)||Re(dxz) and Cu(dx 2 -y 2 )||Re(dxy)), the Re IV magnetic orbitals (dxz/dxy) are not directly interacting with the Cu II (dx 2 -y 2 ) orbital, rather they interact through the long, extended π/π* orbitals of L (Figure , Table ). The contribution from these two interactions to the magnetic exchange interaction is thus expected to be minimal. To further confirm the significance of the Br3 atoms in mediating the exchange interaction, we have replaced Br1 and Br2 with point charges (Figure ) and observe a minimal decrease in the magnitude of antiferromagnetic magnetic exchange interaction (-0.15 cm -1 to -0.12 cm -1 ). This is also supported by natural bonding orbitals (NBOs) analysis, 36, where considerable donoracceptor interactions are observed between hybrid |4s 0.37 4px 0.63 | orbitals of Br3 and the empty 4s and 4p orbitals on Cu (Table ).