Room temperature reaction of Cu(NO 3 ) 2 ·6H 2 O and pyrazine-2,3,5,6-tetracarboxylic acid (ptecH 4 ) in the presence of pyridine (py) in water–methanol (1:1) mixture results in the formation of {[Cu 2 (ptec)·(py) 2 ·(H 2 O) 3 ]·4H 2 O} n (1). With pyridine-2,4,6-tricarboxylic acid (pytcH 3 ) and Cu(NO 3 ) 2 ·6H 2 O, crystals of {[Cu(pytc)]·1/2[Cu(H 2 O) 6 ]·H 2 O} n (2) could be obtained hydrothermally at 180°C. The structure of 1 consists of 2D polymeric sheets. These sheets are stacked on top of one another due to strong C–H⋯π interactions forming an overall 3D structure. The structure of 2, on the other hand, consists of twin-chain coordination polymers. The void spaces between two polymeric chains are occupied by [Cu(H 2 O) 6 ] 2+ ions which are H-bonded to the polymeric chains. The variable temperature magnetic measurements for 1 and 2 show weak antiferromagnetic interaction between Cu(II) centers. The EPR spectra of the compounds are consistent with their structures.