Synthesis of 2,3′,4′-tricyanobiphenyl derivatives and tetraphenylphthalocyanines based thereon

Abstract

The nitration of 2,3',4'-tricyanobiphenyl with subsequent transformations of the obtained product provided 4-X-2,3',4'-tricyanobiphenyls (X = NO 2 , NH 2 , NHCOCH 3 , Br, I). The condensation of the initial biphenyl or its 4-X-derivatives (X = NO 2 , NHCOCH 3 , Br, I) in the presence of zinc acetate afforded the corresponding zinc complexes of tetra(4-X-2-cyanophenyl)phthalocyanines.The interest to compounds from the phthalocyanine class notably grew recently due to the appearance of a number of their new applications in technology, chemical engineering, medicine etc. [1][2][3][4]. Because of the demand of materials with versatile properties a necessity arose of a wide variation in the structure of phthalocyanines that could be attained in two ways: either by the synthesis of "building blocks," or by the modifi cation of the already assembled phthalocyanines. In both events the presence in the molecule of the basic compounds of easily modifi ed fragments, e.g., of a phenyl group, is of fundamental importance. Besides, the arylsubstituted phthalocyanines possess their proper interest with respect to the practical application [2][3][4].The assembling of the aryl-substituted phthalocyanine core is performed with the use of arylated phthalonitriles as the "building blocks". The latter till recently were prepared by complex procedures [3,5], and this circumstance impeded the synthesis of this type phthalocyanines. The recently discovered reductive condensation of the proper phthalonitrile giving 2,3',4'-tricyanobiphenyl (I) [6] opened a short way to its derivatives and consequently to 2-cyanophenyl-substituted phthalocyanines based thereon. This study as the fi rst stage in the development of this research concerns the synthesis of 4-X-2,3',4'-tricyanobiphenyls (X = NO 2 , NH 2 , NHCOCH 3 , Br, I) and the preparation of phthalocyanines both from biphenyl I proper and its 4-X-substituted derivatives [7].The nitration of biphenyl I by analogy with the nitration of 2-chlorobenzonitrile [8] was performed by treating with concn. nitric acid at room temperature and afforded 4-nitro-2,3',4'-tricyanobiphenyl (II) containing 92% of the main substance with the yield of the purifi ed product of 50% (Scheme 1). Its formation is the natural result of the combined effect of all substituents present in the initial biphenyl.The reduction of compound II under the conditions analogous to those used in the reduction of 4-nitrobiphenyl [9] gave 4-amino-2,3',4'-tricyanobiphenyl (III) in 69% yield, and the threatment of the latter with acetic anhydride in DMSO resulted in 4-acetylamino-2,3',4'-tricyanobiphenyl (IV) in 57% yield (Scheme 1).Further modifi cation was performed by the diazotization of amine III followed by the transformations of diazonium salt V. In the dilute sulfuric acid at -10°C this salt formed in virtually quantitative yield as showed the formation of biphenyl I in a high yield at the treatment of the diazotization products with ethanol (Scheme 2).

Microwave-Assisted Synthesis of Phthalocyanine Zinc Complexes Derived from Aminotricyanobiphenyl-Based Azo Dyes

“…[8] 4-((4-(Dibutylamino)phenyl) diazenyl)biphenyl-2,3',4'-tricarbonitrile (9) was synthesized according to known procedure. [25,26] Pc syntheses were performed in a Discover SP microwave oven at exposure rate 200 W. …”

“…[8] A mixture of compound 12 (40 mg, 0.14 mmol) and Zn(CH 3 COO) 2 ·2H 2 O (7 mg, 0.03 mmol) in 1-pentanol (0.5 ml) was heated at 155 °С in microwave oven for 10 minutes. After cooling the solvent was evaporated.…”

“…Zinc tetra-(2-cyano-4-bromophenyl)phthalocyanine (16) [8] was obtained from phthalonitrile 13 (19 mg) in 88 % yield. [8] was prepared from phthalonitrile 14 (20 mg) in 70 % yield.…”

“…[8] was prepared from phthalonitrile 14 (20 mg) in 70 % yield. (19) was synthesized from phthalonitrile 9 (20 mg) in 84 % yield (brown powder).…”

“…In this connection aryl substituted Pcs are especially interesting as starting compounds for the synthesis of new functionalised species, given the great potential of chemical modification on the aryl moieties, and directly as the component materials for practical use. [2,3,5] New opportunities here open up due to the recent development of the one-step conversion of phthalonitrile into 2,3',4'-tricyanodiphenyl [6] giving rise to 4-amino-2,3',4'-tricyanodiphenyl (1) [7,8] -the base compounds with potentially broad application for the synthesis of functionalized Pcs with aryl moiety. The most important spectral feature of such Pcs is the presence of absorption only at the edges of the visible region in the electronic spectra of Pc chromophore, namely Q-band in the region of 650-670 nm and B-band at around 350 nm.…”