Synthesis and photophysical properties of peripherally and non-peripherally mercaptopyridine substituted metal free, Mg(II) and Al(III) phthalocyanines

The syntheses and photophysical properties of metallophthalocyanines containing Mg2+ and Al3+ as central metal ions and their unmetallated derivative (complexes 3–8) tetra- substituted at the non-peripheral (α) and peripheral (β) positions with 2-mercaptopyridine are reported. The trends in triplet and fluorescence quantum yields are described for these compounds. The complexes exhibited relatively high triplet quantum yields (ΦT) ranging from 0.33 to 0.54 and fluorescence quantum yields (ΦF) ranging from 0.02 to 0.29. Triplet state lifetimes of the complexes were long ranging from 120 to 460 μs, indicating a potential use of these complexes as photosensitizers.

Graphical abstractMetallophthalocyanines containing Mg2+ and Al3+ as central metal ions and tetra- substituted at the non-peripheral (α) and peripheral (β) positions with 2-mercaptopyridine exhibit relatively high triplet quantum yields (ΦT) ranging from 0.33 to 0.54 and fluorescence quantum yields (ΦF) ranging from 0.02 to 0.29, hence the latter value showing potential for imaging.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Mercapto phthalocyanine complexes of Mg, Al and metal free are synthesized. ► The complexes are substituted at the peripheral and non-peripheral positions. ► Triplet lifetimes were higher for the Mg derivatives. ► Peripheral substitution resulted in longer fluorescence lifetimes.