Search

• Three NNN pincer type Ru(II) complexes were synthesized and characterized by various spectroscopic methods. Molecular structures of the complexes were characterized by X-ray crystallography. • Density functional theory was utilized to elucidate the electronic properties of the complexes. • Synthesis of quinolines and N-alkylation reactions were examined using Ru(II) complexes as catalysts. • In-situ generated reaction intermediates were investigated by HRMS and NMR spectroscopy. • Plausible reaction mechanisms have been proposed for quinolines and N-alkylation reactions. Amines, N-heterocyclic compounds, and their derivatives are ubiquitous in all naturally occurring compounds, particularly alkaloids, and are widely used in pharmaceuticals, agrochemicals, lubricants, and surfactants. The design of pincer type ligands and corresponding metal complexes is a fundamental step with a unique reactivity. In this article, the NNN-pincer type of ruthenium complexes were synthesized and analyzed using a variety of spectroscopic techniques, including UV-Visible, infrared, and NMR. The molecular structures of the complexes were examined by X-ray crystallography. These complexes were also employed to activate carbon and nitrogen (C-N bond) bonds in C-N coupling processes. This paper describes the synthetic approach, product purification, and spectroscopic characterization, and nuclear magnetic resonance (NMR) spectroscopy was used to demonstrate the catalytically synthesized substrates. A total number of 16 quinolines and 22 N-alkylated substrates were synthesized and characterized by NMR spectroscopic technique. Three pincer type ruthenium(II) complexes as catalysts (C1-C3) were synthesized and characterized. These catalysts showed excellent reactivity towards quinolones synthesis of carbonyl compounds and alcohols with low catalyst loading (0.5 mol%) and highly effective for N-alkylation reaction of anilines with different derivatives of alcohol with catalyst loading of as low as 0.5 mol%. [Display omitted] [ABSTRACT FROM AUTHOR]

Intermolecular interactions involving organic fluorine have been the contemporary field of research in the area of organic solid state chemistry. While a group of researchers had refuted the importance of “organic fluorine” in guiding crystal structures, others have provided evidences for in favor of fluorine mediated interactions in the solid state. Many systematic studies have indicated that the “organic fluorine” is capable of offering weak hydrogen bonds through various supramolecular synthons, mostly in the absence of other stronger hydrogen bonds. Analysis of fluorine mediated interaction in the presence of strong hydrogen bonds has not been highlighted in detail. Hence a thorough structural investigation is needed to understand the role of “organic fluorine” in crystal engineering of small organic fluorinated molecules having the possibility of strong hydrogen bond formation in the solution and in the solid state. To fulfil this aim, we have synthesized a series of fluorinated amides using 3-methoxyphenylacetic acid and fluorinated anilines and studied their structural properties through single crystal and powder X-ray diffraction methods. Our results indicated that the “organic fluorine” plays a significant role in altering the packing characteristics of the molecule in building specific crystal lattices even in the presence of strong hydrogen bond. [ABSTRACT FROM AUTHOR]

The studies of weak interactions involving “organic fluorine” have resulted in a number of conflicts in the literature. Although the involvement of a C–F group in influencing the crystal packing has been demonstrated in various compounds, no one has emphasized the consistency of the synthons formed by C–H…F–C hydrogen bonds. Herein, we have attempted to draw a correlation between the formation of a particular synthon and the positions of the fluorine substitutions from the structural analyses of a model system of tetrafluoro substituted N-benzylideneanilines. A few frequently occurring supramolecular synthons involving C–H…F–C hydrogen bonds have been identified in these and related molecules, and have been quantified by ab initio calculations using the MP2 level of theory and the 6-31+G* basis set in the gas phase. The topological properties of these C–H…F–C hydrogen bonds have been calculated using AIM2000. The nature, strength, directionality and synthon reproducibility of the C–H…F–C hydrogen bonds are the key features presented in this article. [ABSTRACT FROM AUTHOR]

TheC–F group, which is found in a large number of smallorganic molecules and drugs available in the market, has still notbeen fully understood in terms of the strength and directionalityof the interactions offered by this group in guiding the formationof crystal lattices. In this manuscript, we have tried to understandthe role played by the C–F group, using a model system of N-benzylideneanilines, on which we have previously donea systematic study with fluorine as a substituent on both rings. Theeffect on the packing of these molecules by replacing one of the fluorineatoms by either Cl or Br has been comprehended in this manuscript.It was observed that the features of the difluorinated analogues remainedintact when the noninteracting fluorine atom was replaced by Cl orBr, while with the replacement of the interacting fluorine by Cl orBr, completely different packing characteristics were found to bedeveloped. To quantify the strength of the interactions offered by“organic fluorine”, stabilization energies of the dimers(which has been found to interact through the C–H···Fhydrogen bond) have been calculated by Gaussian 09 at the MP2 levelusing a 6-31+G* basis set. These values were found to be between −0.3and −6.0 kcal/mol. To study the topological properties of theinteracting molecular pair, AIM calculations have also been done usingAIM2000. In the studied dimers, the existence of bond critical points (BCPs)at the C–H···F hydrogen bond have always beenseen and Laplacian at those BCPs has also been found to be positive,which is clearly an indication of a closed shell type of interactionbetween the C–H and F–C groups. [ABSTRACT FROM AUTHOR]

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]

Abstract: To investigate the interactions between hydrogen bond donor and acceptor giving rise to three dimensional networks, compounds [Ni(H2O)6](ClO4)2 ·2{(CH2)6N4}·2H2O (1), [Ni(H2O)6]Cl2 ·2{(CH2)6N4}·4H2O (2) and [Cd(H2O)4{(CH2)6N4}2](ClO4)2 ·2H2O (3) (where (CH2)6N4 =hexamethylenetetramine) have been prepared and their crystal structures were investigated. In all three complexes, the metal coordination is octahedral. The hexamine molecules are complexed in the cadmium compound, 3 but are free in the nickel salts, 1 and 2. The supramolecular structures of 1 and 2 show motif linking the cationic moieties with hexamine which are in turn interwoven with anionic moieties via water molecules. In contrast the supramolecular structure of 3 shows motif. [Copyright &y& Elsevier]

Azobenzene-based unnatural amino acid motifs were synthesized via Pd(II)-catalyzed diastereoselective C(sp3)–H arylation of amino acid carboxamides with iodoacetanilides and Mills azo coupling. [ABSTRACT FROM AUTHOR]

A series of Cd(II) complexes, [(PPh3)2Cd(SCOf)2] (1), [PPh4]2[Cd(SCOf)2(μ-Br)]2 (2), [(PPh3)2Ag(μ2-SCOf)2Cd(SCOf)] (3), Na2[(PPh3)Cd(MeOH)(SCOf)3]2 (4a) and Na2[(PPh3)Cd(SCOf)3]2.C7H8 (4b) (Where SCOf = furan-2-thiocarboxylate), have been synthesized and characterized by single crystal X-ray analysis and other spectroscopic techniques. Complexes 1 and 2 show distorted tetrahedral and distorted trigonal bipyramidal geometries around Cd(II), respectively. In the case of 3, Cd(II) exhibits a trigonal prismatic structure, whereas, Ag(I) is at the center of a distorted tetrahedron. Complex 4, has a trigonal pyramidal geometry, hitherto unknown for a Cd(II) center. The catalytic activities of complexes for the synthesis of dihydropyrimidinone have been investigated. Out of four complexes, complex 4 is the most efficient catalyst for the one-pot multicomponent Biginelli-type coupling toward the synthesis of dihydropyrimidinone. Excellent yields of the desired products were obtained with very low catalyst loadings (1 mol%). With a few examples, the versatility and scope of the method have also been demonstrated. The catalysts were also tested for their recyclability. [ABSTRACT FROM AUTHOR]

Treatment of copper iodide with 1,1′-bis(diphenylphosphino)ferrocene in 1:1 equivalent ratio afforded centrosymmetric dimer product of composition [{Cu(µ-I)(dppf)}2] (1a). However, similar reactions of 1,1′-bis(diphenylchalcogenophosphoryl)ferrocene (dppfE2) (E = S, Se) with [Cu(CH3CN)4]+ in 1:2 equivalents yielded [{Cu(dppfS2)}n]+ (1b) and [{Cu2(dppfSe2)3}n]2+ (1c) compounds, respectively. These reported compounds have synthesized with slight modifications. All the mentioned complexes were characterized by Uv–Vis, IR, 1H, 31P{1H} NMR spectroscopy and Mass spectrometry. The molecular structure of complex [{Cu(µ-I)(dppf)}2] was established through single crystal X-ray analysis, which suggests distorted tetrahedral geometry around the copper metal center. All the synthesized complexes were studied as a catalyst for synthesis of benzofuran derivatives under an environmentally friendly approach. [ABSTRACT FROM AUTHOR]

The mechanism of fluorescence enhancement of Tb3+ in Tb3+‐trimesic acid‐Gd3+ systems has been explored using dynamic light scattering. In earlier work, the mechanism of fluorescence enhancement of Tb3+ in these systems was proposed to be due to the formation of a polynuclear complex involving Tb3+, trimesic acid and Gd3+. However, no direct experimental evidence was presented for the mechanism in that work. In this work, we have used dynamic light scattering (DLS), to measure changes in the mean hydrodynamic diameter (Zavg) of the Tb3+‐trimesic acid‐Gd3+ complex, as a function of time. The Zavg was found to increase monotonically as a function of time, indicating a continuous growth in the particle size. The Eu3+‐β‐diketones‐Gd3+ system also shows enhancement of Eu3+ fluorescence; though a different mechanism was believed to be operating in this case; namely intermolecular energy transfer. If the two systems followed different mechanisms for fluorescence enhancement, the Eu3+‐β‐diketones‐Gd3+ system, is expected to show a different time evolution of particle size. The DLS study showed that the Zavg increased rapidly to a maximum value and then remained nearly constant throughout our measurements; that is, no gradual increase in Zavg was seen as in the Tb3+‐trimesic acid‐Gd3+ system. These DLS studies of the Tb3+‐trimesic acid‐Gd3+ and Eu3+‐β‐diketones‐Gd3+ systems, therefore confirms that different mechanisms of fluorescence enhancement are operative in the two systems. The study has demonstrated that the increase in fluorescence intensity with time when Gd3+ is added to the Tb3+‐trimesic acid complex is accompanied with an increase in particle size as revealed by dynamic light scattering studies. These observations are explained invoking the role of polynuclear complexes in the mechanism of fluorescence enhancement. [ABSTRACT FROM AUTHOR]

A dinuclear Cu(II) complex was synthesized and crystallographically characterized. The compound was found to have antiferromagnetic interaction in between the Cu(II) centres in the molecule. It had weak intermolecular ferromagnetic interaction. The compound was found to be tyrosinase and catecholase active. In case of tyrosinase activity, the diphenol formed was isolated using thin layer chromatography (TLC) and characterized through 1 H NMR as well as mass spectrometry. The o -quinone derivative formed in this reaction was characterized using GC–MS. The latter activity was monitored spectrophotometrically and the product o -quinone derivative was isolated (in MeOH and MeCN) column chromatographically and characterized using melting point determination. These were followed by Michealis–Menten kinetics with turnover numbers 4.95 × 10 3 and 1.58 × 10 3  h −1 in MeOH and MeCN, respectively. [ABSTRACT FROM AUTHOR]

Strong hydrogen bonds play a significant role in crystal packing. In particular, the involvement of interactions involving fluorine in controlling the crystal packing requires appropriate attention, especially in the presence of other strong hydrogen bonds. In the present study, a detailed quantitative assessment has been performed of the nature, energetics and topological properties derived from the electron density in model compounds based on fluorinated benzamides (a total of 46 fluorine-substituted benzamides containing multiple fluorine atoms) in the solid state. The primary motivation in the design of such molecules is to enhance the acidity of the interacting H atoms in the presence of an increasing number of F atoms on the molecular scaffold, resulting in increased propensity towards the formation of intermolecular interactions involving organic fluorine. This exercise has resulted in the identification of new and frequently occurring supramolecular synthons involving F atoms in the packing of molecules in the solid state. The energetics associated with short and directional intermolecular C sp2-H...F-C sp2 interactions with significantly high electrostatic contributions is noteworthy, and the topological analysis reveals the bonding character of these ubiquitous interactions in crystal packing in addition to the presence of C sp2-F...F-C sp2 contacts. [ABSTRACT FROM AUTHOR]

Borrowing hydrogenation (BH) is a powerful methodology, which is widely adopted for the N-alkylation of amines with alcohols using homogeneous molecular catalysts. To explore the chemistry, herein two novel monomeric Ru(II) complexes [(η6-p-cymene)Ru(L1)Cl2] [Ru-1] bearing 4-trifluromethoxyaniline (L1) and [(η6-p-cymene)Ru(L2)Cl] [Ru-2] bearing quinaldic acid (L2) were synthesized and their structural features were revealed by utilizing analytical and spectroscopic methods like FTIR, 1H and 13C NMR, ESI-MS, and elemental analysis. The lattice structures of both [Ru-1] and [Ru-2] were elucidated by Single Crystal XRD (SC-XRD). Also, aniline-based complex [Ru-3] was synthesized according to the literature and used for comparison. The catalytic efficacy of [Ru-(1–3)] was examined for N-alkylation of amines utilizing alcohols as alkylating agents in benign and solvent-free conditions. The catalytic performance was monitored by GC–MS and HPLC analyses. The primary amine-based (L1) complex [Ru-1] showed a very impressive and efficient conversion of 96%, whereas –N, O donor ligand based (L2) complex [Ru-2] and the unsubstituted aniline based [Ru-3] were able to achieve 25% and 90% conversion, respectively in similar reaction conditions. This drastic variation in catalytic performance was observed due to the co-operative effect of –NH2 in [Ru-1] and [Ru-3]. Metal–ligand cooperation (MLC) in both the complexes stabilizes the intermediate transition state and also the electron deficient Ru(II) center in [Ru-1] has very good binding affinity towards the substrate, which leads to superior catalytic conversion with [Ru-1] compared to [Ru-2] and [Ru-3]. [ABSTRACT FROM AUTHOR]

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, [(MeBICAAC)2NiX2] (X=Cl (1), Br (2), and I (3)) by employing the bicyclic (alkyl)(amino)carbene (MeBICAAC) ligand. The reduction of complexes 1–3 using KC8 afforded the two coordinate low valent, Ni(0) complex, [(MeBICAAC)2Ni(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. [ABSTRACT FROM AUTHOR]

We report the peculiar characteristics of a polydentate Schiff base towards zinc(II) ions in the presence of pseudohalides (thiocyanate and azide) and the charge transport properties of zinc complex mediated devices in the solid state. The designed polydentate chelator, [HL = (Z)-2-methoxy-6-(((2-methoxy phenyl)imino)methyl)phenol)], was synthesized by coupling of o-anisidine and o-vanillin in ethanol under reflux, and the ligand was isolated in a single-crystalline phase in an orthorhombic system with the Pbca space group. Interestingly, the ligand bears unique structural features towards the coordination with zinc ions in the presence of thiocyanate and azide ions leading to mononuclear and dinuclear zinc–Schiff base–pseudohalide complexes (ZnP11NCS and ZnP11N3), respectively. In the ZnP11NCS complex, the Schiff base ligand becomes protonated to a zwitterionic form, which causes their monodentate/bidentate behaviour towards Zn(II) ions. In contrast, the ligand, P11, under identical reaction conditions, behaves as a tridentate chelating ligand towards Zn(II) ions in the ZnP11N3 complex having a symmetric μ1,1-phenoxo-bridge. In both complexes, NCS and N3 ions coordinate with Zn(II) ions in a terminal coordination mode. Crystal engineering approaches and Hirshfeld surface and energy framework analysis of the complexes delineate the dominant contribution of H⋯S and H⋯N hydrogen bonding and C–H⋯π interactions for a structural assortment of the compounds. Further, the complexes have been employed to construct devices to explore the charge transport properties in the dark and a shower of photons. The ZnP11N3 complex exhibits better charge transport properties than ZnP11NCS as evident from high DC conductivity measurement values and relaxation times caused by optical phonon activation under dark and light conditions. This feature might be utilized to explore their template applications in designing electronic devices as per the industry's needs. [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]

Twenty-five (Ia–Iu, IIa–IIb, IIIa, and IVa) diarylidene-N-methyl-4-piperidones (DANMPs) were synthesized and characterized via UV, FT-IR, NMR, and MS while Id was characterized also by single crystal XRD. Twenty-one compounds shortlisted after initial in vitro anti-plasmodial activity successive screenings at 100 μM and 10 μM were evaluated for their IC50s against chloroquine-sensitive Pf3D7, chloroquine-resistant PfINDO, and artemisinin-resistant PfMRA-1240 strains. The four most promising compounds were Ie (IC50s μM 0.35MRA, 1.39INDO, 1.923D7), If (IC50s μM 1.07MRA, 1.36INDO, 3.393D7), Ir (IC50s μM 0.74MRA, 2.45INDO, 1.443D7), and In (IC50s μM 1.27MRA, 1.8INDO, 1.73D7). Resistance indices as low as 0.2 to 0.5 for these potent compounds and <1 for most other compounds suggest their greater potency against drug resistant strains than the drug sensitive strain. The parasiticidal action of Ir was seen within 4 h against the trophozoite stage of the parasite, which is known to express the highest levels of PLP synthase. In silico docking scores of −7.0 to −8.0 kcal mol−1 between potent DANMPs and PfPLP synthase, the direct binding of Ir studied by SPR to recombinantly expressed and purified PfPdx-1 and inhibition of Pdx1 enzymatic activity by Ir suggest this vital enzyme to be a probable target for the DANMPs. The non-hemolytic nature of Ir and conformity of most DANMPs to Lipinski's parameters indicate their potential as new anti-plasmodial leads with PfPLP synthase as one of their targets. [ABSTRACT FROM AUTHOR]

This research study reports the synthesis, structural characterization and phenoxazinone synthase‐like activity of two structurally similar copper(II) complexes developed with a benzimidazole functionalized Schiff base (L). The ligand, L, was designed and synthesized in high yield by the reaction of p‐methoxy benzaldehyde with o‐phenylenediamine. The reaction of L with CuCl2 and Cu(NO3)2 leads to the formation of two isostructural complexes, [Cu(L)2Cl2]2 (1) and [Cu(L)2(NO3)2]2 (2). Single crystal X‐ray structural study reveals that both the Cu(II) centre in 1 and 2 adopts a square planar geometry. An attempt has also been made to understand the role of coordinated co‐ligands on the catalytic oxidation of 2‐aminophenol (2‐AP) to 2‐amino‐3H‐phenoxazine‐3‐one (2‐APX) in methanol. The presence of coordinated nitrate to Cu(II) ions imparts a more labile character to complex 2, and the catalytic efficiency (kcat/KM) for complex 2 (1.50 × 107) was determined almost double compared with that of complex 1 (8.78 × 106). Electro‐chemical and electrospray ionization mass spectrometry studies of 1 and 2 with 2‐AP suggests that the square planar geometries of the Cu(II) centres remain the driving force to develop enzyme‐substrate adducts and excellent catalytic performance of the complexes. Electrochemical and EPR spectral analysis of the reaction mixture confirm the presence of active 2‐AP−/2‐AP•− redox species in the course of catalytic oxidation and suggest the radical driven oxidative coupling of 2‐AP in an aerobic environment. Temperature‐dependent kinetic measurements were carried out to evaluate the activation parameters (Ea, ΔH‡, ΔS‡), which favours the higher rate of catalytic oxidation of 2‐AP for complex 2 than complex 1. [ABSTRACT FROM AUTHOR]

In pursuit of the significant contribution of copper ion in different biological processes, this research work describes the synthesis, X‐ray structure, Hirshfeld surface analysis, oxidative dimerization of 2‐aminophenol and antibacterial activity of a newly designed copper (II)‐Schiff base complex, [Cu(L)2] (1), [Schiff base (HL) = 2‐(2‐methoxybenzylideneamino)phenol]. X‐ray structural analysis of 1 reveals that the Cu (II) complex crystallizes in a cubic crystal system with Ia‐3d space group. The Cu (II) centre adopts an unprecedented tetragonal bipyramidal geometry in its crystalline phase. The Schiff base behaves as a tridentate chelator and forms an innermetallic chelate of first order with Cu (II) ion. The copper (II) complex has been tested in the bio‐mimics of phenaxozinone synthase activity in acetonitrile and exhibits good catalytic activity as evident from high turnover number, 536.4 h−1. Electrochemical analysis exhibits the appearance of two additional peaks at −0.15 and 0.46 V for Cu (II) complex in presence of 2‐AP and suggests the development of AP−/AP•− and AP•−/IQ redox couples in solution, respectively. The presence of iminobenzosemiquinone radical at g = 2.057 in the reaction mixture was confirmed by electron paramagnetic resonance and may be considered the driving force for the oxidative dimerisation of 2‐AP. The existence of a peak at m/z 624.81 for Cu (II) complex in presence of 2‐AP in electrospray ionization mass spectrum ensures that the catalytic oxidation proceeds through enzyme‐substrate adduct formation. The copper (II) complex exhibits potential antibacterial properties against few pathogenic bacterial species like Staphylococcus aureus, Enterococcus and Klebsiella pneumonia and scanning electron microscope studies consolidates that destruction of bacterial cell membrane accounts on the development of antibacterial activity. [ABSTRACT FROM AUTHOR]

Two‐coordinate Cu(I) and Au(I) complexes supported by bicyclic (alkyl)(amino)carbene, [BICAAC‐CuCl] (1), [BICAAC‐CuI] (2), [(BICAAC)2Cu]+[PF6]– (3) and [(BICAAC)2Au]+[AuCl2]– (6) have been synthesized. The reaction of cyclic (alkyl)(amino)carbene, CAACcy with CuCl afforded [CAACcy‐CuCl] (4) and its further reaction with KPF6 gave [(CAACcy)2Cu]+[PF6]– (5). Complexes 1–6 have been characterized by multinuclear NMR, IR and UV‐Vis. spectroscopic method and high‐resolution mass spectrometry (HRMS). Single crystal X‐ray structure of heteroleptic complexes 1 and 4 and homoleptic complexes [(BICAAC)2Cu]+[CuI2]– (2'), 3 and 6 have also been determined. The crystal structure of these complexes confirmed linear two‐coordinate geometry around the metal centers. In the solid‐ state, complexes 1, 2', 4 and 6 displayed C−H⋯M (M=Cu, Au) and weak non‐covalent C−H⋯X (X=Cl, I) and C−H⋯H−C interactions. Computational calculations correlate well to the experimentally observed geometry and help elucidate the absorption characteristics type of transitions and the frontier orbitals involved in them. [ABSTRACT FROM AUTHOR]

Recently, an unprecedented observation of polar order, thermochromic behavior, and exotic mesophases in new chiral, bent‐shaped systems with a −CH3 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 −CH3 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. [ABSTRACT FROM AUTHOR]

The reactivity of a bicyclic (alkyl)(amino)carbene (BICAAC) towards different boranes has been examined in the present work. The reactions with boranes BX3·SMe2 (X = H, Cl, Br), BF3·OEt2 and BCl3 yield Lewis adducts [BICAAC·BH3] (1), [BICAAC·BHCl2] (2), [BICAAC·BH2Cl] (3), [BICAAC·BF3] (4), [BICAAC·BCl3] (5) and [BICAAC·BBr3] (6) respectively, whereas more hydridic boranes, 9-borabicyclo[3.3.1]nonane (9-BBN) and catecholborane (HBcat), enable the insertion of the carbene carbon into the B–H bond to form [BICAAC(H)-(9-BBN)] (7) and [BICAAC(H)-Bcat] (8). These complexes are the first examples of BICAAC–boron compounds and have been characterized using IR, multinuclear NMR spectroscopy, HRMS spectrometry and single crystal X-ray diffraction. Computational analyses were also performed to gain insight into the mechanism of B–H bond activation and adduct formation. Furthermore, the reactions of the BICAAC with boranes have been compared with the known reactions of CAACs and NHCs. [ABSTRACT FROM AUTHOR]

Abstract A non-heme tetra-iron cluster, [Fe 4 III(μ- O) 2 (μ- OAc) 6 (2,2′-bpy) 2 (H 2 O) 2 ](NO 3 −)(OH−) (1), [OAc = acetate; 2,2′-bpy = 2,2′-bipyridine] containing oxido- and acetato-bridges was synthesized and structurally characterized by different spectroscopic methods including single crystal X-ray diffraction studies. X-ray crystal structure analysis of 1 revealed that tetra-iron complex was crystallized in monoclinic system with C 2/ c space group. Each of the Fe centres in 1 was found to exist in octahedral geometry and interconnected by oxido- and acetato-bridges. Bond valence sum (BVS) calculation recommended the existence of iron centres in +3 oxidation state. Variable temperature magnetic measurement authenticated the dominating antiferromagnetic ordering among the iron centres in the solid state of 1. This tetra-iron cluster was also evaluated as an efficient catalytic system towards the oxidation of both linear & cyclic alkanes without production of primary C H bond oxidation products. Oxidation of secondary C H bonds attested the formation of both the corresponding alcohols & ketones in 27–900 TONs. The tetra-iron catalytic system with Alcohol/Ketone values 0.2–1.7 indicated the involvement of freely diffusing carbon-centered radicals rather than metal based oxidant. Graphical abstract This paper represents synthesis of a new oxido-acetato-bridged tetra-iron(III) complex, [Fe 4 III(μ- O) 2 (μ- OAc) 6 (2,2′-bpy) 2 (H 2 O) 2 ](NO 3 −)(OH−) which displays excellent catalytic activity towards C H activation property based on carbon centered radical in solution. Image 1 Highlights • Synthesis and characterization of an oxido-acetato-bridged tetrairon(III)-bipyridine complex. • The iron(III) complex displays antiferromagnetic ordering of iron centres in the solid state. • The iron complex efficiently activate C H bond of both linear & cyclic alkanes. • Probably generation of freely diffusing carbon-centered radical account for such activity. [ABSTRACT FROM AUTHOR]

Abstract Reactions of cyclic (alkyl)(amino)carbenes, cAACMe and cAACcy with equimolar quantity of HgX 2 salts afforded their corresponding halide bridged dimeric complexes, [cAACMeHgCl(μ-Cl)] 2 (1), [cAACcy∙HgCl(μ-Cl)] 2 (2), [cAACMe∙HgI(μ-I)] 2 (3) and [cAACcy∙HgI(μ-I)] 2 (4) (Me = methyl and cy = cyclohexyl). It has been possible to perform stepwise substitution of Br− in [cAACcy∙HgBr(μ-Br)] 2 with NO 3 − leading to the isolation and characterization of the mononitrate species, cAACcy∙HgBr(NO 3) (5) and the dinitrate compound [cAACcy∙Hg(NO 3)(μ-NO 3)] 2 (6). The cationic mercury species, [(cAACMe) 2 Hg(NO 3)]+[NO 3 ]‒ (7) has also been synthesized by the reaction of adduct, [cAACMe∙HgBr(μ-Br)] 2 with 2 eq. of AgNO 3. On reaction of [cAACcy∙HgCl(μ-Cl)] 2 (2) with AgClO 4 , only one chlorine could be substituted by perchlorate resulting in the formation of chlorine bridged dimeric complex, [cAACcy∙Hg(ClO 4)(μ-Cl)] 2 (8). On performing the reaction between cAACcy and HgCl 2 in 2:3 relative stoichiometry, a dicationic mercury species [(cAACyc) 2 Hg]2+[Hg 2 Cl 6 ]2‒ (9) was isolated in moderate yield. Graphical abstract Syntheses and structural characterization of dimeric cyclic (alkyl)(amino)carbene mercury complexes, [cAACMe/cy·HgX(μ-X)] 2 (X = Cl, I; Me = methyl, cy = cyclohexyl) have been reported. Reactivity of [cAACMe/cy·HgBr(μ-Br)] 2 complexes for stepwise substitution of bromides with nitrates have also been studied and the neutral complexes cAACcy∙HgBr(NO 3) and [cAACcy∙HgNO 3 (μ-NO 3)] 2 , the cationic mercury compound, [(cAACMe) 2 Hg(NO 3)]+[NO 3 ]‒ have been obtained. Compound [cAACcy∙Hg(ClO 4)(μ-Cl)] 2 formed on reaction of [cAACcy∙HgCl(μ-Cl)] 2 with AgClO 4 and [(cAACcy) 2 Hg]2+[Hg 2 Cl 6 ]2‒ was isolated by reacting cAACcy and HgCl 2 in 2:3 ratio. All compounds reported in this work have been characterized by spectroscopic and single crystal X-ray diffraction methods. Image 1 Highlights • We report facile syntheses of adducts of cyclic (alkyl)(amino)carbene (cAACs) with HgX 2 (X = Cl and I). • The cAAC-Hg(II) adducts form halide bridged dimers as [cAACHgX(μ-X)] 2. • The dimers [cAACHgX(μ-X)] 2 have been useful in the syntheses of cationic complexes of Hg(II). [ABSTRACT FROM AUTHOR]

Graphical abstract This paper reports a novel addition of a Schiff base as chemosensor for nickel(II) ion in a wider range of concentration. Highlights • We developed a new chemosensor for Nickel(II) ion with high selectivity & sensitivity. • Spin state switching of nickel ion by the Schiff base remains the driving force for super stable compound. • Ratiometric fluorescence changes are observed during sensing. • This sensing technique may be applied in a wider concentration range for Ni(II) ion. • This is a pH independent sensor. Abstract A novel tetradentate (N,O)-donor salen type Schiff base was designed, prepared and structurally characterized by different analytical techniques. This Schiff base ligand, (L = 2 , 2 '-((1,2 phenylenebis(methanylylidene))bis(azanylylidene))diphenol) behaved as an effective chemosensor towards Ni(II) ion with specific selectivity. The Schiff base (L) displayed a remarkable ratiometric fluorescence enhancement upon binding with Ni(II) ion in acetonitrile (ACN) medium. The L -Ni(II) solution was distinguished indisputably with the naked eye colour change and the crystal was found to be red colour. L selectively detected Ni(II) ion in presence of other competitive cations like Mn(II), Fe(II),Co(II), Cu(II), Zn(II), Cd(II) and Hg(II) ions. This simple but novel Schiff base might be used as a potential pH independent colorimetric and naked-eye chemosensor for Ni(II) ion. Most significantly, L exhibited geometry preferred selectivity towards Ni(II) ion and formed highly stable square planar Ni(II)-Schiff base complex. Single crystal X-ray diffraction study further authenticated that the nickel complex crystallized in orthorhombic system with P 2 1 2 1 2 1 space group in solid state. Density functional theory (DFT) calculations attested the experimental results very well. This sensing method could be applied in a wider concentration range and might be used as an alternative qualitative and quantitative test for the detection of Ni(II) ion in analytical chemistry. [ABSTRACT FROM AUTHOR]

Graphical abstract Herein, the synthesis, structural characterisation and potential catalytic activity of a tetrazinc(II) complex were investigated with experimental techniques and DFT calculations. The diverse coordination aspect of methanol in the architect of the complex and it's crucial role in oxidative coupling of 2-aminophenol through ligand centred radical pathway were comprehensively ascertained. Abstract Herein, the synthesis, structural characterization and catalytic activity of a novel tetranuclear zinc(II)–Schiff base complex, [Zn 4 (L) 2 (µ 3 -OCH 3) 2 (CH 3 OH) 2 ]·2CH 3 OH (1), [ L = N,N′- bis(3-methoxysalicylidene)-1,3-diamino-2-propanol] was presented. Single crystal X-ray diffraction structural analysis revealed that the tetra-zinc(II) cluster crystallized in a monoclinic system with P 2 1 / c space group. Interestingly, three different molecular bridges (methoxido-, alkoxido- and phenoxido-) simultaneously co-existed in assembling tetra-zinc(II) core, which was a very rare observation. To the best of our knowledge, this compound would be the first compound where a diverse coordination aspect was covered by a single solvent as terminal coordinator (CH 3 OH), bridging (µ 3 -CH 3 OH) and solvent for crystallization in the existing scientific literature. The compound showed good photo-stability and excellent luminescence property with higher lifetime at transition state in ethanol. This zinc(II) complex revealed crucial role as an effective catalytic system towards oxidation of 2-aminophenol (2-AP) in ethanol. Additionally, the tetra-zinc(II) complex displayed potential phenoxazinone synthase like activity with momentous turn over number, k cat (h−1) = 6.19 × 102 in ethanol under aerobic condition. ESI-MS and EPR spectral analysis of the reaction mixture between Zn(II) complex and 2-AP recommended that the course of catalysis proceeded through substrate–catalyst adduct formation and authenticated the radical mechanistic pathway in favor of oxidative coupling product. This tetranuclear zinc(II)–Schiff base complex would be considered as the first example that catalyzed the oxidative coupling of 2-aminophenol to aminophenoxazino compound under usual aerobic condition. As complementary, detailed quantum chemical computations, performed with density functional theory (DFT) were well corroborated with the experimental results. This was the first and rarest example where a tetrazinc(II)–Schiff base cluster exhibited catalytic oxidation of 2-AP through ligand centered radical activity. [ABSTRACT FROM AUTHOR]

• Synthesis and characterization of efficient Ru(II) catalysts. • N-alkylation of anilines under milder and solvent-free conditions. • Electron-deficient [Ru-1] as more effective catalyst than electron-rich [Ru-2]. Efficient Ru(II) catalysts with substituted aniline based ligands were synthesized having chemical formula [Ru(η6- p-cymene)Cl 2 (L1)] [Ru-1] and [Ru(η6- p-cymene)Cl 2 (L2)] [Ru-2] (where, L1 = 3,5-bis(trifluoromethyl)aniline and L2 = 3,4,5- trimethoxy aniline). The structural features of both the complexes were authenticated by ESI-MS, 1H and 13C NMR, FT-IR, elemental analyses, and single-crystal X-ray diffraction studies. Catalytic performance of both [Ru-1] and [Ru-2] was investigated for conversion of primary amine to secondary amine using alcohols under milder and solvent-free conditions and compared with the reported aniline-based Ru(II)-arene complex [Ru-3]. Among them, [Ru-1] could achieve 100% selectivity towards mono N-alkylated amines with > 99% conversion without formation of any imine derivatives. The results suggested that the lone pair of electrons of benzyl alcohol binds easily to the electron-deficient Ru(II) center of [Ru-1] catalyst making it more effective compared to electron-rich [Ru-2] and [Ru-3] catalysts. The catalytic performance of [Ru-1] demonstrates that it is one of the most active primary amine ligated Ru(II) based catalytic systems for N-alkylation of anilines under milder and solvent-free conditions. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, we have developed a new one-dimensional cadmium(II) coordination polymer, [Cd(phen)(NO 3 ) 2 (H 2 O)] n ( 1 ) (phen = 1,10-phenanthroline) and structurally characterized by different spectroscopic techniques including single crystal X-ray diffraction analysis. Single crystal X-ray structural analysis of 1 indicates that Cd(II) ion in the coordination polymer crystallizes in a monoclinic system with P 2 1 space group and adopts a distorted pentagonal bipyramidal coordination geometry. This will be the first citation of a 1D Cd(II) polymer till date where nitrate ions exhibit diverse coordination motifs. Solid state emission suggests good luminescence behavior of the polymer. Spectroscopic studies reveal that the polymer is unstable in polar solvents and dominates in monomeric form. Molar conductivity and electrospray ionization mass spectral analysis in methanolic solution confirm the instability of the polymer at room temperature and authenticates the decomposition of the polymer into monomer in solution. In addition, all the structural parameters and spectroscopic behaviors have been well corroborated with the theoretical findings. [ABSTRACT FROM AUTHOR]

The first examples of group 13 element containing pyridinophanes have been assembled using heteroatom N–E–N bridges (E = B, Al). The presence of B and Al as acceptor atoms in the bridges and their coordination with pyridine nitrogen has a very strong influence on the conformational rigidity of the pyridinophanes. [ABSTRACT FROM AUTHOR]

Abstract: In this present work, we report the synthesis and structural characterization of two copper(II) complexes, [Cu(bpy)Cl2] (1) & [Cu(μ‐Cl)(phen)Cl]2 (2) [bpy=2,2′‐bipyridine; phen=1,10‐phenanthroline]. We have also studied their catalytic fate towards phenoxazinone synthase and catechol dioxygenase activity. X‐ray structural analyses revealed that 1 & 2 crystallize in triclinic & monoclinic system with P 1 and Cc space group respectively. The copper complexes catalyse the oxidative coupling of 2‐amino phenol (2‐AP) to aminophenoxazin‐3‐one with significant turn over number, kcat(h−1)=2.08×103 & 2.16×103 for 1 & 2 resectively. During investigation of catechol dioxygenase activity, stoichiometric addition of 1 & 2 to 3,5‐di‐tert‐butylcatechol (DTBC) in acetonitrile produce in situ catecholate‐to‐Cu(II) absorption bands at 812 and 821 nm respectively. The in situ Cu(II)‐catecholate species for both 1 & 2 react with molecular oxygen at the rate, kobs: 7.95×10−4 and 1.30×10−3 min−1 respectively and produce intradiol cleavage products in exclusive amount. Minor amount of benzoquinone is also found in solution. Intradiol products are found as major product in solution and accounts in favour of substrate activation mechanism. [ABSTRACT FROM AUTHOR]

We have demonstrated stepwise functionalization of chlorophosph(III)azane, [ClP(μ-NtBu)]2 with organic azides and chalcogens (S and Se). The in situ 31P{¹H} NMR spectroscopic investigations reveal that conversion of the basic PIII2N2 framework, leading to PV 2N2 proceeds via (PIII/PV)N2 intermediates. Under controlled conditions, the (PIII/PV)N2 intermediate species can be isolated, providing details of the reaction pathway and distribution of the cis and trans isomers of the PV2N2 products. It has also been demonstrated that neat reactions at elevated temperatures expedite the formation of PV2N2 products, without significantly affecting the yields and relative distribution of the cis and trans isomers. All new compounds reported here are potential building blocks for the assembly of inorganic macrocycles and polymers. [ABSTRACT FROM AUTHOR]

A mononuclear nickel(II) complex, [Ni(bpy) 2 (OH 2 )(NO 3 )](NO 3 ) ( 1 ) [bpy = 2,2′-bipyridine], has been synthesised and structurally characterised by routine analytical techniques including a single crystal X-ray diffraction study. X-ray crystal structure analysis shows that 1 crystallises in the triclinic system with the P 1 ¯ space group and adopts an octahedral geometry. The nickel(II) complex has been evaluated as a functional model for phosphatase and catechol dioxygenase enzymes by using 4-nitrophenylphosphate (PNPP) and 3,5-di- tert -butylcatechol (DTBC) as model substrates in aqueous-DMF and acetonitrile media respectively. This mononuclear nickel complex exhibits good hydrolytic phosphoester cleavage efficiency, viz. a k cat value of 8.42 × 10 3 h −1 , and produces mostly benzoquinone ( k obs = 2.3 × 10 −3 min −1 ) and intradiol cleavage products during an investigation of catechol dioxygenase activity. [ABSTRACT FROM AUTHOR]

Two equivalents of 1-benzyl-3-bromoethylbenzimidazolium bromide couple with Na2Se to produce the first selenoether bridged bis-benzimidazolium salt (LH2)Br2. The nitrate (LH2)(NO3)2 and tetrafluoroborate (LH2)(BF4)2 salts were also synthesized from (LH2)Br2. The reaction of Hg(OAc)2 with (LH2)Br2 gave the first pseudo pincer carbene mercury complex, [Hg(L-κ2C)][HgBr4] (C1). Different complexes of Pd(ii) with selenoether bridged carbene were obtained using (LH2)Br2 and (LH2)(NO3)2. Syntheses of these complexes were dependent on the counter anion and the temperature. Thus, the pincer type ionic complex [PdBr(L-κ3CSeC)]Br (C2) was isolated at 80 °C and the pseudo pincer type neutral complex cis-[PdBr2(L-κ2C)] (C3) was isolated at room temperature from (LH2)Br2 and Pd(OAc)2 in DMSO. The nitrate precursor (LH2)(NO3)2 on palladation with Pd(OAc)2 afforded [Pd(L-κ4CBzCSeC)]NO3 (C4) showing an unprecedented intramolecular metallation at the ortho position of the benzyl wingtip of the benzimidazole moiety. The ligand salts and metal complexes have been characterized using HRMS, heteronuclear NMR and IR spectroscopy. Single crystal X-ray structures of the ligand salts (LH2)Br2 and (LH2)(BF4)2 and complexes C1–C4 have also been elucidated. Complex C2 showed good activity for C–C coupling in the mono-Heck reaction of methyl acrylate and arylbromides. Interestingly, the less common bis-arylation was also observed with deactivated arylbromides as the result of double-Heck coupling. [ABSTRACT FROM AUTHOR]

A mononuclear iron(II) complex, [Fe(phen)3]Cl2 ( 1) (phen =1,10-phenanthroline), has been synthesized in crystalline phase and characterized using various spectroscopic techniques including single crystal X-ray diffraction. Crystal structure analysis revealed that 1 crystallizes in a monoclinic system with C2/m space group. Complex 1 acts as a functional model for a biomimetic catalyst promoting the aerobic oxidation of 3,5-di- tert-butylcatechol (3,5-DTBC) through radical pathways with a significant turnover number ( kcat =3.55 × 103 h−1) and exhibits catechol dioxygenase activity towards the same 3,5-DTBC substrate at room temperature in oxygen-saturated ethanol medium. The existence of an isobestic point at 610 nm from spectrophotometric data indicates the presence of Fe3+ −3,5-DTBC adduct favouring an enzyme-substrate binding phenomenon. Upon stoichiometric addition of 3,5-DTBC pretreated with two equivalents of triethylamine to the iron complex, two catecholate-to-iron(III) ligand-to-metal bands (575 and 721 nm) are observed and the in situ generated catecholate reacts with dioxygen ( kobs =9.89 × 10−4 min−1) in ethanol medium to afford exclusively intradiol cleavage products along with a small amount of benzoquinone, and a small amount of extradiol cleavage products, which provide substantial evidence for a mechanism. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

An X-ray structurally characterized vanadium(V) complex, [VO 2 (L–H)] [L–H = H 2 L derived ligand (H 2 L = N,N′-(salicyaldimine)-1,3-diaminopropan-2-ol], was found to behave as an effective catalyst towards the oxidation of 3,5-di-tert-butylcatechol in methanol to its corresponding quinone derivative in aerial oxygen. The reaction follows Michaelis–Menten enzymatic reaction kinetics with a turnover number ( K cat ) of 2.063 × 10 3 h −1 . [ABSTRACT FROM AUTHOR]

A mononuclear copper(II) complex [Cu(phen)(OH 2 ) 2 (NO 3 )](NO 3 ) ( 1 ) [phen = 1,10-phenanthroline] has been synthesized and structurally characterized by different spectroscopic characterization methods including single crystal X-ray diffraction study. X-ray crystal structure analysis shows that 1 adopts square pyramidal geometry with CuN 2 O 3 chromophore and the molecule crystallises in P 2 1 / n space group. 1 has been evaluated as model system for the catechol oxidase enzyme by using 3,5 -di -tert-butylcatechol (DTBC) as the substrate in methanol medium, revealing that 1 exhibits greater catalytic activity with K cat value 3.91 × 10 3 h −1 compared to a few copper(II) complexes of the same class. Electrochemical analysis suggests that the mononuclar Cu(II) complex mimics the catechol oxidase enzyme in methanolic medium through radical pathway. The complex cleaves the double strand of pBR 322 plasmid DNA in a concentration-dependent manner so as for the DNA to change from super coiled form to both nicked circular and linear forms. The complex is cytotoxic to the human hepatocarcinoma cell HepG2, as revealed in MTT assay. AO/EB and Hoechst 33528 fluorescent staining techniques were used to find the mode of cell death. Interestingly, AO/EB and Hoechst stained cells observed at IC 50 concentration shows that 1 brings about conformational change on DNA to induce apoptosis which would be the basis underlying its cytotoxic property. [ABSTRACT FROM AUTHOR]

Interactions involving fluorine is an area of contemporary research. To unravel the importance of weak C–H⋯F hydrogen bonds and C–H⋯π interactions in organic compounds in the presence of strong hydrogen bond, a series of N -benzylideneanilines with simultaneously hydroxyl (–OH) and fluorine substitutions were synthesized for structural analysis. These compounds have been studied through experimental single crystal X-ray diffraction analysis and computational methods (Gaussian09 and AIM2000). The hydroxyl group present in all the molecules were found to form strong O–H⋯N hydrogen bond, but the spatial arrangement of the molecules connected by this hydrogen bond have been found to be controlled by the weak C–H⋯F and C–H⋯O hydrogen bonds, weak C–H⋯π and π⋯π interactions. This manuscript illustrates the importance of several weaker interactions in altering the packing modes in the presence of strong hydrogen bonds. [ABSTRACT FROM AUTHOR]

[Display omitted] • "Nature-to-new" as a medicinal chemistry strategy. • Iterative Scaffold-hopping to identify new chemotype. • Organocatalysed Umpolung Chemistry to construct Arylidene heterocyclic-fused imidazolone scaffold. • Polyphosphoric acid-mediated ester-lactam exchange. • In silico study reveals good drug-like properties. A strategy of "Nature-to-new" with iterative scaffold-hopping was considered for investigation of privileged ring/functional motif-elaborated analogs of natural aurones. An organocatalyzed umpolung chemistry based method was established for molecular-diversity feasible synthesis of title class of chemotypes i.e. (Z)-2-Arylideneimidazo[1,2– a ]pyridinones and (Z)-2-Arylidenebenzo[ d ]imidazo[2,1–b]thiazol-3-ones. Various biophysical experiments indicated their important biological properties. The analogs showed characteristic anticancer activities with efficiency more than an anticancer drug. The compounds induced apoptosis with arrest in the S phase of the cell cycle regulation. The compounds' significant effect in up/down-regulation of various apoptotic proteins, an apoptosis cascade, and the inhibition of topoisomerases-mediated DNA relaxation process was identified. The analysis of the structure-activity relationship, interference with biological events and the drug-likeness physicochemical properties of the compounds in the acceptable window indicated distinctive medicinal molecule-to-properties of the investigated chemotypes. [ABSTRACT FROM AUTHOR]

An undecairon(III) oxo-hydroxo-carboxylato bridged aggregate [Fe 11 (μ 3 -O) 6 (μ 3 -OH) 6 (μ-O 2 C-f) 15 ] ( 1 ) has been synthesized and characterized by single crystal X-ray diffraction study. The anionic ligand N -(2-hydroxyethyl)-3-methoxysalicylaldimine (L) has been used as template to synthesize such high nuclearity complex. Interestingly, the ligand neither enters into the coordination sphere nor crystallizes with the iron cluster. Bond distance data indicate that all the iron atoms in 1 are high-spin Fe(III) in O-donor environment. 1 behaves as an effective catalyst towards oxidation of 3,5-di- tert -butylcatechol in different solvents, viz. methanol, dichloromethane and acetonitrile, to its corresponding quinone derivative in aerial oxygen. The reaction follows Michaelis–Menten enzymatic reaction kinetics with turnover numbers (K cat ) 3.21 × 10 3 , 1.23 × 10 3 and 1.11 × 10 3 h −1 in methanol, dichloromethane and acetonitrile, respectively. [ABSTRACT FROM AUTHOR]

A new one-dimensional (1-D) Pb(II) coordination polymer, [Pb(2,2′-bpy)(NO3)2(H2O)]n(1) (2,2′-bpy = 2,2′-bipyridine), has been synthesized and characterized by different spectroscopic techniques and X-ray single-crystal analysis. From the X-ray crystal structure of1, the Pb2+can be best described as a highly distorted pentagonal bipyramid with O4 (water) and O6 (nitrate) at apical positions (O4–Pb–O6 of 143.7(1)°). Variability in bond distances reveals that Pb2+is unsymmetrically surrounded by two nitrates, one 2,2′-bpy and one water. Nitrates bridge between monomers. The molecule crystallizes in the monoclinicP21/n(14) space group. This is the first example of a 1-D Pb(II) polymer in which nitrates show three different coordination motifs (terminal, chelating, and bridging). Solid state as well as solution phase UV–vis spectral analysis and mass spectrometric studies clearly reveal instability with breakdown of Pb(II) polymer in aqueous solution. The arrangement of the 2,2′-bpy, water, and nitrates leaves a coordination gap at the Pb(II) occupied probably by a stereo-active lone pair of electrons. [ABSTRACT FROM AUTHOR]

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 (Hg2+). 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. [ABSTRACT FROM AUTHOR]

A perfectly linear trinuclear zinc(II) complex [Zn3L2(µ-O2CCH3)2] (1) containing a (N,O)-donor Schiff base ligand, (H2L = N,N'-bis(salicyaldehydene)-1,3-diaminopropan-2-ol) has been synthesized and characterized by single crystal X-ray diffraction study. The X-ray crystal structure of 1 contains three zinc(II) centers which are inter-connected through µ2-phenolato and µ-acetato bridges. The terminal zinc centers are in square pyramid geometry and central zinc ion is in distorted octahedral coordination geometry. Both H2L and 1 exhibit good fluorescence properties in solution. 1 has been used as a precursor to fabricate zinc oxide nanoparticles (ZnONPs) by pyrolytic method. ZnONP has been characterized by powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), FT-IR spectroscopy and UV-Vis spectroscopy techniques. ZnONP has been employed as photocatalytic agent to degrade the organic dye, viz. Methylene blue under visible light and by exposing to visible light for 1 h, ZnONP degraded methylene blue dye nearly 80%. [ABSTRACT FROM AUTHOR]

Two iridium(III) diimine complexes [mono(1,10-phenanthroline)bis(triphenylphosphine)(dihydrido)iridium(III) hexafluorophosphate ( 1) and mono(1,10-phenanthroline)bis(triphenylphosphine)(hydrido)(chloro)iridium(III) hexafluorophosphate ( 2)] have been synthesized from a single two-step reaction. The structures of 1 and 2 both adopt distorted octahedral geometries, as established by single-crystal X-ray diffraction. The complexes, upon irradiation with UV light at 365 nm, emit faint light in solution and bright light in the solid state. The ground- and excited-state properties of these complexes were investigated through density functional theory (DFT) and time-dependent DFT calculations. The calculated energies for the transitions from the ground state to the singlet and triplet excited states were close to those determined from the experimental absorption and emission. Their molecular orbitals were also exploited to compute the ground-state dipole moments and redox potentials. Several experiments were performed to demonstrate the 'aggregation-induced emission' (AIE) activity of these complexes. AIE was triggered by the restricted intramolecular rotation of the rotating units (phenyls in triphenyphosphines) in these molecules in the solid state. The solid thin films of 1 and 2 exhibit solvent-polarity-dependent vapour-responsive emission properties (vapoluminescent). The rationale for the different emission behavior in the solid state has been thoroughly investigated. The packing diagrams of 1 and 2 show that there is enough space available to accommodate small organic solvent molecules inside the crystal lattices. [ABSTRACT FROM AUTHOR]

Abstract: The syntheses of greenish-blue light emitting [Ir(ppy)2(dppel)] (2), [Ir(ppy)2(dppp)] (3) and [Ir(ppy)2(dppe)] (4) [ppy, 2-phenylpyridine; dppel, 1,2-bis(diphenylphosphino)ethylene; dppp, 1,3-bis(diphenylphosphino)propane; dppe, 1,2-bis(diphenylphosphino)ethane] complexes were carried out using [(ppy)2Ir(μ-Cl)2Ir(ppy)2] (1) as a starting material. These complexes were characterized by elemental analyses and NMR (1H, 13C and 31P) spectral studies. A single-crystal X-ray diffraction study confirmed a distorted octahedral geometry for 3. Complexes 2–4 were found to exhibit blue-shifted emission as compared to [Ir(ppy)2(acac)] (acacH=acetylacetone) and [Ir(ppy)2pic] (pic=2-picolinic acid) because of the presence of strongly π-accepting, Ph2P^PPh2 units. The solution quantum efficiency for 2–4 was measured and 2 showed the highest quantum efficiency. Ground state geometry optimizations for 2–4 were performed using density functional theory (DFT) with the B3LYP hybrid functional and excitation energies for low lying singlet and triplet excited states were obtained via time-dependent DFT (TDDFT) calculations. Further, complexes 1–4 were synthesized by a Microwave Irradiation technique (MW) in a reasonably shorter time. This facile and expeditive synthetic route has been extended and successfully verified for other heteroleptic complexes of Ir(III) with varying different bidentate [(N^N) (5), (O^O) (6), (N^O) (7)] and monodentate [PPh3 (8)] ancillary ligands. [Copyright &y& Elsevier]

The December 2011 release of a draft United States Food and Drug Administration (FDA) guidance concerning regulatory classification of pharmaceutical cocrystals of active pharmaceutical ingredients (APIs) addressed two matters of topical interest to the crystal engineering and pharmaceutical science communities: (1) a proposed definition of cocrystals; (2) a proposed classification of pharmaceutical cocrystals as dissociable “API-excipient” molecular complexes. The Indo–U.S. Bilateral Meeting sponsored by the Indo–U.S. Science and Technology Forum titled The Evolving Role of Solid State Chemistry in Pharmaceutical Sciencewas held in Manesar near Delhi, India, from February 2–4, 2012. A session of the meeting was devoted to discussion of the FDA guidance draft. The debate generated strong consensus on the need to define cocrystals more broadly and to classify them like salts. It was also concluded that the diversity of API crystal forms makes it difficult to classify solid forms into three categories that are mutually exclusive. This perspective summarizes the discussion in the Indo–U.S. Bilateral Meeting and includes contributions from researchers who were not participants in the meeting. [ABSTRACT FROM AUTHOR]

• Synthesis and characterization of a copper(II) complex. • Solvent induced distortion to the coordination environment of Cu(II) centre. • Bio-mimics of catecholase activity with high turnover number, 4.75 × 102 h–1. • Exploitation of fungicidal and anti-proliferative property. This research work reports the synthesis, single crystal X-ray structure, catechol oxidation, fungicidal and antiproliferative activity of a newly synthesized copper(II) complex, [Cu(L) 2 ]H 2 O . CH 3 OH (1) containing an azo-functionalized Schiff base, H L = 2-methoxy-6-((Z)-((4-((E)-phenyldiazenyl)phenyl)imino)methyl)phenol. The crystal structure analysis reveals that the Cu(II) centre exists in a highly distorted square planar geometry. The crystallize water and methanol form a strong intermolecular association through H-bonding. More importantly, the H atoms of the lattice water interact with the O atoms of ligand units leading to 5- and 6-membered cycles through the H-bonding network and distort the square planar geometry. The copper(II) complex has emerged as a bioinspired catalyst in the oxidative transformation of 3,5-di- tert -butylcatechol (DTBC) to o-benzoquinone in methanol with a high turnover number, 4.75 × 102 h–1. Electrochemical analysis of the copper(II) complex in presence of DTBC recommends the generation of catechol/o-benzosemiquinone redox couple in the course of oxidation. The EPR spectral analysis of 1 in presence of DTBC was found silent and suggested the antiferromagnetic interaction between copper centre and benzosemiquinone species. The copper(II) complex turns out to be a potential fungicidal agent against clinical candida albicans and scanning electron microscope studies confirm the destruction of the fungal cell membrane with the deposition of copper. The IC 50 value of the copper complex was determined as 15 µg/mL which suggests the excellent antiproliferative potency of the synthetic compound against the breast cancer cell lines, MCF-7. [Display omitted] [ABSTRACT FROM AUTHOR]

• Three halogen substituted benzothiazole crystals were grown by slow evaporation technique. • One crystal is found to be elastically bendable and the other two were found to be brittle. The crystals were fluorescent as well. • Crystal packing analysis, Hirshfeld analysis etc. were done to get insights of structure-property correlation. We have synthesized 3 benzothiazole crystals (1–3) based on existing knowledge of combining flexibility and optical properties towards achieving applications for flexible optoelectronics. However, one crystal was found to be elastically bendable and was found to comply necessary packing features for elasticity. Other two crystals do not obey packing features for elasticity hence they are brittle in nature. Further, Hirshfeld analysis illustrates that elastic crystal 1 possess more number of weak and dispersive interactions compared to other crystals. These interactions were instrumental in invoking elasticity. Moreover, crystals 1–3 were found to be fluorescent as well at specific excitation wavelengths. Therefore, among these crystals, particularly crystal 1 is considered as more promising candidate for flexible optoelectronics. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Diastereotopically nonequivalent π-facial 1,6-annulated-1,3-cyclohexadienes have been explored as probe molecules to assess the face-selectivities in cycloadditions. Steric factors have been found to be important in controlling the face-selectivities with these dienes. Studies with the hitherto unexplored diene 5 were also consistent with the order C–H>C–C for hyperconjugative stabilization of the transition state. [Copyright &y& Elsevier]