Novel non-symmetric tridentate N,N,O-ligand was obtained by direct substitution of hydrogen in 3-(2-pyridyl)-6-phenyl-1,2,4-triazine. Three binuclear cobalt(II), copper(II) and zinc(II) carboxylate complexes of 3-(2-pyridyl)-5-(2-hydroxynaphthalen-1-yl)-6-phenyl-1,2,4-triazine anion (HL1), [M2(Piv)2(L1)2] (M = Co, Cu, Zn; Piv = Me3CCO2-), were synthesized and characterized by elemental analysis and IR spectroscopy. The complexes structures were determined by single crystal X-ray diffraction analysis. The magnetic property studies indicate that cobalt(II) complex exhibits weak ferromagnetic coupling (J = 1.2(1) cm−1) between two high-spin Co(II) ions linked by double μ-O phenoxo bridges. According to magnetic property studies as well as X- and Q-band EPR spectra for copper(II) complex, the specific structure of the Cu2O2 fragment leads to the predominance of dipole–dipole interactions and weak antiferromagnetic coupling (J = -3.64(3) cm−1).