Complexation of the bridging bidentate ligand N,N'-(pyridine-2,6-diyl) dinicotinamide, L with palladium(II) resulted in a single discrete M 2L4 self-assembly, 1, in a quantitative manner. The entropically-controlled assembly of 1 resulted in a rare saturated, quadruple-stranded metallo-helicate, in which both the left-handed (M) and right-handed (P) helicates exist in the crystal structure. © The Royal Society of Chemistry 2012.

Dillip Kumar Chand

Department Of Chemistry

- DebakantaTripathy

BRIDGING BIDENTATE

HELICATES

PYRIDINE-2

Self assembly

Palladium compounds

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IIT Madras

Dalton Transactions

A self-assembled discrete Pd3L′3L3 type circular helicate of hitherto unknown architecture is disclosed in this work where L′ stands for 1,10-phenanthroline (phen) and L for a triazole appended bidentate nonchelating ligand, i.e., 1,4-bis((1H-1,2,3-triazol-1-yl)methyl)benzene. The coordination environment of palladium(II) in any given PdN4 coordination planes of the helicate is described by one phen moiety and two triazole moieties belonging to different ligand strands. All the three bound phen moieties are uniquely turned inside and lodged in the internal cavity of the molecule; hence the term "intro-vertere circular helicate" is introduced. One of the PdN4 square planes is sandwiched between the other two via phen-inspired intramolecular π-stacking making a cylindrical stacking arrangement. A racemic pair designated as MPP and PMM isomers, where M and P stand for the handedness of the ligand L, is observed in the crystal structure. In the crystal packing, the trinuclear intro-vertere circular helicate molecules are arranged in a columnar hexagonal stacking. The two exposed phen moieties of a given molecule participated in the intermolecular π-stacking. The MPP and PMM isomers are arranged in an alternate manner in the stacks. © 2017 American Chemical Society.

Crystal Growth and Design

Trinuclear Intro-Vertere Circular Helicate and Its Columnar Hexagonal Stacking

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. © 2016 American Chemical Society.

Double-Stranded Binuclear Helicates and Helicity Modulation

The simple combination of PdII with the tris-monodentate ligand bis(pyridin-3-ylmethyl) pyridine-3,5-dicarboxylate, L, at ratios of 1:2 and 3:4 demonstrated the stoichiometrically controlled exclusive formation of the "spiro-type" Pd1L2 macrocycle, 1, and the quadruple-stranded Pd3L4 cage, 2, respectively. The architecture of 2 is elaborated with two compartments that can accommodate two units of fluoride, chloride, or bromide ions, one in each of the enclosures. However, the entry of iodide is altogether restricted. Complexes 1 and 2 are interconvertible under suitable conditions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemistry - A European Journal

Stoichiometrically controlled revocable self-assembled "spiro" versus quadruple-stranded "double-decker" type coordination cages

Palladium(II) has four coordination sites and forms square planar complexes. Discrete self-assemblies are generated by the combination of a variety of palladium(II) components and ligands ranging from bi- to polydentate. The Pd(II) components used are generally of two varieties: cis-protected Pd(II) and unprotected Pd(II). Most common cis-protecting units (X-X) such as ethylenediamine, 2,2'-bipyridine and 1,3-bis(diphenylphosphino)propane and a few other related chelating systems have been exploited for the complexation reactions. The self-assemblies formed are generally represented as [{cis-Pd(X-X)} x(L) y](monoanion) 2x and [Pd m(L) n](monoanion) 2m when generated from the complexation of a suitable ligand (L) with cis-protected Pd(II) and simple Pd(II) units, respectively. When Pd(solvent) 2Cl 2 is complexed with ligands, the solvent molecules are replaced with the incoming ligands, leading to complexes in which the trans positions are occupied by the chloride anions. © 2012 Elsevier B.V.

Coordination Chemistry Reviews

Self-assembled coordination complexes from various palladium(II) components and bidentate or polydentate ligands

Ligand N,N′-bis(3-pyridylformyl)piperazine, L1, exists in syn and anti conformers in solution state almost in equal proportion. Formation of a saturated quadruple stranded helicate is observed when Pd(NO 3)2 is reacted with ligand L1. In the complexed form the ligand exists in a flattened boat conformation with anti form. © 2010 The Royal Society of Chemistry.

Conformation of N,N′-bis(3-pyridylformyl)piperazine and spontaneous formation of a saturated quadruple stranded metallohelicate

The pyridine-appended non-chelating bidentate ligands 1,4-bis(3-pyridyl) benzene (1) and 4,4′-bis(3-pyridyl) biphenyl (2) were complexed with a naked PdII ion for the construction of molecular cage compounds. Prior to these experiments, the complexation of the ligands with cis-[Pd(en)(NO3)2] was also examined, because self-assemblies from the cis-protected PdII ion were expected to be simple motifs that constitute the assemblies from naked PdII ion. The structures of the self-assembled compounds resulting from 1 and [Pd(en)(NO 3)2] depended on the solvent employed. In aqueous solution, an M2L2 trenchlike compound was obtained. In dimethyl sulfoxide, however, a mixture of the M2L2 trench and an M3L3 macrocycle was found in equilibrium, the dynamic nature of which was confirmed by the concentration-dependent nature of the species. At higher concentration, an M4L4 macrocycle was mostly observed. The complexation of 1 with naked PdII ions was expected to produce novel structures that are combinations of the M nLn type frameworks. A peculiar tetrahedral M 4L8 assembly was obtained quantitatively from 1 and Pd(NO3)2, rather than the smallest possible M 3L6 double-walled triangle. Interestingly, the use of Pd(CF3SO3)2 resulted in the sole formation of the latter structure. Thus, the anion is important as a template in the formation of these assemblies. Ligand 2, which contains an extra p-phenylene unit compared to 1, behaved in a similar manner when treated with [Pd(en)(NO3)2], but showed subtle differences with naked PdII ions. With Pd(NO3)2, 2 gave mostly a tetrahedron along with a double-walled triangle. With Pd(CF3SO 3)2, this longer ligand formed a double-walled triangle with a negligible amount of tetrahedra. A single discrete assembly of a perfect tetrahedron was obtained from 2 and PdII ions by choosing p-tosylate as a counterion. © 2006 Wiley-VCH Verlag GmbH &amp; Co. KGaA.

Chemistry - An Asian Journal

Dynamic self-assembly of an M3L6 molecular triangle and an M4L8 tetrahedron from naked PdII ions and bis(3-pyridyl)-substituted arenes

Nanoscale

Design and characterization of a plasmonic Doppler grating for azimuthal angle-resolved surface plasmon resonances

Supramolecular Chemistry

Definition and Emergence of Supramolecular ChemistryAdapted in part fromSupramolecular Chemistry, J. W. Steed and J. L. Atwood, Wiley: Chichester, 2nd Ed., 2009.

Journal	Dalton Transactions
ISSN	14779226
Open Access	No