A ligand 5-(2′-carboxylphenyl) nicotic acid (H 2 cpna) has been successfully applied to construct a series of coordination complexes {[Cd(Hcpna) 9), Nd (10), Eu (11), and Gd (12), 2,2′-bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline) under hydrothermal conditions. By adjusting the reaction pH, H 2 cpna ligand is partially deprotonated to form Hcpna − in 1 and completely deprotonated to create cpna 2− in 2−7, and both forms are observed in 8−12. Complexes 1−5 and 8 possess two-dimensional (2D) layered structures, which are further extended into 3D metal−organic supramolecular frameworks by C−H•••O hydrogen bond and/or π−π stacking interactions. Complexes 6, 7, and 9−12 exhibit one-dimensional (1D) chain structures, which further build three-dimensional (3D) supramolecular architecture via C−H•••O hydrogen-bonding and/or π−π stacking interactions. The results revealed that the pH value of the reaction system and auxiliary ligand play an important role in determining the structures of the complexes. Magnetic susceptibility measurements indicate that compounds 4−10 and 12 have dominating antiferromagnetic couplings between metal centers. Furthermore, thermal stabilities for 1−12 and luminescent properties for 1−3, and 11 are also discussed in detail.

Four achiral two-dimensional (2D) coordination polymers of [M(HIDC)(H 2 O)(prz) 0.5 ] n (M ) Fe, 1; Mn, 2; Cd, 3) and [Co(HIDC)(H 2 O)(pyz) 0.5 ] n (4), one chiral 2D coordination polymer of [Mn(HIDC)(H 2 O)] n (5), and one 2D coordination polymer of [Fe(HIDC)(H 2 O)] n (6) (H 3 IDC ) imidazole-4,5-dicarboxylic acid, prz ) piperazine, pyz ) pyrazine) were hydrothermally synthesized and characterized by single-crystal X-ray diffraction. In 1-3, the HIDC 2anions alternately bridge the M(II) cations to form a one-dimensional (1D) infinite helical chain of [M(HIDC)] ∞ along the 2 1 axis. The chirality of the original formed helical chain is transferred oppositely to neighboring helical chains through the parallel coordination interactions of prz molecules between two adjacent chains, resulting in an achiral 2D sheet of [M(HIDC)(H 2 O)(prz) 0.5 ] n , in which the helical chains are packed in an alternating left-and right-handed chirality. A similar achiral 2D coordination polymer of 4 was obtained when pyz was used as a linker. Compound 5 crystallizes in a chiral space group P2 1 . In 5, the HIDC 2anions also alternately bridge the Mn(II) to form a 1D right-handed helical chain of [MnHIDC] ∞ along the 2 1 axis, and the right-handed chirality of [MnHIDC] ∞ is transferred to neighboring helical chains through the zigzag interchain coordination interactions, leading to the formation of a homochiral 2D sheet, in which all the helical chains are packed in right-handed chirality. In addition, the bulk crystallization of 5 is enantiomeric excess rather than racemic, as evidenced by the results of solid-state vibrational circular dichroism (VCD) and CD spectroscopy. In the 2D structure of 6, the HIDC 2anions alternately bridge the Fe(II) to form a 1D zigzag chain of [FeHIDC] ∞ instead of a 1D helical chain, in which all the HIDC 2anions locate on the same side within the chain. Compound 3 displays strong blue fluorescent emission at room temperature. Magnetic susceptibility measurements of 2 and 5 exhibit antiferromagnetic interactions between the nearest Mn(II) within the sheet, with J ) -0.48 cm -1 , g ) 2.10 for 2, and J ) -0.51 cm -1 , g ) 2.03 for 5.

A 3D porous metal-organic framework (MOF) with 1D open channels has been constructed hydrothermally using Zn(II) and a rigid planar ligand IDC(3)- (imidazole-4,5-dicarboxylate). This MOF can adsorb water selectively over organic solvents and can be regenerated and reused. It also represents a rare example of a MOF with open channels that form/collapse reversibly upon hydration/dehydration.