Thermodynamics of Dissociation of <Emphasis Type="Italic">ortho</Emphasis>-Hydroxyphenylhydrazo-<Emphasis Type="Italic">β</Emphasis>-diketones and of Their Complexation with Copper(II) in Aqueous–Ethanol Solutions |
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| Authors: | Kamran T Mahmudov Maximilian N Kopylovich Maxim L Kuznetsov Abel M Maharramov Rafiga A Aliyeva Ismayil A Aliyev Abdulseyid A Azizov Armando J L Pombeiro |
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| Institution: | 1.Centro de Química Estrutural, Complexo I, Instituto Superior Técnico,TU Lisbon,Lisbon,Portugal;2.Baku State University,Baku,Azerbaijan |
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| Abstract: | The thermodynamics of dissociation of 3-(2-hydroxyphenylhydrazo)pentane-2,4-dione (H
2
L
1
), 5,5-dimethyl-2-(2-hydroxyphenylhydrazo)cyclohexane-1,3-dione (H
2
L
2
), 5,5-dimethyl-2-(2-hydroxy-4-nitrophenylhydrazo)cyclohexane-1,3-dione (H
2
L
3
), 1-ethoxy-2-(2-hydroxyphenylhydrazo)butane-1,3-dione (H
2
L
4
) and 1-ethoxy-2-(2-hydroxy-4-nitrophenylhydrazo)butane-1,3-dione (H
2
L
5
) and of their complexation with copper(II) was studied in aqueous–ethanol solutions by potentiometry and UV–vis spectrophotometry.
It was found that the thermodynamic parameters of the proton dissociation in H2L1–5 and of their complexation with copper(II) depend on the substituents in the aromatic and β-diketone fragments of the molecules. Thus, the acidic properties of H2L increase from H2L1 to H2L5, reflecting the electron-acceptor character of the substituents, whereas all of the thermodynamic functions tend to decrease
with increasing electron-withdrawing capacity of the substituents. The complexation of Cu(II) with H2L1–5 is exothermic, which is connected with the formation of two stable chelating cycles. |
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| Keywords: | |
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