Gold(II) Phthalocyanine Revisited: Synthesis and Spectroscopic Properties of Gold(III) Phthalocyanine and an Unprecedented Ring-Contracted Phthalocyanine Analogue

• Published in: Chemistry : a European journal Vol. 18; no. 39; pp. 12404 - 12410
• Main Authors: Wong, Edwin W. Y., Miura, Akito, Wright, Mathew D., He, Qi, Walsby, Charles J., Shimizu, Soji, Kobayashi, Nagao, Leznoff, Daniel B.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 24-09-2012; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Analogue; aromaticity; Chemical industry; Chemistry; Chlorides; Gold; phthalocyanine; Spectroscopy; Synthesis; triphyrin; UV/Vis spectroscopy; Valence
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201201701

In 1965, gold(II) phthalocyanine (AuPc, 1) was described to be synthesized from unsubstituted 1,3‐diiminoisoindoline and gold powder or AuBr. Compound 1 has been regarded as a rare example of a paramagnetic gold(II) complex. However, its chemistry, especially the oxidation state of the central gold ion, has not been previously explored due to the inherent insolubility of 1 caused by its unsubstituted structure. In our attempt to synthesize soluble AuPcs by using 5,6‐di‐substituted 1,3‐diiminoisoindolines, gold(III) phthalocyanine chloride (3) and a gold(III) complex of an unprecedented ring‐contracted phthalocyanine analogue ([18]tribenzo‐pentaaza‐triphyrin(4,1,1), 4) were isolated. With this discrepant result from the original literature in hand, a reinvestigation of the original AuPc synthesis by using unsubstituted 1,3‐diiminoisoindoline and various gold salts (including gold powder and AuBr) was performed, finding that only unsubstituted analogues of 3 and 4 or free‐base phthalocyanine were obtained. No gold(II)‐containing species could be isolated.
Reinvestigation of a putative gold(II) phthalocyanine, which was synthesized in 1965 and has not been fully characterized, provided only gold(III) complexes, gold(III) phthalocyanine chloride, and a gold(III) complex of an unprecedented ring‐contracted phthalocyanine (see figure). Interconversion reaction of the ring‐contracted species to gold(III) phthalocyanine was also revealed.