Synthesis,crystal structure and antibacterial activity of manganese(III) and cobalt(III) complexes containing pentadentate Schiff bases of a common amine and thiocyanate

Abstract

Four new mononuclear Schiff base manganese(III) and cobalt(III) complexes viz. [Mn(L¹)(NCS)] (1), [Mn(L²)(NCS)] (2), [Co(L³)(NCS)] (3), and [Co(L⁴)(NCS)]·0.5CH₃OH·0.5H₂O (4), containing thiocyanate as a common pseudohalide ion are reported. The pentadentate Schiff base ligands H₂L¹, H₂L², H₂L³, and H₂L⁴ were obtained by the condensation of substituted salicylaldehydes with N-(3-aminopropyl)-N-methylpropane-1,3-diamine. The syntheses of the complexes have been achieved by the reaction of manganese(II) perchlorate or cobalt(II) perchlorate with the respective Schiff bases in the presence of thiocyanate in methanol medium. Complexes 1–4 have been characterized by microanalytical, spectroscopic, single-crystal X-ray diffraction and other physicochemical studies. Structural studies reveal that 1–4 adopt nearly similar structures containing the MN₄O₂ (M?=?Mn, Co) chromophore in which each central M(III) ion adopts a distorted octahedral geometry. Weak intermolecular H-bonding interactions are operative in these complexes to bind the molecular units. The antibacterial activity of 1–4 and their constituent Schiff bases has been tested against some common bacteria.     

Cryptanalytic results on ‘Dual CRT’ and ‘Common Prime’ RSA

In this paper we study weaknesses of two variants of RSA: Dual RSA and Common Prime RSA. Several schemes under the framework of Dual RSA have been proposed by Sun et al. (IEEE Trans Inf Theory 53(8):2922–2933, 2007). We here concentrate on the Dual CRT-RSA scheme and present certain range of parameters where it is insecure. As a corollary of our work, we prove that the Dual Generalized Rebalanced-RSA (Scheme III of Sun et al.) can be efficiently broken for a significant region where the scheme has been claimed to be secure. Next we consider the Common Prime RSA as proposed by Wiener (IEEE Trans. Inf. Theory 36:553–558, 1990). We present new range of parameters in Common Prime RSA where it is not secure. We use lattice based techniques for the attacks.     

Oxoclusters of the lanthanides begin to resemble solid-state materials at very small cluster sizes: structure and NIR emission from Nd(III)

The reaction of Nd(SePh)3 with SeO2 and Hg in pyridine gives the dodecanuclear cluster [(py)18Nd12O6Se4(Se2)4(SePh)4(Se2Ph)2Hg2(SePh)4][(Hg(SePh)3]2. In this compound the 12 Nd(III) ions are stacked in four sets of Nd3, with pairs of tetrahedral oxo ligands separating the Nd3 planes and Se, SeSe, SePh, pyridine, and HgSePh groups encapsulating the oxo core. Both the Nd-O bond lengths and the geometries about the oxo ions are remarkably similar to those found in solid-state Nd2O3. Near-IR emission experiments indicate that the cluster emission properties are less intense than those of highly emissive (DME)2Nd(SC6F5)3 or (THF)8Nd8O2Se2(SePh)16 but brighter than the nonemissive solid-state compound Nd2O3. Intensity variations are interpreted in terms of concentration quenching and phonon relaxation.     

N-Prolinylanthranilic acid derivatives as bifunctional organocatalysts for asymmetric aldol reactions

Several N-prolinylanthranilic acid derivatives were prepared and tested as bifunctional organocatalysts in the direct asymmetric aldol reaction of cyclohexanone with p-nitrobenzaldehyde. It was found that methyl substitution ortho to the carboxylic acid improves enantioselectivity, but substitution ortho to the anilide group does not. The catalyst derived from 2-amino-6-methylbenzoic acid was tested over a range of direct asymmetric aldol reactions and its overall performance is equal to or better than many of the known prolinamide catalysts in terms of yield, diastereoselectivity, and enantioselectivity.     

Quantification of α-Asarone in Acorus calamus by Validated HPTLC Densitometric Method

JPC – Journal of Planar Chromatography – Modern TLC -     

Rhodamine-linked pyridyl thiourea as a receptor for selective recognition of F–, Al3+ and Ag+ under different conditions

A new rhodamine-labelled pyridyl thiourea-based compound 1 has been designed and synthesised. While the receptor selectively recognises F^– and Al³⁺ ions in CH₃CN, Al³⁺ and Ag⁺ ions are selectively screened from other cations in CH₃CN/water (4/1, v/v; 10 μM Tris–HCl buffer, pH 6.8) by observing different emission characteristics and colour changes. While Ag⁺ is sensed through an increase in emission at 416 nm, Al³⁺ is detected by a ratiometric change in emission of 1 with a band at 585 nm. The receptor shows in vitro detection of both the ions in human cervical cancer (HeLa) cells.     

Formation and bonding of alane clusters on Al(111) surfaces studied by infrared absorption spectroscopy and theoretical modeling

Alanes are believed to be the mass transport intermediate in many hydrogen storage reactions and thus important for understanding rehydrogenation kinetics for alanates and AlH3. Combining density functional theory (DFT) and surface infrared (IR) spectroscopy, we provide atomistic details about the formation of alanes on the Al(111) surface, a model environment for the rehydrogenation reactions. At low coverage, DFT predicts a 2-fold bridge site adsorption for atomic hydrogen at 1150 cm(-1), which is too weak to be detected by IR but was previously observed in electron energy loss spectroscopy. At higher coverage, steps are the most favorable adsorption sites for atomic H adsorption, and it is likely that the AlH3 molecules form (initially strongly bound to steps) at saturation. With increasing exposures AlH3 is extracted from the step edge and becomes highly mobile on the terraces in a weakly bound state, accounting for step etching observed in previous STM studies. The mobility of these weakly bound AlH3 molecules is the key factor leading to the growth of larger alanes through AlH3 oligomerization. The subsequent decomposition and desorption of alanes is also investigated and compared to previous temperature programmed desorption studies.     

Arbitrary self-assembly of peptide extracellular microscopic matrices

Two faces for one matrix: A single bifaceted cyclopeptide block forms highly branched, porous, and intricate fibrillar networks, which span microscopic dimensions and mimic the extracellular matrix to support cell growth and proliferation. The peptide block has two domains connected with triglycine linkers (GGG); the domains consist of positively (blue) and negatively (red) charged heptads that provide interactions between different blocks.     

Composites of graphene and other nanocarbons with organogelators assembled through supramolecular interactions

Carbon nanomaterials (CNMs), such as exfoliated graphene (EG), long-chain functionalized EG, single-walled carbon nanotubes (SWNTs), and fullerene (C(60)), have been investigated for their interaction with two structurally different gelators based on all-trans tri-p-phenylenevinylene bis-aldoxime (1) and n-lauroyl-L-alanine (2) both in solution and in supramolecular organogels. Gelation occurs in toluene through hydrogen bonding and van der Waals interactions for 1 and 2 in addition to π-π stacking specifically in the case of 1. These nanocomposites provide a thorough understanding in terms of molecular-level interactions of dimensionally different CNMs with structurally different gelators. The presence of densely wrapped CNMs encapsulated fibrous network in the resulting composites is evident from various spectroscopic and microscopic studies, indicating the presence of supramolecular interactions. Concentration- and temperature-dependent UV/Vis and fluorescence spectra show that CNMs promote aggregation of the gelator molecules, leading to hypochromism and quenching of the fluorescence intensity. Thermotropic mesophases of 1 are altered by the inclusion of a small amount of CNMs. The gel-CNM composites show increased electrical conductivity compared with that of the native organogel. Rheological studies of the composites demonstrate the formation of rigid and viscoelastic solidlike assembly due to reinforced aggregation of the gelators on CNMs. Synergistic behavior is observed in case of the composite gel of 1, containing a mixture of EG and SWNT, when compared with other mixtures of CNMs in all combinations with EG. This affords new nanocomposites with interesting optical, thermal, electrical, and mechanical properties.