Influence of ligand nature on the retention of heterocyclic azonaphthols and their chelates in thin-layer chromatography

摘要

The retention of Ni(II). Fe(III), Co(II, lID, Cu(II), and Pd(II) chelates of heterocyclic azonaphthols [l-(2-pyridylazo)-2-naphthol (PAN), l-(2-thiazolylazo)-2-naphthol (TAN), I-(5-chloro-2-pyridylazo)-2-naphthol (ClPAN). l-(5-bromo-2-pyridylazo)-2-naphthol (Bt-PAN), l-(5-bromo-2-thiazolylazo)-2-naphthol (Br-TAN), and l-(8-quinolylazo)-2-naphthoi (QAN)] was comparatively studied by thin-layer chromatography on silica gel (Silufol plates). For the majority of studied stationary phases and chelate, mobility increases in the order Cl-PAN < TAN < PAN < QAN, which corresponds to the order of protonation constants of the heterocycle nitrogen atom. The mobility of Bt-TAN chelates is higher than that of TAN chelates. In reversed-phase high-performance liquid chromatography, the retention increases in the order PAN < Cl-PAN < Bt-PAN: TAN < BrTAN, which is opposite to the order of retention in thin-layer chromatography. Evidently, it is the solubility of reagents and chelates in the mobile phase that determines their chromatographic behavior in thin-layer chromatography.