CO2 Complex Research Articles

Thermodynamic studies on metal complexes of Co2+, Ni2+, Cu2+ and Cd2+ with 8-hydroxy 5-quinolinesulfonic acid in water, methanol and water-methanol binary solvent systems at 303.15 K, 313.15 K and 323.15 K by conductometric method

Thermodynamic studies on metal complexes of Co2+, Ni2+, Cu2+ and Cd2+ with 8-hydroxy 5-quinolinesulfonic acid in water, methanol and water-methanol binary solvent systems at 303.15 K, 313.15 K and 323.15 K by conductometric method

QSPR ensemble modelling of the 1:1 and 1:2 complexation of Co²⁺, Ni²⁺, and Cu²⁺ with organic ligands: relationships between stability constants.

Quantitative structure-property relationship (QSPR) modeling of stability constants for the metal:ligand ratio 1:1 (logK) and 1:2 (logβ2) complexes of 3 transition metal ions with diverse organic ligands in aqueous solution was performed using ensemble multiple linear regression analysis and substructural molecular fragment descriptors. The modeling was performed on the sets containing 396 and 132 (Co(2+)), 613 and 233 (Ni(2+)), 883 and 257 (Cu(2+)) logK and logβ 2 values, respectively. The models have been validated in external fivefold cross-validations procedure as well as on the external test set containing new ligands recently reported in the literature. Predicted logK and logβ 2 values were calculated as arithmetic means of several hundred individual models (consensus models) using their applicability domains in averaging. The root mean squared error of predictions varies from 0.94 to 1.2 (logK) and from 1.2 to 1.4 (logβ2) which is close to observed experimental systematic errors. Linear correlations between experimental logK values for pair of metal ions were evaluated. For all metal ions and ligands forming both 1:1 and 1:2 complexes the following ratio is observed: logβ2/logK = 1.8 ± 0.1, n = 492.

A Salen–Co3+ Catalyst for the Hydration of Terminal Alkynes and in Tandem Catalysis with Ru–TsDPEN for the One‐Pot Transformation of Alkynes into Chiral Alcohols

AbstractThe cobalt–salen complex (C1:[(salen)Co3+(OAc)]; salen= N,N′‐bis(salicylidene)ethylenediamine, OAc=acetate) was found to efficiently promote the hydration of terminal alkynes to give methyl ketones in the presence of the H2SO4 cocatalyst. In addition, the one‐pot transformation of alkynes into chiral alcohols through tandem catalysis by catalyst C1 coupled with a ruthenium–TsDPEN complex (C3: [(R,R‐TsDPEN)Ru2+(cymene)]; TsDPEN=(1R,2R)‐N‐(p‐toluenesulfonyl)‐1,2‐diphenylethylenediamine, cymene=1‐methyl‐4‐(1‐methylethyl)benzene) catalyst was realized with excellent yields and enantioselectivities.

Dendrimer‐Encapsulated Cobalt Nanoparticles as High‐Performance Catalysts for the Hydrolysis of Ammonia Borane

AbstractDendrimer‐encapsulated Co nanoparticles (G6‐OH(Co60)) have been synthesized through the complexation of Co2+ cations to the internal tertiary amine of sixth‐generation hydroxyl‐terminated poly(amidoamine) dendrimers followed by reduction by both sodium borohydride and ammonia borane in aqueous solution. The highly dispersed G6‐OH(Co60), in which the average diameter of Co nanoparticles is approximately 1.6±0.4 nm, have been confirmed by TEM analysis. The catalytic activity of G6‐OH(Co60) for the hydrolysis of ammonia borane has been studied in aqueous solution at different reaction temperatures, demonstrating a high catalytic performance.

A complexation study of 15-crown-5 with Co2+ cation in some pure and mixed organic solvents

The stability constant (log Kf) and the thermodynamic parameters (free energies, enthalpies, and entropies) of the complexation of Co2+ cation with 15-crown-5 (15C5) in acetonitrile-methanol (AN/MeOH), acetonitrile-nitrobenzene (AN/NB), acetonitrile-dichloromethane (AN/DCM) and acetonitrile-1,2-dichloroethane (AN/DCE) binary solvent solutions were calculated from the experimental conductance data at different temperatures. The complexation behavior of the crown ether used in these media was discussed in view of the estimated parameters. In all solvent systems, 15-crown-5 formed a 1: 1 complex with Co2+ cation. The stability order of (Co-15C5)2+ complex in the binary mixed solvents at 25°C was found to be: AN/NB > AN/DCM ≈ AN/DCE > AN/MeOH. In most cases, a non-linear relationship was observed for changes of log Kf of (Co-15C5)2+ complex versus the composition of the binary mixed solvent systems. The experimental results show that the standard thermodynamic parameters of the complexation process change with the nature and composition of the binary solvent solutions.

Thermodynamic studies on metal complexes of Co2+, Ni2+, Cu2+ and Cd2+ with 8-hydroxy 5-quinolinesulfonic acid in water, methanol and water-methanol binary solvent systems at 303.15 K, 313.15 K and 323.15 K by conductometric method

Thermodynamic studies on metal complexes of Co2+, Ni2+, Cu2+ and Cd2+ with 8-hydroxy 5-quinolinesulfonic acid in water, methanol and water-methanol binary solvent systems at 303.15 K, 313.15 K and 323.15 K by conductometric method

Characterization of CO2 and mixed methane/CO2 hydrates intercalated in smectites by means of atomistic calculations

The recent increase in anthropogenic CO2 gas released to the atmosphere and its contribution to global warming make necessary to investigate new ways of CO2 storage. Injecting CO2 into subsurface CH4 hydrate reservoirs would displace some of the CH4 in the hydrate crystal lattice, converting simple CH4 hydrates into either simple CO2 hydrates or mixed CH4CO2 hydrates. Molecular simulations were performed to determine the structure and behavior of CO2 and mixed hydrate complexes in the interlayer of Na-rich montmorillonite and beidellite smectite. Molecular Dynamics (MD) simulations used NPT ensembles in a 4×4×1 supercell comprised of montmorillonite or beidellite with CO2 or mixed CH4/CO2 hydrate complexes in the interlayer. The smectite 2:1 layer surface helps provide a stabilizing influence on the formation of gas hydrate complexes. The type of smectite affects the stability of the smectite-hydrate complexes, where high charge located on the tetrahedral layer of the smectites disfavor the formation of hydrate complexes.

Kinetics of ionization and recombination of atmospheric sodium

Characteristic times of photoionization from the ground 3S- and excited 3P-states of the sodium atom have been calculated. A model of balance equations of ionization and recombination kinetics of atmospheric sodium has been constructed for the optically thin case based on the experimental scheme of reactions of the formation of complex ions with the participation of sodium. The model also takes into account photoprocesses for the ground and excited levels of sodium. The numerical solution of the balance equations describes the density dynamics of sodium atoms, sodium ions, and Na+H2O, Na+N2, and Na+CO2 complex ions with allowance for laser illumination at the resonance transition with a wavelength of 0.589 μm.

Fundamental Investigation of the Factors Controlling the CO2 Permeability of Facilitated Transport Membranes Containing Amine-Functionalized Task-Specific Ionic Liquids

Task-specific ionic liquid (IL)-based facilitated transport membranes were prepared with tetrabutylphosphonium amine-functionalized glycinate or 2-cyanopyrrolide ILs. CO2 permeabilities and viscosity and CO2 absorbance of ILs were evaluated. Viscosities of glycinate- or methylglycinate-containing ILs drastically increased with CO2 absorption, probably from hydrogen bonding between their CO2 complexes. The temperature dependence of the CO2 permeability of the IL-based membranes was opposite to that of the viscosity of the corresponding ILs. The CO2 permeability at low temperature under dry conditions was improved by using tetrabutylphosphonium 2-cyanopyrrolide, which barely forms hydrogen bonds among its CO2 complexes. However, above 363 K, the tetrabutylphosphonium 2-cyanopyrrolide-based membrane had a lower CO2 permeability than the tetrabutylphosphonium glycinate-based membrane because tetrabutylphosphonium 2-cyanopyrrolide absorbed less CO2. The major factors controlling CO2 permeability of task-specif...

Chloride Encapsulation by a Tripodal Tris(4-pyridylurea) Ligand and Effects of Countercations on the Secondary Coordination Sphere

A series of anion complexes of the 4-pyridyl-functionalized tripodal tris(urea) receptor (L) have been synthesized. Ligand L forms the 1:1 anion complex [Cl⊂L]− with various metal chloride salts, MClx (M = Na, K, Mg, Ca, Mn, Co, x = 1 or 2). When M = Na, K, Mg, and Ca, the metal ions are not coordinated by the pyridyl groups of L but are involved in second-sphere coordination to form three-dimensional structures. However, in the complex of Co2+, the transition metal ions are directly coordinated by the pyridyl groups. Interestingly, the Mn2+ ion forms two complexes with both of the above two types of structure. In all complexes, one chloride ion is “half” encapsulated in the cleft of one ligand by N–H···Cl hydrogen bonds to form the [Cl⊂L] units, which are further linked via intermolecular interactions into three-dimensional structures. Moreover, the fluoride and carbonate complexes of L have also been obtained. The solution anion binding properties of L have been studied by 1H NMR spectroscopy and electrospray ionization mass spectrometry.

Structural, energetic and vibrational properties of some van der Waals complexes of CO2, OCS and OCSe

As part of a study of the properties of some chalcogen-bonded complexes with NH3, H2O, PH3 and H2S, we have investigated the oxygen-bound species containing CO2, OCS and OCSe by means of molecular orbital calculations at the ab initio level. The structures of the NH3, H2O and PH3 complexes are all similar, with a primary C…X interaction (X = N, O, P) and one of the hydrogen atoms approaching an oxygen atom in a weak secondary attraction. The H2S complexes show a greater variety of alternative structures. The changes in the monomer geometrical parameters, the interaction energies and the harmonic vibrational spectra vary in general in a systematic way as the acid and the base are changed. Deviations from this systematic behaviour have been rationalised.

X·F (X=C, N, O and S) Noncovalent Weak Intermolecular Interactions

A number of X···F (X=C, N, O and S) noncovalent weak intermolecular interaction systems of CH3-F···XO2 (X=C, N, O and S) has been investigated at B3LYP/6-311++G(d, p) computational level. A topological analysis of the electron density for the X···F (X=C, N, O and S) noncovalent weak bonds was performed using Baders theory of atom-in-molecules (AIM). The interaction content of the F···X in H3CF···CO2 complex would mainly represent more π property than others. The interaction energies data without (ΔE) and with (ΔEcp) BSSE correction showed that the stability of the four complexes of the H3CF···DB2 system increases in the order of H3CF···O3 < H3CF···NO2 < H3CF···CO2 < H3CF···SO2.

Redox and complexation chemistry of the CrVI/CrV-d-glucaric acid system

When an excess of uronic acid over Cr(VI) is used, the oxidation of D-glucaric acid (Glucar) by Cr(VI) yields D-arabinaric acid, CO2 and Cr(III)-Glucar complex as final redox products. The redox reaction involves the formation of intermediate Cr(IV) and Cr(V) species. The reaction rate increases with [H(+)] and [substrate]. The experimental results indicated that Cr(IV) and Cr(V) are very reactive intermediates since their disappearance rates are much faster than Cr(VI). Cr(IV) and Cr(V) intermediates are involved in fast steps and do not accumulate in the redox reaction of the mixture Cr(VI)-Glucar. Kinetic studies show that the redox reaction between Glucar and Cr(VI) proceeds through a mechanism combining one- and two-electron pathways: Cr(VI) → Cr(IV) → Cr(II) and Cr(VI) → Cr(IV) → Cr(III). After the redox reaction, results show a slow hydrolysis of the Cr(III)-Glucar complex into [Cr(OH2)6](3+). The proposed mechanism is supported by the observation of free radicals, CrO2(2+) (superoxo-Cr(III) ion) and oxo-Cr(V)-Glucar species as reaction intermediates. The continuous-wave electron paramagnetic resonance, CW-EPR, spectra show that five-coordinate oxo-Cr(V) bischelates are formed at pH ≤ 4 with the aldaric acid bound to oxo-Cr(V) through the carboxylate and the α-OH group. A different oxo-Cr(V) species with Glucar was detected at pH 6.0. The high g(iso) value for the last species suggests a mixed coordination species, a five-coordinated oxo-Cr(V) bischelate with one molecule of Glucar acting as a bi-dentate ligand, using the 2-hydroxycarboxylate group, and a second molecule of Glucar with any vic-diolate sites. At pH 7.5 only a very weak EPR signal was observed, which may point to instability of these complexes. This behaviour contrasts with oxo-Cr(V)-uronic species, and must thus be related to the Glucar acyclic structure. In vitro, our studies on the chemistry of oxo-Cr(V)-Glucar complexes can provide information on the nature of the species that are likely to be stabilized in vivo.

Superbasicity of silylene derivatives achieved via non-covalent intramolecular cation···π interactions and exploited as molecular containers for CO2.

We have reported for the first time designed silylene superbases involving intramolecular H(+)···π interaction using density functional theory (DFT) calculations. The non-covalent interactions augment the proton affinity values by 13 kcal mol−1 in the designed superbase (1) compared to the acyclic silylene, [:Si(NMe2)2]. These divalent Si(II) compounds can act as powerful neutral organic superbases in gas and solvent phases. The DFT calculations performed at the B3LYP/6-311+G**//B3LYP/6-31+G* level of theory showed that the gas phase proton affinity of the paracyclophane based silylene superbase (8) reaches up to ~271.0 kcal mol(−1), which is the highest in paracyclophane Si(II) compounds. In tetrahydrofuran solvent medium, the calculated proton affinity of 8 was found to be 301.4 kcal mol(−1). The paracyclophane-based silylene systems are used for binding with small alkali metal ions. The calculated results showed that these systems selectively bind to lithium ions over sodium ions due to the small size of lithium ions which is well fitted in the space between the silicon atom and the phenyl ring. Furthermore, we have used the lithiated silylene 1 and 9 (which exhibits bis-protonation) for gas storage (CO and CO2). The calculated results showed both the lithiated silylene 1 and 9 bind preferentially to CO2 than CO. The calculated gravimetric density of CO2 is found to be 26.97 wt% for 9-Li2–(CO2)4. The energy decomposition analysis (EDA) has been performed to investigate the role of various contributing factors to the total binding strength of the CO2 or CO molecules with lithiated silylene superbases. EDA reveals that the electrostatic energy and polarization energy are the major driving force for higher total interaction energy of the lithiated-silylene–CO2 complex than the lithiated-silylene–CO complex. The lithiated silylene systems showed a higher binding energy with CO2 than the previously reported imidazopyridamine at the same level of theory. These results suggest that the lithiated silylene systems can be used as a more efficient CO2 storage material than the aforementioned system. The calculated desorption energies per CO2 and CO (ΔEDE) also indicate the recyclable property of the materials.

Correlated ab initio molecular dynamics simulations of the acetone–carbon dioxide complex: implications for solubility in supercritical CO2

Ab initio molecular dynamics simulations of the acetone–CO2 complex (MP2/6-31G(d) level) were performed to investigate the effect of dynamics at finite temperature on the weak electron donor–acceptor intermolecular interactions. In addition, we carried out a study of the free energy of formation of the complex by means of umbrella sampling technique at the MP2 level with a perturbative CCSD(T) correction. The potential of mean force was obtained along a reaction coordinate describing the acetone–CO2 interaction. The results obtained here support some hypothesis that we already explored in past works using static electronic calculations. In particular, when interacting with a molecule having a carbonyl function, carbon dioxide displays both Lewis acid and Lewis base behaviour. This property can be exploited to design molecular systems that are easily solubilised in supercritical CO2.

DFT Study of Polyaniline NH3, CO2, and CO Gas Sensors: Comparison with Recent Experimental Data

Density functional theory studies (DFT) have been carried out to evaluate the ability of polyaniline emeraldine salt (PANI ES) from 2 to 8 phenyl rings as sensor for NH3, CO2, and CO. The sensitivity and selectivity of nPANI ES among NH3, CO2, and CO are studied at UB3LYP/6-31G(d) level of theory. Interaction of nPANI ES with CO is studied from both O (CO(1)) and C (CO(2)) sides of CO. Interaction energy, NBO, and Mulliken charge analysis were used to evaluate the sensing ability of PANI ES for different analytes. Interaction energies are calculated and corrected for BSSE. Large forces of attraction in nPANI ES-NH3 complexes are observed compared to nPANI ES–CO2, nPANI ES-CO(1), and nPANI ES-CO(2) complexes. The inertness of +C≡O– in nPANI ES-CO(1) and nPANI ES-CO(2) complexes are also discussed. Frontier molecular orbitals and energies indicate that NH3 changes the orbital energy of nPANI ES to a greater extent compared to CO2, CO(1), and CO(2). Peaks in UV–vis and UV–vis–near-IR spectra of nPANI ES are ...

IR Spectroscopy of Gas Phase V(CO2)n+ Clusters: Solvation-Induced Electron Transfer and Activation of CO2

Ion-molecule complexes of vanadium and CO2, i.e., V(CO2)n(+), produced by laser vaporization are mass selected and studied with infrared laser photodissociation spectroscopy. Vibrational bands for the smaller clusters (n < 7) are consistent with CO2 ligands bound to the metal cation via electrostatic interactions and/or attaching as inert species in the second coordination sphere. All IR bands for these complexes are consistent with intact CO2 molecules weakly perturbed by cation binding. However, multiple new IR bands occur only in larger complexes (n ≥ 7), indicating the formation of an intracluster reaction product whose nominal mass is the same as that of V(CO2)n(+) complexes. Computational studies and the comparison of predicted spectra for different possible reaction products allow identification of an oxalate-type C2O4 anion species in the cluster. The activation of CO2 producing this product occurs via a solvation-induced metal→ligand electron transfer reaction.

Roles of the Lewis Acid and Base in the Chemical Reduction of CO2 Catalyzed by Frustrated Lewis Pairs

We employ quantum chemical calculations to discover how frustrated Lewis pairs (FLP) catalyze the reduction of CO2 by ammonia borane (AB); specifically, we examine how the Lewis acid (LA) and Lewis base (LB) of an FLP activate CO2 for reduction. We find that the LA (trichloroaluminum, AlCl3) alone catalyzes hydride transfer (HT) to CO2 while the LB (trimesitylenephosphine, PMes3) actually hinders HT; inclusion of the LB increases the HT barrier by ∼8 kcal/mol relative to the reaction catalyzed by LAs only. The LB hinders HT by donating its lone pair to the LUMO of CO2, increasing the electron density on the C atom and thus lowering its hydride affinity. Although the LB hinders HT, it nonetheless plays a crucial role by stabilizing the active FLP·CO2 complex relative to the LA dimer, free CO2, and free LB. This greatly increases the concentration of the reactive complex in the form FLP·CO2 and thus increases the rate of reaction. We expect that the principles we describe will aid in understanding other catalytic CO2 reductions.

Synthesis and structure of new polynuclear cobalt(ii) complexes with 3,5-di-tert-butylbenzoic acid anions

Trinuclear complex Co3(O2CR)6(EtOH)2 (1) crystals were obtained in good yield (75%) by the exchange reaction between cobalt(II) chloride and potassium 3,5-di-tert-butylbenzoate (KO2CR) in EtOH. Complex 1 undergoes hydrolysis during recrystallization from non-anhydrous benzene to form the hexanuclear hydroxocarboxylate complex Co6(OH)2(O2CR)10(HO2CR)4 (2).

A novel development of dithizone as a dual-analyte colorimetric chemosensor: Detection and determination of cyanide and cobalt (II) ions in dimethyl sulfoxide/water media with biological applications

The behavior of dithizone (DTZ), an easily available dye has been studied for the first time in chromogenic sensing of CN− as an anionic species and for Co2+ as a cationic species in DMSO/H2O media. So employing DTZ an efficient colorimetric chemosensor was afforded with a chromogenic selectivity for Co2+ over other cations with detection limit of 0.04μmolL−1. The complex of Co2+ with DTZ also displayed ability to detect up to 0.43μmolL−1 CN− (K+ salts) among other competing anions through a fast response time of less than 30s which is much lower than most recently reported chromogenic probes. The linear dynamic ranges for the determination of Co2+ and CN− were 0.3–4.4 and 3.3–58.6μmolL−1 respectively. This method could have potential application in a variety of cases requiring rapid and accurate analysis of Co2+ and CN− for human serum and water samples.