Double-Stranded Binuclear Helicates and Helicity Modulation

Abstract

All of the reported self-assembled complexes of cis-Pd2L′2L2 formulation, where L′ stands for a chelating bidentate ligand and L for a nonchelating bidentate ligand, are “non-helical”. We disclose here the debut of the long awaited “helicate” type architecture of the cis-Pd2L′2L2 formulation. In the present work, the term L′ stands for tetramethylethylenediamine (tmeda) and L stands for a (1H-imidazolyl)­methyl-appended bidentate nonchelating ligand having a rigid spacer. The torsion angle between the two coordination PdN4 planes of a given “helicate” is considered here as its magnitude of helicity. Length of spacer unit (i.e., 1,4-benzene, 4,4′-biphenyl and 4,4′-p-terphenyl) crafted in the backbone of L is found to impart such conformation to the bound ligand moieties that the magnitude of helicity is modulated.

Molecular Recombination Phenomena in Palladium(II)-Based Self-Assembled Complexes

“…The bond lengths and bond angles around the palladium­(II) centers in these complexes are found to be in the usual ranges. The role of self-assembled coordination complexes as tectons in crystal engineering have been less explored, and we are interested in this aspect. ,− Therefore, in addition to the description of the crystal structures of 2 , 4 , and 5 , the intermolecular interactions in their corresponding packing pattern is also briefly described in the next section. However, the solid-state packing in the crystal structure of 4 is emphasized due to its suitability as a tecton.…”

Structural and Dynamic Aspects of Palladium(II)‐Based Self‐Assembled Binuclear Coordination Complexes

“…Inspired by our previous progress on synthesis of self‐assembled binuclear complexes,–,,,,, we envisioned that the introduction of the 4,4′‐diphenylmethane moiety as spacer into a ligand back‐bone would end up self‐assembled complexes with large cavities. For this purpose, we considered a “C‐shaped” lengthy bidentate pyridine appended ligand, L containing two urea functionalities and a central 4,4′‐diphenylmethane spacer, (Scheme ).…”

Multi-Stimuli-Responsive Metallogel Molded from a Pd2L4-Type Coordination Cage: Selective Removal of Anionic Dyes

“…In this context, [2]catenanes were prepared via the solvent-promoted interlocking of already self-assembled coordination rings (in the solution phase); 18 a few relevant complexes are also employed as tectons, aiming at intermolecular entanglement (in the gel phase) 19 and predefined packing (in the solid phase). 16,17,20,22 Complexation of palladium(II) with a wide variety of nonchelating bidentate ligands is known to afford a series of Pd m L 2m -type self-assembled coordination cages. 11 The Pd 2 L 4type compounds are among the simplest yet most utilized cages of this series.…”

“…The combination of selected metal ions with suitable organic ligands is an elegant method for the construction of discrete self-assembled coordination cages. − In this regard, palladium­(II) is one of the choicest metal centers that is usually employed either in its cis -protected or bare form for complexation with bi/polydentate nonchelating ligands to achieve a variety of exotic complexes. − Bidentate chelating ligands possessing either nitrogen or occasionally phosphorus as the donor atom are typically used for cis protection around a palladium­(II) center. Our research effort is directed toward the construction of homo- and heteroleptic self-assembled coordination complexes, prepared from a variety of palladium­(II) components and nitrogen-donor ligands. − Further, we have been systematically investigating the self-assembly of already self-assembled palladium­(II)-based coordination complexes in solution, gel, and solid phases. In this context, [2]­catenanes were prepared via the solvent-promoted interlocking of already self-assembled coordination rings (in the solution phase); a few relevant complexes are also employed as tectons, aiming at intermolecular entanglement (in the gel phase) and predefined packing (in the solid phase). ,,, …”