Five new dioxomolybdenum(VI) complexes of the general formula [MoO 2 (Rdtc) 2 ], 1-5, where Rdtc -refer to piperidine (Pipdtc), 4-morpholine (Morphdtc), 4-thiomorpholine (Timdtc), piperazine (Pzdtc) or N-methylpiperazine (N-Mepzdtc) dithiocarbamates, respectively, have been prepared. The complexes were characterized by elemental analysis, conductometric measurements, electronic, IR and NMR spectroscopy. The complexes 1-5 contain a cis-MoO 2 group and have an octahedral geometry. Two dithiocarbamato ions join as bidentates with both the sulfur atoms to the molybdenum atom. The presence of different heteroatoms in the piperidinо moiety influences the ν(C N) and ν(C S) vibrations, which wavelengths decrease in the order: Pipdtc > N--Mepzdtc > Morphdtc > Pzdtc > Timdtc ligands. Based on their spectral data, the molecular structures of complexes 1-5 were optimized at the semi-empirical molecular-orbital level, and the geometries, as obtained from calculations, are described. The antimicrobial activities of the complexes were tested against nine different laboratory control strains of bacteria and two strains of the yeast Candida albicans. All the tested strains were sensitive. Complexes bearing heteroatom in position 4 of piperidine moiety were significantly more potent against the tested bacteria compared to the corresponding ligands.