Tanusree Kar

Use of π–π forces to steer the assembly of chromone derivatives into hydrogen bonded supramolecular layers: crystal structures and Hirshfeld surface analyses

Two chromone derivatives C11H10O3 (1) and C11H10O2 (2) have been synthesized and characterized by X-ray structural studies with a detailed analysis of the Hirshfeld surfaces and fingerprint plots facilitating a comparison of intermolecular interactions in building different supramolecular architectures. The title compounds are associated through π–stacking interactions and the linear stacking of π–π forces can be thought as the influencing agent for the organization of the title compounds into hydrogen bonded supramolecular layers and are responsible as well for the strengthening of the molecular assembly. Investigation of the intermolecular interactions and crystal packing via Hirshfeld surface analysis reveals that more than two-thirds of the close contacts are associated with weak interactions. The fingerprint plots demonstrate that these weak interactions are important for both local and crystal packing. A comparison of the Hirshfeld surface in the compounds with similar substituted chromone derivatives in the Cambridge Structural Database (CSD) has been presented.

Insight into supramolecular self-assembly directed by weak interactions in acetophenone derivatives: crystal structures and Hirshfeld surface analyses

The crystallographic study of four acetophenone derivatives (1–4) is reported in the context of crystal engineering with a detailed analysis of Hirshfeld surfaces and fingerprint plots facilitating a comparison of intermolecular interactions in building different supramolecular self-assemblies. The X-ray study reveals that molecules of 1–4 are linked by cooperative weak C–H⋯O, C–H⋯π and π⋯π stacking interactions which are responsible for the formation and strengthening of molecular assembly. The substituting benzyl units are used as a potential scaffold for designing supramolecular self-assemblyvia C–H⋯π forces. Investigation of Hirshfeld surface analysis reveals a much more detailed scrutiny in comparison to these weak forces experienced by each compound. A comparison of Hirshfeld surfaces in the title derivatives with similar substituted and unsubstituted structures retrieved from the Cambridge Structural Database (CSD) has been presented.

Vicker's Microhardness Studies of L-arginine Hydrobromide Monohydrate Crystals (LAHBr)

Vickers microhardness study of (100), (010) and (001) faces of a non-linear optical crystal, L-arginine hydrobromide monohydrate (LAHBr)have been reported.(100) plane is found to be the weakest plane. It has been observed that the microhardness decreases with increasing load for the three crystal planes. The microhardness behaviour have been explained successfully with the help of the PSR model proposed by Li and Bradt. Work hardening index n for the three planes are found to be greater than 1.6 which indicates that LAHBr is a soft crystal.

A successive layer-by-layer assembly of supramolecular frameworks driven by a novel type of face-to-face π+–π+ interactions

The solid-state complex [PTPH3](NO3)3·2(HNO3) (1) has been synthesized and characterized by X-ray studies, where PTPH3 is the triply protonated form of 4′-(4-pyridyl)-2,2′:6′,2′′-terpyridine (PTP). The solid-state structure of the complex reveals that the π+–π+ interactions are the major driving force in the crystal packing while π+–π, π–π and π–anion interactions assist the overall stabilization of self-assembly. Complex 1 exhibits two different π-stack layers, where layer 1 is generated through π+–π+ interactions and the mutual forces of π+–π+ and π+–π form layer 2. The interaction energies of the main driving forces (π+–π+, π+–π and π–anion interactions) observed in the crystal structure have been calculated using dispersion-corrected density functional theory (DFT-D). An analysis of the Hirshfeld surface of complex 1 shows the intermolecular interactions involved within the crystal structure and corresponding quantitative information are presented by fingerprint plots.

Molecular architecture using novel types of non-covalent π-interactions involving aromatic neutrals, aromatic cations and π-anions

A solid-state complex utilizing non-covalent interactions between two aromatic cations is synthesized and characterized. The X-ray study of the structure shows that the anion templated π+–π+ interactions are the major driving force in the crystal packing, while π+–π, π–π, π–anion and π+–anion interactions assist the overall stabilization of self-assembly. In addition, we also identify the cation-mediated non-covalent interaction between two π anions (π−–π− interaction). The interaction energies of the important driving forces (π+–π+, π+–π, π–anion, π+–anion, and π−–π− interactions) observed in the crystal structure are calculated using dispersion-corrected density functional theory (DFT-D).

Structural, thermal and spectroscopic investigation of nonlinear optical crystal L-arginine hydrobromide monohydrate

Abstract l -Arginine hydrobromide monohydrate (LAHBr) has been found to be a new semiorganic material for nonlinear optical devices. In this communication, synthesis, material purification, and single crystal growth, followed by structural, optical, thermal characterization of LAHBr by X-ray diffraction, infrared spectroscopy, differential thermal analysis, and thermogravimetric analysis, are demonstrated. The infrared absorption bands indicate the mode of vibrations of different molecular groups present in LAHBr and confirm the protonation of the amino group. Thermogravimetric analysis and differential thermal analysis results ruled out the possibility of structural changes independent of mass changes.

Biocompatible nanocrystalline natural bonelike carbonated hydroxyapatite synthesized by mechanical alloying in a record minimum time.

Single phase nanocrystalline biocompatible A-type carbonated hydroxyapatite (A-cHAp) powder has been synthesized by mechanical alloying the stoichiometric mixture of CaCO3 and CaHPO4.2H2O powders in open air at room temperature within 2h of milling. The A-type carbonation in HAp is confirmed by FTIR analysis. Structural and microstructure parameters of as-milled powders are obtained from both Rietvelds powder structure refinement analysis and transmission electron microscopy. Size and lattice strain of nanocrystalline HAp particles are found to be anisotropic in nature. Mechanical alloying causes amorphization of a part of crystalline A-cHAp which is analogous to native bone mineral. Some primary bond lengths of as-milled samples are critically measured. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay test reveals high percentage of cell viability and hence confirms the biocompatibility of the sample. The overall results indicate that the processed A-cHAp has a chemical composition very close to that of biological apatite.

Surface Micromorphology of Different Crystallographic Faces of L-arginine Hydrochloride Monohydrate Etched in Organic Solvents

The surface micromorphology of {100}, {010}, {001} and {110} faces of L-arginine hydrochloride monohydrate (LAHCl) crystals etched in various organic solvents and their mixtures with water has been studied by optical microscopy. Selective behaviour of the etchants for revealing screw and edge dislocations, etch channels, etch grooves and terraced etch pits has been demonstrated. It is observed that addition of impurity like FeCl3, to the etchants facilitates the formation of dislocation etch pits and is interpreted in terms of Cabreras thermodynamic theory of dislocation etch pit formation. Crystallinity of the as grown crystals is determined from etch pits count in unit area of different faces and the average dislocation density is found to be ~104 cm-2.

Anion-π interaction stitching 2-D layers formed by self-assembly of cations of a mononuclear copper(II) complex: synthesis, crystal structure and magnetism of [Cu(OAc)(2,2′-dypam)2](ClO4) [HOAc = acetic acid, 2,2′-dypam = 2,2′-dipyridylamine]

A mononuclear Cu(II) compound [Cu(OAc)(2,2′-dypam)2](ClO4) (1), where HOAc and 2,2′-dypam are, respectively, acetic acid and 2,2′-dipyridylamine, has been synthesized and characterized by single crystal X-ray diffraction analysis. The cations of 1 link by N–H ··· O hydrogen bonds to form infinite 1-D zig-zag chains, which run along the b axis. Two adjacent chains along the c axis are joined by C–H ··· O hydrogen bonds to form a 2-D network. These 2-D layers are further bridged by perchlorate anions via weak anion-π interactions that act as a supramolecular glue to build the 3-D supramolecular network. Variable temperature (1.7–300 K) magnetic measurements revealed very weak intermolecular antiferromagnetic interactions at temperatures below 20 K between Cu(II) ions mediated by hydrogen bonds, C–H ··· π and π ··· π interactions. At temperatures ≥20 K, susceptibility data corresponds to isolated Cu(II) ions, indicating that the weak interactions affect the magnetism of 1 only at very low temperatures.

Structural studies and physicochemical properties of L-valine hydrochloride monohydrate

Nonlinear optical material L-valine hydrochloride monohydrate (VHM) was synthesized and single crystals were grown by slow evaporation of its aqueous solution at a constant temperature (42 °C). The crystal structure of VHM was redetermined by single crystal X-ray diffraction analysis. The physicochemical properties of the grown crystal were characterized by thermal and optical analysis and a measurement of hardness. The second harmonic generation efficiency of VHM was investigated by a powder method and it was found to be 0.3 times that of potassium dihydrogen phosphate (KDP).