Abstract Three ion-pair complexes, [4-NH 2-Py] 2[M(mnt) 2] (4-NH 2-Py 1+ = 4-amino-pyridinium; mnt 2− = maleonitriledithiolate; M = Pt ( 1), Pd ( 2) or Ni ( 3)), have been synthesized and characterized. In the crystal of 1, the strong H-bonding interaction was found from the protonated N-atom of pyridinium to the CN group of [Pt(mnt) 2] 2− together with a weak Pt…H interaction between the anion and the cation. The crystals of 2 and 3 are isostructural with very similar lattice parameters and packing structures, which are distinct from the crystal of 1. Two kinds of strong H-bonding interactions are observed in the crystals of 2 and 3 between the CN groups of [M(mnt) 2] 2− anion and the protonated N-atom of 4-NH 2-Py 1+ cation as well as the CN groups of [M(mnt) 2] 2− anion and the amino group of 4-NH 2-Py 1+ cation. Complex 1 shows an intense near-IR absorbance in acetonitrile and solid state, such an absorption band is probably assigned to IPCT transition as well as a trace amount of [Pt(mnt) 2] 1− species; complex 3 possesses a weak near-IR absorption band which can be attributed to the mixture of d–d transition in [Ni(mnt) 2] 2− and IPCT transition as well as a trace amount of [Ni(mnt) 2] 1− species.