Magnesium tetrapyrazinoporphyrazines: tuning of the pK of red-fluorescent pH indicators.

Magnesium(ii) tetrapyrazinoporphyrazines (TPyzPzs) are excellent red fluorophores (λF ∼ 663 nm, ΦF ∼ 0.53 in THF). In this work, a series of magnesium(ii) complexes of unsymmetrical TPyzPzs bearing one or two phenol substituents was prepared.