SYNTHESIS AND COMPUTATIONAL STUDIES OF 1-4-η- CYCLOHEXA-1,3-DIENE DERIVATIVES OF IRONTRICARBONYL COMPLEXES ________________________________________________________ OLAWALE FOLORUNSO AKINYELE April, 2015 SYNTHESIS AND COMPUTATIONAL STUDIES OF1-4-η- CYCLOHEXA-1,3-DIENEDERIVATIVES OF IRONTRICARBONYL COMPLEXES BY OlawaleFolorunsoAKINYELE B.Sc (Hons), M.ScIbadan. Matriculation Number 38303 A Thesis in the Department of Chemistry, Submitted to the Faculty of Science in partial fulfilment of the requirements for Degree of DOCTOR OF PHILOSOPHY of the UNIVERSITY OF IBADAN April, 2015. i ABSTRACT Metal complexes have interesting properties and varied applications in light emitting diodes. A number of substituted pyridine metal (Rhenium, Ruthenium and Iridium) complexes have been synthesised and characterised. However, the synthesis and characterisation of substituted pyridine iron complexes such as Tricarbonyl (1-4-η- pyridino-cyclohexa-1,3-diene) iron complexes for its light emitting property remain scanty. Therefore, this research was designed to synthesise, characterise and calculate the electronic properties of Tricarbonyl (1-4-η-5-exo-N-pyridino-2-cyclohexa-1,3-diene) iron complexes. TwelveTricarbonyl (1-4-η-5-exo-N-pyridino-cyclohexa-1,3-diene) iron complexeswere synthesised by the addition of pyridines to the dienyl ring of Tricarbonyl-1-5- η- cyclohexadienyl irontetrafluoroborate at room temperature, in solutions of acetonitrile. They were characterised using elemental analysis, infra-red (IR) and proton-nuclear magnetic resonance (1H NMR) spectroscopy. Their theoretical studies were carried out using Molecular Mechanics Force Field (MMFF), semi-empirical Parameterization Method three (PM3), Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TDDFT) with Becke three, Lee, Yang and Parr at 6-31G* level. The MMFF was used to obtain the stable conformer before subjecting each complex to geometry calculations. The geometrical and thermodynamic properties were obtained from PM3 while the electronic energy [Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO)], chemical potential, chemical hardness and electrophilicity index were obtained from DFT. The calculation of electronic-excited state was carried out using TDDFT. The calculated elemental compositions of the synthesised complexes were in agreement with the observed values. All the complexes had very sharp IR peaks at 1980 and 2055 cm-1 corresponding to the stretching vibrations of carbonyl bond attached to the metal. The 1H NMR spectra displayed well separated overlapping multiplets which are characteristic of the outer diene protons H1 and H4 at 3.2 ppm while the inner protons H2 and H3 appeared at 4.7 and 5.3 ppm respectively. The geometrical parameters ranged from 1.374 to 1.795 Å (bond lengths), 105.1 to 128.8 o (bond angles) and -8.9 to 128.5 o (dihedral angles). These properties were functions of the substituents on the rings. The thermodynamic parameters were: free energy change (-412.6 to -188.5 kJmol-1), enthalpy change (-237.3 to +4.7 kJmol-1) and entropy change (+595.2 to +697.3 Jmol-1K- 1) indicating that the formation of these complexes was spontaneous. The electronic ii properties were within the range of -9.8 to -9.1 eV and -6.1 to -4.8 eV (HOMO and LUMO energies) respectively, 3.3 to 4.5 eV (energy band gap), -6.9 to -7.9 eV (chemical potential), 1.6 to 2.2 eV (chemical hardness), 11.4 to 18.1 eV (electrophilicity index). These values were indicative of reactivities of these molecules. The electronic- excited state of methyl and dimethyl substituted complexes were triplets having 3.46, 3.42 and 3.40 eV excitation energies with 0.022, 0.039 and 0.019 oscillator strength. The amino substituted complexes were singlets with 4.34 eV excitation energy and 0.024 oscillator strength indicating their light emitting ability. The electronic-excited state of synthesised methyl, dimethyl, and amino substituted Tricarbonyl (1-4-η-pyridino-cyclohexa-1,3-diene) iron complexes are capable of emitting light via phosphorescence and fluorescence, and may be useful in light emitting diodes. Keywords: Molecular characterisation, Geometry optimisation, Quantum mechanical calculation, Electronic parameters. Word count: 489 iii ACKNOWLEDGEMENTS To God be the glory, great things He had done. Being a Ph D student in the University of Ibadan has been the most exciting part of my life. During my studentship, I had the fulfilment of working with a few talented individuals, who filled me with the valued knowledge, hard-work and good company. Firstly, I am grateful to the Department of Chemistry and the Postgraduate School for enrolling me for the graduate programme. My sincere thanks and gratitude go to Professor T. I. Odiaka and Dr I. A. Adejoro for their endless efforts and enthusiasm in administering and giving me the opportunity to learn and discover my intellectual ability. My special thanks go to Dr Semire who taught me how to use the Spartan programme. It is my pleasant duty to express my gratitude to all whose support and encouragement made my task much easier. I am short of words to thank, admire and appreciate the following people for their contribution towards making this dream a reality. They are Drs, A.J. Odola (of blessed memory), A.O. Bosede, I. A. Oladosu, N. O. Obi-Egbedi, OlufemiAdewuyi, Prof. M. O. Faborode and Mr Rufus Olasunkanmi. I wish to express my thanks to my colleagues at Adeyemi College of Education, Ondo for their most friendly cooperation and support in the needy hours, among whom are Adebayo Adesuyi, NiyiOmodara, OluwaseunFehintola, OlumuyiwaObijole and NiyiFamobuwa. Anthony Izuagie deserves a special mention. I express my profound thanks to the Head of Department of Chemistry, Professor A. AAdesomoju and other members of Staff of Chemistry Department, University of Ibadan. Finally I want to express my gratitude to my wife, Makanjuola for her intimate love and sacrifices that have brought and will continue to bring happiness into my life and the lives of our children, Damilola, Olamide and Moyosore. My appreciation goes to my junior brother Bimbola for his contribution and encouragement. To my parents, for their many years of love, support and expectations, I say a big thank you. iv CERTIFICATION This is to certify that Mr OlawaleFolorunsoAkinyelecarried out this research work in the Department of Chemistry, University of Ibadan, Ibadan Nigeria, under the supervision of Professor T.I. Odiaka and Dr I.A. Adejoro. ----------------------------------------- -------------------------------Timothy I.Odiaka. (Professor) Dr I. A. Adejoro, B.Sc, Ph.D (Wales), C.Chem. M.R.S.C. (London) B.Sc, M.Sc, Ph.D (Ibadan) Professor in Inorganic/Organometallic Chemistry Senior Lecturer in Physical Department of Chemistry ChemistryUniversity of Ibadan Department of Chemistry Ibadan, Nigeria. University of Ibadan Ibadan, Nigeria. v DEDICATION This research work is dedicated to my lovely wife Mrs M. A. Akinyele andthechildren, Damilola, Olamide and Moyosore for their understanding. vi TABLE OF CONTENTS ContentPage Title i Abstract ii Acknowledgements iv Certification v Dedication vi Table of Contents vii List of Figures x List of Plates xiii List of Tables xv List of Abbreviations xix CHAPTER ONE: INTRODUCTION 1-5 1.1 Introduction to Organometallic Chemistry 1 1.2 Historical background 1 1.3 Nature of bonding in Transition metal π-hydrocarbon complexes 2 1.4 The Concept of effective atomic number rule 2 1.5 Introduction to Computational Organometallic Chemistry 3 1.6 Organometallic complexes and luminescence 4 1.7 Aims of the research 5 CHAPTER TWO: THEORETICAL BACKGROUND AND LITERATUREREVIEW 6 2.1 Theoretical models 62.2 The Schrödinger’s wave Equation 7 2.3 Born-Oppenheimer Approximation 8 2.4 Hartree-Fock Approximation 9 2.5 Linear Combination of Atomic Orbitals Approximation 10 2.6 Correlated models 10 2.7 Semi empirical Molecular Orbital Models 11 2.8 PM3 Model or Method 11 2.9 Density Functional Theory(DFT) 12 2.10 Hybrid Functionals 14 vii 2.11 Basis sets 14 2.12 Band Energy 162.13 Quantum mechanical foundation for determination of Geometry and Energy 18 2.14 Reactivity indices 192.15 Electrophilicity index 21 2.16 Dipole moment 21 2.17 Polarizability 21 2.18 Koopman’s theory 22 2.19 Survey of synthetic methods 22 2.20 Literature review of theoretical methods 28 CHAPTER THREE: SYNTHESIS, MODELING AND COMPUTATIONAL DETAILS 44 3.1 Synthetic method 44 3.2 Addition of pyridines toTricarbonyl (1-5-η-cyclohexadienyl) iron tetrafluoroborate [Fe(CO)3(1-5-η-C6H7)]BF4 44 3.3 Addition of pyridines toTricarbonyl (1-5-η-2-methoxycyclohexadienyl) iron tetrafluoroborate [Fe(CO)3(1-5-η-MeOC6H6)]BF4 46 3.4 Methodology and software 48 3.5 General Description of SPARTAN 48 3.6 Computational methodology 49 3.7 Computation of Tricarbonyl (1-4-η-5-exo-N-X-pyridino-cyclohexa-1,3-diene) iron tetrafluoroborate complexes 51 3.8 Computation of Tricarbonyl (1-4-η-5-exo-N-X, X-dimethylpyridino-cyclohexa- 1,3-diene) irontetrafluoroboratecomplexes 54 3.9 Computation of Tricarbonyl (1-4-η-5-exo-N-X-pyridino-2-methoxycyclohexa- 1,3-diene) irontetrafluoroboratecomplexes 58 3.10 Computation of Tricarbonyl (1-4-η-5-exo-N-X, X-dimethylpyridino-2- methoxycyclohexa-1,3-diene) irontetrafluoroboratecomplexes 61 3.11 Computation of Tricarbonyl (1-4-η-5-exo-N-X-aminopyridino-cyclohexa-1,3- diene) irontetrafluoroboratecomplexes 65 viii 3.12 Computation of Tricarbonyl (1-4-η-5-exo-N-X-aminopyridino-2-methoxy- cyclohexa-1,3-diene) irontetrafluoroborate complexes