Driving the Emission Towards Blue by Controlling the HOMO‐LUMO Energy Gap in BF<sub>2</sub>‐Functionalized 2‐(Imidazo[1,5‐<i>a</i>]pyridin‐3‐yl)phenols
Gioele Colombo, G. Attilio Ardizzoia, Julien Furrer, Bruno Therrien, Stefano Brenna
Abstract
Abstract Several boron compounds with 2‐(imidazo[1,5‐ a ]pyridin‐3‐yl)phenols, differentiated by the nature of the substituent (R) in the para position of the hydroxy group, have been synthesized and thoroughly characterized both in solution ( 1 H, 13 C, 11 B, 19 F NMR) and in the solid state (X‐ray). All derivatives displayed attractive photophysical properties like very high Stokes shift, high fluorescence quantum yields and a good photostability in solution. Time‐Dependent Density Functional Theory (TD‐DFT) calculations allowed to define the main electronic transitions as intra ligand transitions ( 1 ILT), which was corroborated by the Natural Transition Orbitals (NTOs) shapes. The HOMO‐LUMO energy gap was correlated to the electronic properties of the substituent R on the phenolic ring, as quantified by its σ p Hammett constant.