The title complex triaqua (3-hydroxy-5-hydroxymethyl-2-methylpyridine-4-carboxaldehyde-3-methylisothiosemicarbazone-k³,O³,N⁷,N¹⁰)Ni(II) nitrate ([Ni(PLITSC)(H₂O)₃](NO₃)₂, 1) represents the second transition metal complex incorporating an isothiosemicarbazide-pyridoxal based Schiff base that has been crystallographically characterized. Complex 1 crystallizes in a P21/n space group, with lattice constants: a = 11.2254(1) Å, b = 12.9941(2) Å, c = 12.8663(2), β = 96,7713(5)°, V = 1863.64(4) Å³, Z = 4, F(000) = 1016, R ₁ = 0.0681, wR ₂ = 0.1201. The central Ni(II) cation is found in a six-coordinate octahedral geometry formed by the tridentate Schiff base ligand PLITSC and three water molecules. The identity of 1 was further confirmed by elemental analysis, IR spectra, and conductometric and magnetochemical measurements.

The coordination sphere of the Ni(II) cation in the green, paramagnetic complex [Ni(C₁₀H₁₄N₄O₂S₁)(H₂O)₃](NO₃)₂ (1, Fig. 1), which crystallizes in P21/n space group, consists of three water molecules and a single tridentate ligand (Schiff base) obtained from isothiosemicarbazide and pyridoxal (pyridoxal is 3-hydroxy-5-hydroxymethyl-2-methylpyridine-4-carboxaldehyde) moieties.