The binding energies of a number of metal cations with phenol and indole in the gas phase were studied experimentally by radiative association kinetics analysis, supplemented by density functional calculations. Radiative association kinetics measurements were carried out in the Fourier transform ion cyclotron resonance mass spectrometer. Reaction in most cases resulted in adduct formation often followed by sequential addition of a second neutral molecule to the ion. The association kinetics were analyzed to yield binding energy values either by using a variational transition state theory-based approach, incorporating quantum-chemical calculations of vibrational frequencies and infrared intensities, or by using the semiquantitative standard hydrocarbon approach. The competitive collision-induced dissociation (CLD) technique was used to confirm the order of relative binding energies for several complexes. Calculations of the structures and energies of a number of complexes were performed, by means of the B3LYP-density functional approach, both to complement and compare with the experimental binding energies and also to address the question of pi versus heteroatom bonding. With phenol, the two binding sites are close in energy for nontransition metals, but the pi-site is. relatively more favorable for Fe+ and probably Cr+. Experimental, literature, and calculated values were combined to give best-estimate binding energies for a variety of metal ions. For the nontransition-metal ions characterized, phenol binding is similar tb benzene binding, whereas for Cr+ and especially Fe+ phenol binding is stronger than benzene binding. With indole, binding is always enhanced by similar to 5-10 kcal mol(-1) relative to benzene. Formation of dimer ML2+ complexes followed patterns similar to those of previous benzene results, except that phenol dimer complexes with Mg+ and Al+ were unexpectedly observed, suggesting involvement of an oxygen binding site in these cases.