Undergraduate Research at FIU (URFIU) Conference

Synthesis, Characterization and Hectorite Intercalation of Cationic Trinuclear Cu(II)- pyrazolate Complexes

Smectite clays are layered silicate minerals with space for cations in between and are naturally occurring as Na+, Ca2+ or Mg2+ variants, among others.1–3 The clays are thermally stable and are known to “swell” to incorporate even large cationic species.4–6 Since the layers of the silicate mineral are ordered in the z-direction, they offer the opportunity to orient molecules in a certain fashion suitable for a desired application, for example, asymmetric catalysis.7 Trinuclear Cu(II)-pyrazolato complexes possess a wide variety of structural, electrochemical and magnetic properties.8 Our laboratory has published several cationic trinuclear complexes with the general formula, [Cu3(µ3-OH)(µ-4-R-pz)3(py)3]2+, where, pz- = pyrazolato anion, py = pyridine, R = H or Cl as their triflate (CF3SO3-) salts.8 The complexes exhibit an approximately planar arrangement of the metal centers and pyrazolate ligands, and it has been observed that the position of the µ3-ligand strongly influences the magnetic properties of the complexes. The goal of this research is to synthesize the above complexes and other analogs, where R = Br, I or NO2, using py or pyrazole as terminal ligands to study the effect of intercalation into hectorite, a smectite clay, on their spectroscopic and magnetic properties. To this end, several Cu(II)-pyrazolate compounds were synthesized using a Cu(II) salt (Cu(ClO4)2 or Cu(CF3SO3)2), pyrazole, a base (NaOH or Et3N), and a terminal ligand (either 1H-pyrazole or pyridine) with methanol, acetonitrile or dichloromethane as solvent. The compounds have been purified by crystallization and new compounds have been structurally characterized using single-crystal X-ray diffraction. The compounds were then reacted with hectorite and studied using FT-IR and X-ray powder diffraction. Preparation of various Cu3-pyrazolate-hectorite composites for magnetic studies are in progress in our laboratory. We present here our findings from the project.