A series of three-dimensional lanthanide(III) coordination polymers of 2,5-dihydroxy-1,4-benzenedicarboxylic acid based on dinuclear lanthanide units

The reactions of Ln(NO3)(3) with 2,5-dihydroxy-1,4-benzenedicarboxylic acid (H-2-DHBDC) under solvothermal conditions produce a series of isomorphous lanthanide coordination polymers with the empirical formula {[Ln(2)(DHBDC)(3)(DMF)(4)](DMF)(2)}(n) (Ln = La(1), Nd(2), Sm(3), Gd(4), and Er(5)). Compound {[Ln(2)(DHBDC)(3)(DMF)(4)](DMF)(2)}(n) contains dinuclear Ln(2)(COO)(6) units, which are linked by the -C6H2(OH)(2)- spacers to form a three-dimensional framework exhibiting alpha-Po topology (pcu-(4(12).6(3)) net) based on dinuclear Ln(2)(COO)(6) nodes. The three-dimensional framework shows one-dimensional open channels that accommodate the coordinated and guest DMF molecules. Gas adsorption measurements on compound 4 indicate that the desolvated solid of 4 adsorbs CO2 and shows nonporous behavior toward N-2. The adsorption favoring CO2 over N-2 may arise from the chemical environments of the host framework, which contains the polar -OH groups of the phenyl and the p-electrons of the ligands. Magnetic measurements on compound 4 indicate that there is an antiferromagnetic interaction between Gd3+ ions.