The 50 top-scoring molecules from the final populations of 4,000 GA searches are selected, which results in 1,234 unique NBD/QC systems. The energy storage, TBR barrier height, and absorption spectra of these molecules are then recomputed using GFN2-xTB and sTDA-xTB, respectively. Then, the 230 systems with energy densities, absorption spectra, and TBR barriers above 0.2 MJ/kg, 350 nm, and 160 kJ/mol, respectively, are reoptimised at the M06-2X/6-311+G(d) level of theory (using the lowest energy GFN2-xTB structures as starting point) followed by vibrational analysis to ensure correct convergence. TDDFT calculations on all 230 molecules reveal that 116 molecules have absorption maxima above 350 nm. The energy densities for these 116 molecules are then computed and the 38 molecules with energy densities higher than 0.4 MJ/kg are selected for barrier computations. The TS search fail for four of the 38 molecules while the TBR barrier is higher than 150 kJ/mol for 15 of the 34 molecules (shown in Table Five of the molecules have energy densities greater than 0.45 MJ/kg, which is similar to the highest values observed so far for NBD-dimer systems and considerably higher than any previously observed for NBD-monomers. The absorption spectra of these five molecules are shown in Figure . However, most of the molecules have one or more amine and hydroxy groups directly attached to the NBD scaffold and may undergo keto-enol or imine-enamine tautomerisation, which may adversely impact the properties. The main conclusion of this study is that the largest energy storage value that can be obtained for a single NBD/QC moiety with these substituents, while maintaining a long half-life and absorption in the visible spectrum, is around 0.55 MJ/kg. (1-5). Furthermore, the UV-Vis spectrum of the parent NBD isomer is given as a reference (NBD). All the spectra are obtained using the time-dependent analog of M06-2X/6-311+G(d) and simulated using Eq. S1 from the supporting information.