Showing papers by "Dillip Kumar Chand published in 2017"

Polyaromatic molecular peanuts.

Abstract: Mimicking biological structures such as fruits and seeds using molecules and molecular assemblies is a great synthetic challenge. Here we report peanut-shaped nanostructures comprising two fullerene molecules fully surrounded by a dumbbell-like polyaromatic shell. The shell derives from a molecular double capsule composed of four W-shaped polyaromatic ligands and three metal ions. Mixing the double capsule with various fullerenes (that is, C60, C70 and Sc3N@C80) gives rise to the artificial peanuts with lengths of ∼3 nm in quantitative yields through the release of the single metal ion. The rational use of both metal–ligand coordination bonds and aromatic–aromatic π-stacking interactions as orthogonal chemical glue is essential for the facile preparation of the multicomponent, biomimetic nanoarchitectures. The complex, multicomponent structures often found in nature are difficult to mimic synthetically. Here, the authors assemble a molecular analogue of a peanut through coordinative and π-stacking interactions, in which a polyaromatic double capsule ‘pod’ held together by metal ions encapsulates fullerene ‘beans’.

A Truncated Molecular Star.

Abstract: A pentanuclear coordination complex assembled from any palladium(II) component and non-chelating ligands is hitherto unreported. The pentanuclear complex [Pd5(L1)5(L2)5](BF4)10, 1 reported here was prepared by the spontaneous complexation of [Pd(DMSO)4](BF4)2 with the non-chelating bidentate ligands 1,4-phenylenebis(methylene) diisonicotinate, L1 and 4,4′-bipyridine, L2 in a one-pot method at room temperature. The planar polycyclic complex 1 with outer diameters of ≈3 nm is termed as a “molecular star” owing to its resemblance with a pentagram shape. Interim paths leading to the star were also probed to decipher related dynamics of the system.

cis-Protected palladium(II) based binuclear complexes as tectons in crystal engineering and the imperative role of the cis-protecting agent

Abstract: A survey of the Cambridge Structural Database (CSD) for crystal structures of binuclear coordination complexes, formed by the combination of suitable ligand(s) and Pd(II) centres which are protected in a cis fashion by 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen), tetramethylethylenediamine (tmeda) or ethylenediamine (en), was carried out. The structures of these binuclear complexes could be classified into five different categories – “opened jaws”, “helicate”, “plateau”, “step” and “bow-shaped” based on the relative spatial orientation of the Pd(II) square planes of the cations and the conformation of the ligand(s). Investigation of the molecular packing in these complexes revealed involvement of the cis-protected Pd(II) units in the self-assembly of the cations. Cations in the complexes that contained bpy and phen moieties often assembled via π⋯π stacking and C–H⋯π interactions between the aromatic rings of the cis-protecting Pd(II) units. In contrast, in the en and tmeda complexes, molecular self-organisation in most cases occurred through noncovalent interactions between the cis-protected Pd(II) units and the ligand, counteranion or included solvent molecules. Hence, the cations can be defined as ‘tectons’, each of which contains two cis-protecting units, which play the role of ‘supramolecular synthons’ in the self-assembly of these binuclear complexes. The study of these crystal structures provides information about preferred patterns of molecular association in these complexes, which is invaluable for the crystal engineering of pre-designed self-assembled coordination complexes for desired functions or properties.

Trinuclear Intro-Vertere Circular Helicate and Its Columnar Hexagonal Stacking

Abstract: 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 m...

Fluorescent 1‐Arylidene‐1,3‐dihydroisobenzofuran: Ligand‐Free Palladium Nanoparticles, Catalyzed Domino Synthesis and Photophysical Studies

Abstract: The present work describes synthesis and photophysical studies of a class of fluorophores containing biologically relevant 1,3-dihydroisobenzofuran scaffold. Ligand-free palladium nanoparticles have been utilized for domino synthesis of 1-arylidene-1,3-dihydroisobenzofurans from 2-iodobenzyl alcohol and terminal arylacetylenes under mild reaction conditions. Reaction of terminal alkylacetylenes with 2-iodobenzyl alcohol however, provided only the Sonogashira products (2-(alk-1-ynyl)phenyl)methanols. The 1-arylidene-1,3-dihydroisobenzofuran derivatives showed structured fluorescence spectra in non-polar cyclohexane, originated from a locally excited state and structureless emission in polar acetonitrile involving intramolecular charge transfer process. The vibronic structures in the locally excited emission were confined to the ring C=C stretching of the dyes. A detailed structure-property relationship of the 1-arylidene-1,3-dihydroisobenzofuran dyes is presented in this study.

Synthesis and spectral investigation of colorimetric receptors for the dual detection of copper and acetate ions: application in molecular logic gates

Abstract: Colorimetric receptors L1, L2 and L3 possessing –OH functionality as binding site and –NO2 as signalling unit with varied positional substitution of –OMe functionality has been designed and synthesised by simple Schiff base condensation reaction. Receptors L1, L2 and L3 showed selective response towards AcO− ion among other interfering monovalent anions viz., F−, Cl−, Br−, I−, NO3−, and . L2 imparts high selectivity towards AcO− ion assisted by push-pull effect of –NO2 and –OMe functionality in conjugation with imine linkage. The binding constant for L2–OAc complex was found to be 9.04 × 104 M−2. L2 exhibited a detection limit of 0.61 ppm towards NaOAc. The selectivity of L1 towards Cu2+ ions with a lower detection limit of 1.81 ppm implies the role of electron donating –OMe in favouring the coordinative interaction of hetero atoms of L1 with Cu2+ ions. The selective detection of AcO− and Cu2+ ions is further established with OR and INHIBIT logic gate application of receptors L1, L2 and L3 corresp...