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Varughese S.,Indian National Institute for Interdisciplinary Science and Technology | Hoser A.A.,University of Warsaw | Jarzembska K.N.,University of Warsaw | Pedireddi V.R.,Solid State and Supramolecular Structural Chemistry Laboratory | Wozniak K.,University of Warsaw
Crystal Growth and Design | Year: 2015

Mutual disposition and conformational preferences of functional groups can induce variations in the nature and types of interactions and hence the molecular arrangements in the rigid crystal environment. We comprehensively analyzed this effect in a series of 13 (of which 9 are novel) (Khan et al. Cryst. Growth Des. 2009, 9, 2354-2362; Varughese et al. Chem. - Eur. J. 2006, 12, 1597-1609) molecular complexes of positional isomers of dihydroxybenzoic acid with trans-1,2-bis(4-pyridyl)ethene and 1,2-bis(4-pyridyl)ethane. Seven of the complexes exist as salts, with an observed carboxyl to pyridine heteroatom proton transfer, which can be explained on the basis of ΔpKa analysis. In all the complexes, carboxyl/carboxylate functionalities interact consistently with pyridine/pyridinium moieties. The -OH groups, in contrast, are more versatile with the formation of diverse interaction types: -OH···carboxyl (O-H···O), -OH···carboxylate (O-H···O-), and -OH···pyridine (O-H···N) hydrogen bonds. Hirshfeld surface analysis and computed interaction energy values were utilized to determine the hierarchical ordering of the interactions and further to highlight the significance of weak interactions such as π···π and C-H···π in structure stabilization. In ionic complexes, these secondary interactions become more expressed, with an enhanced contribution from electrostatic elements. The energetic bias toward the complex formation is evident from the calculated cohesive energies of the complexes vis-à-vis their parent components. (Figure Presented). © 2015 American Chemical Society.

Reddy J.P.,Brandeis University | Swain D.,Indian Institute of Science | Pedireddi V.R.,Solid State and Supramolecular Structural Chemistry Laboratory
Crystal Growth and Design | Year: 2014

We report the preparation, analysis, and phase transformation behavior of polymorphs and the hydrate of 4-amino-3,5-dinitrobenzamide. The compound crystallizes in four different polymorphic forms, Form I (monoclinic, P21/n), Form II (orthorhombic, Pbca), Form III (monoclinic, P21/c), and Form IV (monoclinic, P21/c). Interestingly, a hydrate (triclinic, P1¯) of the compound is also discovered during the systematic identification of the polymorphs. Analysis of the polymorphs has been investigated using hot stage microscopy, differential scanning calorimetry, in situ variable-temperature powder X-ray diffraction, and single-crystal X-ray diffraction. On heating, all of the solid forms convert into Form I irreversibly, and on further heating, melting is observed. In situ single-crystal X-ray diffraction studies revealed that Form II transforms to Form I above 175 °C via single-crystal-to-single-crystal transformation. The hydrate, on heating, undergoes a double phase transition, first to Form III upon losing water in a single-crystal-to-single-crystal fashion and then to a more stable polymorph Form I on further heating. Thermal analysis leads to the conclusion that Form II appears to be the most stable phase at ambient conditions, whereas Form I is more stable at higher temperature. © 2014 American Chemical Society.

Shimpi M.R.,Lulea University of Technology | Biswas S.N.,Solid State and Supramolecular Structural Chemistry Laboratory | Sarkar S.,Solid State and Supramolecular Structural Chemistry Laboratory | Pedireddi V.R.,Solid State and Supramolecular Structural Chemistry Laboratory
Journal of Molecular Structure | Year: 2016

Synthesis and structural features of five new coordination assemblies, [Co(bpyH)(H2O)5](BPCH)·(bpyH2)0.5·(H2O) (1a), [{Cu(H2O)3}·{Cu0.5(bpy)0.5(H2O)0.5}2(μ-BPCH)] (1b), [{Cd0.5(BPCH)}2·{Cd0.5(bpy)(H2O)2}2]·6(H2O) (1c), [Cu(BPCH2)(bpyeaH)]·2(H2O) (1d) and [Cd2 (bpyea)0.5(oxalate)0.5(μ-BPC) (H2O)]·(bpyeaH2)·2(H2O) (1e), have been reported. All the assemblies were prepared by co-crystallization of benzenepentacarboxylic acid (BPCH5) either with 4,4′-bipyridine (bpy) or 1,2-bis(4-pyridyl)ethane (bpyea) in the presence of a transition metal ion (either Co(II), Cu(II) or Cd(II)) as the case may be. All the five compounds were synthesized by hydrothermal method and structures were determined by single crystal X-ray diffraction. All the obtained compounds, 1a–1e, exhibit distinct 3-D polymeric architectures either in the form of stacked layers or host-guest networks in which water molecules play a pivotal role providing additional stabilization by coordinate bonds as well as hydrogen bonds. Other non-covalent interactions such as C–H … π and π … π stacking also participate in the formation of exotic 3-D structures of these complexes. © 2016 Elsevier B.V.

Giri L.,Solid State and Supramolecular Structural Chemistry Laboratory | Pedireddi V.R.,Solid State and Supramolecular Structural Chemistry Laboratory
Journal of Molecular Structure | Year: 2015

Abstract Supramolecular assemblies of rac-1,3-cyclohexanedicarboxylic acid (1) with melamine (a), 1,2-bis(4-pyridyl)ethene (b); 1, 2-bis(4pyridyl)ethane (c) in the presence of Co(II), and 1,10-phenanthroline (d) along with Cu(II) and Ni(II), respectively 1a - 1d and 1d', have been reported. All the assemblies were prepared by crystallization method, through slow-evaporation process, at ambient conditions. All the complexes yield sheet structures that are stacked in three-dimensional arrangement, however, each structure is unique within three-dimensional networks with varied arrangements of either organic entities or coordinated ensembles. For instance, while a host-guest type assembly was observed in 1a, only crinkled tapes are observed in 1b. Among coordination complexes, 1c has an interpenetrated cubic network, whereas 1d and 1d' form host-guest networks. A noteworthy feature to highlight is that the water molecules in the channels of 1d organize in the form of pentamers, which are further held together through tetrameric network, with the aid of hydrogen bonds. A further interesting feature is the presence of acid 1 in different conformations in the complexes as cis form in 1b, 1c and 1d and trans form in 1d'. However, in 1a both cis and trans conformers are observed. © 2015 Elsevier B.V.

Talwelkarshimpi M.,Lulea University of Technology | Oberg S.,Lulea University of Technology | Giri L.,Solid State and Supramolecular Structural Chemistry Laboratory | Pedireddi V.R.,Solid State and Supramolecular Structural Chemistry Laboratory
RSC Advances | Year: 2016

Molecular complexes of the active pharmaceutical ingredient (API) theophylline, 1 with 4-halophenylboronic acids [4-chlorophenylboronic acid (a), 4-bromophenylboronic acid (b), 4-iodophenylboronic acid (c)], 4-hydroxyphenylboronic acid (d) and 1,4-phenylene-bis-boronic acid (e) have been reported. The complexes were characterized and analysed using the intensity data obtained by X-ray diffraction techniques. All the halo substituted boronic acid complexes are found to be isostructural (1.a, 1.b and 1.c) irrespective of the variations in size and electronegativity of halogen atoms while complexes with non-halogenated boronic acids, 1.d and 1.e, show distinctly different features between themselves as well as with that of 1.a-c, both in two and three-dimensional arrangements. Complexes 1.a-c are noted to be crystallized in the form of sheet structures, which are stacked in three dimensional arrangements, while channels and square grid networks are observed in 1.d and 1.e, respectively. Further the homomeric and heteromeric interactions which occur in the complexes have been analysed by a DFT-D3 method. © The Royal Society of Chemistry 2016.

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