New organic ligand L (1) resulting from a condensation reaction of semicarbazide with 2,3-dihydroxybenzaldehyde has been prepared and investigated by modern physicochemical methods. 1H, 13C and 15N NMR data of 1 have been obtained on the basis of 1D (1H, 13C) and 2D 1H/13C and 1H/15N HETCOR experiments in DMSO-d6 solution. The 1H NMR spectrum of 1 shows the characteristic resonances, namely the broad singlet of amide protons at δ 6.37 ppm, the multiplets of aromatic protons in the 6.63– 7.17 ppm range, the azomethine proton at δ 8.13 ppm, the phenolic OH protons at δ 9.20 and 9.42 ppm and the amine proton at δ 10.20 ppm, as well. The interaction between NiCl2·6H2O and L in methanol resulted in an ionic compound [Ni(L-H)(L)]Cl (2) with its mononuclear cation stabilized by a chlorine counteranion in the lattice. Compound 2 was characterized by elemental analysis and IR spectroscopy, and the crystalline structure was determined by the X-ray diffraction study. Single-crystal X-rayanalysis revealed that compound 2 crystallizes in the triclinic space group P-1, a=13.168(2), b=19.735(3), c=22.599(5) Å, α=106.19(2), β=93.84(2), γ=98.56(2)°, V= 5541.1(2) Å3. The Ni(II) ion possesses a distorted octahedral coordination geometry with two tridentate Schiff-base ligands coordinated in a meridional configuration via phenolic and ketone oxygen atoms, and azomethine nitrogen atom. One of the ligands in 2 appears as a neutral entity (L), while the second is deprotonated and appears as an anion (L-H)-. Such behavior of the tridentate Schiff base in a Ni(II) complex is quite unusual, although it has been previously described in literature [1]. 1. D. Sadhukhan, A. Ray, G. Pilet, C. Rizzoli, G. M. Rosair, C. J. Gomez-García, S. Signorella, S. Bellu, S. Mitra. Inorg. Chem., 2011, 50, 8326-8339.