Computational efficiency is a challenge as we study increasingly large substituted molecules. EOM-CCSD provides higher accuracy than CC2, but severely limits the number of tractable computations. CC2 appears to systematically underestimate the singlet-triplet gaps (Figure ), which makes it suitable for screening given there will be few false negatives. The singlettriplet gaps we report will inherently be small, making accuracy essential. In this regard, even EOM-CCSD is a compromise, but EOM-CCSD seems to slightly overestimate the gaps towards more positive values. For example, we compute E(S 1 -T 1 ) of azulene (Figure ) to be +73 meV with EOM-CCSD/aug-cc-pVDZ and -5 meV with CC2/aug-cc-pVDZ. The experimentally determined value of +49 meV is between these. Based on this offset with EOM-CCSD, azupyrene (Figure ) is thus likely to be almost gapless. Here, we only report vertical excitation energies computed with EOM-CCSD as it provides a conservative estimate of singlettriplet gaps. CC2 values are included in the ESI, Table -S3.