To characterize these successfully geometry optimized de novo complexes, we computed their HOMO-LUMO gap with DFT (see Methods). Intuitively, we might expect to see a strong system size dependence of the HOMO-LUMO gap. The range in number of atoms (molecular weights) in our studied systems is from 32 to 132 (511 to 1032 amu), with an average size of 80 atoms (Figure , SI Appendix, Figure ). While the mean HOMO-LUMO gap is 2.83 eV, the range is large from 1.12 to 4.44 eV (279 to 1108 nm, Figure ). Comparing MAT and EA complexes, we observe that MAT has the higher average HOMO-LUMO gap (2.97 vs. 2.78 eV), potentially due to the greater compatibility of tridentate ligand combinations with the MAT symmetry group (Figure , SI Appendix, Figure and Table ). Nevertheless, even for a fixed size and the same neutral charge, we observe a wide variation in HOMO-LUMO gaps, regardless of symmetry (Figure ). For example, our set includes one EA and one MAT complex with 4 ligands each and are 63 and 64 atoms in size and both have gaps of over 4.32 eV (Figure ). Conversely, we observe EA and MAT complexes with a gap as low as 1.95 eV (Figure ). The cluster of seven EA complexes with HOMO-LUMO gaps less than 2.00 eV and between 100 and 125 atoms all contain the same bidentate 2-(4,5-Dimethyl-1,3-dithiol-2-ylidene)-1,3-dithiole-4,5dithiolate ligand and monodentate di-tert-butylhydroxyphosphine ligand, along with various combinations of other ligands with group 16 coordinating atoms (i.e., O or S, Figure ). The lack of significant trend for HOMO-LUMO gaps with the size of the molecule highlights the potential for discovering complexes with novel structure-property relationships through use of our de novo generation approach (Figure ). Overall, the high 75% success rate of executed calculations combined with the diversity of properties of the studied complexes suggests that the model should be useful in de novo transition metal complex discovery. One possible route to further improvements is to explicitly require higher confidence in coordination atom assignment or to compute multiple potential binding modes when model predictions of coordinating atoms are uncertain.