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.

Dillip Kumar Chand

Department Of Chemistry

Mili C. Naranthatta

Venkatachalam Ramkumar

Complexation

Crystal orientation

Crystal Structure

Palladium compounds

1 ,10-phenanthroline

Bridging ligands

COMPLEXATION REACTION

Conformational change

imidazole

MOLECULAR TRIANGLE

RELATIVE ORIENTATION

Stacking interaction

Self assembly

Fulltext

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

Journal of Chemical Sciences

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

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

Bis(pyridin-3-ylmethyl) pyridine-3,5-dicarboxylate (L) possessing one internal and two terminal pyridine moieties displayed differential coordination ability when combined with suitable PdIIcomponents. The compound L acted as a bidentate chelating ligand to form mononuclear complexes when combined with cis-[Pd(tmeda)(NO3)2] or Pd(NO3)2in calculated ratios. The combination of Pd(NO3)2with L in a ratio of 3:4, however, afforded the trinuclear “double-decker” cage [(NO3)2⊂Pd3(L)4](NO3)4, in which L acts as a nonchelating tridentate ligand and the counter anion (i.e., NO3–) acts as template. The encapsulated NO3–can be replaced by F–, Cl–, or Br–but not by I–. The F–-encapsulated cage could not be isolated due to its reactivity, whereas the Cl–or Br–encapsulated cages could be isolated. Although anionic guests such as NO3–, Cl–, or Br–stabilized the cages, the presence of excess Cl–or Br–(not NO3–) facilitated decomplexation reactions releasing the ligand. The complexation of Pd(Y)2(Y = BF4–, PF6–, CF3SO3–, or ClO4–) with L afforded the corresponding mononuclear complexes under appropriate conditions. However, these counter anions could not act as templates for the construction of double-decker cages. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

European Journal of Inorganic Chemistry

Double-Decker Coordination Cages

Complexation of 1,4-phenylenebis(methylene) diisonicotinate, L1, with cis-protected PdII components, [Pd(L′)(NO3)2], in an equimolar ratio yielded binuclear complexes, 1 a-d of [Pd2(L′)2(L1)2](NO3)4 formulation where L′ stands for ethylenediamine (en), tetramethylethylenediamine (tmeda), 2,2′-bipyridine (bpy), and phenanthroline (phen). The combination of 4,4′-bipyridine, L2, with the cis-protected PdII units is known to yield molecular squares, 2 a-d. However, 2 b-d coexist with the corresponding molecular triangles, 3 b-d. Combination of an equivalent each of the ligands L1 and L2 with two equivalents of cis-protected PdII components in DMSO resulted in the D-shaped heteroligated complexes [Pd2(L′)2(L1)(L2)](NO3)4, 4 a-d. Two units of the D-shaped complexes interlock, in a concentration dependent fashion, to form the corresponding [2]catenanes [Pd2(L′)2(L1)(L2)]2(NO3)8, 5 a-d under aqueous conditions. Crystal structures of the macrocycle [Pd2(tmeda)2(L1)(L2)](PF6)4, 4 b′′, and the catenane [Pd2(bpy)2(L1)(L2)]2(NO3)8, 5 c, provide unequivocal support for the proposed molecular architectures. Interlock game: A series of D-shaped self-assembled molecules are prepared from a three-component mixture of cis-protected PdII, rigid rod-like and flexible C-shaped ligands in a 2:1:1 ratio in DMSO. These molecules are considered as molecular karabiners bearing coordination bond loaded gates. The D-shaped molecules are interlocked in aqueous conditions, forming the corresponding [2]catenanes (see figure). © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemistry - A European Journal

Reversible Mechanical Interlocking of D-Shaped Molecular Karabiners bearing Coordination-Bond Loaded Gates: Route to Self-Assembled [2]Catenanes

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

Self-assembled binuclear coordination cages of general formula [Pd 2(N-N)2(L)2](X)4, 1a/b-4a/b are prepared by the combination of N,N′-bis(m-pyridyl)urea, L, with a variety of cis-protected palladium(II) components, Pd(N-N)(X)2. The cis-protecting units "N-N" employed for the synthesis of 1-4 are ethylenediamine (en), tetramethylethylenediamine (tmeda), 2,2′-bipyridine (bpy), and 1,10-phenanthroline (phen), respectively. The term "X" stands for nitrate and perchlorate for a and b, respectively. The assemblies are characterized by NMR and electrospray ionization mass spectrometry (ESI-MS) techniques, and in some cases (i.e., 1a, 2b, 3b, 4a, and 4b) the structures are confirmed by single crystal X-ray diffraction. The conformations of bound L in the crystal structures of all the Pd(II) complexes are found to be syn-syn. The influence of the presence and absence of π cloud at the cis-protecting units on the crystal packing has been studied in detail. In the packing of [Pd 2(phen)2L2](NO3)4, 4a, one unit of [Pd2(phen)2L2]4+ is associated with two other units by π-π stacking interactions thus giving a one-dimensional growth as envisioned on the basis of a design principle. In the case of [Pd2(en)2(L)2](NO3) 4, 1a, and [Pd2(tmeda)2(L)2] (ClO4)4, 2b, such packing is not observed due to the absence of π-cloud at the strategic locations, instead notable H-bonding interactions are seen. However, [Pd2(bpy)2(L) 2](ClO4)4, 3b, displays a π-π interactions using only two units of [Pd2(bpy)2(L) 2]4+(ClO4)-. © 2012 American Chemical Society.

Consequence of presence and absence of π-clouds at strategic locations of designed binuclear Pd(II) complexes on packing: Self-assembly of self-assembly by intermolecular locking and packing

Chem. Soc. Rev.

Molecular architectures of multi-anthracene assemblies

Crystal Growth & Design

Reflections on the Hydrogen Bond in Crystal Engineering

Coordination Chemistry Reviews

Spacer directed metallo-supramolecular assemblies of pyridine carboxylates

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

Journal	Data powered by TypesetJournal of Chemical Sciences
Publisher	Data powered by TypesetSpringer India
ISSN	09743626
Open Access	Yes