Intercalation of aromatic amines into α-tin(IV) hydrogenphosphate monohydrate

Abstract

Aromatic amines such as o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, benzidine, and 2-amino-4-methylpyridine were intercalated into tin(IV) hydrogen phosphate monohydrate (α-Sn(HPO4)2•H2O). o-Phenylenediamine and 2-amino-4-methylpyridine form a bilayer, while m-phenylenediamine, p-phenylenediamine, and benzidine form a monolayer. Phenylenediamines are monoprotonated on the interlayer surface of the phosphate, whereas benzidine is diprotonated. 2-Amino-4-methylpyridine exhibits a different behaviour with respect to pyridine, because the positive charge is localized between the two nitrogen atoms and not delocalised along the aromatic ring as in pyridine. The intercalation of benzidine causes a great shift in the relative position of the phosphate layers to accommodate the organic molecules. All products were characterized by chemical analysis, DTA-TG, IR spectroscopy, diffuse reflectance spectroscopy, and X-ray diffractometry. Keywords: intercalation, aryldiamines, benzidine, 2-amino-4-methylpyridine, α-Sn(HPO4)2•H2O.