Download Determining structure of copper complexes with nicotinic

25th Croatian meeting of chemists and chemical engineers, Poreč, 2017.
Determining structure of copper complexes with nicotinic acid
aroylhydrazones using attenuated total reflectance (ATR)
Određivanje strukture kompleksa bakra s aroilhidrazonima nikotinske kiseline
tehnikom prigušene totalne refleksije (ATR)
Adriana Kenđel,1 Snežana Miljanić,1 Darko Kontrec,2 Nives Galić1
1
Department of Chemistry, Faculty of Science, University of Zagreb, Zagreb, Croatia
Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Zagreb, Croatia
2
E-mail: [email protected]
Attenuated total reflectance (ATR) technique was used to study structure of copper
complexes with aroylhydrazones derived from nicotinic acid hydrazide and salicylaldehide
derivatives having different substituents on the benzene ring.
Aroylhydrazones can be involved in keto-enol tautomeric interconversion, when the
hydrogen atom in keto form moves from amino to carbonyl group, forming an enol form [1].
In addition, if aldehyde moiety has a hydroxyl group situated in ortho-position with respect
to the C=N double bond, the aldehyde part of the molecule can participate in keto-enol
equilibrium. Considering different tautomeric forms, aroylhydrazones can act as neutral,
monoanionic or dianionic O, N, O tridentate ligands [2]. Different tautomeric forms are
characterized by distinctive spectral features and can be distinguished by means of various
spectrometric methods, including vibrational spectroscopy.
In our previous studies it was found that in solid state and in solvents of different
polarities aroylhydrazones appear in keto-amine form, which is generally the most stable
one [1,3]. The ATR spectra of the complexes, formed due to complexation with copper(II)
chloride in molar ratios hydrazone/Cu 1/1 and 2/1, pointed that the form of hydrazone was
changed depending on substituents on the benzene ring. The spectra of the complexes in
1/1 ratio implied that hydrazones with hydroxyl group on the ortho-position alone or in
combination with chloro or methoxy group on the meta-position according to the C=N bond,
converted from keto-amine form to enol-imine form. If the two hydroxyl groups were
positioned on the ortho- or para-position according to the C=N bond, the ligand retained in
keto-amine form. It was also shown that the higher amount of the ligand (2/1 ratio) did not
affect complexation, except in case of hydrazone with the methoxy group, for which
different spectra were obtained, implying different tautomeric forms in 1/1 and 2/1
complexes.
References
[1] N. Galić, A. Dijanošić, D. Kontrec and S. Miljanić, Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy 95 (2012) 347‒353.
[2] N. Galić, M. Rubčić, K. Magdić, M. Cindrić and V. Tomišić, Inorganica Chimica Acta 366 (2011) 98‒
104.
[3] N. Galić, I. Brođanac, D. Kontrec and S. Miljanić, Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy 107 (2013) 263‒270.
The research was supported by the Croatian Science Foundation (project IP-2014-09-4841).