This paper reports stretching frequencies of the novel NLnO lanthanide nitride, oxide molecules and the NCeO- and NPrO-anions in solid argon. Combination bands observed for NCeO, NPrO, NNdO, and NTbO confirm these assignments, and density functional calculations are presented to model the vibrational potentials of NCeO, NPrO, NNdO, NGdO, NToO, and NLuO. The Ln-O frequencies of the NLnO molecules range from 800 to 720 cm(-1), except for the case of NEuO, which is lower, near the EuO diatomic molecule. The Ln-N frequencies of the NLnO molecule depend on the availability of electrons for the LnN bond after the LnO double bond has been satisfied and, therefore, suggest the presence of three different bond orders, depending on the metal center. In NLuO, the Lu-N mode is 425.6 cm(-1), and the Lu atom retains a filled f-shell; the Ce-N bond of NCeO has a higher frequency, 690.8 cm(-1), and NPrO has a Pr-N mode at 900.8 cm(-1), which is even higher than the PrN diatomic mode (857.9 cm(-1)). In addition, NO complexes with Ln, LnO, and CeO2 have been identified. The increase in yield of these complexes and NLnO insertion products on annealing may be useful in the development of models for the catalytic activity of Ln atoms in the conversion of NO to N-2.