Spectrofluorometric studies on the binding interaction of bioactive imidazole with bovine serum albumin: a DFT based ESIPT process

Bioactive imidazole derivatives were synthesized and characterized by NMR spectra, mass and CHN analysis. An excited state intramolecular proton transfer (ESIPT) process in hydroxy imidazole has been studied using emission spectroscopy. In hydrocarbon solvent, the tautomer emission predominates over the normal emission and in alcoholic solvent like ethanol; a dramatic enhancement of normal emission is observed which was due to increased solvation. DFT calculation on energy, charge distribution of the rotamers in the ground and excited states of the imidazole derivative were performed and discussed. PES calculation indicates that the energy barrier for the interconversion of two rotamers is too high in the excited state than in the ground state. The interaction between bioactive imidazole derivative and bovine serum albumin (BSA) was investigated.     

Solvatochromic analysis of some N-nitroso oxime derivatives--Taft and Catalan approach

Some novel N-nitroso oxime derivatives were synthesized and characterized by (1)H, (13)C, (1)H-(1)H and (1)H-(13)C COSY NMR spectra. The spectra of all these N-nitroso oximes reveal the presence of two isomers labelled as E (-NOH group is anti to N-N=O moiety) and Z (-NOH group is syn to N-N=O moiety) in solution and the coupling constants ruled out the possibility of normal chair conformation. From the theoretical studies and coupling constant values it was found that both E (major) and Z (minor) isomers of N-nitroso oximes exist as an equilibrium mixture of CA and boat conformation (B(1)) and this was also supported by DFT calculation. The photophysical properties of these oxime derivatives were studied and the observed lower fluorescence quantum yield may be due to an increase in the non-radiative deactivation rate constant. This is attributed due to the presence of non-chair conformation of N-nitroso oxime derivatives.     

Copper(I)-catalyzed cascade sulfonimidate to sulfonamide rearrangement: synthesis of imidazo[1,2-a][1,4]diazepin-7(6H)-one

A novel strategy of copper(I)-catalyzed cascade intramolecular nucleophilic attack on N-sulfonylketenimine followed by rearrangement of sulfonimidates to sulfonamides resulting in a library of substituted 8,9-dihydro-5H-imidazo[1,2-a][1,4]diazepin-7(6H)-ones has been developed.     

Photophysical Properties of Novel Picrate Derivatives – Solvent Effect

H and ¹³C NMR spectra were recorded for some novel picrate derivatives derived from 3,3-dimethyl-2,6-diarylpiperidin-4-ones and 3-benzyl-2,6-diarylpiperidin-4-one. The photophysical properties of the picrate derivatives were studied in several solvents, which include a wide range of apolar, polar and protic media. The observed lower fluorescence quantum yield may be due to an increase in the non-radiative deactivation rate constant. This is attributed due to the presence of increased electrostatic interaction between N-protonated piperidone ring and picryl anion ring so that the picryl anion ring lies perpendicular to the plane of the N-protonated piperidone ring i.e., non co-planarity. Such a geometrical change in the excited state leads to an important Stokes shift, reducing the reabsorption and reemission effects in the detected emission in highly concentrated solutions. The higher fluorescence quantum yield of the picrate derivatives are observed in polar media.     

Investigation of the role of 1,3,4-oxadiazole on the spectroscopic, optical, and electrochemical properties of benzimidazolophanes

The synthesis of 1,3,4-oxadiazole (OXD)-based dicationic cyclophanes has been achieved via an N-alkylation route, and UV-vis spectra proved the absence of charge transfer interactions. Electrochemical studies showed interference of the OXD unit on the characteristic redox properties of dicationic benzimidazolophanes.     

Convenient Synthesis of α,α1 - bis (Substituted Furfurylidene) Cycloalkanones and Chalcones Under Microwave Irradiation.

Condensation of furfural with cycloalkanones and substituted acetophenones catalyzed by solid NaOH results in α, α¹-bis (substituted furfurylidene) cycloalkanones and chalcones in high yield under microwave irradiation for a duration of 2 minutes.     

Galactose Grafted Two-Dimensional Nanosheets as a Scaffold for the In Situ Synthesis of Silver Nanoparticles: A Potential Catalyst for the Reduction of Nitroaromatics

Two major hurdles in NP-based catalysis are the aggregation of the NPs and their recycling. Immobilization of NPs onto a 2D support is the most promising strategy to overcome these difficulties. Herein, amphiphilicity-driven self-assembly of galactose-hexaphenylbenzene-based amphiphiles into galactose-decorated 2D nanosheet is reported. The extremely dense decoration of reducing sugar on the surface of the sheets is used for the in situ synthesis and immobilization of ultrafine catalytically active AgNPs by using Tollens’ reaction. The potential of the system as a catalyst for the reduction of various nitroaromatics is demonstrated. Enhanced catalytic activity is observed for the immobilized AgNPs when compared to the corresponding discrete AgNPs. Recovery of the catalytic system from the reaction mixture by ultrafiltration and its subsequent recycling for several cycles without dropping its activity is shown. This is the first report demonstrating the in situ synthesis and immobilization of ultrafine AgNPs onto a 2D nanosheet that exhibits excellent catalytic performance for the reduction of nitroaromatics.     

Experimental and theoretical comparison of actinide and lanthanide bonding in M[N(EPR(2))(2)](3) complexes (M = U, Pu, La, Ce; E = S, Se, Te; R = Ph, iPr, H)

Treatment of M[N(SiMe3)2]3 (M = U, Pu (An); La, Ce (Ln)) with NH(EPPh2)2 and NH(EPiPr2)2 (E = S, Se), afforded the neutral complexes M[N(EPR2)2]3 (R = Ph, iPr). Tellurium donor complexes were synthesized by treatment of MI3(sol)4 (M = U, Pu; sol = py and M = La, Ce; sol = thf) with Na(tmeda)[N(TePiPr2)2]. The complexes have been structurally and spectroscopically characterized with concomitant computational modeling through density functional theory (DFT) calculations. The An-E bond lengths are shorter than the Ln-E bond lengths for metal ions of similar ionic radii, consistent with an increase in covalent interactions in the actinide bonding relative to the lanthanide bonding. In addition, the magnitude of the differences in the bonding is slightly greater with increasing softness of the chalcogen donor atom. The DFT calculations for the model systems correlate well with experimentally determined metrical parameters. They indicate that the enhanced covalency in the M-E bond as group 16 is descended arises mostly from increased metal d-orbital participation. Conversely, an increase in f-orbital participation is responsible for the enhancement of covalency in An-E bonds compared to Ln-E bonds. The fundamental and practical importance of such studies of the role of the valence d and f orbitals in the bonding of the f elements is emphasized.     

DNA‐Decorated,Helically Twisted Nanoribbons: A Scaffold for the Fabrication of One‐Dimensional,Chiral, Plasmonic Nanostructures

Crafting of chiral plasmonic nanostructures is extremely important and challenging. DNA‐directed organization of nanoparticle on a chiral template is the most appealing strategy for this purpose. Herein, we report a supramolecular approach for the design of DNA‐decorated, helically twisted nanoribbons through the amphiphilicity‐driven self‐assembly of a new class of amphiphiles derived from DNA and hexaphenylbenzene (HPB). The ribbons are self‐assembled in a lamellar fashion through the hydrophobic interactions of HPB. The transfer of molecular chirality of ssDNA into the HPB core results in the bias of one of the chiral propeller conformations for HPB and induces a helical twist into the lamellar packing, and leads to the formation of DNA‐wrapped nanoribbons with M‐helicity. The potential of the ribbon to act as a reversible template for the 1D chiral organization of plasmonic nanomaterials through DNA hybridization is demonstrated.     

Synthesis, characterization and ion transportation studies of some novel cyclophane amides

Various novel cyclophane amides with a large cavity have been synthesized. The structures of cyclophane amides 14 and 15 were resolved using XRD studies. Cyclophane amide 28 shows a shift in λ_max in the UV/Vis. spectra when treated with Cu (II) ion as well as with Pb (II) ion. Ion transportation studies were carried out with cyclophane amide 14 which proved that the Na⁺ ion passes through the cavity while K⁺ ions are retained.