Four new cobalt(II) complexes of the general formula [Co 2 (Rac)tpmc](ClO 4 ) 3 , where tpmc and Rac refer to N,N',N'',N -tetrakis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane and β-diketonato ligands i.e. 2,4-pentanedionato (acac), 1,3-diphenyl-1,3-propanedionato (dibzac), 1,1,1,5,5,5-hexafluoro-2,4-pentanedionato (hfac) or 2,2,6,6-tetramethyl-3,5-heptanedionato (tmhd) ions, respectively, have been prepared. Elemental analyses, conductometric measurements, UV/VIS, IR, EPR and mass spectroscopy were used for the complex characterization. Each cobalt(II) ion is coordinated with four nitrogen atoms in an exo arrangement of tpmc groups while the additional β-diketone bridges metal-ion centers through the both enolate oxygens. The presence of different R-groups on the diketone influence the ν(CO) and ν(CC) vibrations in the IR spectra. These frequencies decrease in the order of the complexes with coordinated hfac>dibzac>acac>tmhd ligands. The mechanism of the mass spectral fragmentation of the complexes entails a multi-step decomposition process. The g e f f -factors estimated from EPR spectra suggest a similar molecular character of the complexes. Molecular modeling calculations were used to characterize the complex species.