The infrared spectra (4000–100 cm−1) of the complexes [M(picO)2(H2O)2] and [M(picO)2(D2O)2] (picO = picolinateN-oxide; M = Mn, Fe, Co, Ni, Cu, Zn) are discussed. The spectra show that coordination of picO occurs through the carboxyl andN-oxide oxygen atoms and that the water molecules are coordinated to the metal ions. Assignments for the three species of metal-oxygen stretching frequencies are proposed on the basis of the effects of metal ion substitution, replacement of H2O by D2O and dehydration of the copper(II) complex.