Theoretical and experimental study of triphenylphosphonium Schiff base of 5-hydroxy-3-methyl-1-phenyl-4-formylpyrazole

ABSTRACT

The Schiff base (HLBr), containing a chelating unit and triphenylphosphonium moiety has been synthesized in the reaction of 4-aminobenzyl(triphenyl)phosphonium bromide with 5-hydroxy-3-methyl-1-phenyl-4-formylpyrazole. The composition and structure of HLBr have been determined by elemental analysis, IR, 1D and 2D NMR, electronic spectroscopy and mass spectrometry. Density functional theory (DFT) calculations (6-311G(d,p) level of theory) have been carried out to investigate tautomeric forms of HL⁺ and the reaction mechanism of its formation and spectral properties. The most stable form in the solid state and in DMSO solution is pyrazolone (keto-amine) tautomeric form.

GRAPHICAL ABSTRACT

KEYWORDS:

• phosphonium salts
• quantum-chemical calculations
• schiff base
• tautomerism

Acknowledgments

This work was supported by the RA MES SCS, within the frames of the «RA MES SCS – YSU-RF SFEDU» joint project No. VnGr-07/2017–35, Ministry of Education, Science and Technological development of the Republic of Serbia (Grant OI 172055) and taking advantage of the facilities of Resource Centers of SFEDU (“Molecular spectroscopy”, “High-productive calculations” and “Nanoscale structure of matter”).

Additional information

Funding

RA MES SCS – YSU-RF SFEDU (VnGr-07/2017-35) Ministry of Education, Science and Technological development of the Republic of Serbia (Grant OI 172055).