It is known that some of semicarbazones have the medical properties: in vivo anticancer [1], potential agentsanti-Trypanosoma cruzi [2], antituberculous activity [3] and are used as anticonvulsants [4]. In our previous work we have successful obtained the Cu(II) complex with o-vanillin semicarbazone ligand L1[Cu(L1-H)(H2O)]2(SO4)·5.25H2O (1) [5] and herein we report the synthesis, IR spectroscopy of novel Cu(+2) complex with semicarbazone of 2.3dihydroxybenzaldehyde L2 [Cu(L2-H)(H2O)]2(SO4)·nH2O (2) (Figure) and antimicrobial properties of ligands and their complexes.Figure. The chemical diagram for 1 (R = OCH3, L1) and 2(R = OH, L2) Green crystals of 2similar to crystals of 1were obtained by the same procedure described for 1. The complexes have been characterized by elemental analysis (Cu, C, H, N) and powder diffraction method for polycrystalline samples. The IR spectra of 1 and 2display the characteristic band for SO42- ion at 1076-1034 and 1097-1048 cm-1, respectively. The other main bands: vN-H 3311 and 3328 cm-1(bs) cm-1, vC=O 1664 and 1658 (s) cm-1, vC=N 1548 and 1554 cm-1 (s), vC-O 1244, 1219 and 1262, 1214 cm-1, respectively for 1 and 2. Antimicrobial activity of aqueous solutions of compounds 1 and 2, as well as organic ligands L1 and L2 in DMSO with initial concentrations of 1%, was studied by the method of serial double dilutions and was conducted on gram-positive and gram-negative test microorganisms (Bacillus subtilis CNMN BB-01 4,8·108 UFC/mL, Pseudomonas fluorescens CNMN-PFB-01 4,8·108 UFC/mL, Pseudomonas aurantiaca CNMN PsB-08 4,8·108 UFC/mL, B. cereus fluorescens CNMN-BB-07 4,8·108 UFC/mL). Thus, it has been established that MBC L1 is equal to 0.12% in a DMSO solution, and MBC 1 is equal to 0.12% in water solution; MBC L2 is 0.06% in a solution of DMSO and MBC 2 is 0.5% in an aqueous solution with respect to the test microorganisms under study (MBC of DMSO is 12% and MBC of CuSO4·5H2O is 0.12%).