Halasyamani, P. Shiv2017-08-162017-08-16May 20152015-05May 2015Previously published articles are reproduced or reproduced in part in this document with permission from: Tran, T. Thao, and P. Shiv Halasyamani. "New fluoride carbonates: centrosymmetric KPb2 (CO3) 2F and noncentrosymmetric K2. 70Pb5. 15 (CO3) 5F3." Inorganic chemistry 52, no. 5 (2013): 2466-2473. DOI: 10.1021/ic302357h. Copyright 2013 American Chemical Society; and from: Tran, T. Thao, P. Shiv Halasyamani, and James M. Rondinelli. "Role of acentric displacements on the crystal structure and second-harmonic generating properties of RbPbCO3F and CsPbCO3F." Inorganic chemistry 53, no. 12 (2014): 6241-6251. DOI: 10.1021/ic500778n. Copyright 2014 American Chemical Society; and from: Tran, T. Thao, Melissa Gooch, Bernd Lorenz, Alexander P. Litvinchuk, Maurice G. Sorolla, Jakoah Brgoch, Paul CW Chu, and Arnold M. Guloy. "Nb2O2F3: A reduced niobium (III/IV) oxyfluoride with a complex structural, magnetic, and electronic phase transition." Journal of the American Chemical Society 137, no. 2 (2015): 636-639. DOI: 10.1021/ja511745q. Copyright 2014 American Chemical Society.http://hdl.handle.net/10657/2019This dissertation focuses on the synthesis and structure-property relationships of new complex metal fluorides of (i) alkaline-metal lead fluorocarbonates, alkaline-metal magnesium fluorocarbontes and (ii) a reduced niobium oxyfluoride. We have designed new structure building units, PbO6F and PbO6F2, in layered compounds of KPb2(CO3)2F and K2.70Pb5.15(CO3)5F3, that were then developed to three-dimensional noncentrosymmetric RbPbCO3F and CsPbCO3F. Powder second-harmonic generation (SHG) measurements on K2.70Pb5.15(CO3)5F3, RbPbCO3F and CsPbCO3F using 1064 nm radiation revealed SHG efficiencies of approximately 40, 250 and 300 x a-SiO2, respectively. The Mg2+ substitution of the Pb2+ cation in APbCO3F (A = alkaline-metal) resulted in KMgCO3F and RbMgCO3F with unique coordination environments of magnesium, i.e., pentagonal arrangements in the ab-plane. These compounds are second-harmonic generation (SHG) phase-matching at both 1064 nm (120 and 160 x a-SiO2) and 532 nm (0.33 and 0.6 x b-BaB2O4) with short UV cut-off edges, below 200 and 190 nm for KMgCO3F and RbMgCO3F, respectively. These mixed-metal fluorocarbonates were also characterized by infrared spectroscopy, thermogravimetric and differential thermal analysis. In addition, we report a new highly correlated electron system, Nb2O2F3. It is a new low-valent niobium (III/IV) oxyfluoride that features [Nb2X10] units (X = O, F) with short (2.5739(1) Å) Nb-Nb metal-metal bonds. The [Nb2X10] units are connected through shared O/F vertices to form a 3D structure. Nb2O2F3 undergoes a structural transition (below 90 K), from a monoclinic to a triclinic structure, which can be described as a charge ordering or disproportionnation of [Nb2]7+dimers. That resulted in a doubly (2.5000(9) Å) and a singly bonded (2.6560(9) Å) Nb2 dimers. The structural change is associated with unusual field-independent ‘spin-gap-like’ magnetic and electronic phase transition.application/pdfengThe author of this work is the copyright owner. UH Libraries and the Texas Digital Library have their permission to store and provide access to this work. UH Libraries has secured permission to reproduce any and all previously published materials contained in the work. Further transmission, reproduction, or presentation of this work is prohibited except with permission of the author(s).Nonlinear opticsHighly correlated electron2017-08-16Thesisborn digital