Date on Master's Thesis/Doctoral Dissertation

8-2020

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Chemistry

Degree Program

Chemistry, PhD

Committee Chair

Grapperhaus, Craig A.

Committee Member

Buchanan, Robert

Committee Member

Kozlowski, Pawel

Committee Member

Sumanasekera, Gamini

Author's Keywords

Water cluster motifs; hydrated structures; N-methyl imidazole derivatives; tunable conductivity; reversible moisture adsorption/desorption

Abstract

Water is a remarkable molecule and in all of its forms exhibits an amazing collection of properties and functions. Besides its crucial role in life and many technological processes, water displays some unusual and anomalous properties at various interfaces and under different conditions. Although the role of hydrogen-bonding interactions and their fluctuations are well known to determine the properties of water, the main obstacle exists in the complexity of correctly describing the interactions between water molecules. The key to understanding the behavior of water is to collect precise structural data of various H-bonded water networks in diverse environments. In this dissertation, the formation of various water cluster motifs is investigated in a series of structurally similar complexes. Their thermal and electrical properties are studied using characterization techniques including, X-ray crystallography, UV-visible spectroscopy, IR, thermal analyses, electrochemical impedance spectroscopy (EIS) and two-probe resistance measurement studies. Chapter III focuses on a group of structurally related Ni(II) complexes containing N3X (X = S or O) donors. The complexes crystallize with water of hydration forming extended H-bonding networks. The morphology of the network is dependent on small changes in the ligand framework leading to different orientations of the carboxamido oxygens, which influences the solid state packing, H-bonding patterns and accordingly thermal and electrical properties. Chapter IV builds on chapter III through modification of the steric bulk around the carboxamido-O which result in isostructural complexes confining 1D coiled water wires in their crystal lattice and show quite similar packing pattern and thermal properties. Chapter V continues to study on electrical properties of one of synthesized complexes in Chapter IV. It explains the reversible surface conductivity changes upon variation of water vapor pressure for a single crystal.

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