Crystal Growth And Characterization Of Reduced Early Transition Metal Compounds Grown Via Hydrothermal And Molten Flux Methods

Author

Anthony J. Cortese, University of South Carolina

Date of Award

2016

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

Sub-Department

College of Arts and Sciences

First Advisor

Hans-Conrad zur Loye

Abstract

Interest in new and facile ways to prepare early transition metal reduced oxides has recently been increasing. In the past difficult flux techniques involving vacuum furnaces, expensive metal tubing, complicated electrolytic reduction apparatuses, were used to achieve in situ reduction of fully oxidized transition metal precursors. Often times these techniques were coupled with use of a difficult flux, such as boric acid, which is hard to remove due to its insolubility in water at room temperature. These limitations can be circumvented in multiple ways, including carefully choosing a redox neutral flux, using evacuated fused silica tubes for reaction vessels, and employing metallic reducing agents such as powered molybdenum, vanadium, or zinc. Virtually no work has been done outside the realm of flux crystal growth. Nevertheless, the hydrothermal method for crystal growth can be employed to yield hybrid materials containing reduced early transition metals.

Through the successful utilization of a two-step hydrothermal method, four oxovanadium(IV) tartrates have been prepared and characterized with three out four having confirmed second harmonic generation activity and one exhibiting spin dimer magnetic behavior. Via a one step hydrothermal method involving an in situ reduction, one oxovanadium(IV) phosphate has been prepared and found to exhibit filled channels in two crystallographic directions.

Using the flux method many reduced molybdenum oxides and a related material have been prepared and characterized including the following series: Na_xLn_1-xMoO₄Ln = La, Ce, Pr,Nd, Sm, and Eu; Ln_~5Mo₃O₁₆ Ln = Ce, Pr, Nd and Sm; and Ln₅Mo₂O₁₂ Ln = Eu, Tb, Dy, Ho, and Er. Evidence of direct molybdenum to molybdenum bonding was in the Ln₅Mo₂O₁₂ series, and all compounds were found to order antiferromagnetically. A related material, La₂₀Mo₁₂O₆₃Cl₄, was found to exhibit an optical band gap in the visible region and is the first example of a purely inorganic material that contains molybdenum in a trigonal prismatic coordination environment.

Rights

© 2016, Anthony J. Cortese

Recommended Citation

Cortese, A. J.(2016). Crystal Growth And Characterization Of Reduced Early Transition Metal Compounds Grown Via Hydrothermal And Molten Flux Methods. (Doctoral dissertation). Retrieved from https://scholarcommons.sc.edu/etd/3742