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Bell & Howell Information and Leaming 300 North Zeeb Road, Ann Arbor, MI 48106-1346 USA 800-521-WOO National Library Bibliothèque nationale 1*1 ofCanada du Canada Acquisitions and Acquisitions et Bibliographic Services services bibliographiques 395 Wellington Street 395. me Wellington Ottawa ON KIAON4 Ottawa ON KIA ON4 Canada Canada Your ii& Votre rélérence Our fib Notre reYrance The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sel1 reproduire, prêter, distribuer ou copies of this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/^ de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fiom it Ni la thèse ni des extraits substantiels may be printed or othenvise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. To TW and GS, two guys who were young and died. Abstract Ab initio, second-order, Meller-Plesset (MP2) perturbation theory calculations of the equilibrium geometries, harrnonic vibrational frequencies, relative stabilities, dipole moments, and static dipole polarizabilities are reported for 87 different 6n-electron monocycles containing boron and nitrogen. These include al1 17 azaborinines (cornmonly called azaborines) isosteric to benzene, 26 azaborinines isosteric to pyridine, 16 azaboroles, and 28 oxazaboroles. The rnost stable isomers have as many as possible consecutive BHNH groups and, where applicable, contain the substructure XBHNH, where X = N, NH, or O is the base- ring heteroatom. Planar conformations are stable minima for dl but 15 five-membered rings and one six-membered ring. Lower level calculations are unreliable in predicting which molecules are planar. Good agreement is found with the available electron diffraction and X-ray structures of substituted rings. The ratio of MP2 to Hartree-Fock (HF) hannonic frequencies is found to Vary around an average of 0.94. The polarizabilities, along with earlier results for the azoles, oxazoles, and azines, constitute a uniform quality data set for 120 heteroaromatic rings. Additive atom and bond polarizability modeIs which are accurate to within a few percent are constructed for the 104 planar molecules. The presence of boron causes scatter of the polarizabilities of isomers; hence the additive models of polarizability are less accurate than if only heterocycles containing C, N, and O are included. The relative aromaticities of azines, azoles, oxazoles, and thiazoles are analyzed using polarizabilities and bond orders. The MP2 polarizability anisotropy and the iii anisotropy of the n-polarizability-calculated through a combination of uncoupled Hartree-Fock and electron correlated data-predict quite different scales of arornaticity. HF bond orders combined with the accurate MP2 geometries, an alternative to the popular Gordy bond orders derived from assorted experimental geometries, are used in order to improve previously proposed geometry-based aromaticity indexes-the Harrnonic Oscillator Mode1 of Aromaticity, Pozharskii, Ring Current, and Bird Indexes. Acknowledgements My motivation to study science stems from my desire to think God's thoughts after him, to discover the bountiful creation in al1 its diversity, to bnng order out of chaos. The first and biggest thanks go to my wife, Chen Yu-Chu. Her tender encouragement helped me to overcome every obstacle on the path to my Ph.D. But more than that, she has made Our life together a wondehl adventure. Thanks to my little Rosalie Shinwei. Thanks to Dr. Thakkar, who motivated me to be careful, thoughtful, and productive. Thanks for generous financial support to Dr. Thakkar, NSERC for a Postgraduate Scholarship, the Department of Chemistry for three PhysicaVTheoretical Awards, and the School of Graduate Studies for conference travel. Thanks to Room 304 colleagues: Drs. Bündgen, Das, Hoffmeyer, Hu, Kassimi, Lin, Ms. Steeves, and visitors Drs. Koga and Sharma, al1 of whom contributed to a congenial, work-oriented atmosphere. Their example forrns much of my experience: ZL for leaving first, REH for endurance, PJB for doing charrning calculations first and reporting them later, HCH for being systematic, VJS for being a chemist, AKD for combined pride and humility, BKS for efficacious workmanship, TK for tenaciously pursuing furtdamentals. Most importantly, thanks to Dr. N. El-Bakali Kassimi, who taught me much about science and about Iife. Thanks to al1 the librarians of UNB for a11 their help. Thanks to Cornputer Services Department personnel for services rendered. In particular, thanks to Mr. Brian Kaye for cornputer time on his workstation. Thanks to al1 the secretaries of the Department of Chemistry. Thanks to Mr. Dan Drummond for mass spectrometry and other assistance. Thanks to al1 Department professors, including members of my Advisory Cornmittee: Dr. Fritz Grein for being a dynarnic, living example of a theoretical chemist to contrast with my own boss; Dr. Allan Adam, for his enthusiastic partiipation in Our Department; and Dr. Dave Magee for being a friendly, encouraging professor. Thanks to Dr. Jack Passmore for many things, including recommending this department. Thanks to Dr. Merrill Edwards for his kind words of encouragement along my joumey . Thanks to rny fellow students for giving me a bit of themselves through sharing their experiences. May life be long and worthy in this world and beyond! Thanks to my brothers, Daniel J. and Alan. V. W. for helping to create an atmosphere conducive to love of life, from my first memory till now. Finally, thanks to my parents, Mrs. Nan (Enns) Doerksen and Dr. Daniel W. Doerksen. Without their love for each other and for me, 1 would not be standing here today. Table of Contents O. Front Matter Title Page . i Dedication . ii Abstract . iii Acknowledgements . v Table of Contents . vi List of Tables xi List of Figures . xiv 1. Introduction 1.1 Overview of Introduction 1.2 Molecules Studied in this Thesis 1 .S. 1 Motivation for molecule choice . 1.2.1.1 Motivation for work on BN-containing heterocycles 1.2.1.2 Overview for the series 1.2.1.3 Details of the pattern of molecufes . 1 -2.2Nomenclature 1.2.2.1 General comments 1.2.2.2 Options and recommended narnes . 1.2.3 Previous work 1.2.3.1 Molecules not containing boron 1.2.3.2 Molecules containing boron . 1.2.3.2.1 Summary of review references . 1.2.3-2.2 Summary of moIecules previously synthesized 1.3 Properties 1.3.1 Geometries . 1.3.1.1 Experimental . 1.3.1.2 Calculated 1.3.1.2.1 Levels used 1.3.1.2.2 Choice of and accuracy of MP216-3 lG(d) . 1.3.1.2.3 Methods used for deteknining nonplanar geometries . 1.3.1.3 Comparison between experirnental and calculated geometries 1.3.2 Bond orders 1.3.3 Energies . 1.3.3.1 Ground state and zero-point . 1.3.3.2 Relative stabilities 1.3.3.3 Orbital energies . 1.3.4 Frequencies . 1.3.5 Dipole moments . 1.4 Polarizabilities . 1.4.1 Definition . 1.4.2 Practical uses of polarizability data 1.4.3 Experimental polarizabiIities 1 -4.4Theoretical polarizabilities . 1.4.4.1 Uncoupled Hartree-Fock 1.4.4.2 Coupled Hartree-Fock . 1.4.4.3Finite-field 1.4.4.4 Other . 1.4.4.5 Basis sets, and selection of ours 1.4.5 Theory vs experiment 1.4.6 Available polarizabilities of monocycles . 1.4.7 Additive models of polarizability . 1.4.7.1 Motivation for making additive models 1.4.7.2Explanation of Our procedure . 1.4.7.3 Other additive models of polarizability 1.4.7.4 Comparison with other models 1.5 Aromaticity . 1.5.1 Definition . 1.5.2 Brief introduction to criteria not included in this work . 1 S.2.1 Energetic 1 S.2.2 Magnetic 1.5.3 Summary of work of others on quantifying aromaticity . 1.6 Overview of Thesis . 1.6.1 OveraIl purpose . 1.6.2 Summary of thesis . 1.6.3 My contribution to work with CO-authors . 1.6.4 Publication details of chapters . 1.7 List of References 2. Azaborinines: Structures, Vibrational Frequencies, and Polarizabilities 2.1 Introduction . 2.2 Computational Methods 2.3 Equilibrium Geometries 2.3.1 Results 2.3.2 Comparison with Previous Calculations 2.3.3 Comparison with Experiment .