Phase Transitions in a Vanthoffite-Type Compound, NaZn(SO): Insights from PXRD and Raman Spectroscopy.

The study of phase transitions in minerals or synthetic compounds analogous to mineral structures is of fundamental interest in different scientific disciplines, with applications ranging from understanding the Earth's geological history to advancing materials science and technology. They provide valuable data and insight into developing new functional materials with desired properties. In this context, we have investigated the structural phase transitions of NaZn(SO), a synthetic compound analogous to the Vanthoffite mineral NaMg(SO), which occurs abundantly in nature as oceanic salt deposits.

Realizing the Lowest Bandgap and Exciton Binding Energy in a Two-Dimensional Lead Halide System.

Finding stable analogues of three-dimensional (3D) lead halide perovskites has motivated the exploration of an ever-expanding repertoire of two-dimensional (2D) counterparts. However, the bandgap and exciton binding energy in these 2D systems are generally considerably higher than those in 3D analogues due to size and dielectric confinement. Such quantum confinements are most prominently manifested in the extreme 2D realization in ()PbI ( = 1 or 2) series of compounds with a single inorganic layer repeat unit.

The Relevance of Experimental Charge Density Analysis in Unraveling Noncovalent Interactions in Molecular Crystals.

The work carried out by our research group over the last couple of decades in the context of quantitative crystal engineering involves the analysis of intermolecular interactions such as carbon (tetrel) bonding, pnicogen bonding, chalcogen bonding, and halogen bonding using experimental charge density methodology is reviewed. The focus is to extract electron density distribution in the intermolecular space and to obtain guidelines to evaluate the strength and directionality of such interactions towards the design of molecular crystals with desired properties. Following the early studies on halogen bonding interactions, several "sigma-hole" interaction types with similar electrostatic origins have been explored in recent times for their strength, origin, and structural consequences.

Minerals to Functional Materials: Characterization of Structural Phase Transitions and Raman Analysis of a Superionic Phase in NaCo(SO).

In search of promising Na ion conductors, we have detected a superionic phase in a Vantoffite mineral, NaCo(SO), at 570 °C, thus enhancing the use of minerals to produce futuristic solid state electrolytes. NaCo(SO) crystallizes concomitantly to produce di- and tetrahydrate forms from an aqueous solution. Both the crystal forms belong to a triclinic system, space group 1.

Syn vs Anti Carboxylic Acids in Hybrid Peptides: Experimental and Theoretical Charge Density and Chemical Bonding Analysis.

A comparative study of syn vs anti carboxylic acids in hybrid peptides based on experimental electron density studies and theoretical calculations shows that, in the anti form, all three bond angles surrounding C of the -COOH group are close to ∼120°, as expected for a C-sp atom, whereas in the syn form, the ∠C-C(O)-O angle is significantly smaller by 5-10°. The oxygen atom in the carboxyl group is more electronegative in the anti form, so the polarity of the acidic O-H bond is higher in the anti form compared to the syn form, as observed within the limitations of H atom treatment in X-ray diffraction. Consequently, the investigated anti carboxylic acid forms the strongest O-H···O hydrogen bond among all model compounds.

Do halogen bonds dictate the packing preferences in solid solutions?

The isomeric compounds, 4-bromo-2-chloro benzoic acid (4Br) and 2-bromo-4-chlorobenzoic acid (2Br), crystallize in entirely different space groups, P2/n and P1[combining macron] respectively. Both structures are stabilized by a strong O-HO hydrogen bonds generating a carboxylic acid dimer along with an unusual triangular halogen bonded motif in the former and a well-defined halogen bond in the latter. Charge density analysis establishes the nature of halogen bonds by bringing out significant changes in the packing features of the two structures as well as the quantification of the interaction energies involved in the formation of the motifs.

Exploring the rare S-H...S hydrogen bond using charge density analysis in isomers of mercaptobenzoic acid.

Experimental and theoretical charge density analyses on isomers of mercaptobenzoic acid have been carried out to quantify the hydrogen bonding of the hitherto less explored thiols, to assess the strength of the interactions using the topological features of the electron density. The electron density study offers interesting insights into the nature of the S-H..

Superionic Behavior and Phase Transition in a Vanthoffite Mineral.

Crystals of a Vanthoffite mineral, NaMn(SO), grown from an aqueous solution, belong to a monoclinic system, P2/c, Z = 2, at ambient temperature. Thermal analysis indicates a phase transition at 455 °C, which was substantiated by in situ variable-temperature powder X-ray diffraction. The structure is orthorhombic (Pmmm) after the phase transition and reverts to the monoclinic system upon cooling.

Synthesis, molecular docking, antimycobacterial and antimicrobial evaluation of new pyrrolo[3,2-c]pyridine Mannich bases.

In this report, we describe the synthesis and biological evaluation of a new series of pyrrolo[3,2-c]pyridine Mannich bases (7a-v). The Mannich bases were obtained in good yields by one-pot three component condensation of pyrrolo[3,2-c]pyridine scaffold (6a-c) with secondary amines and excess of formaldehyde solution in AcOH. The chemical structures of the compounds were characterized by H NMR, C NMR, LC/MS and elemental analysis.

A heuristic approach to evaluate interactions intermolecular interactions in an overcrowded naphthalene.

Octachloronaphthalene (OCN), a serious environmental pollutant, has been investigated by charge density analysis to unravel several unexplored factors responsible for steric overcrowding. The topological features of the enigmatic interactions contributing to steric overcrowding are qualified and quantified from experimental and theoretical charge-density studies. A new facet in the fundamental understanding of interactions is revealed by NCI (non-covalent interaction) analysis.

Probing the influence of non-covalent contact networks identified by charge density analysis on the oxidoreductase BacC.

Bacillus subtilis BacC is an oxidoreductase involved in the biosynthesis of the potent antibiotic bacilysin. The crystal structure of BacC was determined at 1.19 Å resolution.

Is CH3NH3PbI3 Polar?

In view of the continued controversy concerning the polar/nonpolar nature of the hybrid perovskite system, CH3NH3PbI3, we report the first investigation of a time-resolved pump-probe measurement of the second harmonic generation efficiency as well as using its more traditional form as a sensitive probe of the absence/presence of the center of inversion in the system both in its excited and ground states, respectively. Our results clearly show that SHG efficiency, if nonzero, is below the limit of detection, strongly indicative of a nonpolar or centrosymmetric structure. Our results on the same samples, based on temperature dependent single crystal X-ray diffraction and P-E loop measurements, are entirely consistent with the above conclusion of a centrosymmetric structure for this compound in all three phases, namely the high temperature cubic phase, the intermediate temperature tetragonal phase and the low temperature orthorhombic phase.

Acetazolamide polymorphism: a case of hybridization induced polymorphism?

The unusual phenomenon of the formation of the kinetic form as against the thermodynamic form upon slow cooling of boiling aqueous solution in the case of diuretic drug acetazolamide is rationalized in terms of "hybridization induced polymorphism" based on extensive experimental and theoretical investigations.

Halogen Bonding and Chalcogen Bonding in 4,7-Dibromo-5,6-dinitro-2,1,3-benzothiadiazole.

An organic solid, 4,7-dibromo-5,6-dinitro-2,1,3-benzothiadiazole, has been designed to serve as an illustrative example to quantitatively evaluate the relative merits of halogen and chalcogen bonding in terms of charge density features. The compound displays two polymorphic modifications, one crystallizing in a non-centrosymmetric space group (Z' = 1) and the other in a centrosymmetric space group with two molecules in the asymmetric unit (Z' = 2). Topological analysis based on QTAIM clearly brings out the dominance of the chalcogen bond over the halogen bond along with an indication that halogen bonds are more directional compared to chalcogen bonds.

Do carboximide-carboxylic acid combinations form co-crystals? The role of hydroxyl substitution on the formation of co-crystals and eutectics.

Carboxylic acids, amides and imides are key organic systems which provide understanding of molecular recognition and binding phenomena important in biological and pharmaceutical settings. In this context, studies of their mutual interactions and compatibility through co-crystallization may pave the way for greater understanding and new applications of their combinations. Extensive co-crystallization studies are available for carboxylic acid/amide combinations, but only a few examples of carboxylic acid/imide co-crystals are currently observed in the literature.

Synthesis, molecular docking and anti-mycobacterial evaluation of new imidazo[1,2-a]pyridine-2-carboxamide derivatives.

New anti-tubercular agents, imidazo[1,2-a]pyridine-2-carboxamide derivatives (5a-q) have been designed and synthesized. The structural considerations of the designed molecules were further supported by the docking study with a long-chain enoyl-acyl carrier protein reductase (InhA). The chemical structures of the new compounds were characterized by IR, (1)H NMR, (13)C NMR, HRMS and elemental analysis.

Observation of a reversible isomorphous phase transition and an interplay of "σ-holes" and "π-holes" in Fmoc-Leu-ψ[CH2-NCS].

Fmoc-Leu-ψ[CH2NCS] undergoes a reversible isomorphous phase transition upon cooling. The crystal structure at 100 K displays a short N=C=S···N=C=S intermolecular interaction, which has been characterized based on experimental charge density analysis, as a stabilizing interaction with both σ-holes and π-holes acting cooperatively.

Anthrapyrazolone analogues intercept inflammatory JNK signals to moderate endotoxin induced septic shock.

Severe sepsis or septic shock is one of the rising causes for mortality worldwide representing nearly 10% of intensive care unit admissions. Susceptibility to sepsis is identified to be mediated by innate pattern recognition receptors and responsive signaling pathways of the host. The c-Jun N-terminal Kinase (JNK)-mediated signaling events play critical role in bacterial infection triggered multi-organ failure, cardiac dysfunction and mortality.

Temperature-induced reversible first-order single crystal to single crystal phase transition in Boc-γ(4)(R)Val-Val-OH: interplay of enthalpy and entropy.

Crystals of Boc-γ(4)(R)Val-Val-OH undergo a reversible first-order single crystal to single crystal phase transition at Tc ≈ 205 K from the orthorhombic space group P22121 (Z' = 1) to the monoclinic space group P21 (Z' = 2) with a hysteresis of ∼2.1 K. The low-temperature monoclinic form is best described as a nonmerohedral twin with ∼50% contributions from its two components.

Crystal landscape in the orcinol:4,4'-bipyridine system: synthon modularity, polymorphism and transferability of multipole charge density parameters.

Polymorphism in the orcinol:4,4'-bipyridine cocrystal system is analyzed in terms of a robust convergent modular phenol⋯pyridine supramolecular synthon. Employing the Synthon Based Fragments Approach (SBFA) to transfer the multipole charge density parameters, it is demonstrated that the crystal landscape can be quantified in terms of intermolecular interaction energies in the five crystal forms so far isolated in this complex system. There are five crystal forms.

Alkyl chain substituted 1,9-pyrazoloanthrones exhibit prominent inhibitory effect on c-Jun N-terminal kinase (JNK).

N-Alkyl substituted pyrazoloanthrone derivatives were synthesized, characterized and tested for their in vitro inhibitory activity over c-Jun N-terminal kinase (JNK). Among the tested molecules, a few derivatives showed significant inhibitory activity against JNK with minimal off-target effect on other mitogen-activated protein kinase (MAP kinase) family members such as MEK1/2 and MKK3,6. These results suggested that N-alkyl (propyl and butyl) bearing pyrazoloanthrone scaffolds provide promising therapeutic inhibitors for JNK in regulating inflammation associated disorders.