Abstract
Various phenazine derivatives, synthesized according to Wohl-Aue reaction, have been separated and identified by thin layer chromatography using adsorbent mixtures with mixed developers. This reaction gives various phenazine derivatives simultaneously. An attempt was made to investigate the conditions of developing solvents and adsorbents through thin layer chromatography of α- and β-substituted phenazine derivatives and the solvent mixture, benzene : chloroform : ethyl acetate (60 : 40 : 5) and adsorbents, Kiesel Gel H : Avicell SF (2 : 1) were found to give better results. The detection was made by their own yellow or red color, being deepened by addition of conc. HCl.
An influence of the substituents upon the Rf values was investigated and the mono-substituted derivatives which possess substituents at β-position were found to follow the substitution effects, COO> O>NH2>OCH3>H>Cl. However, α-mono-substituted phenazines showed an influence in the following order, COO>OCH3>NH2>O>H>Cl. Among the α-mono-substituted phenazines, OH, NH2 and COOH groups being at the peri position of the nitrogen in phenazine ring and being formed metal chelates, these phenazine derivatives show stronger intramolecular hydrogen bond and hence an internal action between substituents and adsorbents becomes weaker and then the Rf values are considered to be higher. It is characteristic of 1-hydroxyphenazine. Di-substituted phenazines at α-position, such as 1, 6- and 1, 9-phenazines were found to give higher Rf values than those at α- and β-positions, such as 1, 7- and 1, 8-phenazines.
As to the N-oxides, the pKa value of a ring nitrogen of phenazine nucleus is pretty low and so the interaction between the ring nitrogen and adsorbents are comparatively weak. However, with N-oxides of phenazine derivatives, the interaction becomes pretty stronger and so the Rf values will be decreased.
It is also very important to identify the formation of mixed ligand complexes and the identification of parental ligand metal complex formation are much essential. Metal chelates of 1-hydroxyphenazine, such as Cu2+, Ni2+ and Co2+ chelates, are found to be separable in the presence of a little amount of pyridine effectively over thin layer chromatogram. A role of pyridine in the thin layer chromatography of 1-hydroxyphenazine metal chelates is considered to play a formation of the ternary complexes.
