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.

Dillip Kumar Chand

Department Of Chemistry

Isomers

Ligands

Molecules

Nitrogen compounds

Palladium compounds

1 ,10-phenanthroline

Coordination environment

COORDINATION PLANE

CRYSTAL PACKINGS

HEXAGONAL STACKING

INTERNAL CAVITIES

PI-STACKING

SQUARE PLANES

Crystal Structure

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Crystal Growth and Design

A series of binuclear palladium(II)-based self-assembled metallomacrocycles of Pd2L′2L2 type compositions were synthesized by complexation of an imidazole appended non-chelating bidentate ligand L with different cis-protected palladium(II) components (i.e. PdL′). The complexes [Pd2(en)2(L)2](NO3)4, 1, [Pd2(tmeda)2(L)2](NO3)4, 2, [Pd2(bpy)2(L)2](NO3)4, 3, and [Pd2(phen)2(L)2](NO3)4, 4 were characterized by NMR spectroscopy and their nuclearities were established with the help of ESI-MS. Solid state structures of the complexes 2, 3 and [Pd2(phen)2(L)2](OTf)4, 4′ were established by the single-crystal XRD technique. These metallomacrocycles could act as tectons for crystal engineering by using the available π-surface on their architectures. The crystal packing of these molecules revealed the importance of the π-surface on the ligand moiety as well as on the cis-protecting moiety. Utilization of the π-surfaces afforded 1D to 3D supramolecular networks in solid state. © 2018 Elsevier B.V.

Inorganica Chimica Acta

Crystal engineering with palladium(II)-based self-assembled binuclear complexes as tectons

Abstract: Helical self-assembled coordination complexes are broadly classified under linear and circular helicates. While the number of strands of the ligand units in a molecule of the linear helicates is used for further classifications such as single-stranded, double-stranded and so on, the circular helicates are not classified further. The compositions of helicates are considered as M xL y where the terms x and y stand for the number of metal ion(s) and ligand strands, respectively. However, more than one type of metal centers/ligand in helicates are also known. The linear helicates of a given number of strands are further classified under the number of metal centers such as binuclear, trinuclear and so on. Representative examples are included to exemplify the varieties of helicates. Graphical abstract: Synopsis: Helical self-assembled coordination complexes are broadly classified under linear and circular helicates. While the number of strands of the ligand units in the linear helicates is used for further classifications, the circular helicates are put all under one category. Representative examples are included to exemplify the varieties of helicates. Pictogram:[Figure not available: see fulltext.]. © 2018, Indian Academy of Sciences.

Fulltext

Journal of Chemical Sciences

Linear and circular helicates: A brief review

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

A series of self-assembled "double saddle"-type trinuclear complexes of [Pd3L′3L3] formulation have been synthesized by complexation of a series of cis-protected palladium(II) components with a slightly divergent "Eshaped" non-chelating tridentate ligand, 1,1′-(pyridine-3,5-diyl)bis(3-(pyridin-3-yl)urea (L). The cis-protecting agents L′ employed in the study are ethylenediamine (en), tetramethylethylenediamine (tmeda), 2,2′-bipyridine (bpy), and 1,10-phenanthroline (phen), for 1, 2, 3, and 4, respectively. The crystal structures of [Pd3(tmeda)3(L)2](NO3)6 (2), [Pd3(bpy)3(L)3](NO3)3 (3), and [Pd3(phen)3(L)2](NO3 )6 (4) unequivocally support the new architecture. Two of the "double saddle"-type complexes (3 and 4) are suitably crafted with p surfaces at the strategically located cis-protecting sites to facilitate intermolecular p-p interactions in the solid state. As a consequence, six units of the 3 (or 4 ) are assembled, by means of six-pairs of p-p stacking interactions, in a circular geometry to form an octadecanuclear molecular ring of [(Pd3L′3L3)3] composition. The overall arrangement of the rings in the crystal packing is equated with the traditional Indian art form rangoli. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemistry - A European Journal

Octadecanuclear gear wheels by self-assembly of self-assembled "double saddle"-type coordination entities: Molecular "rangoli"

Self-assembled molecular triangles [Pd3(phen)3(imidazolate)3](NO3)3, 1a and [Pd3(phen)3 (imidazolate)3](PF6)3, 1b are prepared by the combination of imidazole with Pd(phen)(NO3)2 and Pd(phen) (PF6)2, respectively. Imidazole was deprotonated during the complexation reactions and the imidazolate so formed acted as a bis-monodentate bridging ligand to form the bowl-shaped trinuclear architectures of 1a/b. Relative orientation of the imidazolate moieties can be best described as syn,anti,antias observed in the crystal structure of 1b. However, in solution state, slow conformational changes are assumed on the basis of 1HNMR spectral data. The molecular triangles are crafted with three peripheral phen units capable of π-π stacking interactions. Well-fashioned intermolecular π-π interactions are observed in the solid-state, wherein further self-assembly of already self-assembled triangle is observed. © 2015 Indian Academy of Sciences.

Role of peripheral phenanthroline groups in the self-assembly of self-assembled molecular triangles

A rare variety of self-assembled molecular triangle [Pd3(bpy)3(imidazolate)3](NO3)3, 1 is prepared by the combination of Pd(bpy)(NO3)2 with imidazole, at 1:1 ratio, in acetonitrile-water. Deprotonation of imidazole happened during the course of the complexation reaction where upon the metallomacrocycle is formed. The bowl-shaped trinuclear architecture of 1 is crafted with three peripheral bpy units capable of π-π stacking interactions. While the solution state structure of 1can be best described as a trinuclear complex, in the solid-state well-fashioned intermolecular π-π and CH- π interactions are observed. Thus, in the solid-state further self-assembly of already self-assembled molecular triangle is witnessed. The triangular panels are arranged in a linear manner utilizing intermolecular π-π interactions where upon two out of three bpy units of each molecule participated in the chain formation. © 2014 Indian Academy of Sciences.

Self-assembly of self-assembled molecular triangles

A series of designed binuclear palladium(II)-based self-assemblies, [Pd2(en)2(L)2](NO3)4, 1a; [Pd2(tmeda)2(L)2](NO3)4, 2a; [Pd2(bpy)2(L)2](NO3) 4, 3a; and [Pd2(phen)2(L)2](NO 3)4, 4a, are synthesized. These complexes are obtained in good to excellent yields by equimolar combination of the nonchelating bidentate ligand bis(4-pyridylmethyl)piperazine, L, with the corresponding cis-protected palladium(II) component, that is, Pd(N-N)(NO3)2, under suitable reaction conditions. The cis-protecting N-N units used are ethylenediamine (en), tetramethylethylenediamine (tmeda), 2,2′-bipyridyl (bpy), and 1,10-phenanthroline (phen). The complexes 1a-4a are well-characterized by 1H NMR, H-H COSY, and HSQC, and the molecular compositions have been established by ESI-MS. The molecular structures are confirmed for the complexes [Pd2(tmeda)2(L) 2](ClO4)4, 2b; [Pd2(bpy) 2(L)2](ClO4)4, 3b; and [Pd 2(phen)2(L)2](NO3)4, 4a, by the single-crystal X-ray diffraction technique. In the cases of the complexes 3b and 4a, the crystal packing diagrams display a unique one-dimensional predefined organization of molecules by intermolecular π-π interactions using the strategically located π-surfaces of the cis-protecting units. This organization resembles a set of toppled dominos. A given set exhibits further interactions with the neighboring sets in the packing pattern that are influenced by the nature of the N-N moiety, for example, bpy or phen. However, no such arrangement is observed in the case of the complex 2b due to the lack of a π-surface at the cis-protecting moiety. © 2013 American Chemical Society.

Journal	Data powered by TypesetCrystal Growth and Design
Publisher	Data powered by TypesetAmerican Chemical Society
ISSN	15287483
Open Access	No