Intercalation behavior of n-alkylamines into a protonated form of a layered perovskite derived from Aurivillius phase Bi2SrTa2O9

Intercalation behavior of n-alkylamines into a protonated form of a layered perovskite, H-1.8[Sr0.8Bi0.2Ta2O7] derived from an Aurivillius phase, Bi2SrTa2O9, has been investigated. H-1.8[Sr0.8Bi0.2Ta2O7] can accommodate n-alkylamines (CmHm+1NH2; m = 4, 8, 12, 18) to form intercalation compounds via an acid-base mechanism. The interlayer distance increases to 2.071(2) (m = 4) 2.840(9) (m = 8), 3.83(1) (m = 12), and 5.17(2) (m = 18) nm. In contrast, H-1.8[Sr0.8Bi0.2Ta2O7] does not form any intercalation compound with pyridine, which is a weaker base, indicating that the protons in H-1.8[Sr0.8Bi0.2Ta2O7] are weakly acidic. The IR spectra of the intercalation compounds with n-alkylamines (m = 12 and 18) clearly show that n-alkyl chains possess an all-trans conformation. A linear relationship is observed between the interlayer distance and the number of carbon atoms in n-alkyl chains, and this corresponds to a bilayer arrangement of the n-alkyl chains with a tilt angle of 60degrees. Despite the relatively high proton content (1.8 H+ per [Sr0.8Bi0.2Ta2O7]), only 0.9-1.0 mol of n-alkylamines per [Sr0.8Bi0.2Ta2O7] is intercalated. This observation can be reasonably interpreted based on the surface geometry of the perovskite-like slab and the size of n-alkylamines.