Series of Comparable Dinuclear Group 4 Neo-pentoxide Precursors for Production of pH Dependent Group 4 Nanoceramic Morphologies

A series of similarly structured Group 4 alkoxides was used to explore the cation effect on the final ceramic nanomaterials generated under different pH solvothermal (SOLVO) conditions. The synthesis of [Ti(mu-ONep)-(ONep)(3)](2) (1, ONep = OCH2C(CH3)(3)) and {[H][mu-ONeP)(3)M-2(ONaP)(5)(OBut)]} where M = Zr (2) and Hf (3, OBut = OC(CH3)(3)) were realized from the reaction of M(OBut)(4) (M = Ti, Zr, Hf) and H-ONep. Crystallization of 1 from py led to the isolation of [Ti(mu-ONep)(ONep)(3)](2)(mu-py) (1a) whereas the dissolution of 2 or 3 in py yielded {(mu-O)(mu(3)-OBut)[(mu-ONep)M(ONep)(2)](3)} M = Zr (2a) and Hf (3a). The structurally similar congener set of 1-3 was used to investigate variations of their resultant nanomaterials under solvothermal conditions at high (10 M KOH), low (conc. (aq) HI), and neutral (H2O) pH conditions. Reproducible nanodots, -squares, and -rods of varied aspect ratios were isolated based on cation and the reaction pH. The hydrolysis products were reasoned to be the seed nucleation sites in these processes, and studying the hydrolysis behavior of 1-3 led to the identification of [Ti-6(mu(3)-O)(7)(mu-O)(mu-ONep)(2)(ONep)(6)](2) (1b) for 1 but yielded 2a and 3a for 2 and 3, respectively. A correlation was found to exist between these products and the final nanomaterials formed for the acidic and neutral processes. The basic route appears to be further influenced by another property, possibly associated with the solubility of the final nanoceramic material.