Michael Peter Sammes Imperial College London, S.11.7. July 1964

SUBSTITUTED PHTHALOCYANINES A Thesis Submitted to the University of London for the Degree of Doctor of Philosophy in the Faculty of Science by Michael Peter Sammes Imperial College London, S.11.7. July 1964 2 ABSTRACT The preparation of a number of chloromethylated derivatives of phthalocyanine copper(II) and phthalocyanine cobalt(II) have been undertaken, and the reactions of some of these with pyridine have been investigated. Some derivatives of phthalocyanine tin(IV) are discussed, including one which may have a 'sandwich' structure. A new general synthetic route to alkyl substituted phthalonitriles is described, which makes use of the Diels-Alder reaction between alkyl substituted 1:3-butadienes and maleic anhydride. A number of preparative methods of these dienes have been investigated. The synthesis has been applied specifically to the preparation of 4-methylphthalonitrile, 3-methylphthalonitrile and 4:5-dimethylphthalonitrile; and from these three dinitriles have been characterised the corresponding phthalocyanines, and a series of metal derivatives. The ultra violet and visible absorption spectra of a number of substituted phthalocyanines and some of their intermediates are included, and the effect of substitution upon line positions and intensities is discussed. The infra red absorption spectra of the three series of methyl substituted phthalocyanines are compared with those of the unsubstituted series, and several new band assignments have been made. 3 The nuclear magnetic resonance spectra of three phthalocyanines are recorded and interpreted. These are dipotassium 1phthalocyahimodicyanoferrate(Id dipotassium Itetrakis-4—methylphthalocyaninedicyanoferrate(II) and dipotassium [tetrakis-3—methylphthalocyaninedicyanoferrate(II)]. 'The water, like a witch's oils, Burnt green, and blue, and white.' Samuel Taylor Coleridge. To ANGELA. 5 ACKNOWLEDGMENTS I am very deeply indebted to Dr. J.A. Elvidge, for his supervision of this work, and for his ever willingness to offer advice and encouragement. My grateful thanks are also extended to Miss J. Cuckney and her staff for microanalyses, Mrs. I. Boston for infrared and nuclear magnetic resonance measurements, and to Mr. J. Peppercorn for his continual help in the laboratory. To the Salters' Institute of Industrial Chemistry I would like to express my sincere thanks for providing a maintenance grant, and for taking such an interest in this work. 6 CONTENTS Introduction Chapter 1. The Chloromethylation of Phthalocyanines A. Introduction 13 B. Phthalocyanine Copper(IX) 16 C. Phthalocyanine Cobalt(II) 26 D. Phthalocyanine 29 E. Experimental Section 30 Chapter 2. The Synthesis of 4-Halomethylphthalonitriles A. Introduction 39 B. Direct chloromethylation of phthalonitrile 39 C. The synthesis of 4-methylphthalonitrile 41 D. The halogenation of 4-methylphthalonitrile 44 E. Experimental section 46 Chapter 3. The Tetrakis-4-methylphthalocyanines A. Introduction 58 B. Tetrakis-4-methylphthalocyanine 58 C. Tetrakis-4-methylphthalocyanine iron(II) 62 D. Totrakis-4-methylphthalocyanine cobalt(II) 63 E. Tetrakis-4-methylphthalocyanine copper(II) 64 F. Tetrakis-4-methylphthalocyanine zinc 65 G. Derivatives of tin(IV) 66 H. Summary of the tetrakis-4-methylphthalocyanines 70 J. Experimental section 71 7 Pave Chapter 4. The Tetrakis-4:5-dimethylphthalocyanines A. Introduction 78 B. The synthesis of 4:5-dimethylphthalonitrile 78 C. Tetrakis-4:5-dimethylphthalocyanines 79 D. Summary of the tetrakis-4:5-dimethylphthalo- 83 cyanine s E. Experimental section 84 Chapter 5. The Tetrakis-3-methylphthalocyanines A. Introduction 92 B. The adduct between 2-methylfuran and maleic 93 anhydride C. The diene synthesis 95 D. The tetrakis-3-methylphthalocyanines 97 E Summary of the tetrakis-5-methylphthalocyanines 100 F. Experimental section 101 Chapter 6. Some Studies of Derivatives of Phthalocyanine Tin(IV) A. Introduction 110 B. Phthalocyanine dichlorotin(IV) 111 C. Diphthalocyanine tin(IV) 118 D. Experimental section 120 Chapter 7. The General Synthesis of Tetrakis-4-substituted Ththalocyanines A. Introduction 124 B. Isopropylbenzene as a starting material 1211.1, C. Synthetic routes to 2-alkylbutadienes 126 8 Chapter 7 Page D. The route to 2-nbutylbutadiene 129 E. The route to 2-isobutylbutadiene 131 F. Derivatives of 3:5-dimethy1-1:3-hexadiene 136 G. Further derivatives from C8 dienes 139 H. General comments on the diene synthesis 147 J. Experimental section 149 Chapter 8. Some Nuclear Magnetic Resonance Studies A. Introduction 166 B. Substituted phthalicanhydrides 168 C. Dipotassium phthalocyaninedicyanoferrate(II) 169 D. Dipotassium ttetrakis-4-methylphthalocyanine- 171 dicyanoferrate(II), E. Dipotassium [tetrakis-3-methylphthalocyanine- 172 dicyanoferrate(II)) F. Summary of N.M.R. spectra 174 Chapter 9. The Infrared Spectra of Substituted Phthalocvanines A. Introduction 176 B. Tabulation of spectra 178 C. Assignments 179 Chapter 10. Ultraviolet and Visible Absorption Spectra A. Introduction 185 B. Phthalic Anhydrides 186 C. Phthalimides 187 D. Phthalonitriles 188 9 Page Chapter 10 E. Chloromethylated Phthalocyanines 190 F. Pyridinium salts of chloromethylated phthalocyanines 191 G. Tetrakis-4-methylphthalocyanines 192 K. Tetrakis-4:5-dimethylphthalocyanines 193 J. Tetrakis-3-methylphthalocyanines 193 K. Metal-free phthalocyanines 194 L. Derivatives of phthalocyanine copper(II) 195 M. Discussion 196 References 198 - 202 10 INTRODUCTION The phthalocyanines are no longer regarded as novel compounds, for they have been established by thirtyfive years of study, and have achieved a wide variety of applications, both inside and outside the chemical industry. Their fourfold properties of high thermal stability, insolubility, intense colour and fastness to light, have brought them a certain notoriety, and in many respects, they are not easy compounds to handle. However, they make excellent pigments for plastics, paper and paints, and every month details of now solublised phthalocyanine dyes appear in the literature. They have been shown to catalyse a number of chemical reactions; they exhibit semi-conductor properties; they have provided useful models in certain x-ray crystallographic measurements, and they have been used to demonstrate perpendicular conjugation - the transference of electronic charge between two perpendicular planes. Although these points go some way towards demonstrating the versatility of the phthalocyanines, there are still a number of gaps in the work that has been published on them. For example, most substituted phthalocyanines are prepared by direct substitution of the pigments by various reagents, this type of reaction being rather random, and difficult to control. There are very few references in the literature to the preparation of substitution products by the cyclisation of substituted derivatives 11 of phthalic acid, although this method has the advantage of introducing a known number of groups into predetermined positions. The infrared data available on the unsubstituted pigments are good and comprehensive but few band assignments have been made, and there are little data available on derivatives with peripheral substituents. Finally, no nuclear magnetic resonance measurements have been made on phthalocyanines in solvents other than concentrated sulphuric acid, in view of their low solubility. The initial purpose of this work had been to attempt a systematic study of the direct chloromethylation of certain phthalocyanines, ins the hope of obtaining from the products, water-soluble pyridinum salts of known configuration. Although fifteen new compounds were prepared, it was quickly realised that this approach was unsatisfactory, since both the nature of the products, and the yields were found to depend on too many factors. Attention was turned briefly to the direct substitution of phthalonitrile, and then to the search for a general synthetic route to substituted phthalonitriles. Such a route has been found, by making use of the Diels-Alder reaction between substituted butadienes and maleic anhydride, and subsequent conversion of the adduct to the aromatic dinitrile. Although this generally results in alkyl substituted products, these may be converted to other derivatives by oxidation, halogeneration etc. 12 The route depends for its success upon the availability of substituted dienes, and a number of synthetic routes to these have been investigated, and others are discussed. The diene synthesis has been successfully applied to the preparation of 4-methylphthalonitrile, 3-methylphthalonitrile, and for the first time, 4:5-dimethylphthalonitrile. From these dinitriles, three new series of phthalocyanines have been prepared, and the physical, and visible and infrared spectroscopic properties of about twentyfive derivatives are recorded. A careful study of the effect of methyl substituents upon the infrared spectra of the phthalocyanines has led to the assignment of a number of new bands, and a useful method for distinguishing the substitution pattern around the periphery of the ring has been discovered. Finally, by making use of the reaction between potassium cyanide and phthalocyanine iron(II), to give a product very soluble in methanol, nuclear magnetic resonance measurements have been made on three phthalocyanines, and the positions of the lines have confirmed the aromatic nature of the tetraza- porphin ring. 13 CHAPTER I THE CHLOROMETHYLATION OF PHTHALOCYANINES A. Introduction The earliest record of what must undoubtedly have been a phthalocyanine was made by Braun and Tcherniac(1)

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