supramolecular complex [Co(C~5H~6N~2O)~2(H~2O)~4](NO~3)~2 was prepared by the reaction of C~5H~6N~2O (4-methyl-6-hydroxypyrimidine) and cobalt nitrate in ethanol solution, and characterized by elemental analysis and IR spectroscopy. The crystal structure was determined by single crystal diffraction analysis: monoclinic, space group C2/m, a=1.9853(4) nm, b=0.7601(5) nm, c=0.6539(13) nm, β=100. 93(3)°, Z=2, R=0.053. Every [Co(C~5H~6N~2O)~2(H~2O)~4](NO~3)~2 unit forms eight hydrogen bonds (of two types: O－H…O and O－H…N) bridging with four [Co(C~5H~6N~2O)~2(H~2O)~4](NO~3)~2 units leading to the two-dimensional network structure. The result of semiempirical calculation method using PM3 basis set is consistent with the crystal structure. Because the two nitrogen atoms of C~5H~6N~2O have different neat charge, their coordination abilitiy is different. Only one nitrogen atom can coordinate with cobalt. The ligand often coordinates with metals as monodentate. It is difficult to form coordination polymers.

Key words: COBALT COMPLEX, PYRIMIDINE P, CRYSTAL STRUCTURE, HYDROGEN BONDS