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Qualitative Identification of Carboxylic Acids, Boronic Acids, and Amines Using Cruciform Fluorophores
Published on: August 19, 2013
Aromatic hydrazones derived from nicotinic acid hydrazide as fluorimetric pH sensing molecules: Structural analysis
T Benković1, A Kenđel1, J Parlov-Vuković2
1Division of Analytical Chemistry, Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, HR-10000 Zagreb, Croatia.
Structural analyses of aroylhydrazones reveal a stable ketoamine form stabilized by hydrogen bonds. Chloro- and methoxy-derivatives exhibit pH-dependent fluorescence, crucial for understanding molecular behavior.
Area of Science:
- Organic Chemistry
- Spectroscopy
- Computational Chemistry
Background:
- Aroylhydrazones are versatile organic compounds with diverse applications.
- Understanding their structural and photophysical properties is essential for designing new materials.
Purpose of the Study:
- To elucidate the structural characteristics of four aroylhydrazone derivatives.
- To investigate their behavior in solid state and solution using various analytical techniques.
- To explore the photophysical properties, particularly fluorescence, of substituted aroylhydrazones.
Main Methods:
- Solid-state and solution-state Nuclear Magnetic Resonance (NMR) spectroscopy (1D and 2D).
- Fourier Transform Infrared (FT-IR) (ATR) and Raman spectroscopy.
- UV-Vis spectrometry and spectrofluorimetry.
- Computational chemistry methods for structural analysis.
Main Results:
- All studied aroylhydrazones exist in a ketoamine (form I, CONHNC) tautomeric form, stabilized by intramolecular hydrogen bonding.
- In the solid state, intermolecular hydrogen bonding involving the CO group was observed.
- Chloro- and methoxy-substituted derivatives displayed pH-dependent and reversible fluorescence, linked to the protonation/deprotonation of the salicylidene moiety.
- Experimental spectroscopic data showed excellent agreement with computational predictions.
Conclusions:
- The ketoamine form is the predominant and stable structure for these aroylhydrazones.
- The electronic properties and fluorescence behavior of aroylhydrazones can be tuned by substituents and pH.
- Combined experimental and computational approaches provide a comprehensive understanding of aroylhydrazone structure-property relationships.
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