Synthesis and crystal structures of terephthalato-bridged macrocyclic nickel(II) complexes with cis configurations

Abstract

Three dinuclear terephthalato-bridged nickel(II) complexes [Ni(rac-L)] 2 (l-TPA)(ClO 4 ) 2 (1), [Ni(RR-L)] 2 (l-TPA)(ClO 4 ) 2 (2), and [Ni(SS-L)] 2 (l-TPA)(ClO 4 ) 2 (3) (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, TPA = terephthalic acid) have been synthesized and characterized. Single-crystal X-ray diffraction analyses revealed that the Ni(II) atoms have six-coordinated distorted octahedral environments, and the terephthalato ligand bridges two Ni(II) centres in a bis bidentate fashion to form dimers in all three complexes. The monomers of {[Ni(RR-L)] 2 (l-TPA)} 2? and {[Ni(SS-L)] 2 (l-TPA)} 2? are connected through intermolecular hydrogen bonds to generate 1D right-handed and left-handed helical chains, respectively. The racemic character of 1 and the homochiral natures of 2 and 3 are confirmed by the results of CD spectroscopy.

Synthesis and Crystal Structure of Two Succinato‐Bridged Macrocyclic Nickel(II) Complexes

“…The design and synthesis of extended bridged polymetallic complexes have attracted special attention due to their potential applications in magneto‐ and materials chemistry 1–7. Many dinuclear complexes, where the metal ions are bridged by extended multidentate ligands such as μ‐terephthalate,8–11 μ‐oxalate,12–17 μ‐N 3 ,18–21 and μ‐butene dicarboxylate,22 have been reported. In our previous report,11 we used rigid terephthalic acid ligand bridging macrocyclic nickel(II) complexes to construct 1D hydrogen bonded helical chains.…”

“…Many dinuclear complexes, where the metal ions are bridged by extended multidentate ligands such as μ‐terephthalate,8–11 μ‐oxalate,12–17 μ‐N 3 ,18–21 and μ‐butene dicarboxylate,22 have been reported. In our previous report,11 we used rigid terephthalic acid ligand bridging macrocyclic nickel(II) complexes to construct 1D hydrogen bonded helical chains. As a continuance of our research on the constructions of chiral helical chains, we employ [Ni( RR ‐L)] 2+ /[Ni( SS ‐L)] 2+ (L = 5, 5, 7, 12, 12, 14‐hexamethyl‐1, 4,‐8, 11‐tetraazacyclotetra‐decane) and flexible succinic acid ligand as building blocks to construct supramolecular isomers, and 1D right‐handed and left‐handed helical chains of {[Ni( RR ‐L)] 2 (μ‐SA)} 2+ and {[Ni( SS ‐L)] 2 (μ‐SA)} 2+ are obtained through the intermolecular hydrogen bonds, respectively.…”