Compared to the copper complex, the nickel complex features an additional δ g,u magnetic orbital pair, while the iron complex contains additional δ g,u , π x/g,u , and π y/g,u magnetic orbital pairs, as illustrated in Figure . Löwdin analyses indicate that the magnetic orbitals in these complexes contain 93-98% metal d character, while the remaining 1-4% are primarily contributed by oxygen 2p orbitals and less than 3% stem from nitrogen 2p orbitals, see SI for details. This composition is sufficiently analogous to that of the σ g,u orbital pair in the copper complex, as well as to predictions from extended Hückel theory, to support the decomposition of the magnetic interactions. Numerous BS-DFT studies have indicated that the orbital overlaps for corresponding δ g,u orbital pairs in different bridged transition metal complexes contribute very little to the overall coupling, making them negligible. These findings are in good agreement with the energy differences seen for the canonical orbitals in our CASSCF calculations. The energy splitting of the σ g,u orbital pair is 10100 cm -1 in the nickel complex and 9650 cm -1 in the iron complex, both in the same order of magnitude as the splitting value found in the copper complex of 7400 cm -1 . In contrast, the energy splitting of the δ g,u orbitals is significantly smaller at 63 cm -1 in the nickel complex and 16 cm -1 in the iron complex. Since the squares of these energy splittings influence the respective antiferromagnetic J couplings, the σ coupling paths in the CASSCF calculations are up to 5-6 orders of magnitude stronger than the δ paths. In the iron complex, the π x/g,u and π y/g,u orbital pairs in the iron complex are split by 8000 cm -1 and 7800 cm -1 , respectively, which is similar to the energy splitting of the σ g,u orbitals across all complexes. Their contribution to the overall coupling path should therefore only be marginally smaller than the σ path in the same complex.