A novel polymeric one-dimensional compound Cu(tn)Cl2 (tn = 1,3-diaminopropane) was prepared and structurally characterized, and its spectral, magnetic, thermodynamic, and thermal properties were studied. The unique structure shows ladderlike chains composed of Cu(II) atoms and chloro bridging ligands [Cu(-mu(3)-Cl-)Cu2] running along the crystallographic c axis. The coordination geometry about copper (4 + 2) approximates that of a strongly elongated octahedron. The equatorial plane of the coordination octahedron is formed by a chelate N-bonded tn ligand and two chloro ligands. One of the chloro ligands is terminal, and the other one, mu3-Cl-, forms two additional longer bonds to the neighboring copper atoms and thus occupies the axial octahedral positions. The electronic ground state of the Cu(II) ion is of d(z)2 symmetry and suggests the activation of intraladder and interladder Cl...H-N hydrogen bonds as exchange paths that form a two-dimensional pattern of a triangular symmetry. The interaction due to the hydrogen bonds seems to play an important role in molecular packing and magnetic coupling. The studies of magneto-structural correlations including electron paramagnetic resonance measurements and thermodynamic and magnetic properties revealed a two-dimensional character of magnetic correlations with the effective intralayer exchange coupling J/k(B) approximately -3 K. No phase transition to the ordered state has been observed down to 60 mK. Cu(tn)Cl2 with the interlayer coupling J' approximately 10(-3)J and moderate intralayer interaction represents an excellent example of a two-dimensional magnetic system.