Synthesis and structural characterization of a (N,N′-bis[2(S)-pyrrolidylmethyl]-propane-1,3-diamine) nickel (II) complex

The nickel(II) complex [Ni(C₄H₃NCH=N–(CH₂)₃–N=CHC₄H₃N)], (1) containing the symmetrical N₄ tetradentate Schiff base ligand, which is the 2:1 condensation product of pyrrole-2-carboxaldehyde and 1,3-diaminopropane respectively, was prepared. Structural investigation shows that it is monomeric, having space group P2₁/c, a = 7.989(7), b = 17.406(14), c = 9.193(5) Å, = 90, = 100.39(6), = 90, and Z = 4. The coordination geometry around the nickel atom is slightly distorted square planar and the conformation of the six-membered ring containing the metal,azomethine nitrogens and three carbon atoms of the connecting 1,3-diaminopropane is a symmetric boat.     

Crystal structure of tylophorine methiodide monohydrate,C25H30NO 4 + I−·H2O

The crystal structure of tylophorine (Chemical name 2,3,6,7 tetramethoxy phenanthro [9,10:6, 7] indolizidine. Contribution No. 0871.) methiodide monohydrate has been determined. C₂₅H₃₀NO ₄ ⁺ I^–·H₂0, triclinic, P,a=8.831(1)Å, b=10.842(2),c=13.902(2), =105.0(1)^o, =104.7(1), =97.3(1),V=1210.22ų, Z=2,D _x =1.428 g./cm^–3, (CuK)=1.54184Å, (CUK)=107.2 cm^–1, F(000)=544,T=295^oK,R=0.038,Rw=0.046, for 2331 observed reflections withI2(I). Apart from van der Waals forces, the structure is stabilized by two hydrogen bonds of the type Ow(H) ... O and Ow(H) ... I^– involving the water molecule as the donor and atom O4 of the methoxy group and I^– as acceptors.     

Physicochemical studies on the interaction of gelatin with cationic surfactants alkyltrimethylammonium Bromides (ATABs) with special focus on the behavior of the hexadecyl homologue

The interaction of a denatured interfacially active protein, gelatin (G) (at pH 9, above its isoelectric pH 4.84, and ionic strength mu=0.005), with a cationic amphiphile, hexadecyl (or cetyl) trimethylammonium bromide, CTAB, has been elaborately studied using a variety of techniques. Two types of protein-surfactant complexes at a concentration below the normal critical micellar concentration (cmc) were formed in solution. The first, G-CTAB (monomer) combined complex (GS(n)(I)) adsorbed at the air/solution interface, followed by its gradual transformation to the poor interfacially active second G-CTAB (aggregate) complex (GS(m)(B)) at a critical aggregation concentration (cac) of the interacting oppositely charged surfactant. In the higher concentration range, upon completion of GS(m)(B) formation, coacervation (association of GS(m)(B)) led to add turbidity. With increasing addition of CTAB, the coacervates became disintegrated and ultimately remained dissolved in the free micellar solution of CTAB. The above features were studied using the techniques of tensiometry, conductometry, turbidimetry, fluorimetry, and microcalorimetry. The interaction features were prominent at [G] >or= 0.05 g %, and several of these were either marginal or absent at [G]<0.05 g %. The denatured protein was found to form viscous as well as gel-forming consistencies at higher [G] and at lower temperature. A temperature variation study on the interaction of G with CTAB has revealed that enhanced interaction takes place at higher temperature. The effect of [G] on its interaction with cationic surfactants of varying chain length in the alkyltrimethylammonium bromide (ATAB) series has been also studied; a similar interactional profile as that of CTAB has been exhibited by octadecyltrimethylammonium bromide; however, the lower homologues (dodecyl- and tetradecyl-) of ATAB have offered different profiles. It has been found that the ATABs with higher alkyl chain lengths were more interactive with negatively charged G than their lower homologues. Quantification of the results in terms of different transition points, counterion binding of the protein-bound surfactant aggregates and free micelles, the enthalpy of binding interactions and energetics of ATAB micellization, and so forth have been studied. The results have been rationalized in terms of an interaction model.     

Halogen-containing tetrametallic aluminium alkoxides

New halogen-containing tetrametallic aluminium alkoxides of formula [Al{(mu-OEt)2AlMeCl}3] ( 2-cis; 2-trans), and [Al{(mu-OEt)2AlBr2}3] ( 4), have been synthesized by combining Al(OEt)3 and Me2AlCl (for 2) or EtAlBr2 (for 4). They were fully characterized by (1H, 27Al) NMR, IR, mp, elemental analysis, and single-crystal X-ray diffractometry. The chloride analogue of 4, [Al{(mu-OEt)2AlCl2}3] ( 3), prepared previously using a different route, was also prepared here by combining Al(OEt)3 and EtAlCl2.     

A New Complex as a Dimer of a Silver Ion with AMTTO and Phosphane Ligands. The Crystal Structure of {[(AMTTO)Ag(PPh3)2]NO3}2·0.5CH3OH·0.5H2O

Reaction of 4‐amino‐6‐methyl‐1,2,4‐triazine‐3‐thione‐5‐on (AMTTO) as a bidentate ligand with silver nitrate and triphenyl phosphine as the co‐ligand make the centrosymmetric dimeric complex {[(AMTTO)Ag(PPh₃)₂]NO₃}₂·0.5CH₃OH·0.5H₂O ( 1 ). 1 was characterized by elemental analyses, IR‐ and NMR spectroscopy as well as X‐ray diffraction studies. The silver atom in 1 has distorted tetrahedral coordination. 1 crystallizes in triclinic space group . Crystal data for 1 at −80 °C: a = 1185.8(1), b = 1314.6(1), c = 1385.3(1) pm, α = 97.78(1)°, β = 111.38(1)°, γ = 92.41(1)°, Z = 2, R₁ = 0.0377.     

Thermal hysteresis of some important physical properties of nanoparticles

Gold nanoparticles show thermal hysteresis with properties such as surface plasmon absorption, conductivity, and zeta potential. The direction of the incremental change in plasmon peak position and its extinction depend on the nature of surface conjugation. The thermal profile of a surface plasmon resonance spectrum for nanoparticles may serve as a signature for the associated small molecule or macromolecule on which it is seeded. The thermal responses of zeta potential and conductivity profile are found to be independent of the surface conjugation with the later being subjected to a phase transition phenomenon as revealed by a temperature criticality.     

Microtrapping characteristics of single and multi-walled carbon nanotubes

Carbon nanotubes (CNTs) possess some highly desirable sorbent characteristics, which make them attractive for a variety of applications including micro-scale preconcentration. The main advantage of CNTs is that they are non-porous, thus eliminating the mass transfer resistance related to diffusion into pore structures. Their high aspects ratio leads to large specific capacity, consequently they have the potential to be the next generation high performance sorbent. In this paper we present the microtrapping. The objective of this paper was to study the sorption of select organic compounds on single and multi-walled nanotubes either packed or self-assembled onto a micro-sorbent trap. The data show that the CNTs show highly favorable adsorption as well as desorption. The former is characterized by relatively large breakthrough volumes and isosteric heats of adsorption (DeltaH(s), close to 64 kJ/mol). Similarly, rapid desorption from CNTs was demonstrated by narrow desorption bandwidth. The elimination of non-tubular carbons (NTC) from the CNT surface is important, as they reduce the performance of these sorbents.     

Variation in coordinative property of two different N<Subscript>2</Subscript>O<Subscript>2</Subscript> donor Schiff base ligands with nickel(II) and cobalt(III) ions: characterisation and single crystal structure elucidation

A nickel(II) and a cobalt(III) complex of two different potentially tetradentate Schiff bases with different binding modes have been synthesised. The nickel(II) complex [NiL¹] · CH₃OH (1) was formed, on reacting the metal salt with a perfectly symmetrical N₂O₂ tetradentate Schiff base ligand H ₂ L ¹ , which is the 1:2 condensation product of 1,3-diamino propane and 2-hydroxyacetophenone. The cobalt(III) complex [Co(HL²)₃] · (ClO₄)₃ · H₂O (2) was synthesised using an asymmetric N₂O₂ tetradentate Schiff base ligand HL ² on condensing N,N-dimethyl-1,3-diamino propane with o-vanillin in 1:1 mmol ratio. Although both Schiff bases are N₂O₂ functionalised, they showed variation in their coordinative property with nickel(II) and cobalt(III) ions. Both the complexes were characterised by IR spectroscopy and cyclic voltammetry and their single crystal structures clearly indicate that 1 is a mononuclear species whereas 2 is a hydrogen-bonded dimer.     

Synthesis,characterization and crystal structure of new silver(I) and palladium(II) complexes containing 1,2,4-triazole moieties

The reaction of 4-amino-5-ethyl-2H-1,2,4-triazole-3(4H)-thione (AETT, L1) with 2-thiophen carbaldehyde in methanol leads to the corresponding Schiff-base HL1a. The reaction of L1 with AgNO₃ in ethanol gives the ionic complex [{[Ag(L1)]NO₃}₂]_n (1). The ionic complex [(PPh₃)₂Ag(HL1a)₂]NO₃ · CH₃CN (2) can be obtained by the reaction of HL1a with [(PPh₃)₂Ag]NO₃ in methanol and acetonitrile solution, while its reaction with [(PPh₃)₂PdCl₂] in the presence of sodium acetate in methanol leads to the neutral complex [(PPh₃)₂Pd(L1a)₂] · 4MeOH (3). All the compounds were characterized by infrared spectroscopy, elemental analyses as well as by X-ray diffraction studies.     

Temperature-dependent solvation dynamics of water in sodium bis(2-ethylhexyl)sulfosuccinate/isooctane reverse micelles

In this paper, for the first time, we report a detailed study of the temperature-dependent solvation dynamics of a probe fluorophore, coumarin-500, in AOT/isooctane reverse micelles (RMs) with varying degrees of hydration (w0) of 5, 10, and 20 at four different temperatures, 293, 313, 328, and 343 K. The average solvation time constant becomes faster with the increase in w0 values at a particular temperature. The solvation dynamics of a RM with a fixed w0 value also becomes faster with the increase in temperature. The observed temperature-induced faster solvation dynamics is associated with a transition of bound- to free-type water molecules, and the corresponding activation energy value for the w0 = 5 system has been found to be 3.4 kcal mol-1, whereas for the latter two systems, it is approximately 5 kcal mol-1. Dynamic light scattering measurements indicate an insignificant change in size with temperature for RMs with w0 = 5 and 10, whereas for a w0 = 20 system, the hydrodynamic diameter increases with temperature. Time-resolved fluorescence anisotropy studies reveal a decrease in the rotational restriction on the probe with increasing temperature for all systems. Wobbling-in-cone analysis of the anisotropy data also supports this finding.