In continuation of our studies on copper(II) hydrazone complexes with new S-methyldithiocarbazate Schiff base ligand H3L, derived from 4-formyl-3-hydroxy-2-naphthoic acid [1], the new complex of the composition [Cu(HL)(Solv)] (1) was synthesized and separated as single crystals. The single crystal X-ray diffraction study revealed that crystals of complex 1 comprise from discrete molecular entities. The elemental and single X-ray analyses suggested the 1:1 metal-ligand stoichiometry and in comparison to the earlier described complexes [6], the coordinated ligand is stabilized in the double-deprotonated form. During coordination, the ligand undergoes the conformational changes associated with rotation along the single C13-N2 bond of hydrazine moiety, and ensures the usual O, N, S coordination, forming five- and six-membered metallocycles. The coordination polyhedron of copper(II) ion is completed to square planar through oxygen atom provided by dmso solvent molecule. The interatomic distances Cu-S, Cu-N, Cu-O(phen), and Cu-O(solv.) are 2.240(2), 1.927(4), 1.928(5), and 1.935(6) Å, respectively.  The polycrystalline sample of the compound was investigated by EPR method at room temperature (295 K). gi > g* > 2.0023 are consistent with a dx2-y2 ground state. The EPR parameters (gII= 2.18, g┴ = 2.039, giso = 2.046) suggest a square planar structure that is in accordance with X ray data analysis. All series of chelate complexes were screened for their antimicrobial activity against some representative bacterial strains namely S.aureus, C.albicans, E.coli, K.pneumonae. The activity data shows that antimicrobial activity depends on the presence of copper(II) ion, the set of donor atoms, keto-enol isomerization, etc. It was revealed the property of controlling both G(+) and G(-) pathogens at concentrations up to 7-15 μg/ml and 60-120 μg/ml, respectively, being more effective for gram-positive bacteria.