Dissertation/Thesis Abstract

Syntheses, Local Environments, and Structure-Property Relationships of Solid- State Vanadium Oxide-Fluorides
by Donakowski, Martin Daniel, Ph.D., Northwestern University, 2014, 373; 3615500
Abstract (Summary)

Vanadium oxide-fluorides can exhibit properties of piezoelectricity, second harmonic generation (SHG) activity, electrochemical activity, and other phenomena. The first two properties derive from the second-order and Jahn-Teller distortions, respectively, of d0 and d1 vanadium; the electrochemistry derives from the reduction of VV to V IV,III,II.

An examination of the immediate environment of a vanadium cation facilitates an understanding of how a cation influences the structure of a compound and its resulting properties. In the inorganic hydrate CuVOF4(H 2O)7, the CuVOF4(H2O)6 basic-building unit (BBU) has a Λ-shape that compels polar packing in a structure that has SHG properties. The compound is a very rare example of a carbonless, SHG-active molecular crystal. Influences for its packing are reasoned with principles previously used within organic molecular crystallography.

The early transition metals (ETMs) of vanadium, niobium, and molybdenum within compounds of formulae K10(M2OnF 11-n)X (M = VV, NbV, n = 2, M = Mo VI, n = 4; X = halide) show a related packing motif of Λ-shaped BBUs in different structures. Owing to the absence or presence of Λ-shaped BBUs, these heterotypical structures crystallize decidedly into SHG-inactive or SHG-active forms when M = VV or M = NbV, MoVI, respectively. The future use and development of Λ-shaped BBUs within solid-state systems can result in SHG-active materials.

The material CuVOF4(H2O)7 presents an interesting coordination: the late transition metal (LTM, CuII) coordinates solely to the oxide anion of the vanadyl cation owing to hard-soft acid-base (HSAB) properties. The materials Na2[M(H2O) 2][V2O4F6] (MII = Co, Ni, Cu) show the LTM coordinates solely to the oxide anions of the V V cation while the alkali cation (NaI) coordinates solely to the fluoride anions. These HSAB properties were used to generate layers of hard or soft cation/anion rich regions in the electrochemically-active double wolframite AgNa(VO2F2)2.

These structure-property examinations of solid state vanadium oxide-fluorides are presented as principles for (i) fundamental understanding of ETM and BBU crystallographic environments, (ii) materials discovery for fundamental investigations, (iii) materials design, and (iv) materials for use in SHG, piezoelectric, and electrochemical processes.

Indexing (document details)
Advisor: Poeppelmeier, Kenneth R.
Commitee: Ellis, Don E., Kanatzidis, Mercouri G., Mirkin, Chad A.
School: Northwestern University
Department: Chemistry
School Location: United States -- Illinois
Source: DAI-B 75/07(E), Dissertation Abstracts International
Subjects: Inorganic chemistry, Physical chemistry, Materials science
Keywords: Electrochemistry, Hydrothermal, Oxide-fluoride, Second-harmonic generation, Synthesis, Vanadium
Publication Number: 3615500
ISBN: 9781303815157
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