Density functional calculations with the hybrid B3LYP functional have been used to study the ground state of norbornadiene bound to the photosensitizer [Cu(8-oxoquinolinato)]. The main bonding interaction between the ligand and the metal is pi back-donation, metal to ligand, which reduces the pi-pi* band gap in norbornadiene. CIS calculations performed on free norbornadiene and on the system where norbornadiene interacts with the photosensitizer have shown that the photosensitizer reduces the excitation energy to promote the system to the first excited singlet state. In terms of wavelength, this difference implies that light with lambda almost 100 nm longer can be used to photoactivate the norbornadiene with respect to free norbornadiene.