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    Robust Co(II)-Based Metal-Organic Framework for the Efficient Uptake and Selective Detection of SO2
    (ACS Publications (American Chemical Society), 2024-03-26) López-Cervantes VB; López-Olvera A; Obeso JL; Torres IK; Martínez-Ahumada E; Carmona-Monroy P; Sánchez-González E; Solís-Ibarra D; Lima E; Jangodaz E; Babarao R; Ibarra LA; Telfer SG
    MUF-16 is a porous metal-organic framework comprising cobalt(II) ions and 5-aminoisophthalate ligands. Here, we measured its reversible SO2 adsorption-desorption isotherm around room temperature and up to 1 bar and observed a high capacity for SO2 (2.2 mmol g-1 at 298 K and 1 bar). The uptake of SO2 was characterized by Fourier transform infrared (FT-IR) spectroscopy, which indicated hydrogen bonding between the SO2 guest molecules and amino functional groups of the framework. The location and packing of the SO2 molecules were confirmed by computational studies, namely, density functional theory (DFT) calculations of the strongest adsorption site and grand canonical Monte Carlo (GCMC) simulations of the adsorption isotherm. Furthermore, MUF-16 showed a remarkable selective fluorescence response to SO2 compared to other gases (CO2, NO2, N2, O2, CH4, and water vapor). The possible fluorescence mechanism was determined by using time-resolved photoluminescence. Also, the limit of detection (LOD) was calculated to be 1.26 mM (∼80.72 ppm) in a tetrahydrofuran (THF) solution of SO2
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    Investigations in vortex molecule dynamics and ring current generation in Bose-Einstein condensates : a dissertation presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Physics at Massey University, Albany, New Zealand
    (Massey University, 2023) Choudhury, Sarthak
    Topological excitations are a special type of long-lived excitation that are impervious to small perturbations in cold atom systems. This thesis aims to investigate properties of two different topological excitations in two-dimensional condensates using the Gross Pitaevskii equations (GPE). The majority of this thesis investigates the dynamics of a vortex molecule in coherently coupled Bose-Einstein condensates in different trap geometries. A vortex molecule consists of two vortices in separate condensates bound together by a Josephson vortex (also called a domain wall). We aim to shed light on vortex molecule dynamics using a simple point-vortex framework. Firstly, we extend the point vortex framework to account for the domain wall using a parametrized interaction energy. The interaction energy is parametrized in special boundary conditions that emulate an infinite plane. We then use this extended point vortex model to investigate the phase space and the dynamics of a vortex molecule in a flat-bottomed channel trap. Our extended model captures all the essential features of the phase space and agrees with GPE simulations of a vortex molecule in a trap. We then expand the point vortex framework further to account for the effect of the boundaries on the Josephson vortex by using a distributed vorticity model. We use this continuous vorticity model to investigate the precession frequency of a vortex molecule in an isotropic disc and find support for our model. Additionally, we investigate a protocol to create persistent supercurrents in a ring shaped single condensate. Though this protocol has been showed to adiabatically create ring currents in ideal one-dimensional rings by Fialko et.al. [Phys. Rev. Lett. 108, 250402 (2012)], we use this protocol for two-dimensional rings and find the emergence of ring currents non-adiabatically.
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    From triangles to rings : colourful clusters of substituted naphthalenediols : a thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemistry, School of Natural Sciences at Massey University
    (Massey University, 2022) Dais, Tyson
    Coordination chemistry is perhaps one of the most base-level fields within chemistry, with a rich past and an ever expanding future. Existing in a relatively newer niche, however, is the field of single molecule magnetism, sitting at an intersection between synthetic chemistry and chemical physics with an aspiring road leading to materials chemistry and advanced information technology. While the fundamentals of the field are established, it has not yet reached the stage of implementing single molecule magnet technology, for which a broader understanding is needed. A crucial part of this is the ability to interpret magneto-structural correlations, to understand the ways in which molecular structure effects the electronic structure of the metal ions, and hence their performance as single molecule magnets. A series of new homo- and heterometallic complexes are reported; which, where possible, have been magnetically characterized. A non-macrocyclic triangular complex featuring a planar Cu₃TbO₆ core represents the first of its class to exhibit slow relaxation of magnetization in zero applied field, a characteristic of single molecule magnets, while similar Cu₃Gd, Cu₃Dy, and Ni₃Gd complexes show field supported magnetic properties. The regularity with which the Cu₃Ln and Ni₃Ln complexes crystallize, and the observation of ferromagnetic ground states for each, exemplifies the reliability of the present synthetic strategy to produce potential single molecule magnets. The Co₃Ln complexes presented here were found to have variable cobalt coordination geometries, a subtle effect induced by the size of each lanthanide, with the Co₃Dy complex being the sole example of purely octahedral cobalt centres. Magnetic measurements of Co₃La revealed a ground state spin of S = 3/2 with a relatively large zero-field splitting parameter, likely associated with the presence of a trigonal bipyramidal cobalt centre. A number of higher nuclearity complexes are also reported. Four variations of a Ni₁₆ molecular wheel have been crystallographically identified, three of which are nearly-isostructural acetate containing polymorphs and the last of which is a formate analogue. One polymorph exhibited a capsule like packing arrangement within its crystal structure, however, attempts to drive the inclusion of a guest molecule were unsuccessful. Synthetic efforts to produce a copper based analogue resulted in the unexpected formation of a Cu₁₄ cluster which exhibited the same binding pattern as Ni₁₆. Two manganese containing complexes, Mn₈ and MnLa₆, were also obtained where the former exhibited the relatively uncommon homometallic square-in-square architecture.
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    Graph theoretic and electronic properties of fullerenes, &, Biasing molecular modelling simulations with experimental residual dipolar couplings : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University, Albany, New Zealand
    (Massey University, 2015) Wirz, Lukas N
    In this thesis two different models, that is levels of abstraction, are used to explore specific classes of molecular structures and their properties. In part I, fullerenes and other all-carbon cages are investigated using graphs as a representation of their molecular structure. By this means the large isomer space, simple molecular properties as well as pure graph theoretical aspects of the underlying graphs are explored. Although chemical graphs are used to represent other classes of molecules, cavernous carbon molecules are particularly well suited for this level of abstraction due to their large number of isomers with only one atom type and uniform hybridisation throughout the molecule. In part II, a force field for molecular dynamics, that is the step wise propagation of a molecular structure in time using Newtonian mechanics, is complemented by an additional term that takes into account residual dipolar couplings that are experimentally measured in NMR experiments. Adding this force term leads to more accurate simulated dynamics which is especially important for proteins whose functionality in many cases crucially depends on their dynamics. Large biomolecules are an example of chemical systems that are too large for treatment with quantum chemical methods but at the same time have an electronic structure that is simple enough for accurate simulations with a forcefield.
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    Static electric dipole polarizabilities of atoms and molecules : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemistry at Massey University, Albany, New Zealand
    (Massey University, 2004) Lim, Ivan S.
    The static dipole polarizabilities and ionization potentials of the first and second main group elements, including the charged ions, are obtained from all-electron relativistic coupled-cluster theory using a scalar relativistic Douglas-Kroll Hamiltonian. Spin-orbit coupling effects are investigated using a fully relativistic four-component Dirac-Coulomb-Hartree-Fock scheme followed by a second-order many-body perturbation treatment to account for electron correlation. Periodic trends in the dipole polarizabilities and the ionization potentials are discussed. In each case, a detailed discussion on electron correlation and relativistic effects are given. A relationship for relativistic and electron correlation effects between the dipole polarizability and the ionization potential is established. Particular attention is paid to the evaluation of a near basis set limit quality of the dipole polarizabilities. This is accomplished by the evaluation of all-electron basis sets used, followed by an extensive study on the convergence behavior of the dipole polarizabilities with respect to a finite basis set expansion. The present all-electron dipole polarizabilities are believed to be very precise, especially for charged ions where the availability of experimental values are limited. Scalar relativistic small-core pseudopotentials are fitted and their performance is tested in terms of static dipole polarizabilities and ionization potentials. It is demonstrated that the small core definition of the pseudopotential (nine-valence electron for the main group 1 and ten-valence electron for the main group 2 elements) enables us to safely omit core-valence correlation without scarifying accuracy. Following atomic dipole polarizabilities, applications are made to molecules starting with alkali dimers and their singly charged ions. The scalar relativistic pseudopotentials of this study are used to calculate equilibrium bond lengths, dissociation energies, vibrational frequencies and the dipole polarizabilities of these dimers. The change in the molecular dipole polarizabilities from the corresponding atomic dipole polarizabilities are discussed in terms of molecular bonding models. Simple ammonia complexes of the alkali-metals and their singly charged ions are studied. The equilibrium geometries, dissociation energies, harmonic vibrational frequencies as well as the dipole polarizabilities of these complexes are given.