Green to Blue Annihilated Upconversion from a Simple Iridium(III) Sensitizer with Carboxylic Group

Abstract

A novel iridium(III) complex with carboxylic group (Bis[6‐(benzo[b]thiophen‐2‐yl)phenanthridine‐C3,N](4‐methyl‐4′‐carboxypropyl‐2,2′‐bipyridine)iridium(III)chloride, named Ir–COOH in this work) is investigated for the first time as a sensitizer in triplet‐triplet annihilation (TTA) upconversion studies. Without the aid of bulky incorporated light‐harvesting groups, this simple iridium(III) sensitizer has moderate absorbance in visible light regions (ϵ=7750 M−1cm−1 at 532 nm, ϵ is molar extinction coefficient). Under the assistant of 9,10‐diphenylanthracene (DPA) as a triplet acceptor, green to blue upconversion from Ir–COOH/DPA system is obviously visible under the naked eyes and the upconversion efficiency is 9.5 % in deaerated DMF.