Crystal structure and spectroscopy of a hydrogen-bridged one-dimensional Cu(II) complex containing both octahedral and square pyramidal geometries in the same unit cell

Single crystals of the helical hydrogen-bridged one-dimensional Cu(II) complex, [Cu(stpy)₂(CH₃COO)₂(H₂O)₂] (1) [Cu(stpy)₂(CH₃COO)₂(H₂O)] (2), are prepared and characterized by elemental and thermal analyses, IR, electronic and X-ray crystal structure determination. The crystals are monoclinic, of space group C2/c, with unit cell parameters a = 31.842(7) Å, b = 5.9829(10) Å, c = 30.970(14) Å, = 111.78(3)°, Z = 4. The asymmetric unit contains two different types of Cu(II) polyhedra, namely, octahedron and square pyramid within the same unit cell. 1 has elongated octahedral geometry with two nitrogen atoms from stpy and two oxygen atoms from synmonodentate acetate ligands, transcoordinated to Cu(II) in the basal plane. The oxygen atoms of the two water molecules occupy the axial positions. 2 has Cu(II) coordination polyhedra similar to 1, except that only one of the apical positions is occupied by a water molecule. The structure consists of two independent linear chains, one involving octahedral (1) and the other involving square-pyramidal (2) polyhedra, held by hydrogen bridges. The Cu–Cu intra- and interchain separations in both 1 and 2 are 5.983 and 8.214 Å. The unit cell packing shows weak -stacking between adjacent coordinated stpy ligands in the chain, resulting in ladder-type structure. Further, the extended packing reveals helical arrangement of Cu(II) polyhedra in the lattice.     

A facile synthesis of bispyrroloquinone and bispyrroloiminoquinone ring system of marine alkaloids

Bispyrroloquinone and bispyrroloiminoquinone are two important polycyclic ring systems present in biologically active marine alkaloids such as Zyzzyanones, tsitsikammamines, and wakayin. A facile synthesis of these two ring systems starting from a 6-benzylamino indole-4,7-quinone or 6-benzylamino pyrroloiminoquinone is described here. This chemistry involves the construction of a pyrrole ring in a single step by treatment of the starting reagents with ethyl acetoacetate or phenylbutane-1,3-dione in the presence of ceric ammonium nitrate in MeOH/CH₂Cl₂ solvent.     

Thermodynamic properties of CO2 absorption in hydroxyl ammonium ionic liquids at pressures of (100–1600) kPa

Solubility of CO₂ in six hydroxyl ammonium ionic liquids 2-hydroxyethanaminium acetate [hea], bis(2-hydroxyethyl)ammonium acetate [bheaa], 2-hydroxy-N-(2-hydroxyethyl)-N-methylethanaminium acetate [hhemea], 2-hydroxyethanaminium lactate [hel], bis(2-hydroxyethyl)ammonium lactate [bheal], 2-hydroxy-N-(2-hydroxyethyl)-N-methylethanaminium lactate [hhemel] at temperatures (298.15, 313.15, and 328.16) K and pressures ranging from (100 to 1600) kPa was determined. From the experimental solubility data, the Henry’s constant of CO₂ for each hydroxyl ammonium ionic liquids was estimated and reported as a function of temperature. Furthermore, enthalpy and entropy of absorption were obtained from estimated Henry’s constant. The results showed that the solubility increase with increasing pressure and decrease with increasing temperature and the solubility of CO₂ in these six hydroxyl ammonium ionic liquids was in sequence: [hea] > [bheaa] > [hel] > [bheal] > [hhemel] > [hhemea].     

One-pot synthesis of Claisen–Schmidt reaction through (E)-chalcone derivatives: Spectral studies in human serum albumin protein binding and molecular docking investigation

An efficient and environmentally benign one-pot multicomponent synthesis of E-chalcones was developed using a mild and reusable new boron nitride-sulphonic acid catalyst. The catalyst was prepared by activating the boron nitride surface with nitric acid, followed by a simple reaction with 3-mercaptopropyl trimethoxysilane. The catalyst was characterized and morphological properties were studied by Fourier transform infrared, X-ray diffraction, transmission electron spectroscopy, scanning electron microscopy, Brunauer–Emmett–Teller theory, and Raman spectroscopy techniques. The solid acid catalyst was recycled five times in a Claisen–Schmidt reaction to synthesize new chalcone derivatives, and X-ray crystallography was used to elucidate the structure of (E)-1-(anthracen-9-yl)-3-(2-(4-methylpiperazin-1-yl)quinolin-3-yl)prop-2-en-1-one. A fluorescence quench titration method was used to assess its binding ability with human serum albumin (HSA), while molecular docking was also performed to get a more detailed insight into their interaction at the binding site of HSA.     

CoMFA and CoMSIA of diverse pyrrolidine analogues as dipeptidyl peptidase IV inhibitors: active site requirements

The inhibition of dipeptidyl peptidase IV (DPP-IV) has emerged as an attractive target in the treatment of type 2 diabetes. In view of this development, a critical analysis of structural requirements of the DPP-IV inhibitors is envisioned to identify the significant features toward design of selective inhibitors. The comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) contour plots of pyrrolidine based analogues are used to analyze the structural requirements of a DPP-IV active site. The CoMFA model has shown a cross-validated q ² of 0.651 with a non-cross-validated r ² of 0.882 and explained 70.6% variance in the activity of external test compounds. In this, the steric and electrostatic fields have respectively contributed 59.8 and 40.2%, respectively, to the explained activity of the compounds. The CoMSIA model has shown optimum predictivity (cross-validated q ² = 0.661; non-cross-validated r ² = 0.803; external test set’s predictive r ² = 0.706) with four molecular fields namely, steric, electrostatic, hydrogen bond (HB)-donor, and HB-acceptor. The contour plots of molecular fields resulting from these studies have suggested: (i) steric restriction with small electron rich substituent at 2- and 3-position of pyrrolidine ring, (ii) presence of electropositive ring linker between the pyrrolidine head and aryl tail, (iii) presence of electron-rich groups around the aryl tail moiety, and (iv) presence of sulfonamide between the ring linker and aryl tail which would increase DPP-IV binding affinity of the compounds. These findings will help in the design of structurally related/new compounds as potential DPP-IV inhibitors.     

Growth, optical, mechanical and dielectric studies on NLO active pure and metal ion doped single crystals of bis-thiourea zinc chloride

Good quality single crystals of pure and metal ion (Ni²⁺) doped bis-thiourea zinc chloride (BTZC) possessing excellent nonlinear optical properties have been grown from aqueous solution by the slow solvent evaporation technique. The lattice parameters of the grown crystals are determined by single crystal X-ray analysis. The well defined sharp peaks in the powder X-ray diffraction pattern reveals the crystalline perfection and the EDAX spectrum confirms the presence of dopant in the lattice of the parent crystal. The DRS UV-visible spectral study reveals improved transparency for the doped crystal, ascertaining the inclusion of metal ion in the lattice. The optical band gap of the pure and doped crystals was calculated to be 4.8 and 5.2 eV respectively from the UV transmission spectrum. The vickers hardness test brings forth higher hardness value for Ni²⁺doped BTZC as compared to pure BTZC crystal. The dielectric measurement exhibits very low dielectric constant and dielectric loss at higher frequencies for both the pure and Ni²⁺doped BTZC. The existence of second harmonic generation signals in the crystal also has been confirmed by performing the Kurtz powder test.     

The valence state of M-ions in the chemically stabilized YSr2Cu3-xMxO7+δ (M=Mo, W and Re) superconductors

 Single phase Ba-free Sr-based YSr₂Cu _3-x M _x O_7+δ (M=Mo, W and Re) compounds have been stabilized by chemical doping. Superconductivity is observed for these phases in the range 30–45 K. X-ray diffraction studies suggest a relatively small orthorhombicity compared to Ba-analogue. X-ray photoelectron spectroscopic investigations reveal that the stabilizing cations are in the hexavalent state. The observation of the higher oxidation state of M-ions accounts for the excess oxygen content in these phases which is in accordence with the diffraction results. Received: 10 June 1996 / Accepted: 20 September 1996     

18‐Crown‐6 Catalyzed Microwave‐mediated Synthesis of Symmetric Bis‐Heterocyclic Compounds under Solvent‐free Condition

An efficient, solvent‐free and 18‐crown‐6 catalyzed method for the synthesis of N‐alkyl‐4‐(4‐(5‐(2‐(alkyl‐amino)thiazol‐4‐yl)pyridin‐3‐yl)phenyl)thiazol‐2‐amine, N‐alkyl‐4‐(5‐(2‐alkyamino)thiazol‐4‐yl)pyridine‐3‐yl)thiazol‐2‐amine, and 4,4′‐bis‐{2‐[amino]‐4‐thiazolyl}biphenyl bis‐heterocyclic derivatives via microwave accelerated cyclization is presented.     

On Doi–Naganuma and Shimura liftings

The Ramanujan Journal - In this paper, we extend the Doi–Naganuma lifting to higher levels by following the methods of Zagier and Kohnen. We prove that there is a Hecke-equivariant linear map...     

A mild, efficient and improved protocol for the synthesis of novel indolyl crown ethers, di(indolyl)pyrazolyl methanes and 3-alkylated indoles using H4[Si(W3O10)3]

Efficient electrophilic substitution reactions of indoles with various aldehydes proceed smoothly in acetonitrile using heteropoly acid (H₄[Si(W₃O₁₀)₃]) to afford the corresponding new indolyl crown ethers and di(indolyl)pyrazolyl methanes. H₄[Si(W₃O₁₀)₃] is also found to catalyze the Michael addition of indoles to ,β-unsaturated compounds for the synthesis of 3-alkylated indoles.