Reaction of freshly-prepared CoCO3, phenanthroline monohydrate and adipic acid (H2L) in CH3OH/H2O produced a mixture of [Co(phen)(H2O)(4)]L(.)0.5H(2)O (1) and [CO2(phen)(2)(H2O)(2)L-2] (2). Complex 1 crystallizes in the orthorhombic space group Pbcn with cell dimensions a = 23.380(2), b = 12.347(1), c = 12.821(1) Angstrom and D-calc = 1.390 g/cm(3) for Z = 8, and complex 2 in the triclinic space group Pi with cell dimensions a=8.203(1), b=9.809(1), c=11.827(1)Angstrom, alpha=70.34(1), beta=74.81(1), gamma=71.54(1)degrees and D-calc=1.592g/cm(3) for Z=1. Complex 1 consists of [Co(phen)(H2O)(4)](2+) complex cations, adipate anions and crystal H2O molecules. The Co atoms are each octahedrally coordinated by one chelating phen ligand and four water molecules with d(Co-O)=2.041-2.097Angstrom and d(Co-N)=2.144, 2.160Angstrom. Through hydrogen bonds, the [Co(phen)(H2O)(4)](2+) complex cations and adipate anions are interconnected into 2D layers, whose assembly could be ascribed to weak pi-pi stacking interactions between interdigitating phen ligands. Complex 2 is composed of centrosymmetric dinuclear [Co-2(phen)(2)(H2O)(2)L-2) molecules, in which the Co atoms are each coordinated by two N atoms of one chelating phen ligand and four 0 atoms of one H2O molecule and two adipato ligands to form distorted octahedra with d(Co-O) = 2.027-2.248 Angstrom and d(Co-N) = 2.112, 2.162 Angstrom. The centrosymmetric molecules are assembled via intermolecular hydrogen bonds and pi-pi interactions into 2D layers.