Syntheses and Properties of One–Three-Dimensional Coordination Polymers Constructed by Metallohelicates of Purin-Containing Carboxylate

An acetate-functionalized purine-containing ligand, 2-(6-oxo-6,9-dihydro-1H-purin-1-yl) acetic acid ( H 2 L ), and its six new one–three-dimensional (1–3D) coordination polymers, [La( HL ) 2 (NO 3 )(H 2 O) 2 ] n ( 1 ), [Ce( HL ) 2 (NO 3 )(H 2 O) 2 ] n ( 2 ), [Pb( HL ) 2 (H 2 O) 2 ] n ( 3 ), [Cd( HL ) 2 (H 2 O) 2 ] n ( 4 ), [Cd( L) ] n ( 5 ), and [Zn( L) ] n ( 6 ), were synthesized and characterized. Single-crystal X-ray diffraction analyses reveal that the architectures of complexes 1 – 6 are built from the metal–organic helixes of ligands H 2 L . The overall structures range from the double helical chains of 1 and 2, and the 2D helical networks of 3 and 4, to the 3D coordination polymers of 5 and 6, containing 2D homochiral layers based on 1D metal–organic helixes. In those meso compounds, ligands H 2 L display differently anionic states, bridge modes, and especially unsymmetrical configurations with the sharp distortion between the acetate and purin in favor of constructing helical assemblies as expected. The plentiful hydrogen-bonding sites and π···π interactions originating from the bioactive purin group of ligand H 2 L greatly contribute to the formation of helical structures and the structural dimension, showing an intriguing ability in the supramolecular assembly. At room temperature, complexes 1 – 6 exhibit solid-state photoluminescences, with their emission wavelengths and intensities varying according to the central metal ions and the coordination patterns of ligand H 2 L . Additionally, the thermostabilities of these new complexes have been discussed in detail. In particular, 3D polymers 5 and 6 have extra high thermostabilities and stronger blue emissions, indicating potential applications in photoluminescent materials.