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Conjugated Schiff Base-Type Metal-Containing Polymers

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Conjugated Schiff Base-Type Metal-Containing Polymers CONJUGATED SCHIFF BASE-TYPE METAL-CONTAINING POLYMERS by ALFRED CHI WOOK LEUNG B.Sc. (Hon,), The University of British Columbia, 2001 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (Chemistry) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) July 2008 © Alfred Chi Woon Leung, 2008 Abstract The work in this thesis describes the synthesis and characterization of a series of conjugated polymers containing Schiff base transition metal complexes. High molecular weight poly(salphenyleneethynylene)s (PSPEs) were synthesized using the Sonogashira-Hagihara protocol and they were characterized using nuclear magnetic resonance spectroscopy and gel permeation chromatography. Their optical properties were investigated by UV-vis and fluorescence spectroscopies. PSPEs containing Zn saiphen moieties were found to exhibit strong aggregation that is facilitated by the presence of Zn to 0 interactions, and it was discovered that the polymers interact with various Lewis bases to undergo aggregation and deaggregation. New ladder-type conjugated polymers, as well as a series of model compounds that are representative of the repeating units of the polymers, were synthesized using Schiff base condensation methods. The electronic and magnetic properties of these ladder-polymers were studied using cyclic voltammetry, electron paramagnetic resonance spectroscopy, and magnetic susceptibility measurements. 11 .Table of Contents Abstract ii Table of Contents iii List of Tables v List of Figures vi List of Schemes x List of Symbols and Abbreviations xiii Acknowledgements xviii Dedication xix Co-Authorship Statement xx CHAPTER 1 Introduction .1 Metal-Containing Polymers 1 1.2 Schiff Base Complexes 4 1.3 Scope of Introduction 5 1.4 Early Research 6 1.5 Chemically Polymerized Schiff Base Polymers 8 1.5.1 Salen-Containing Homopolymers 8 1.5.2 Salen-Containing Copolymers 10 1.6 Helical Schiff Base polymers 26 1.7 Electrochemically Polymerized Schiff Base Polymers 37 1.8 Goals and Scope 49 1.9 References 53 CHAPTER 2 Poly(salphenyleneethynylene)s : Soluble, Conjugated, Metal- 58 Containing Polymers 2.1 Introduction 58 2.2 Monomer Synthesis and Characterization 63 2.3 Polymer Synthesis and Characterization 69 2.4 Conclusions 73 2.5 Experimental 74 2.5.1 General 74 2.5.2 Procedures 75 2.5.3 X-Ray Diffraction Studies 80 2.6 References 83 111 CHAPTER 3 Poly(salphenyleneethyynylene)s and Their Unique 88 Supramolecular Crosslinking Behavior 3.1 Introduction 88 3.2 Synthesis of Monomers and Polymers 92 3.3 Polymer Characterization 96 3.4 Aggregation and Sensing 100 3.5 Conclusions 108 3.6 Experimental 109 3.6.1 General 110 3.6.2 Procedures 110 3.7 References 120 CHAPTER 4 The Ladder-Chelate Approach to Soluble Conjugated Metal- 123 Containing Polymers 4.1 Introduction 123 4.2 Synthesis of Starting Materials 129 4.3 Synthesis and Characterizations of Model Compounds 133 4.3.1 Model Compounds Synthesis and NMR Studies 133 4.3.2 Electrochemical, EPR, and Magnetic Susceptibility 148 Studies of the Model Compounds 4.4 Synthesis and Characterization of Ladder Polymers 154 4.5 Conclusions 165 4.6 Experimental 166 4.6.1 General 166 4.6.2 Procedures 167 4.6.3 X-Ray Diffraction Studies 185 4.7 References 191 CHAPTER 5 Conclusions and Future Directions 194 5.1 Overview 194 5.2 Poly(salphenyleneethynylene)s (PSPEs) 195 5.3 Schiff Base Ladder Metallopolymers 197 5.4 Future Directions 200 5.5 References 205 iv Lists of Tables Table 2.1 X-ray diffraction data for compound 196b 81 Table 2.2 Selected bond lengths (A) and angles (°) for 196b 82 Table 3.1 Molecular weights (Mm, M) and polydispersities of polymers 98 216a-c and 217a-c. Measurements were made with a GPC system equipped with triple detection (refractive index, light-scattering, and viscosity). Table 4.1 X-ray diffraction data for compound 231a 185 Table 4.2 Selected bond lengths (A) and angles (°) for 231a 188 V List of Figures Figure 1.1. 1-D phthalocyanine coordination polymer 1 (“shish-kebab” 3 polymers), monomer for the synthesis of 2-D phthalocyanine sheets 2 (“parquet” polymers), and porphyrin-containing PPE 3. Figure 1.2. 3-D representation of nickel helical polymer (a) 89 and (b) 93 28 Reprinted with permission from reference 47b. Copyright 1997 American Chemical Society. Figure 1.3. SEM images of(a) Cu polymer 110 and analogous (b) Ni (c) Zn and 34 (d) Co polymer. Scale bar represents 1 JIm, and the inset shows a plot of the frequency vs. microsphere diameter. Reprinted with permission from reference 52a. Copyright 2003 Wiley-VCH. Figure 1.4. Structure of model compound 113 as determined by X-ray 36 crystallography. Hydrogen atoms and tert-butyl groups are omitted for clarity. Figure 1.5. SEM images of 117 electrochemically synthesized in (a) MeCN and 40 (b) CH2C1. Reprinted with permission from reference 56. Copyright 1989 American Chemical Society. Figure 1.6. General structures of the target polymers prepared in this thesis 51 Figure 2.1. Fast synthesis and screening of conjugated polymers. Dibromoaryl 62 monomers I-XII and diethynylaryl monomers A-H were polymerized through Pd-catalyzed Sonogashira coupling. Figure 2.2. Solution fluorescence of the 96 polymers measured at 530 nm 63 Polymers GXI and GXII correspond to PPEs containing Zn and Ni Schiff base complexes 191a and 192a. 3 65 Figure 2.3. ‘H NMR spectrum (300 MHz) of Ni monomer 196b in CDC1 Figure 2.4. Single crystal X-ray diffraction structure of monomer 196b (a) 66 perpendicular and (b) parallel to the plane of the salphen ligand. Thermal ellipsoids are shown at the 50% probability level. Solvent molecules are removed for clarity. Red = oxygen, blue = nitrogen, purple = iodine, green = nickel. The packing pattern of 196b in the solid state is illustrated in (c), and the packing pattern along the b axis is shown in (d). Figure 2.5. Photograph of thin films of polymers 202a-c. In THF, the polymers 70 form intensely colored solutions (ca. 10 mg mL’). Figure 2.6. Gel permeation chromatogram for polymer 202c. Weight averaged 71 molecular weight M for 202c is 84,000 Da. vi Figure 2.7. (a) UV-visible spectra for polymers 202a-c in THF, (b) Emission 72 spectrum of polymer 202a in THF (2exc = 406 nm). Figure 3.1. PPE sensor 203 has superior sensitivity over molecular sensor 205 89 to electron deficient molecules such as paraquat (204). Figure 3.2. Porphyrin containing polymer 190 self-assembled into a 90 supramolecular polymer ladder 206 in the presence of 4,4’-bipyridine. Figure 3.3. Intensely colored films of polymers 216a-c were obtained through 95 simple suction filtration. The polymers dissolve in THF to give red solutions. 3 + 1% pyridine-d5) 96 Figure 3.4. 1H NMR spectrum of polymer 217a. (CDCI Inset: Expanded view of region from 3 to 9 ppm. Figure 3.5. UV-vis absorption (normalized) spectra of polymers 216a-c 2C1and 99 217a-c in CH2CI (the polymers were dissolved in THF and diluted with CH to appropriate concentration, see procedures on P.24 for details). 2C1 99 Figure 3.6. UV-Vis absorption (normalized) spectra of 218 and 219 in CH Figure 3.7. Illustration of dimerization in Zn salphen complexes. Strong 101 interactions between the Zn2 center and the phenolic oxygens of the metal complexes hold the dimer together. 2C1, 5.00 x l0 M) 103 Figure 3.8. UV-vis and fluorescence spectra of 216a (CH titrated with a) pyridine (1.03 x 106_ 1.13 x l0 M; step size: 1.03 x 10.6 M) and b) 4,4’ bipyridine (4.30 x i0 —6.45 x l0 M; step size: 4.30 x M). 2C1, 5.00 x 10 M) 104 Figure 3.9. UV-vis and fluorescence spectra of 219 (CH titrated with a) pyridine (1.03 x 108 — 1.65 x i0 M; step size: 1.03 x 10 M) and b) UV-vis and fluorescence spectra of 219 titrated with 4,4’ bipyridine (1.08 x o 6_2.40 x x 6M). step size: 1.08 10 2C1, 5.00 x 10 M) 107 Figure 3.10. UV-vis and fluorescence spectra of 217a (CH titrated with a) pyridine (1.03 x 106 — 1.03 x M; step size: 1.03 x 10.6 M) and b) 4,4’ bipyridine (4.30 x 10-5 — 3.01 x M; step size: 4.30 x i0 M). Figure 3.11. Cartoon illustrating the disruption of the polymer crosslinks upon 108 the addition of pyridine. Figure 4.1. Oligoacenes 220, hexa-peri-benzocoronenes (HBCs) 221, and 125 polyrylene 222 are examples of highly conjugated organic compounds investigated for applications as organic electronics. Figure 4.2. Target Schiff base ladder polymers 230 and 232, and bimetallic 129 model compounds 229 and 231. (R = alkoxy) vii Figure 4.3. Phenylenediamine derivatives with pendant solubilizing groups that 133 were used in the preparation of Schiff base ladder polymers. Figure 2C1, 4.4. ‘H NMR spectrum (CD 300 MHz) of proligand 248b showing 138 the expected resonance signals. Inset: Expanded view of region from 6.7 to 8.7 ppm. 6, Figure 4.5. 1H NMR (DMSO-d 300 MHz) spectrum of bimetallic Zn model 139 compound 229a. Inset: Expanded view of region from ö 6.3 to 9 ppm. Figure 4.6. 1H NMR titration experiments illustrating the aggregation of 229a in 141 non-coordinating 6 solvents. CD2C1 was added to a solution of DMSO-d containing 229a, concentration 6/CD2C1. Significant up to a of 1:4 DMSO-d signal broadening and upfield shift of the aromatic signals suggests aggregation of 229a in the presence of non-coordinating solvents.
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