EFFECTS OF MOLECULAR-STRUCTURE UPON COMPLEX-SUPPORT INTERACTIONS

Two cationic, copper metal complexes with different ligands were synthesized: ethylenediamine (en) [Cu(C2N8N2)(ClO4)2] and diethanolamine (Deta) {[CuC8H21N2O4]ClO4}. These complexes were mounted on Cab-O-Sil using nonaqueous impregnation techniques, and the loadings were determined at which multilayers formed. These samples were analyzed for copper, carbon, nitrogen and hydrogen content to determine if ligand dissociation occurred during the impregnation. Samples were decomposed in a thermal gravimetric apparatus to determine the kinetics of the thermolysis reaction in air, and the evolved gases were analyzed by gas chromatograph-mass spectrometry to determine the products of the thermolysis reaction. The results of these and earlier studies are summarized in a model that describes the effects of molecular structure upon complex-support interactions. Complexes with the ability to form hydrogen bond interactions between the ligand and the support form strong interactions with the surface of silica, whereas complexes without such hydrogen bond interactions are only weakly attracted to the silica surface. Strong interactions with the surface may also arise as a result of ligand dissociation and direct interaction of the metal ion with the surface oxygens. The charge on the complex and its shape play less important roles in determining the affinity of the metal complex with the silica.