Figure presents the HOMO and LUMO isosurfaces and orbital energies of Npe, TCNB, TCNQ, Npe:TCNB, and Npe:TCNQ. One of the most striking features of the orbital isosurfaces is the similarity of the Npe:acceptor complexes' HOMO and Npe HOMO isosurfaces, as well as those of the Npe:acceptor complexes' LUMO and acceptor LUMO. Because a large degree of CT is observed in the S1 states (HOMO→LUMO) of each complex, we look for correlations between the degree of similarity between isolated vs. complexed orbitals and the degree of S1 CT, using our recently developed method, shown in Table . In the case of Npe:TCNB, we find an overlap of 0.99 between the Npe HOMO and Npe:TCNB HOMO (Npe-Npe:TCNB) and an overlap of 0.99 between the TCNB LUMO and Npe:TCNB LUMO (TCNB-Npe:TCNB). In the case of Npe:TCNQ, overlap values are calculated to be 0.98 between the Npe HOMO and Npe:TCNQ HOMO (Npe-Npe:TCNQ) and 0.98 between the TCNQ LUMO and Npe:TCNQ LUMO (TCNQ-Npe:TCNQ). Our explicit calculations of the degree of CT in S1 using TDM analysis (See Figures &) reveal a high degree of CT in both complexes, with 0.97e in the S1 state of Npe:TCNB and 0.95e in the S1 state of Npe:TCNQ. Comparing HOMO overlap between Npe-Npe:TCNB (0.99) and Npe-Npe:TCNQ (0.98), Npe-Npe:TCNB exhibits a 1% higher overlap than that of Npe-Npe:TCNQ. The LUMO overlap between TCNB-Npe:TCNB (0.99) is also 1% higher than that of TCNQ-Npe:TCNQ LUMO (0.98). Taking the average of the HOMO and LUMO values for each complex, as shown in Table , we see that the average orbital similarity for Npe:TCNB is 0.99 vs. 0.98 for Npe:TCNQ, revealing that Npe:TCNB has a slightly higher orbital similarity (1%) than Npe:TCNQ, as expected from the slightly higher degree of S1 CT in Npe:TCNB (0.97e vs. 0.95e in Npe:TCNQ). While these differences in orbital similarity between Npe:TCNB and Npe:TCNQ are quite small, we find that the degree of orbital similarity is very high for both complexes, as expected from the large degree of S1 CT in both systems. We now turn to comparing orbital energies using well-established techniques. Prior studies have used the metric EHOMO donor -ELUMO acceptor to identify the degree of CT in the ground state, with larger values of EHOMO donor -ELUMO acceptor representing higher values of S0 CT. The energy difference between isolated Npe HOMO and TCNB LUMO (EHOMO Npe -ELUMO TCNB ) is (-7.02 eV) -(-3.04 eV) = -3.98 eV. In the Npe and TCNQ orbital analysis, we observe an EHOMO Npe -ELUMO TCNQ difference of -(-7.02 eV) -(-3.98 eV) = -3.04 eV. Comparing the EHOMO Npe -ELUMO acceptor values between the two systems, we observe that EHOMO Npe -ELUMO TCNQ = -3.04 eV is higher than EHOMO Npe -ELUMO TCNB = -3.98 eV, indicating a larger degree of S0 CT.