Aromatic hydrazones derived from nicotinic acid hydrazide as fluorimetric pH sensing molecules: Structural analysis by computational and spectroscopic methods in solid phase and in solution

作者：Benkovic T; Kendel A; Parlov Vukovic J; Kontrec D; Chis V; Miljanic S; Galic N

来源：Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy , 2018, 190: 259-267.

DOI：10.1016/j.saa.2017.09.038

• 1D and 2D NMR
• FT-IR
• Raman
• UV-Vis spectroscopy
• Fluorescence
• Computational study
• Fluorimetric pH sensors

Structural analyses of aroylhydrazones were performed by computational and spectroscopic methods (solid state NMR, 1 and 2D NMR spectroscopy, FT-IR (ATR) spectroscopy, Raman spectroscopy, UV-Vis spectrometry and spectrofluorimetry) in solid state and in solution. The studied compounds were N'-(2,3dihydroxyphenylmethylidene)-3-pyridinecarbohydrazide (1), N'-(2,5-dihydroxyphenylmethylidene)-3pyridinecarbohydrazide (2), N'-(3-chloro-2-hydroxy-phenylmethylidene)-3-pyridinecarbohydrazide (3), and N'-(2-hydroxy-4-methoxyphenyl-methylidene)-3-pyridinecarbohydrazide (4). Both in solid state and in solution, all compounds were in ketoamine form (form I, -CO-NH N=C), stabilized by intramolecular H-bond between hydroxyl proton and nitrogen atom of the C=N group. In solid state, the C=O group of 1-4 were involved in additional intermolecular H-bond between closely packed molecules. Among hydrazones studied, the chloro- and methoxy-derivatives have shown pH dependent and reversible fluorescence emission connected to deprotonation/protonation of salicylidene part of the molecules. All findings acquired by experimental methods (NMR, IR, Raman, and UV-Vis spectra) were in excellent agreement with those obtained by computational methods.

• 出版日期2018-2-5