Dimeric aza-BODIPY and Dichloro-aza-BODIPY: A DFT Study

Density functional theory (DFT) computations were performed to unveil the electronic structures and the Kohn-Sham Molecular Orbitals (MOs) of the dimeric aza-BODIPY molecule and its chlorinated form. The optimized conformation of dimers is well in alignment with the one provided in the literature. The HOMO-LUMO gap of dichloro-derivative is smaller than that of the dimeric aza-BODIPY molecule by 35.0 meV. The predicted HOMO energies of -6.40 and -6.60 eV point out the good stabilities of both compounds. They were reported to demonstrate bathochromic shifts of 40 and 57 nm compared to their monomers substituted by H and Cl, respectively. The intriguing photophysical behaviors of these molecules were investigated by conducting the Tamm-Dancoff density functional theory (TDA-DFT) calculations. The lambda(max) values emerge from the HOMO-1 -> LUMO+1 (83-86%) transitions, whereas the low energy transitions arise from HOMO -> LUMO (89%). Therefrom predicted E-LUMO -> HOMO of the dimeric aza-BODIPY and dichloro-derivative are 1.89 and 1.87 eV, respectively, which are matching well with the reported literature values.