The rational design and synthesis of molecule based magnetic materials have attracted considerable interest last years. The manganese(III) complexes derived from quadridentate Schiff-base with a high-spin ground state of the central ion (S = 2) and the apparent magnetic anisotropy of hexacoordinated Mn(III) centers due to Jahn–Teller distortion, are ideal candidates as paramagnetic building blocks for constructing expanded structures with appealing magnetic properties. Therefore the chemistry of manganese-based coordination complexes obtained via self-assembly of the metal ions with different organic spacers and suitable bridging ligands have been extensively developed. In this context, we investigate the manganese(III) complexes with the derivative of thiosemicarbazide ligands, in particular with salen-like type and namely N1,N4-bis(salicylidene)-Salkyl- isothiosemicarbazide, (H2L1), which ones possess interesting chelating and coordinating properties. Thus the interaction of salicylaldehyde S-methyl isothiosemicarbazone and salicylaldehyde with manganese(II) in the presence of triethylamine as alkaline agent, gives rise to the formation of a new manganese(III) complex, (1 fig.1.a) containing as ligand the triply deprotonated addition product (H3L2) instead of expected condensation derivative (H2L1). Fig.1. Structure of manganese(III) complexes: (a) - 1, (b) – 2 The obtained complex 1 has the composition [MnL2·CH3OH], displays a molecular structure. The atom C(9) of the second salicylaldehyde attached to the isothiosemicarbazide is sp3 hybridized and is bound to a methoxy group, which appeared as a result of esterification. The complex 1 crystallizes into a monoclinic crystal system and P21/c space group with four molecules in the unit cell. The Mn(III) center has a square pyramidal geometry. The base of the pyramid is occupied by tetradentate ligand (L)3- linked with metal centre through two phenol atoms O and two marginal N atoms from isothiosemicarbazide moiety. The Mn-N bond distances (average 1.951 Å) are greater than the Mn-O bonds (average 1.877 Å). The fifth position is occupied by oxygen atom of coordinated methanol situated at 2.177 Å. After passing hydrogen chloride through the chloroform solution of 1, a binuclear manganese(III) complex was separated (2, fig.1) [1]. The complex 2 of the composition [MnL1Cl] was described in [1] and contains as ligand the N1,N4-bis(salicylidene)-Smethyl- isothiosemicarbazide. Structure of 2 is binuclear and is presented in fig.1b. This result testifies that before the condensation, a reaction of nucleophilic addition is developed in this system. The compound 2 has a single molecule magnetic behavior [2].