Quadrupole Moment Of CO2 Research Articles

Capturing CO2 in Quadrupolar Binding Pockets: Broadband Microwave Spectroscopy of Pyrimidine-(CO2)n, n = 1,2.

Pyrimidine has two in-plane CH(δ+)/N̈(δ-)/CH(δ+) binding sites that are complementary to the (δ-/2δ+/δ-) quadrupole moment of CO2. We recorded broadband microwave spectra over the 7.5-17.5 GHz range for pyrimidine-(CO2)n with n = 1 and 2 formed in a supersonic expansion. Based on fits of the rotational transitions, including nuclear hyperfine splitting due to the two 14N nuclei, we have assigned 313 hyperfine components across 105 rotational transitions for the n = 1 complex and 208 hyperfine components across 105 rotational transitions for the n = 2 complex. The pyrimidine-CO2 complex is planar, with CO2 occupying one of the quadrupolar binding sites, forming a structure in which the CO2 is stabilized in the plane by interactions with the C-H hydrogens adjacent to the nitrogen atom. This structure is closely analogous to that of the pyridine-CO2 complex studied previously by (Doran, J. L. J. Mol. Struct. 2012, 1019, 191-195). The fit to the n = 2 cluster gives rotational constants consistent with a planar cluster of C2v symmetry in which the second CO2 molecule binds in the second quadrupolar binding pocket on the opposite side of the ring. The calculated total binding energy in pyrimidine-CO2 is -13.7 kJ mol-1, including corrections for basis set superposition error and zero-point energy, at the CCSD(T)/ 6-311++G(3df,2p) level, while that in pyrimidine-(CO2)2 is almost exactly double that size, indicating little interaction between the two CO2 molecules in the two binding sites. The enthalpy, entropy, and free energy of binding are also calculated at 300 K within the harmonic oscillator/rigid-rotor model. This model is shown to lack quantitative accuracy when it is applied to the formation of weakly bound complexes.

Investigating CO2 storage properties of Pd(II) and Co(II) chelates of a Schiff's base ligand

A new metal complexes are made from the ligands derived from amoxicillin based Schiff's base coordinated with Pd(II) and Co(II) have been synthesized and characterized via different spectroscopic methods. FT-IR spectroscopy have shown a formation of tetrahedral and square planar geometry for Co(II) and Pd(II) complexes, respectively. Surface morphology was inspected via field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The Brunauer–Emmett–Teller surface area of the metal complexes samples is about 6.63 to 8.71 m2/g, with pore diameters and volume of 0.030–0.0501 cm3/g and 18.39–22.98 nm, respectively. The quadrupole moment of CO2 has a great effect on the adsorption capacity as it is highly diffusible of 21.38, 26.16 cm3.g−1 for Co(II) and Pd(II) complex.

Sorption, Structure and Dynamics of CO₂ and Ethane in Silicalite at High Pressure: A Combined Monte Carlo and Molecular Dynamics Simulation Study.

Silicalite is an important nanoporous material that finds applications in several industries, including gas separation and catalysis. While the sorption, structure, and dynamics of several molecules confined in the pores of silicalite have been reported, most of these studies have been restricted to low pressures. Here we report a comparative study of sorption, structure, and dynamics of CO2 and ethane in silicalite at high pressures (up to 100 bar) using a combination of Monte Carlo (MC) and molecular dynamics (MD) simulations. The behavior of the two fluids is studied in terms of the simulated sorption isotherms, the positional and orientational distribution of sorbed molecules in silicalite, and their translational diffusion, vibrational spectra, and rotational motion. Both CO2 and ethane are found to exhibit orientational ordering in silicalite pores; however, at high pressures, while CO2 prefers to reside in the channel intersections, ethane molecules reside mostly in the sinusoidal channels. While CO2 exhibits a higher self-diffusion coefficient than ethane at low pressures, at high pressures, it becomes slower than ethane. Both CO2 and ethane exhibit rotational motion at two time scales. At both time scales, the rotational motion of ethane is faster. The differences observed here in the behavior of CO2 and ethane in silicalite pores can be seen as a consequence of an interplay of the kinetic diameter of the two molecules and the quadrupole moment of CO2.

INVESTIGATION OF CARBON BLACK AND SILICA SURFACE STRUCTURE BY STATIC GAS ADSORPTION WITH VARIOUS GASES

ABSTRACT The surface of various carbon black and silica grades is characterized via static gas adsorption using different gases. From decomposition of the adsorption isotherm into distinct energetic contributions, the adsorption energy distribution as well as the surface area are obtained. The decomposition is done by an iterative expectation maximization algorithm specifically designed for this problem. It is found that the adsorption isotherms of the various gases differ significantly in the low-pressure regime, leading to characteristic energy distributions with distinct maxima. As expected, the mean adsorption energy generally increases with the cross section of the gases, and systematic deviations are found reflecting the polar and dispersive interaction characteristics of silica and carbon black, respectively. The surface fractal dimension of two different carbon black grades is estimated using the yardstick method. The obtained values 2.6 and 2.7 agree with previous findings that the carbon black surface morphology is very rough. The adsorption of CO2 on both carbon blacks delivers unexpectedly low values of the monolayer coverage or specific surface area, indicating that mainly high energetic sites of the surface are covered. In consequence, compared with N2, a relatively high value of the mean adsorption energy is found. For both investigated silicas, the mean adsorption energy scales with the quadrupole moments of CO2 and N2, which is indicative of a large polar contribution to interaction energy.

Environmental effects on noble-gas hydrides: HXeBr, HXeCCH, and HXeH in noble-gas and molecular matrices

Noble-gas hydrides HNgY (Ng is a noble-gas atom and Y is an electronegative group) are sensitive probes of local environment due to their relatively weak bonding and large dipole moments. We experimentally studied HXeBr in Ar, Kr, and N2 matrices, HXeCCH in Ne and N2 matrices, and HXeH in an N2 matrix. These are the first observations of noble-gas hydrides in an N2 matrix. An N2 matrix strongly increases the H-Xe stretching frequency of HXeBr and HXeCCH with respect to a Ne matrix, which is presumably due to a strong interaction between the HNgY dipole moment and quadrupole moments of the surrounding lattice N2 molecules. The spectral shift of HXeBr in an N2 matrix is similar to that in a CO2 matrix, which is a rather unexpected result because the quadrupole moment of CO2 is about three times as large as that of N2. The H-Xe stretching frequencies of HXeBr and HXeCCH in noble-gas matrices show a trend of ν(Ne) < ν(Xe) < ν(Kr) < ν(Ar), which is a non-monotonous function of the dielectric constants of the noble-gas solids. The MP2(full) calculations of HXeBr and HXeCCH with the polarizable continuum model as well as the CCSD(T) calculations of the HXeBr···Ng and HXeCCH···Ng (Ng = Ne, Ar, Kr, and Xe) complexes cannot fully explain the experimental observations. It is concluded that more sophisticated computational models should be used to describe these experimental findings.

Enhanced CO2 Adsorption in Metal-Organic Frameworks via Occupation of Open-Metal Sites by Coordinated Water Molecules

CO2 is one of the most important greenhouse gases and its removal from flue gas and natural gas has become increasingly important. We report an interesting discovery in which the CO2 uptake and its selectivity over N2 and CH4 in the metal-organic framework (MOF) Cu-BTC were significantly increased by the presence of water molecules coordinated to open-metal sites in the framework. This was first predicted by molecular simulations and later validated by experiments. A detailed analysis of simulation data revealed that interaction between the quadrupole moment of CO2 and the electric field created by water molecules is responsible for the enhanced CO2 uptake. These findings could open new possibilities for tuning the adsorption behavior of MOFs for CO2 capture and other applications.

Ab initio calculation of quadrupole moments of CO2 and N2 molecules as functions of nuclear geometry

Ab initio multireference configuration interaction calculations of the static dipole and quadrupole moments of CO2 and N2 as functions of the internuclear distances have been carried out using the multireference single and double excitation configuration interaction method (MRDCI). The results are compared with the outcome of Hartree-Fock calculations and help shed light on the effect of such moments on the low energy interaction of these molecules during scattering processes, and hence on their influence on the threshold behaviour of the inelastic cross-sections involving vibrational degrees of freedom.

Ab initio calculation of quadrupole moments of CO2 and N2 molecules as functions of nuclear geometry

Ab initio calculation of quadrupole moments of CO2 and N2 molecules as functions of nuclear geometry

The temperature variation of the far infrared absorption in compressed CO2

The collision-induced absorption spectrum of gaseous CO2 has been measured in the far infrared at temperatures of 200 K, 293 K, 323 K and 373 K. The peak of the induced absorption band is observed to shift to lower frequency and to increase in magnitude as the temperature is reduced. Values of the absorption coefficient measured at frequencies across the band, and the integrated band absorption coefficient are presented as functions of temperature. The data have been used in two ways to obtain a value of the quadrupole moment of CO2, yielding the mean values of (6.4+or-1.0)*10-26 esu cm2 and (7.6+or-1.0)*10-26 esu cm2. A discussion of possible mechanisms of absorption in addition to that due to the quadrupole- induced dipole moment is given.

Extended Basis-Set LCSTO—MO—SCF Calculations on the Ground State of Carbon Dioxide

Extended basis-set SCF—STO—MO wavefunctions for the ground state of CO2 are reported. In particular, the effect of doubling the number of 2pσ basis functions and the effect of changing their orbital exponents has been investigated, together with the effect of addition of 3dσC basis functions. The effect of expanding the π basis set by addition of extra 2pπC basis functions and 3dπO1, O2 basis functions is also shown. A wave-function using the best σ basis set together with the best π basis set used in these calculations would give a molecular energy of approximately 9 eV below that obtained from a `best atom' minimal basis-set calculation. This is to be compared with the estimated Hartree—Fock molecular energy which is approximately 24 eV below the ``best atom'' minimal basis-set value. This highlights the importance of the choice of basis functions and minimization of the total energy with respect to orbital exponents in the case that the number of basis functions out of which MO's can be constructed is limited. The quadrupole moment of CO2 is computed from two of the wavefunctions reported.