Meso-Helicates with Rigid Angular Tetradentate Ligand: Design, Molecular Structures, and Progress Towards Self-Assembly of Metal–Organic Nanotubes

Abstract

The self-assembly of two novel metallosupramolecular complexes of the general formulas [L2M2(CH3CN)4][BF4]4 (M = Co, 1a; M = Ni, 1b), where L stands for the tetradentate ligand 3,5-bis[4-(2,2'-dipyridylamino)phenylacetylenyl]toluene, is reported together with their molecular structures ascertained by single-crystal X-ray diffraction studies. Complexes 1a and 1b are isostructural and show the formation of dinuclear meso-helicates with the two octahedral metal centers displaying respectively Δ and Λ configurations. These meso-helicates display large nanocavities with metal---metal separation distance of >2 nm; furthermore, π-π-stacking occurs among individual units to form one-dimensional (1D) polymers which further autoassemble in another direction through π-π contacts among neighboring chains to generate a two-dimensional (2D) network with regular nanocavities. Our approach might be of interest to prepare metal-organic nanotubes via a bottom-up strategy depending on the assembling functional ligand and the geometry of molecular building block.

Recent Developments in the Preparation and Chemistry of Metallacycles and Metallacages via Coordination

“…Amouri and co-workers designed two meso-helicates with M 2 L 2 structures using a ligand with two terminal dipyridylamine groups linked through a series of phenyl and ethynyl groups. 124 This ligand was treated with CoBF 4 hydrate to generate the helical SCC with the remaining coordination sites of both Co centers completed by acetonitrile coordination. A similar Ni analogue was also structurally characterized.…”

Rational Design of Mono- and Bi-Nuclear Cyclometalated Ir(III) Complexes Containing Di-Pyridylamine Motifs: Synthesis, Structure, and Luminescent Properties

“…IR spectra were recorded on a Bruker Tensor 27 equipped with a Harrick ATR. Ligand 3,5-Bis[4-(2,2 -dipyridylamino)phenylethynyl] toluene (L) was prepared, as reported previously by our group [66].…”

Competitive Transmetalation of First-Row Transition-Metal Ions between Trinuclear Triple-Stranded Side-by-Side Helicates

“…Among them metallo-helicates are particularly important as sensors, , DNA binders, ,, and as anticancer agents. , Several bi- and trinuclear homo- and heterometallic helicates for both transition metals − and f-block elements ,,− have been reported following the isolation of the first homometallic helicates by Lehn et al in 1987 . In addition, there are mesocates composed of an even number of metal centers with alternating chirality having a mirror plane at the middle. − In those cases, in which an odd number of metal centers with alternating chirality are present, the ligands bind in a parallel zigzag fashion instead of wrapping around the helix. , Such assemblies are known as side-by-side helicates. Recently, we have introduced a neutral hybrid tris-bidentate ligand ( L ), in which a central 2,2′-bipyridine and two terminal triazolyl-pyridine chelating coordination units are connected by methylene spacers.…”