Cu and metal-free ligands were targeted for tandem mass spectrometry (MS 2 ) experiments to elucidate structural characteristics. LC and HESI source settings were the same as in MS 1 analyses, except the voltage was set to 3.75 kV and MS 1 spectra were collected from 455 to 1015 m/z with a resolution of 600,000 at m/z 400. MS 2 spectra were collected in the ICR cell using an isolation width of 0.6 Da and a maximum ion injection time of 500 ms at a resolution of 600,000 at m/z 400. Ions were fragmented via collision induced dissociation (CID) with a normalized collisional energy of 40, activation Q of 0.25, and an activation time of 10 ms. Select fragment ions were targeted for MS 3 experiments in the linear ion trap using the same settings as for the MS 2 experiments.