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The azobenzenes, known for theirvarious importance in the industry,have been chosen as model compounds to understand the role of weakinteractions involving the C–X (X = F, Cl, and Br) bond usingsingle-crystal X-ray diffraction technique, especially in the absenceof other stronger intermolecular forces such as hydrogen bonds. Thefluorinated compounds have been found to pack in the lattice by utilizingC–H···F hydrogen bonds, whereas the chlorinatedand brominated analogues have been found to prefer C–X···X–C,C–X···π, and π···πinteractions while packing in the lattice. The stabilization energyoffered by the C–H···F hydrogen bonds and theC–X···X–C interactions have been estimatedby computational methods using Gaussian 09, and the topological propertieshave been determined by using the AIM2000 package. The lattice energydecomposition has been done using semiclassical density sums (SCDS)PIXEL method. Our studies indicate that the stabilization energy offeredby each C–H···F hydrogen bond lies in the rangefrom −0.8 to −1.0 kcal/mol, while that for the C–X···X–Cinteraction has been found to be −0.35 kcal/mol for the X =Cl interaction and −0.73 kcal/mol for the X = Br interaction.Further, the analysis of these interaction by atoms in molecules (AIM)theory indicates that the electron densities (ρc)at the bond critical points (BCP) for C–H···Fand C–X···X–C (X = Cl and Br), calculatedusing the AIM2000 package, are small (<0.007 eÅ–3), and the values of Laplacian (∇2ρc) are positive. This indicates that these interactions are of thehydrogen bond type. A detailed study of these interactions by experimentaland computational methods has been described in the manuscript. [ABSTRACT FROM AUTHOR]

Thecrystal structures of anhydrous enrofloxacin (EFC) (1), enrofloxacin hexahydrate (EFC·6H2O) (2), enrofloxacin maleate (EFC-M) (3), enrofloxacin hemifumarate(EFC-F) (4), enrofloxacin hemisuccinate (EFC-S) (5), enrofloxacin hemioxalate (EFC-O) (6), enrofloxacinacetate (EFC-A) (7) and ammonium salt of enrofloxacin(Am-EFC) (8) have been determined by using single crystalX-ray diffraction (SCXRD). The crystals of 1were grownfrom a dilute solution of EFC in dilute ammonium hydroxide. The crystalsof 2were grown from a solution of EFC with nicotinicacid. Solvent drop grinding experiments on enrofloxacin with variousdicarboxylic acids resulted in four new salts (3–6). When a solution of EFC in glacial acetic acid evaporatedto dryness over a period of time, crystals of 7weregrown. Crystals of 8were found to grow when EFC wasdissolved in liquid ammonia and solution was slowly evaporated atroom temperature (RT). All these products (1–8) were characterized by 1H and 13CNMR spectroscopy, Fourier transform infrared (FTIR) spectroscopy,differential scanning calorimetry (DSC) and powder X-ray diffraction(PXRD). Single crystal X-ray diffraction study has indicated thatthe products 3–6had a cation ofenrofloxacin and an anion of the acid in common. Four of these eightproducts have been found to contain water of crystallization. Threeof these salts were found to have one neutral acid molecule. The protontransfer and hydrate stoichiometry were confirmed from single crystalX-ray diffraction. Solubility of 1and 3–6was determined in water (pH = 6.8) using UV–visspectroscopy at RT. The alteration between the neutral, zwitterionic,anionic and cationic forms EFC has led to very interesting structuresof these salt/cocrystals and also the pure forms (1and 2). [ABSTRACT FROM AUTHOR]

This manuscript demonstrates the synthesis, structural characterization, computational studies, and biomimics of the phenazine oxidase activity of a newly designed cobalt (III) complex, [Co (dpa)(dpa‐H+)(N3)2]Cl2 (1) [dpa = 2,2′‐dipyridylamine] under an aerobic condition. The crystal structure analysis reveals that the cobalt (III) center adopts an octahedral geometry, and the complex forms a beautiful supramolecular framework through noncovalent interactions. The cobalt (III) catalyst turns out to be a promising catalyst for the oxidative coupling of o‐phenylenediamine (OPD) in oxygen‐saturated methanol with an excellent turnover number, kcat = 7.85 × 103 h−1. Spectrophotometric, electrochemical, mass spectrometry, and computational analysis ensure that the course of catalysis undergoes through a catalyst‐substrate complexation, facilitating the development of cobalt‐iminobenzoquinone species in the solution. The computational calculations employing the density functional theory (DFT) throw a light to the mechanistic insights of the phenazine oxidase mimics. ETS‐NOCV (extended transition state‐natural orbitals for chemical valence) plots of the reactive intermediates portray the coordination‐driven depletion of electron density from the nitrogens of OPD to cobalt center leading to the enhancement of electrophilic character on para‐positioned C‐atoms with respect to N‐atoms of OPD, therby catalyzing the nucleophilic attack by second OPD to produce the oxidation product, 2,3‐diaminophenazine (DAP). Interestingly, we are able to isolate the oxidation product of the OPD oxidation reaction as a hydrated chloride salt, DAPH+Cl− ·3H2O (2). The crystal engineering perspectives of 2 attribute the intriguing fate of the secondary chlorides for the stabilization of the oxidation product in crystalline phase. [ABSTRACT FROM AUTHOR]

Azobenzene-based unnatural amino acid motifs were synthesized via Pd(II)-catalyzed diastereoselective C(sp 3 )-H arylation of amino acid carboxamides with iodoacetanilides and Mills azo coupling.

Negishi cross-coupling reaction of organozinc compounds as nucleophiles with aryl halides has drawn immense focus for C-C bond formation reactions. In comparison to the well-established library of Pd complexes, the C-C cross-coupling of this particular approach is largely primitive with nickel-complexes. Herein, we describe the syntheses of Ni(II) complexes, [( Me BICAAC) 2 NiX 2 ] (X=Cl (1), Br (2), and I (3)) by employing the bicyclic (alkyl)(amino)carbene ( Me BICAAC) ligand. The reduction of complexes 1-3 using KC 8 afforded the two coordinate low valent, Ni(0) complex, [( Me BICAAC) 2 Ni(0)] (4). Complexes 1-4 have been characterized by spectroscopic techniques and their solid-state structures were also confirmed by X-ray crystallography. Furthermore, complexes 1-4 have been applied in a direct and convenient method to catalyze the Negishi cross-coupling reaction of various aryl halides with 2,6-difluorophenylzinc bromide or phenylzinc bromide as the coupling partner in the presence of 3 mol % catalyst. Comparatively, among all-pristine complexes, 1 exhibit high catalytic potential to afford value-added C-C coupled products without the use of any additive. The UV-vis studies and HRMS measurements of controlled stochiometric reactions vindicate the involvement of Ni(I)-NI(III) cycle featured with a penta-coordinated Ni(III)-aryl species as the key intermediate for 1 whereas Ni(0)/Ni(II) species are potentially involved in the catalytic cycle of 4., (© 2022 Wiley-VCH GmbH.)

Recently, an unprecedented observation of polar order, thermochromic behavior, and exotic mesophases in new chiral, bent-shaped systems with a -CH 3 moiety placed at the transverse position of the central core was reported. Herein, a homologous series of compounds with even-numbered carbon chains from n=4 to 18 were synthesized, in which -Cl was substituted for -CH 3 at the kink position and a drastic modification in the phase structure of the bent-shaped molecule was observed. An unusual stabilization of the cubic blue phase (BP) over a wide range of 16.4 °C has been witnessed. Two homologues in this series (1-12 and 1-14) exhibit an interesting phase sequence consisting of BPI/II, chiral nematic, twist grain boundary, smectic A, and smectic X (SmX) phases. The higher homologues (1-16 and 1-18) stabilize the SmX phase enantiotropically over the entire temperature range. Crystal structure analysis confirmed the bent molecular architecture, with a bent angle of 148°, and revealed the presence of two different molecular conformations in an asymmetric unit of compound 1-4. A DFT study corroborated that the -Cl moiety at the central core of the molecule led to an increase in the dipole moment along the transverse direction, which, in turn, facilitated the unusual stabilization of frustrated structures. Crystal polymorphism has been evidenced in three homologues (1-10, 1-12, and 1-14) of the series. On the application of mechanical pressure through grinding, compound 1-10 transformed from a bright yellow crystalline solid to a dark orange-green amorphous solid, which reversed upon dropwise addition of dichloromethane, indicating reversible mechanochromism in this class of compounds. In addition, excellent thermochromic behavior has been observed for compound 1-10 with a controlled temperature-color combination., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Design and syntheses of 'aggregation induced emission (AIE)' active blue-emitting bis-cyclometalated iridium(III) complexes with appended diphosphine ligands [Ir(F2ppy)2(L1/L2)2(Cl)] (F2ppy = 2-(2',4'-difluoro) phenylpyridine; L1 = 1,2-bis(diphenylphosphino)ethane; L2 = bis(diphenylphosphino)propane) have been realized on a suitable route. The free phosphorous donor atom present on the appended diphosphine is shown to provide selective binding to the mercuric ion (Hg(2+)). The selective binding ability of the probe molecule towards mercuric ions results in a detectable signal due to complete quenching of their AIE properties. The quenching effect of the probe molecule has been explored and found to be the result of the degradation of the probe iridium(III) complex triggered by the presence of mercuric ions due to an interplay of a soft-soft interaction between the free phosphorous atom of the probe molecule and mercuric ions. These complexes were modelled to obtain deeper understanding of excited state properties and the results were tentatively correlated with the experimental data.

Strong solid-state greenish-blue emitting, mono-cyclometalated iridium complexes, [Ir(ppy)(PPh(3))(2)(H)(Cl)], 2a and [Ir(F(2)ppy)(PPh(3))(2)(H)(Cl)], 2b [ppyH = 2-phenylpyridine; F(2)ppyH = 2-(2',4'-difluoro)phenylpyridine], have been synthesized by a convenient route. The 'aggregation induced enhanced phosphorescence (AIEP)' activity exhibited by these complexes has been rationalized.