Strategies to increase the quantum yield: Luminescent methoxylated imidazo[1,5-a]pyridines

A series of methoxylated imidazo[1,5-a]pyridines is presented and their optical and electrochemical properties investigated and interpreted on the basis of density functional theory calculations. The photophysical properties are discussed in relation to the chemical structure. The key role of the 1,3 substitutions on the imidazo[1,5-a]pyridine nucleus on rotational barriers and on frontier molecular orbitals is discussed in relation to the experimental hyperchromic effect, photoemission quantum yield and electrochemical properties. Depending on the position of the introduced methoxy substituents on the imidazo[1,5-a]pyridine nucleus, we are able to tune the Stokes shift and to increase the emission quantum yield from 22% to 50%.