Synthesis of peripherally substituted aza-analogues of Si(IV) phthalocyanines by complexation method

Abstract

Despite many notes about advantageous properties of Si(IV) phthalocyanines, their aza-analogues from the group of tetrapyrazinoporphyrazines (TPyzPzs) are only rarely reported in the literature, especially for macrocycles carrying peripheral groups. Thus, a series of Si(IV) TPyzPzs having alkylamino, aryloxy, alkylsulfanyl or alkyl group at the periphery was prepared by complexation of Si(IV) into corresponding metal-free derivatives by their stirring at 30[Formula: see text] C with trichlorosilane, using tributylamine as a base, and dichloromethane as a solvent. Key factors affecting the feasibility of this method, such as well-chosen excess of trichlorosilane and solvent used, were described. The model compound of the series ([Formula: see text], aryloxy substituted dihydroxy Si(IV) TPyzPz) was then modified at axial positions using trihexylchlorosilane as a ligand. All target Si(IV) TPyzPzs showed strong absorption with Q-band maxima ranging 617–655 nm (extinction coefficients 82 000–341 000 L⋅mol[Formula: see text]⋅cm[Formula: see text] and efficient fluorescence emission with [Formula: see text] values ranging 0.32–0.44 with the exception of alkylamino substituted TPyzPz, whose excited states were efficiently quenched by intramolecular charge transfer. The possibility of axial modification, good spectral and fluorescence properties as well as the ability to quench the excited states upon introduction of alkylamine groups indicate the suitability of these derivatives for fluorescence sensing applications.