FT-IR SPECTROSCOPIC INVESTIGATION OF 4,4'-BIPYRIDINE ADSORPTION ON METAL-OXIDE SURFACES

4,4'-Bipyridine (4bipy) adsorption on the surfaces of silica, alumina, and titania and the infrared (IR) spectra obtained therefrom are repo rted for the first time. This paper constitutes the second part of a m ulti-faceted investigation into the development of a vibrational spect roscopic technique for the determination of distances between surface acid sites of three-dimensional solid acids. The aforementioned oxides were chosen because their surface chemistries are generally well unde rstood and because they constitute the pillars within pillar interlaye red clay (PILC) catalysts. However, there is little information in the literature regarding the surface interactions of this novel and poten tially useful spectroscopic probe. The pore structures of PILC materia ls have been investigated through 4bipy adsorption, the results of whi ch will be reported in a later paper. The spectra obtained for adsorpt ion on the parent oxides are discussed with reference to earlier 4bipy and 2,2'-bipyridine (2bipy) adsorption studies and indicate that the mode of adsorption is a unidentate, ''end-on'' arrangement in agreemen t with that observed for adsorption on MgO. This mode of adsorption re sults in a reduction in molecular symmetry of the adsorbed 4bipy from D-2h to C-2v. A previously unreported observation involving the high-t emperature cleavage of the inter-ring bond of 4bipy adsorbed on gamma- alumina and titania Lewis acid sites is described.