Muscovite mica is a layered silicate mineral made up of ca. Mononuclear, binuclear, and polymeric ruthenium(II) complexes 10 A ˚thick silicate sheets bound together by potassium ions with 2,2-bipyridine (bipy) and tetrapyridophenazine (tppz) ligands (7). It is available as sheets or powders. The surfaces are were adsorbed via ion exchange onto an ultrahigh-surface-area mica molecularly flat, and, for that reason, mica sheets are extenwith exchangeable lithium surface ions. The adsorption isotherms sively used as the substrate in AFM, STM, and surface force were measured. The ion exchange isotherms and desorption experimeasurement studies (8-13). The mica surface ions can be ments show that the affinity of the complexes to mica is higher than exchanged with other organic or inorganic ions ( 14). Dethat of lithium or potassium ions. The surface ion exchange capacities pending on the experimental conditions and the size of the were determined and the space requirements of the complexes on ions, the degree of exchange may be either partial or complete.
the mica surface were calculated. These requirements depend on the ligands. For all the complexes studied, the large dimensions of the From crystal structure determinations the inorganic exchange complexes did not permit a complete exchange of the surface lithium sites on the platelet basal plane surfaces are 3.48 mmol/m 2 or ions. For the initial part of the isotherm, it could be demonstrated approximately 48 A ˚2 per site (15). With adsorbing ions larger that adsorption of the complexes was accompanied by the release of than ca. 48 A ˚2 per charge, it appears that complete exchange two lithium ions per ruthenium ion. The experimentally determined of the surface inorganic ions does not occur. In such cases, space requirements of the ions were in reasonable agreement with both ions are present, presumably in a more or less ordered those estimated by computer modeling. From UV-vis measurements, mosaic structure. In the present studies, the micas used were it appears that, depending on the complex, the ligand sphere is disultrahigh-specific-surface-area powders well suited for ion extorted upon adsorption. ᭧ 1997 Academic Press change adsorption experiments (16, 17). Because of their high