Intercalation of Pyridine in Layered Titanates

The intercalation of pyridine has been examined for four types of layered protonic titanates such as H2Ti3O7, H2Ti4O9·1.2H2O, H2Ti5O11·3H2O, and HxTi2-x/4□x/4O4·H2O (x ∼ 0.7, □: vacancy). Upon the action of gaseous, liquid or aqueous pyridine at ambient temperature, the latter oxide peculiarly yielded a pyridine complex of composition (C5H5N)0.3HxTi2-x/4□x/4O4·0.6H2O while the other three materials did not. The intercalation compound lost weight in two steps of 40−120 and 120−320 °C, which were attributable to evaporation of interlayer water and of pyridine, respectively. Vibrational spectra suggested that pyridine was taken up as its protonated cationic form. Rietveld refinements demonstrated that the intercalation gave rise to an incommensurate gliding of neighboring host layers along the a axis (∼28% of its repeat unit) as well as an interlayer expansion. The pyridine ring is accommodated in an inclined way (∼64° with respect to the layer) having its nitrogen lone pair orientated parallel to the layer. The unique geometry of the interlayer gallery has the aromatic ring nestled into the corrugated host layers.