Intercalation Behavior ofn-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 [Sr 0.8 Bi 0.2 Ta 2 O 7 ], derived from an Aurivillius phase, Bi 2 SrTa 2 O 9, has been investigated. H 1.8 [Sr 0.8 Bi 0.2 Ta 2 O 7 ] can accommodate n -alkylamines (C m H m +1 NH 2; 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 [Sr 0.8 Bi 0.2 Ta 2 O 7 ] does not form any intercalation compound with pyridine, which is a weaker base, indicating that the protons in H 1.8 [Sr 0.8 Bi 0.2 Ta 2 O 7 ] 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 60°. Despite the relatively high proton content (1.8 H + per [Sr 0.8 Bi 0.2 Ta 2 O 7 ]), only 0.9−1.0 mol of n -alkylamines per [Sr 0.8 Bi 0.2 Ta 2 O 7 ] is intercalated. This observation can be reasonably interpreted based on the surface geometry of the perovskite-like slab and the size of n -alkylamines.