Department of Chemistry
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Item Structural analysis of bis(pyridyl)diimines: Factors affecting the molecular geometry and supramolecular packing(Elsevier, 2022-02) Sarkar, MadhushreeSystematic analysis of structural features of a series of bis(pyridyl)diimines is done to have an understanding on the effect of different types of interactions in modulating the molecular geometry and final packing of the molecules in the solid state. Supramolecular synthons that may result from weak interactions such as Csingle bondH···N and aromatic interactions are difficult to predict and hence analyzing homologous series of compounds, which can organize only by weak interactions will lead to generating data sets on various possibilities of synthons. In the series of bis(pyridyl)diimines, small variation in the molecular features such as position of nitrogen on pyridyl ring, presence of hydrogen or methyl group on imine carbon and changing the alkyl spacer length is being related to the observed changes in the occurrence of non-covalent interactions and finally in the crystal packing in the solid state. Cooperative effect of intermolecular interactions and steric factors decide the final structural arrangement, which is being inferred by observing the solid state arrangement of the compounds. Crystallization induced emission of the bis(pyridyl)diimines is also studied and correlated with their structural features and the overall supramolecular architecture.Item Amide-to-Amide Hydrogen Bonds in the Presence of a Pyridine Functionality: Crystal Structures of Bis(pyridinecarboxamido)alkanes(ACS, 2005-09-09) Sarkar, MadhushreeCrystal structures of bis(4-pyridinecarboxamido)alkane and bis(3-pyridinecarboxamido)alkane derivatives were determined and analyzed in terms of hydrogen bond networks. Seven crystal structures out of the eight structures studied exhibited amide-to-amide hydrogen bonds. Out of these seven, five form the anticipated β-sheet network whereas two structures form a doubly interpenetrated (4,4)-network. In only one structure does the pyridyl group interfere in the amide-to-amide hydrogen bond, leading to the formation of an N−H···N hydrogen bond network. The analyses and rationalization of these structures and also related derivatives in the Cambridge Structural Database suggested that amide-to-amide hydrogen bond formation depends on the interplanar angle between amide and pyridine groups.Item Crystal Engineering of Metal−Organic Frameworks Containing Amide Functionalities: Studies on Network Recognition, Transformations, and Exchange Dynamics of Guests and Anions(ACS, 2007-06-07) Sarkar, MadhushreeThe reactions of bis(pyridinecarboxamido)alkanes with copper(II) in the presence of various anions and solvent systems afforded several polymeric crystalline complexes with or without guest inclusion. The crystal structure analyses of these complexes reveal that the coordination networks observed here include open one-dimensional (1D) chains containing cavities and open (4,4)-networks with three types of packing modes, namely, mixed, offset−offset, and trigonal, doubly interpenetrated (4,4)-networks both in parallel and in perpendicular (diagonal/diagonal) modes and a three-dimensional pseudo-diamondoid (658-topology) network. The self-complementary amide groups of the ligands assembled these coordination networks into higher dimensional architectures via N−H···O hydrogen bonds. The exchange of counteranions from the polymeric crystalline complexes was found to trigger the network transformations. The 1D chain, which has rectangular cavities, was transformed into a pseudo-diamondoid network upon exchange of ClO4- with PF6- anions. The exchange of anions from two-dimensional (2D) open (4,4)-networks resulted in 2D-interpenetrated networks. It was found that the reverse exchange that is expected to result in open networks from interpenetrated networks is not allowed. The guest molecules included in these networks range from small molecules such as H2O, EtOH, and CHCl3 to big aromatic molecules such as nitrobenzene, toluene, anisole, p-xylene, benzonitrile, and naphthalene. The exchange of guest molecules in crystal-to-crystal fashion was also found to trigger the transformations in the mode of packing of 2D layers.