engleski

CHEMICAL EQUILIBRIUM AND STRUCTURE OF COMPLEXES IN THE 5, 6-PHENATHROLINE/TRICHLOROACETIC ACID SYSTEM

The phenanthroline systems are frequently employed in complexometric reactions. Their complex compounds are used in wide range of research, from quantitative analytical chemistry to study of reactions in living organisms. Because of their conjugate bonds they show strong absorption signals in IR and UV spectrum and therefore are suitable for spectroscopic study. There are nitrogen atoms present in the structure so they act as weak base. The system 5, 6-phenanthroline-trichloroacetic acid (5, 6-PHEN-TCA) was investigated by IR and UV spectrometry in dichloromethane solutions (CH2Cl2). Carboxyl peaks around 1700 cm− 1 were primarily monitored, while UV spectra showed changes of 5, 6-PHEN peaks, depending in what ratio were acid and base. It was found that TCA exists in the monomeric and dimeric forms and that monomeric form interacts with 5, 6-PHEN by forming complex. When an acid is in excess (ratio 5, 6-PHEN:TCA = 1:2 ; 1:4) there si significant change in color of solution of 5, 6-PHEN. Protonation of 5, 6-PHEN was verified with X-ray structure analysis. 5, 6-PHEN:TCA = 1:2 complex is actually a salt in which a cation is 5, 6-PHEN with one nitrogen atom protonated while an anion is trichloroacetat. The other molecule of TCA is undissociated.

5; 6-phenanthroline; trichloroacetic acid; IR and UV/VIS spectroscopy; X-ray crystallography; beta-cyclodextrin

nije evidentirano