Tuning photophysical properties of phosphorescent benzoporphyrin complexes via 1-step π-extension

Abstract

Complexes of benzoporphyrins are highly promising for application in optical oxygen sensors, as triplet sensitizers for generation of singlet oxygen and upconversion based on triplet-triplet annihilation (TTA). Particularly, they benefit from efficient absorption in red part of the spectrum and strong NIR phosphorescence. In this contribution, we investigate different strategies of tuning the photophysical properties of these readily available complexes via 1-step modification. The new π-extended derivatives are obtained via Friedel-Crafts acylation of tetraphenyltetrabenzoporphyrin (TPTBP) complexes and by Suzuki or Sonogashira cross-coupling reaction of the tetrabromo-substituted benzoporphyrins. The Soret and Q absorption bands of the tetra-substituted dyes shift bathochromically by about 15 nm compared to the parent TPTBP compounds. The modified dyes retain their NIR phosphorescent properties and feature slight improvement of the quantum yield. Application in optical oxygen sensing materials and triplet-triplet annihilation-based upconversion systems is demonstrated.