The interactions between two nickel complexes with the ligand N,N'-bis (2-pyridylmethylene)-1,3-diaminopropyl and the indoles melatonin, serotonin, tryptamine, and tryptophol were characterized using UV-vis and fluorescence spectroscopy. The fluorescence of all the indoles were quenched in the presence of the complex with a hydroxyl group, indicating that hydrogen-bonding is a necessary interaction for quenching to occur. Various quenching parameters were determined using Stern-Volmer analysis and the quenching was determined to be of a mixed nature with high static quenching values (1011-1013M-1). Additional analysis using the finite sink approximation indicated that the bimolecular reactions were not diffusion-limited and had high activation energies (135-199kJmol-1).