Phthalocyanines with biphenyl substituents

Abstract

Porphyrins (Ps) and phthalocynines (Pcs), the two main classes of the tetrapyrrolic macrocycles, differ basically as the porphyrins are formally derived from the porphine molecule, whereas Pcs are constitutionally tetraaza tetrabenzo analogues of porphyrins since they have a porphyrazine type central core with N atoms bridging the pyrrole rings instead of the CH groups present in the porphyrin sceleton. Ps are either naturally occuring molecular systems or original synthetic products, whereas Pcs derive exclusively from synthetic laboratory work. Pcs are 18 π electron aromatic macrocycles comprising four isoindole units linked together through their 1,3 positions by aza bridges. The particular two dimentional π electron delocalization over these macrocycles gives rise to a great number of unique physical properties, resulting in a diverse number of applications ranging from industrial (catalysts, photoconductors) to biomedical. Thus Pcs are chemically and thermally stable compounds that exhibit exceptional optical and electrical behaviour. This work includes three parts. In the first part of this work, we report on the synthesis and characterisation of unsymmetrical metallo pcs which carry two peripheral hexylthio substituents on each of three of the benzenoid groups while the fourth one carries two phenylethynyl groups. Despite the variety of synthetic routes developed to prepare symmetrically substituted pc, relatively few methods can be applied for preparing unsymmetrical ones. The most simple approach to the preparation of Pc bearing different substituents is a mixed cyclization of two precursors with different substituents. The main problem with this method is the isolation of the desired Pc from a product mixture made up of components with similar physical and chemical properties. The second method is synthesis on a polymeric support developed by Leznoff and Hall, which consists in attaching a diimino isoindoline or phthalonitrile to an insoluble polymer, making it react with a different diimino isoindoline and, after removal of the symmetric Pc, releasing the unsymmetrical pc from the polymer support. A third method has been described by Kobayashi and co-workers and involves the ring expansion of a subphthalocyanine (SubPc) to a Pc using a phthalonitrile unit which bears a different type of substituent to that on the SubPc. The first method was prefered in this work. 4,5-di(hexylthio) phthalonitrile (2) and 4,5-di(phenylethynyl) phthalonitrile (3) were chosen as starting materials. 2 was prepared from 4,5-dichloro phthalonitrile (1) and hexanethiol in dry DMF. K2CO3 was used as the base for this nucleophilic aromatic displacement. 3 was synthesised from compound 1. Under typical Sonogashira reaction conditions, the cross coupling reaction between an excess of phenylacetylene and dichloro phthalonitrile (1) in triethylamine (NEt3) with bis(triphenylphosphine) palladium (II) chloride (Pd(PPh3)2Cl2) and copper (I) iodide (CuI) as catalysts at 90 oC under nitrogen atmosphere produced 3. Mixed condensation of 2 with 3 in the presence of the corresponding metal (II) salts (Zn(CH3COO)2, NiCl2, CoCl2) afforded the unsymmetrical zinc-, nickel- and cobalt- substituted complexes (4-6). In the second part of this work, tetrasubstituted metal free and metallo Pcs (Zn (II) and Co (II)) carrying biphenyl carboxylic acid substituents on the periphery were synthesized. Also, all of the biphenyl carboxylic acid substituents of the metal free phthalocyanine were esterified with hexanol. 4-(4′- carboxybiphenyloxy) phthalonitrile (8) was prepared from 4-nitro phthalonitrile (7) and 4′- hydroxy-4-biphenylcarboxylic acid in the presence of K2CO3 in dry DMF. The cyclisation of 8 by using lithium in pentanol, and then acidification with HCl resulted with the formation of metal free pc (9). The reaction of metal free pc (9) with Zn(CH3COO)2 (or CoCl2) in dry DMF gave the desired metallo pcs (10, 11)). To improve the solubility of 9, hexyl substituents were introduced into the biphenyl units (12). The synthesis of compound 12 was accomplished in pyridine in the presence of dicyclohexyl carbodiimide (DCCI) and p-toluenesulfonic acid as catalyst. In the last part of this work, firstly 4-(4′- carbhexyloxybiphenyoxy) phthalonitrile (13) was synthesized by esterification of 8 with hexanol in the presence of dicyclohexyl carbodiimide (DCCI). Then, zinc (14), cobalt (15) and copper (16) Pcs with four carbhexyloxybiphenyloxy pendant groups on the periphery were prepared from compound 13 and the corresponding metal salts. All these new compounds were characterized by elemental analysis, FT-IR, $^1H NMR $, $^{13}C NMR $, UV-Vis and mass spectroscopies. In conclusion, three novel phthalonitrile derivatives and corresponding ten phthalocyanines were synthesized in this study.

Özet

Bu çalışma, üç kısımdan oluşmaktadır. Çalışmanın ilk kısmında, 4,5-di(hekziltiyo)ftalonitril (2) ve 4,5-di(feniletinil)ftalonitril (3) başlangıç maddeleri olarak seçilmiştir. 2 no’lu madde, 4,5- dikloroftalonitril (1) ve hekzantiyolün DMF içerisindeki reaksiyonu ile hazırlamıştır. 3 no’lu madde ise, Sonogashira reaksiyon koşullarına göre, 1 bileşiğinin fenilasetilenin aşırısı ile kenetlenme reaksiyonundan sentezlenmiştir. 2 ve 3 no’lu maddelerin uygun metal tuzlarının (Zn(CH3COO)2, NiCl2, CoCl2) varlığındaki kondenzasyonu asimetrik çinko, nikel ve kobalt komplekslerini (4-6) vermiştir. Çalışmanın ikinci kısmında, 4-(4′-karboksibifeniloksi)ftalonitril (8) bileşiğinden yola çıkılarak, periferal pozisyonlarında asit grupları taşıyan metalsiz (9) ve metalli ftalosiyaninler (Zn ve Co) (10, 11) sentezlenmiştir. Metalsiz ftalosiyanindeki (9) bütün bifenilkarboksilikasit grupları hekzanol ile esterleştirilmiştir (12). 4-(4′-karboksibifeniloksi) ftalonitril bileşiği (8), 4- nitroftalonitril (7) ve 4′-hidroksi-4-bifenilkarboksilik asidin reaksiyonundan elde edilmiştir. 8 bileşiğinin, lityum metali ile siklotetramerizasyonu, daha sonra HCl ile asitlendirilmesiyle 9 bileşiği elde edilmiştir. 9 bileşiğinin, Zn(CH3COO)2 veya CoCl2 ile kuru DMF içerisindeki reaksiyonu ile metalli ftalosiyanin türevlerine geçilmiştir (10, 11). Çalışmanın son kısmında ise, 8 no’lu maddenin hekzanol ile disiklohekzilkarbodiimid (DCCI) varlığındaki reaksiyonundan 4-(4′- karbhekziloksibifeniloksi) ftalonitril (13) bileşiği sentezlenmiş, ardından çinko (14), kobalt (15) ve bakır (16) ftalosiyaninler, 13 bileşiğinin uygun metal tuzları (Zn(CH3COO)2, CoCl2, CuCl2) ile reaksiyonundan hazırlanmıştır. Sentezlenen tüm bu yeni bileşiklerin yapıları FT-IR, $^1H NMR$, $^{13}C NMR $, UV-Vis, elementel analiz ve kütle spektroskopisi ile karakterize edilmiştir.