An Unusual 3D Coordination Polymer Based on Bridging Interactions of the Nucleobase Adenine

The first 3D coordination polymer containing a nucleobase as a bridging ligand, [Cu2(mu-ade)4(H2O)2Cu(ox)(H2O)2 x approximately 14H2O]n (1), has been synthesized by reaction of adenine (Hade) with a basic solution of K2Cu(ox)2 x 2H2O (ox = oxalato dianion). Compound 1 crystallizes in the trigonal space group R3 with a = b = 31.350(1) angstroms, c = 14.285(1) angstroms, V = 12158.7(10) angstroms3, and Z = 9. X-ray analysis shows a covalent 3D network in which the copper(II) centers are bridged by tridentate mu-N3,N7,N9 adeninate ligands. The compound has relatively large, nanometer-sized tubes associated with the self-assembly process directed solely by metal-ligand interactions. The covalent 3D framework remains intact upon removal of the guest water molecules trapped in the nanotubes. Magnetic measurements indicate an overall antiferromagnetic behavior of the compound.