Intercalation behavior of some aromatic heterocyclic amines into alpha-titanium hydrogen phosphate

The aromatic amines 2-, 3-, 4-aminopyridine (2-, 3-, 4-amp), 1,4-phenylened iamine (phed), and 2-amino-4-methylpyridine (ammp) were intercalated into a lpha-titanium hydrogen phosphate, alpha-Ti(HPO4)(2). H2O (TiP). The interca lation was obtained by a batch method at 298 +/- 1 K. The maximum amount in tercalated was 3.37, 3.37, 6.40, 2.12, and 4.52 mmol of 2-, 3-, 4-amp, phed , and ammp, per gram of TiP, respectively. These aromatic amines expanded t he original interlamellar distance of 760 pm to 1338, 1177, 1262, 1338, and 1577 pm, respectively. With the exception of 2-amp and ammp, which are dis posed in an inclined position in the interlayer cavity, all of the other ba ses formed a monolayer in the interlamellar space, oriented in a perpendicu lar position in relation to the inorganic layers of the matrix. The infrare d spectra demonstrated that the basic centers of the aromatic amines are pr otonated by the phosphate groups attached to the inorganic layers, in a typ ical Bronsted acid-base interaction. The intercalated compounds lost water of hydration, organic material, and water of condensation of the phosphate groups on heating, to give pyrophosphate as final product. (C) 2000 Elsevie r Science Ltd.