FT-IR ANALYSIS OF PILLARED CLAY PORE STRUCTURE VIA ADSORBED BIPYRIDINE SURFACE PROBE SPECIES

Adsorption interactions of the bidentate molecules 2,2'-bipyridine and 4,4'-bipyridine with the surfaces of different alumina-pillar interla yered clays have been investigated by FT-IR spectroscopy. These intera ctions were examined in an attempt to establish a spectroscopy method for the determination of interpillar distances in the galleries of pil lared clays. 2,2'-Bipyridine adsorbs in a bidentate C-2v interaction t o single Lewis acid sites on the surfaces of individual pillars and no t to adjacent pillars, indicating that the distances between binding s ites on adjacent pillars are too great to be successfully probed by th is molecule. 4,4'-Bipyridine maintains the D-2h symmetry of the free m olecule through interaction with Lewis acid sites on two adjacent pill ars simultaneously via both ends of the molecule, thereby exhibiting p ossible utility as a probe of the interpillar distance. Surface-adsorb ed monoprotonated 2,2'-bipyridinium cations are formed through interac tion with Bronsted acid sites on the pillared clay surfaces. The IR sp ectrum of the surface-adsorbed protonated species suggests C-2h transo id symmetry and is presented for the first time.