Three novel, homochiral, porous metal–organic frameworks based on the H2PDBAla ligand and different divalent cations (Co­(II)) and Cu­(II)), namely, [M­(PDBAla)­(bipy)­(H2O)2]­·3H2O (M = Co 1 and Cu 2), [Cu­(PDBAla)­(bpea)]­·7H2O (3) (H2PDBAla = pyridine-2,6-dicarbonyl-bis­(l-alanine), bipy = 4,4′-bipyridine, bpea = 1,2-bis­(4-pyridyl)­ethane), have been synthesized and characterized with the assistance of N-donor ligands. The distinctive H2PDBAla ligands are coordinated to divalent metal ions by the different coordination modes, forming various helixes in compounds 1–3. Compounds 1 and 2 are isostructural and feature a 2-fold interpenetrating three-dimensional (3D) framework with the cds topological net built by the combination right-handed helical chains and bipy ligands, whereas a 3D framework with the tcj topological net is observed in compound 3, wherein bpea ligands reinforce the 3D framework constructed by right-handed helical chains. Compounds 1 and 3 display high CO2 absorption capability and superior sorption enthalpies, reflecting the strong affinity of the frameworks for CO2. Moreover, compound 3 exhibits a small enantioselective separation performance for racemic alcohol.

Self-assembly of divalent metal ions and designed amino acid derivatives, 4,4′-biphenyl-bis[carbonyl-N-(alanine)] (H 2 BPBAla) and 4,4′-biphenylbis [carbonyl-N-(proline)] (H 2 BPBPro), as well as ancillary ligands, 1,2-bis(4pyridyl)ethane (bpea) and N,N′-bis(4-pyridyl)isophthalamide (bpipa), generated seven homochiral coordination polymers [Cu 2 (BPBAla) 7). All compounds contain different chiral metal-amino acid derivative helixes, which are tuned by varied conformation and configuration of N-donor ligands. 1 exhibits left-handed, doublestranded Cu-BPBAla helical chains tuned by the trans-conformation bpea ligand, whereas isostructural 2 and 3 exhibit right-handed, single-stranded Co/Ni-BPBAla helical chains tuned by the gauche-conformation bpea ligand. In the absence of an ancillary ligand, 4 displays a two-dimensional (2D) Cd-BPBAla layered network made up of left-handed, single-stranded (−Cd-O−) n helical chains and right-handed, double-stranded Cd-BPBPro-fragment helical chains. When H 2 BPBPro replaces H 2 BPBAla, 5 becomes a three-dimensional (3D) framework composed of right-handed, single-stranded Cu-BPBPro helical chains and transconformation bpea ligand. 6 and 7 are isostructural 3D frameworks and constructed by the coalition of left-handed, single-stranded Cd/Zn-BPBPro and Cd/Zn-bpipa helical chains, and there is an angle of 92.28°between the two Cd/Zn-BPBPro helical chains. The photoluminescence spectra of 4, 6, and 7 reveal the corresponding emission of ligands. More significantly, 6 and 7 can effectively detect the natural acidic amino acids by the enhancement of UV absorption intensity.

Eight new coordination compounds built by an unexplored semi-rigid ether-based unsymmetrical tetracarboxylate and varied dipyridyl ligands have been synthesized. Their variety of structures, photoluminescence and magnetic properties are discussed.

No abstract

No abstract