• Volume 121, Issue 1

January 2009,   pages  5-106

• Editor’s Note % Instance of plagiarism in Journal of Chemical Sciences

• The role of specific interactions on dynamical processes in a room temperature ionic liquid

This article describes our ongoing efforts to comprehend the role of specific interactions on the dynamical processes such as rotational diffusion and photoisomerization in a typical room temperature ionic liquid. Rotational diffusion studies carried out with a pair of structurally similar non-dipolar solutes indicate that organic solutes do experience strong specific interactions even with the highly associative ionic liquids such that their rotation is hindered. Similar measurements carried out with a nonpolar and a dipolar solute in an ionic liquid and a conventional solvent reveal that even in ionic liquids, apart from the viscosity of the medium, the important parameters, which govern the solute rotation are the solvent-size and free volume in case of non-polar solutes, whereas for charged and dipolar solutes, it is the solute-solvent interaction strength. Photoisomerization studies dealing with a pair of carbocyanine derivatives have shed light on the influence of solvent viscosity and specific interactions on the rates of photoisomerization. Our results point to the fact that the positively charged as well as the negatively charged cyanine derivatives do not experience specific interactions with the ionic liquid such that the isomerization rates are affected. However, when the isomerization rates are compared with a conventional isoviscous solvent, it has been noticed that the rates of isomerization are solely governed by viscosity of the medium in case of the positively charged cyanine derivative. In contrast, photoisomerization rates of the negatively charged cyanine derivative are significantly faster in a conventional isoviscous solvent compared to the ionic liquid due to the specific interactions between the solute and the former, which lower the barrier height for isomerization.

• Allenylphosphonates with a 1,3,2-dioxaphosphorinane ring: Synthesis, structures, stability and utility

Synthesis, structures and stability (thermal and air) of allenylphosphonates of the type (OCH2CMe2CH2O)P(O)C(R)=C=CR'R" and [R"R'C=C=C(R)P(O)(OCH2)2]2C are discussed. Thermally activated dimerization (cycloaddition) of (OCH2CMe2CH2O)P(O)C(H)=C=CMe2 leads to the phosphonocyclobutane [(OCH2CMe2CH2O)P(O)C(H)=]2[C-CMe2]2 (18). Many of these allenes undergo addition of diethylamine to lead to enaminophosphonates that are readily hydrolysed by water to lead to 𝛽-ketophosphonates. The latter compounds are useful as Horner-Wadsworth-Emmons (HWE) reagents. Molecular structures of (OCH2CMe2CH2O)P(O)C(CH2OH)=C=CH2 (6), [H2C=C=C(H)P(O)(OCH2)2]2C (9), (OCH2CMe2CH2O)P(O)CH=C=CH2 (12), [(OCH2CMe2CH2O)P(O)C(H)=]2[C-CMe2]2 (18), and the 𝛽-ketophosphonate (OCH2CMe2CH2O)P(O)CH2)-C(O)CHMe2 (24) have been determined. In compound 6, intermolecular hydrogen bonding between the phosphoryl oxygen and the hydroxyl group leading to an infinite chain is observed. In 6, there is a significant deviation (ca 7°) from the orthogonality expected between the planes containing 4 atoms of (a) H2C=C and (b) C=C(H)P in the allene part. In 9, weak C-H…O interaction between the phosphoryl oxygen atom and a CH2 proton of the six-membered ring is present.

• Oxidation of phosphine by sulfur or selenium involving a catalytic cycle in the interconversion of monomer and tetramer forms of copper-maleonitriledithiolate complexes

The addition of triphenylphosphine (PPh3), into [Et4N]4[Cu4(mnt)4] shifted its characteristic electronic spectral band at 377 nm to 372 nm which is identical to that of the monomeric species, [Et4N][Cu(mnt)(PPh3)]. This reaction was followed by electrochemical study and also by 31P NMR spectroscopy. Such interconversion with the participation of breaking of bridging copper-$\mu_3$-sulfur bond with the formation of new copper-phosphorous bond led to the development of a catalytic cycle using excess PPh3 and S or Se as the reacting substrates. The turnover number for the oxidation of PPh3 by S was found to be $0.8 \times 10^{-2} s^{-1}$ and that with Se was $0.6 \times 10^{-2} s^{-1}$ using this catalytic system.

• Synthesis, spectroscopic and redox properties of the mononuclear NiII, NiII(BPh2)2 containing (B-C) bond and trinuclear CuII-NiII-CuII type-metal complexes of $N,N'$-(4-amino-1-benzyl piperidine)-glyoxime

The novel vic-dioxime ligand containing the 4-amino-1-benzyl piperidine group, $N,N'$-(4-amino-1-benzyl piperidine)-glyoxime, (LH2) has been prepared from 4-amino-1-benzyl piperidine with anti-dichloroglyoxime at -15°C in absolute THF. Mononuclear NiII metal complex has been obtained with 1 : 2 metal/ligand ratio. The NiII complex of this ligand is proposed to be square planar geometry. IR spectra show that the ligand acts in a tetradentate manner and coordinates N4 donor groups of LH2 to NiII ion. The detection of H-bonding (O-H$\cdots$O) in the [Ni(LH))2] (${\rm 1}$) metal complex by IR spectra supported the square-planar MN4 coordination of mononuclear complex. The disappereance of H-bonding (O-H$\cdots$O) in the [Ni(L)2(BPh2)2] (2) complex shows that the BPh$^+_2$-capped groups (BPh$^+_2$ cation formed BPh4 anion) attaches to the main oxime core. MN4 coordination of the [Ni(LH)2] (1) and [Ni(L)2(BPh2)2] (2) metal complexes were also determined by 1H-NMR spectroscopy. In the trinuclear CuII-NiII-CuII metal complexes, the NiII ion centered into the main oxime core by the coordination of the imino groups while the two CuII ions coordinate dianionic oxygen donors of the oxime groups and linked to the ligands of 1,10-phenanthroline, $2,2'$-bipyridine, and $4,4'$-bipyridine. The ligand and their mono and trinuclear metal complexes were characterized by elemental analyses, FT-IR, UV-Vis, 1H and 13C-NMR spectra, magnetic susceptibility measurements, molar conductivity, cyclic voltammetry, mass spectra and X-ray powder techniques. The cyclic voltammetric results show that the cathodic peak potential of [Ni(L)2(BPh2)2] shifted toward more negative value compared to that of [Ni(LH)2], probably due to a decreasing effect of back donation of metal-oxime moieties as a result of the BPh$^+_2$-bridged complex formation. Also, the formation of the trinuclear CuII-NiII-CuII metal complexes caused considerable changes on the CV behaviour of mononuclear [Ni(LH)2] (1) complex. The spectroelectrochemical study of [Ni(L)2(BPh2)2] (2) showed distinctive spectral changes that the intensity of the band (𝜆 = at 364 nm, assigned to $n \to \pi^\ast$ transitions) decreased and a new broad band in low intensity about 460 nm appeared as a result of the reduction of the nickel centered in the oxime core.

• Synthesis, magnetic and spectral studies on polystyrene-anchored coordination complexes of bi-, tri-, tetra- and hexavalent metal ions with unsymmetrical dibasic tetradentate ONNO donor Schiff base derived from 3-formylsalicylic acid, ethylenediamine and 2-benzoylacetanilide

Polystyrene-anchored Cu(II), Zn(II), Cd(II), Ni(II), Mn(II), MoO2(II), UO2(II), Fe(III) and Zr(IV), complexes of the unsymmetrical dibasic tetradentate ONNO donor Schiff base derived from the condensation of chloromethylated polystyrene, 3-formylsalicylic acid, ethylenediamine and 2-benzoylacetanilide (PS-LH2) has been synthesized. The polystyrene anchored complexes have the formulae: PS-LM (where M = Cu, Zn, Cd, Ni, MoO2, UO2), PS-LFeCl.DMF, PS-LMn$.2$DMF and PS-LZr(OH)$_2.$DMF. The polystyrene-anchored coordination compounds have been characterized by elemental analysis, IR, reflectance, ESR and magnetic susceptibility measurements. The per cent reaction conversion of polystyrene anchored Schiff base to polystyrene supported coordination compounds lies between 28.98 and 85.9. The coordinated dimethylformamide is completely lost on heating the complexes. The shifts of the ν(C=N)(azomethine) and ν(C-O)(phenolic) stretches have been monitored in order to find out the donor sites of the ligands. The Cu(II) complex is paramagnetic with square planar structure; the Ni(II) complex is diamagnetic with square planar structure; the Zn(II) and Cd(II) complexes are diamagnetic and have tetrahedral structure; the Mn(II) and Fe(III) complexes are paramagnetic and have octahedral structure; the MoO2(II) and UO2(II) complexes are diamagnetic and have octahedral structure and the Zr(IV) complexes are diamagnetic and have pentagonal bipyramidal structure.

• A simple protocol for the michael addition of indoles with electron deficient olefins catalysed by TBAHS in aqueous media and their broad spectrum antibacterial activity

Tetrabutylammonium hydrogen sulfate catalysed addition of indoles to electron deficient olefins in water generated the corresponding Michael adducts in good to excellent yield. The Michael addition of indole occurred regioselectively at position 3 and the 𝑁-alkylated products have not been observed. The synthesized compounds were tested for their antibacterial activity against four microorganisms namely, E. coli NCIM 2931, S. aureus NCIM 5021, P. vulgaris NCIM 2813, P. aeruginosa NCIM 5029 by micro dilution method. These compounds showed MIC (Minimum Inhibitory Concentration) values in the range of $0.16-2.67$ 𝜇M.

• Unsymmetrical extended 𝜋-conjugated zinc phthalocyanine for sensitization of nanocrystalline TiO2 films

We have designed and synthesized a new unsymmetrical zinc phthalocyanine based on `push-pull’ and extended 𝜋-conjugation concept, PCH008. The new sensitizer was fully characterized by CHN anlysis, UV-Vis., fluorescence spectroscopies and cyclic voltammetry. The new sensitizer which upon anchoring onto nanocrystalline TiO2 film exhibit a short circuit current of 5.63 mA cm-2, open circuit potential of 557.0 mV and a fill factor of 0.75 corresponding to an overall conversion efficiency of 2.35% under standard global air mass (AM) 1.5 solar conditions and compared its performance with literature reported phthalocyanine dyes.

• Preparation of amine coated silver nanoparticles using triethylenetetramine

This article presents a simple method towards the preparation of functionalized silver nanoparticles in a continuous medium. Silver nanoparticles were obtained through AgNO3 chemical reduction in ethanol and triethylenetetramine was used to stabilize and functionalize the metal. The product was characterized with X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FTIR), UVvisible spectroscopy, thermal gravimetric analysis (TGA) and transmission electron microscopy (TEM). Monocrystalline silver particles with cubic structure and an average size of 20 nm were obtained. The results reveal that it is possible to synthesize Ag nanoparticles functionalized with amine groups and that particle size is influenced by the processing route.

• Sucrose/bovine serum albumin mediated biomimetic crystallization of calcium carbonate

To understand the role of the sucrose/bovine serum albumin system in the biomineralization process, we have tested the influence of different concentration of the sucrose/bovine serum albumin (BSA) on calcium carbonate (CaCO3) precipitation. The CaCO3 crystals were characterized by scanning electron microscope (SEM), Fourier transform infrared spectrograph (FT-IR) and powder X-ray diffractometry (XRD). The possible formation mechanism of CaCO3 in the sucrose/bovine serum albumin system was discussed.

• Excited state intramolecular charge transfer reaction in 4-(1-azetidinyl)benzonitrile: Solvent isotope effects

Excited state intramolecular charge transfer reaction of 4-(1-azetidinyl) benzonitrile (P4C) in deuterated and normal methanol, ethanol and acetonitrile has been studied in order to investigate the solvent isotope effects on reaction rates and yields. These quantities (reaction rates and yields) along with several other properties such as quantum yield and radiative rates have been found to be insensitive to the solvent isotope substitution in all these solvents. The origin of the solvent isotope insensitivity of the reaction is discussed and correlated with the observed slowing down of the solvation dynamics upon isotope substitution.

• A X-ray diffraction analysis on graphene layers of Assam coal

The so-called turbostatic structure of carbons in coal with randomly oriented stacking of the lamellae (graphene) produces intense peaks, which are the dominant features in its X-ray diffraction profiles. The diffractogram may be conveniently divided into two regions of reciprocal space, the medium S region (1 &lt; S &lt; 3 Å) and a high S region (S &gt; 3 Å) where $S = 4\pi \lambda^{-1} \sin \theta$. To better understand the molecular level structure of high sulphur Assam coal, two coal samples (Tirap-1 and Tirap-2) from Tirap colliery of Makum coalfield, Assam (India) has been interpreted in this study by using the X-ray diffraction profiles. Random layered (graphene) structural parameters of these coals were determined by using X-ray diffraction technique, which showed that the $L_a$ and $L_c$ are 64.99 Å and 22.63 Å for Tirap-2 and 55.54 Å and 23.80 Å for that of Tirap-1 coals respectively. The position of 𝛾 band was found to be at 4.34 Å and 4.13 Å for Tirap-2 and Tirap-1 coals respectively. The number of layers and average number of carbon atoms (N) per aromatic graphene were found to be 21 and 8 for both the coal samples. Proximate, ultimate and ash analysis of the two coal samples were also carried out in this investigation.

• # Journal of Chemical Sciences

Volume 132, 2019
All articles
Continuous Article Publishing mode

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019