Effect of Nitro Group Position on the Optical Properties of Pyrrolidinone-Fused-1,2-Azaborine Chromophores
Primary Investigator (PI) Name
Carl J. Saint-Louis
Department
CSM - Chemistry and Biochemistry
Abstract
Due to the nitro (NO2) group's strong electron-accepting capability, aromatic compounds with NO2 groups are frequently used in n-type organic conjugates. However, adding NO2 groups to the chromophores' cores can reduce or quench the fluorescence, particularly in heterocyclic aromatic compounds containing three coordinate borons, such as pyrrolidinone-fuse-1,2-azaborines (PFAs). Due to strong intermolecular π-π stacking interactions, these NO2-PFAs tend to aggregate at high concentrations, causing emission quenching, also known as aggregation-caused quenching (ACQ). In this work, we synthesized a series of PFAs substituted with a NO2 group at positions (2-, 3-, and 4-) to investigate the influence of the location of the NO2 group on the optical characteristics of PFAs. Surprisingly, changing the placement of the nitro group on the pyrrolidinone hemisphere of PFAs resulted in distinct optical properties. Compared to 2-substituted NO2-PFA, substitution of the NO2 group to position 3- resulted in significant blue-shifted emission, with no signs of intramolecular charge transfer and increased in fluorescence. 4-substituted NO2-PFA is also blue shifted but at a longer wavelength with respect to 3-, resulting in less fluorescence.
Disciplines
Materials Chemistry | Organic Chemistry
Effect of Nitro Group Position on the Optical Properties of Pyrrolidinone-Fused-1,2-Azaborine Chromophores
Due to the nitro (NO2) group's strong electron-accepting capability, aromatic compounds with NO2 groups are frequently used in n-type organic conjugates. However, adding NO2 groups to the chromophores' cores can reduce or quench the fluorescence, particularly in heterocyclic aromatic compounds containing three coordinate borons, such as pyrrolidinone-fuse-1,2-azaborines (PFAs). Due to strong intermolecular π-π stacking interactions, these NO2-PFAs tend to aggregate at high concentrations, causing emission quenching, also known as aggregation-caused quenching (ACQ). In this work, we synthesized a series of PFAs substituted with a NO2 group at positions (2-, 3-, and 4-) to investigate the influence of the location of the NO2 group on the optical characteristics of PFAs. Surprisingly, changing the placement of the nitro group on the pyrrolidinone hemisphere of PFAs resulted in distinct optical properties. Compared to 2-substituted NO2-PFA, substitution of the NO2 group to position 3- resulted in significant blue-shifted emission, with no signs of intramolecular charge transfer and increased in fluorescence. 4-substituted NO2-PFA is also blue shifted but at a longer wavelength with respect to 3-, resulting in less fluorescence.