Absence Of Counterion Research Articles

Spectroscopic studies, density functional theory calculations, non-linear optical properties, biological activity of 1-hydroxy-4-((4-(N-(pyrimidin-2-yl)sulfamoyl)phenyl)diazenyl)-2-naphthoic acid and its chelates with Nickel (II), Copper (II), Zinc (II) and Palladium (II) metal ions

Novel Nickel (II), Copper (II), Zinc (II) and Palladium (II) chelates with 1‑hydroxy-4-((4-(N-(pyrimidin-2-yl)sulfamoyl)phenyl)diazenyl)-2-naphthoic acid (H3L) have been produced and clarified using several physicochemical techniques. Quantum mechanical calculations of energies, geometries were achieved by using the density functional theory with Becke's three parameter exchange functional, the Lee_Yang_Parr correlation functional (B3LYP/GEN) combined with 6.311 G (d,p) and LANL2DZ basis sets. The analyses of Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) have been used to justify the charge transfer within the ligand and its chelates. The considered small energy gap between Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) energies expressions that the charge transfer occurs within the ligand and its chelates. The results show that the azo dye ligand exists in two tautomeric structures, the first structure (H3L), the sulphonamide (SO2NH), while the second one, the sulphonamide group in enolic form (H2L-OH). The H2L-OH tautomer has energy of 12.93 kcal/mol higher than that of H3L. The structure of H3L was found to be the most stable and used as the ligand in this study. The bond lengths of Ni(II) ion with the donating sites of the ligand in Ni-(H2L)2 chelate suggest a distorted octahedral geometry, Cu2-(L) chelate, suggests a highly distorted tetrahedral geometry, Zn-(HL) chelate displays a distorted octahedral geometry, Pd-(H2L) chelate approves a distorted square planar geometry around its own central metal ion. Geometrical parameters, molecular electrostatic potential maps and total electron densities analyses of the ligand and its chelates have been carried out. Molecular stability, hyper conjugative interactions, intramolecular charge transfer and bond strength have been examined by applying of natural bond orbital (NBO) analysis. Total static dipole moment, mean polarizability, anisotropy of the polarizability, mean first-order hyperpolarizability have been also achieved. From the molecular hyperpolarizability (˂β˃), The computed (˂β˃) values show that for the ligand (H3L) and its Ni-(H2L)2, Cu2-(L), Zn-(HL) and Pd-(H2L) are ~23, ~70, ~44, ~132 and ~38 times greater than that of Urea, indicating all the studied ligand and its chelates reveal significant polarizability and first-order hyperpolarizability and are predicted to be successful for Non-Linear Optical (NLO) materials. The analyses of the chelates indicate that the Zn(II) and Pd(II) form 1:1, Ni(II) form 1:2 while Cu(II) ion form 2:1 (M:L) and non-electrolytic behavior of chelates indicate the absence of counter ion. Ni-(H2L)2 complex had zero antibacterial activity against E. coli while its activity is higher than the azo dye against Staphylococcus aureus. Pd-H2L complex had almost the same activity as the azo dye against both types of bacteria. The higher activity of Zn-HL and Cu2-L complexes can be explained by their chelation.

Novel Zn(II) complexes of 1,3-diphenyl-4-(arylazo)pyrazol-5-one derivatives: Synthesis, spectroscopic properties, DFT calculations and first order nonlinear optical properties

Eight novel Zn(II) complexes with substituted 1,3-diphenyl-4-(arylazo)pyrazol-5-one (L1-L4) derivatives have been synthesized and elucidated using various physicochemical techniques. Quantum mechanical calculations of energies, geometries were done by DFT using B3LYP/GEN functional combined with 6.311G (d,p) and LAN2DZ basis sets. The analyses of HOMO and LUMO have been used to explain the charge transfer within the ligands and complexes. The calculated small energy gap between HOMO and LUMO energies shows that the charge transfer occurs within Zn(II) complexes. Geometrical parameters, molecular electrostatic potential maps (MEP) and total electron densities analyses of the ligands and their Zn complexes have been carried out. Molecular stability, hyperconjugative interactions, intramolecular charge transfer (ICT) and bond strength has been investigated by the applying of natural bond orbital (NBO) analysis. Total static dipole moment (μ), the mean polarizability (<α>), the anisotropy of the polarizability (Δα), the mean first-order hyperpolarizability (<β>) have been also performed. The obtained values show that Zn(II) complexes is brilliant candidate to NLO materials. The analyses of the 1:1 complexes indicate that the Zn(II) ion is five-coordinated with water molecules at axial position in case of L1, L2 and L4 whereas, six-coordinated with L3 and non-electrolytic behaviour of complexes indicates the absence of counter ion.

Synthesis, characterization and crystal structure of some bidentate heterocyclic Schiff base ligands of 4-toluoyl pyrazolones and its mononuclear Cu(II) complexes

We depict the synthesis of a new set of six bidentate heterocyclic Schiff base ligands, formed by the condensation of three different 4-toluoyl pyrazolones with various aromatic amines in ethanolic medium. All of these ligands have been characterized on the basis of elemental analysis, IR, 1H NMR, 13C NMR and Mass spectral data. The molecular geometries of three of these ligands have been determined by single crystal X-ray study. It reveals that these ligands exist in amine-one tautomeric form in the solid state. The reaction of these ligands with copper(II) resulted in the formation of mononuclear complexes having the general composition [CuL 2(H 2O) 2] with two water molecules at axial positions. These complexes have been characterized on the basis of elemental analysis, Cu-estimation, molar conductivity, magnetic measurements, IR, UV–Visible, FAB–Mass, TG–DTA–DSC data, cyclic voltametric measurements and ESR spectral studies. ESR spectra and magnetic susceptibility measurements indicates distorted octahedral stereochemistry of Cu(II) complexes, while non-electrolytic behaviour of complexes indicates the absence of counter ion.

Synthesis, spectral, crystallography and thermal investigations of novel Schiff base complexes of manganese (III) derived from heterocyclic β-diketone with aromatic and aliphatic diamine

The Schiff base tetradentate ligands N,N-bis-(3,5-dimethyl-1-p-tolyl-1H-pyrazol-4-ylmethylene)-ethane-1,2-diamine (H(2)L(1)), N,N-bis-(3,5-dimethyl-1-p-sulfonyl-1H-pyrazol-4-ylmethylene)-ethane-1,2-diamine (H(2)L(2)), N,N-bis-(3,5-dimethyl-1-p-tolyl-1H-pyrazol-4-ylmethylene)-benzene-1,2-diamine (H(2)L(3)) and N,N-bis-(3,5-dimethyl-1-p-sulfonyl-1H-pyrazol-4-ylmethylene)-benzene-1,2-diamine (H(2)L(4)) were prepared from the reaction between 5-oxo-3-methyl-1-p-tolyl-1H-pyrazole-4-carbaldehyde or 4-(4-formyl-5-oxo-3-methyl-pyrazol-1-yl)-benzenesulfonic acid and o-phenylenediamine or ethylenediamine. And these are characterized by elemental analysis, FT-IR, (1)H NMR and GC-MS. The corresponding Schiff base complexes of Mn(III) were prepared by condensation of [Mn(3)(mu(3)-O)(OAc)(6)(H(2)O)(3)].3H(2)O with ligands H(2)L(1), H(2)L(2), H(2)L(3) and H(2)L(4). All these complexes have been characterized by elemental analysis, magnetic susceptibility, X-ray crystallography, conductometry measurement, FT-IR, electronic spectra and mass (FAB) spectrometry. Thermal behaviour of the complexes has been studied by TGA, DTA and DSC. Electronic spectra and magnetic susceptibility measurements indicate octahedral stereochemistry of manganese (III) complexes, while non-electrolytic behaviour complexes indicate the absence of counter ion.

Framework and grafted nickel ethylenediamine complexes in 2D hexagonal mesostructured templated silica

Well-ordered periodic mesoporous organosilicas (PMOs) of the MCM-41 type of structure containing framework Ni(II) complexes (Ni@PMOs) were synthesized via a one-pot synthesis route in mild conditions, using cheap and environmental friendly reactants. These materials were obtained using the N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AAPTMS) ligand in three different molar ratios of Ni, X = 1, 2, 3 and co-condensed with sodium silicate in the presence of cetyltrimethylammonium tosylate as a templating agent. The latter named OP-Ni-1, OP-Ni-2 and OP-Ni-3, respectively, were submitted to a treatment using a mixture of chlorotrimethylsilane (CTMS) and hexamethyldisilazane (HMDSA) that simultaneously removed the surfactant and capped the silanol groups leading to materials OP-Ni-1TA, OP-Ni-2TA and OP-Ni-3TA (∼2 wt% Ni content). For comparison, a series of mesoporous materials were prepared via a post-synthesis route to locate the Ni(II) complexes in the channel (∼2.4 wt% Ni). The latter were prepared using the “molecular stencil patterning” (MSP) technique based on sequential grafting of trimethylsilyl (TMS) groups and the same ligand cited above using AAPTMS/Ni molar ratios of 2 and 3. These steps lead to intermediate materials LUS to LUS-PSE and final materials LUS-MSP-Ni-2 and LUS-MSP-Ni-3. Both series of materials were thoroughly investigated in terms of (i) coordination state compared to molecular analogues, (ii) Ni(II) to Cu(II) exchange ability and (iii) coordination accessibility using ethylenediamine (en) or thiocyanate (SCN−) as probe ligands. All materials were investigated using XRD, TEM, N2 sorption isotherms, UV-visible, FT-IR and EPR spectroscopies. In particular, FT-IR and EPR data were treated quantitatively to monitor both the TMS loading and the concentration of isolated Cu(II) in conjunction with elemental analysis. Pore size decrease, pore volume reduction, nickel to copper exchangeability (> 90%) and ligand accessibility were observed for materials LUS-MSP-Ni-2 and LUS-MSP-Ni-3 as expected with grafted Ni(II) complexes located in the channel. By contrast, a clear opposite trend, observed for Ni@PMOs, OP-Ni-1, OP-Ni-2 and OP-Ni-3, was fully consistent with a complete insertion and captation of the Ni complexes in the siliceous pore walls despite the very small thickness (ca. 1.4 nm) of the wall. This is explained by the state of Ni(II) both in terms of coordination and cavity effect. Indeed, both absence of counterion coming from the solution (nitrate) and bathochromic shift of the d-d electronic transitions, are consistent with the presence of silanolate groups counterbalancing the electrical charges and mainly leading to neutral framework species of formula, [Ni(AAPS)2(SiO)2], [Ni(AAPS)(OL)2(SiO)2], with neutral ligand OL = H2O, SiOH, SiOSi and AAPS = N-(2-aminoethyl)-3-aminopropylsilyl moities.

Spectral Tuning in Bacteriorhodopsin in the Absence of Counterion and Coplanarization Effects

The basis for wavelength regulation in bacteriorhodopsin (BR) and retinylidene proteins in general has been studied for decades but is still only partially understood. Here we report the preparation and spectroscopic characterization of BR analogs aimed at investigating the existence of spectral tuning mechanisms other than the two widely accepted mechanisms, weakened counterion interactions and ring/chain coplanarization. We synthesized two novel retinal analogs containing a saturated 13-14 bond, which interrupts the interaction of the protein counterions with the chromophore conjugation system. Furthermore, one of the analogs has a planar polyene system so that the contribution to the red shift of BR by retinal ring/chain coplanarization is also absent. We incorporated these analogs into bacterioopsin and discovered a sizable amount of red shift, which can be accounted for by interactions between the polar or polarizable groups of the protein and the retinal polyene chain. Our results suggest that the wavelength regulation in BR is achieved by synergistic chromophore/protein interactions including ring/chain coplanarization, excited state stabilization by polar or polarizable protein side chains located along the polyene chain, and weakened counterion interactions near the Schiff base positive charge.

Sulfate transport by flounder renal tubule brush border: presence of anion exchange.

Transport of sulfate into brush border membrane (BBM) vesicles from renal tubules of southern flounder, Paralichthys lethostigma, was investigated. Imposition of a 21 mM HCO-3 gradient, in greater than out, produced concentrative sulfate uptake (overshoot) fourfold higher than equilibrium. Gradient conditions were necessary to produce this response; no overshoot was produced by the mere presence of HCO-3. Generation of potassium diffusion potentials with KCl gradients and valinomycin or short-circuiting of possible other ionic diffusion potentials had no effect on sulfate uptake. The rate-limiting step in HCO-3:SO2-4 exchange is, therefore, an electroneutral process. Although HCO-3 was the most effective counterion for sulfate, SCN-, Cl-, and S2O2-3 were also capable of promoting concentrative sulfate uptake. Sulfate uptake in the absence of counterion and bicarbonate-dependent sulfate uptake were both shown to be saturable processes. HCO-3-driven sulfate uptake could be inhibited by disulfonic stilbene, HgCl2, probenecid, chlorophenol red, and bromcresol green. Phloridzin, p-aminohippuric acid, 2,4-dinitrophenol, isethionic acid, and citric acid had no significant effect on HCO-3:SO2-4 exchange. The role of this sulfate:anion exchanger in active renal tubule sulfate secretion is discussed.