Robust route toward cationic phthalocyanines through reductive amination

• Published in: Dyes and pigments Vol. 207; p. 110768
• Main Authors: Bunin, Dmitry A., Martynov, Alexander G., Safonova, Evgeniya A., Tsivadze, Aslan Yu, Gorbunova, Yulia G.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2022
• Subjects: Cationic photosensitizers; Photodynamic therapy; Phthalonitriles; Reductive amination; Singlet oxygen; Water-soluble phthalocyanines; Reductive amination; Cationic photosensitizers; Singlet oxygen; Photodynamic therapy; Phthalonitriles; Water-soluble phthalocyanines
• ISSN: 0143-7208; 1873-3743
• DOI: 10.1016/j.dyepig.2022.110768

New synthetic pathway toward water-soluble phthalocyanines (Pc) bearing cationic 4-(N,N,N-trialkylammonium-methyl)-phenoxy groups has been elaborated. It involves the convenient reductive amination of various (4-formylphenoxy)-substituted phthalonitriles with diethylamine and NaBH(OAc)3, leading to 3-, 4- and 4,5-(p-diethylaminomethyl-phenoxy)-substituted phthalonitriles as precursors to new Zn(II), Mg(II) and metal-free phthalocyanines (4α-MPc, 4β-MPc and 8β-MPc, M = 2H, Mg, Zn) containing four or eight cationic groups in non-peripheral (α-) or peripheral (β-) positions. Novel compounds have been characterized by different spectroscopic techniques (1H, 13C NMR, FTIR, UV–Vis) and MALDI TOF mass spectrometry. All cationic Pcs exhibited strong absorption in the phototherapeutical spectral range from 670 to 700 nm (εmax > 105 M−1cm−1) and high quantum yields of singlet oxygen generation in DMSO where all phthalocyanines existed in monomeric forms. Also, cationic complexes showed moderate solubility in water with high tendency to aggregation, however α-substituted Zn(II) and Mg(II) complexes existed in water in predominantly monomeric states. Further monomerization of Zn(II) complex 4α-ZnPc in aqueous solution can be achieved by interaction either with non-ionic surfactant Tween-80 or bovine serum albumin (BSA). The advantage of our results is not limited to new convenient synthetic approach to the cationic phthalocyanines but it also consists in preparation of new phototherapeutic agents with promising photophysical and photochemical properties. [Display omitted] •Reductive amination provides access to new water-soluble cationic phthalocyanines (Pc) with ammonium groups.•Structure of cationic Pcs affects their photophysical properties and behaviour in solution.•Interaction with non-ionic surfactant and bovine serum albumin affords monomerization of cationic Pcs in aqueous solution.