos, Luís M. N. B. F. ; Cardoso, Inês C. S. ; Silva, Vera L. M. ; Rangel, Maria ; Silva, Ana M. G.
  • Assuntos: Alkylation ; Chemical compounds ; Derivatives ; Fluorescence ; Fluorescence spectroscopy ; Fluorophores ; Heating ; Iodides ; Nitrogen ; NMR ; Nuclear magnetic resonance ; nucleophilic addition ; ohmic-heating ; Oxidation ; Phenols ; photophysical properties ; Physicochemical properties ; Propionic acid ; Reaction kinetics ; rosamines ; Spectral analysis ; Spectrum analysis ; Xanthene ; xanthenes
  • É parte de: Chemistry : a European journal, 2019-11, Vol.25 (66), p.15073-15082
  • Notas: ObjectType-Article-1
    SourceType-Scholarly Journals-1
    ObjectType-Feature-2
    content type line 23
  • Descrição: A series of pyridyl analogues of rosamines was prepared by employing two methodologies: (i) the conventional‐heating condensation of a pyridinecarboxaldehyde with 3‐(diethylamino)phenol in propionic acid, and (ii) the novel ohmic‐heating assisted condensation under “on water” conditions, followed by oxidation. The 4‐pyridyl substituted rosamine was further converted into the N‐methylpyridinium derivative through N‐alkylation using methyl iodide. The influence of the position and cationization of the nitrogen atom of the pyridyl ring in the physicochemical properties of fluorophores was investigated by 1H, 13C, 15N NMR spectral analysis, UV/Vis and fluorescence spectroscopy, single‐crystal X‐ray diffraction (4‐pyridyl and N‐methylpyridinium derivatives) and thermal‐behavior analysis. Curiously, for ethanolic solutions of 4‐pyridyl and N‐methylpyridinium derivatives an extinction of color and fluorescence over time was observed. This phenomenon was further studied and the data revealed that it is the result of nucleophilic addition of ethoxide ion to the central 9‐position of the xanthene. The kinetics of the process is slower for the 4‐pyridyl rosamine, which emphasizes the importance of the charge in the N‐methylpyridinium analogue in the reactivity of the molecule towards a nucleophile agent. This phenomenon is reversible, meaning that the compounds can be rapidly recovered by decreasing the pH, opening new avenues in the sensing applications of this class of rosamines. Pyridyl and N‐methylpyridinium analogues of rosamines: The ohmic‐heating approach to synthesize triarylmethane derivatives, followed by oxidative cyclization, is presented. The influence of the position and cationization of the nitrogen atom in the pyridyl ring was evaluated by photophysical and thermal behavior analysis. In addition, the quenching behavior of the highly reactive N‐methylpyridinium rosamine in ethanol is reported for the first time.
  • Editor: Germany: Wiley Subscription Services, Inc
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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