We report infrared photodissociation spectra of [Bi(CO₂)_n]⁻ (n=2−9) cluster anions. We determine the charge carrier geometry by comparing calculated vibrational frequencies based on density functional theory to the experimental spectra. The vibrational frequencies and the charge carrier geometry depend strongly on the solvation environment present in the cluster. We discuss the interaction of bismuth and CO₂ in the presence of an excess electron in the context of heterogeneous catalytic reduction of CO₂.

We present infrared photodissociation spectra of [Fe(CO₂)_n]⁻ (n=3−7) cluster anions. We use density functional theory to compare calculated vibrational frequencies to our experimental spectra to determine plausible structures for the molecular charge carriers. The spectra display similar characteristics to those of other complexes of first-row transition metals with CO₂ ligands, and show signatures of several structural motifs.

We have systematically investigated the van der Waals complexes consisting of the one from each of the two groups: (Rg, CO, N₂ or CO₂) and (dimethyl ether, dimethyl sulfide, ethylene oxide or ethylene sulfide), by using Fourier transform microwave spectroscopy supplemented by ab initio MO calculations, in order to understand the dynamical behavior of van der Waals complexes and to obtain information on the potential function to internal motions in complexes.Y. Kawashima, A. Sato, Y. Orita, and E. Hirota, J. Phys. Chem. A 2012 116 1224wo examples of the N₂ complex were investigated: N₂-DME (dimethyl ether), for which we reported a preliminary resultY. Kawashima, Y. Tatamitani, Y. Morita, and E. Hirota, 61st International Symposium on Molecular Spectroscopy, TE10 (2006)nd N₂-EO (ethylene oxide).Y. Kawashima and E. Hirota, J. Phys. Chem. A 2013 117 13855n the present study we focused attention to the N₂-ES (ethylene sulfide) complex. We have detected two sets of the b-type transitions for the ¹⁵N₂-ES in ortho and para states, and have analyzed them by using the asymmetric-rotor program of A-reduction. In contrast with the N₂-EO, for which each of the ortho and para states were found split into a strong/weak pair, only some transitions of the ¹⁵N₂-ES were accompanied by two or three components. The observed spectra of the ¹⁴N₂-ES were complicated because of hyperfine splittings due to the nuclear quadrupole coupling of the two nitrogen atoms. We concluded that the N₂ moiety was located in the plane perpendicular to the C-S-C plane and bisecting the CSC angle of the ES. Two isomers were expected to exist for ¹⁵NN-ES, one with ¹⁵N in the inner and the other in the outer position, and in fact two sets of the spectra were detected. We have carried out ab initio molecular orbital calculations at the level of MP2 with basis sets 6-311++G(d, p), aug-cc-pVDZ, and aug-cc-pVTZ, to complement the information on the intracomplex motions obtained from the observed rotational spectra.

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Y. Kawashima, A. Sato, Y. Orita, and E. Hirota, J. Phys. Chem. A 2012 116 1224T Y. Kawashima, Y. Tatamitani, Y. Morita, and E. Hirota, 61st International Symposium on Molecular Spectroscopy, TE10 (2006)a Y. Kawashima and E. Hirota, J. Phys. Chem. A 2013 117 13855I

This paper presents an extension of the preceding talk on the FTMW spectroscopy of N₂-ES (ethylene sulfide), namely the results on N₂-DMS (dimethyl sulfide). We have previously investigated two N₂ complexes: N₂-DME (dimethyl ether), for which we reported a prelimanary result,Y. Kawashima, Y. Tatamitani, Y. Morita, and E. Hirota, 61st International Symposium on Molecular Spectroscopy, TE10 (2006)nd N₂-EO (ethylene oxide).Y. Kawashima and E. Hirota, J. Phys. Chem. A 2013 117 13855e have observed the ground-state rotational spectrum of the N₂-DMS complex, i.e. c-type transitions in the frequency region from 5 to 24 GHz, which we assigned to the normal, ¹⁵N₂-DMS, and ¹⁵NN-DMS species of the N₂-DMS. We have found both the ortho and para states for the ¹⁴N₂-DMS and ¹⁵N₂-DMS species. In the case of the ¹⁵N₂-DMS, some transitions with K_a = 2 and 3 were observed slightly split by the internal rotation of the two methyl tops of the DMS. The observed spectra of the ¹⁵N₂-DMS were analyzed by using the XIAM program. In the case of the para state of the ¹⁵N₂-DMS, three rotational and five centrifugal distortion constants with the V₃ barrier to the methyl group internal rotation, whereas, in the case of the ortho state of the ¹⁵N₂-DMS, two more centrifugal distortion constants, Φ_JK and Φ_KJ, were needed to reproduce the observed spectra. For the N₂-DMS complex, we concluded that the N₂ moiety was located in a plane perpendicular to the C-S-C plane and bisecting the CSC angle of the DMS.
We have carried out ab initio molecular orbital calculations at the level of MP2 with basis sets 6-311++G(d, p), aug-cc-pVDZ, and aug-cc-pVTZ, to complement the information on the intracomplex motions obtained from the observed rotational spectra. We have applied a natural bond orbital (NBO) analysis to the N₂-DMS and N₂-ES to calculate the stabilization energy CT (=∆E_σσ*), which was closely correlated with the binding energy E_B, as found for other related complexes.

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Y. Kawashima, Y. Tatamitani, Y. Morita, and E. Hirota, 61st International Symposium on Molecular Spectroscopy, TE10 (2006)a Y. Kawashima and E. Hirota, J. Phys. Chem. A 2013 117 13855W

Combined Photoelectron Spectroscopy (PES) and theoretical calculations have found that anion boron clusters (B_n⁻) are planar and quasi-planar up to B₂₅⁻. Recent works show that anion pure boron clusters continued to be planar at B₂₇⁻,B₃₀⁻,B₃₅⁻ and B₃₆⁻. B₃₅⁻ and B₃₆⁻ provide the first experimental evidence for the viability of the two-dimensional (2D) boron sheets (Borophene). The 2D to three-dimensional (3D) transitions are shown to happen at B₄₀⁻,B₃₉⁻ and B₂₈⁻, which possess cage-like structures. These fullerene-like boron cage clusters are named as Borospherene. Recently, borophenes or similar structures are claimed to be synthesized by several groups. Following an electronic design principle, a series of transition-metal-doped boron clusters (M©B_n⁻, n=8-10) are found to possess the monocyclic wheel structures. Meanwhile, CoB₁₂⁻ and RhB₁₂⁻ are revealed to adopt half-sandwich-type structures with the quasi-planar B₁₂ moiety similar to the B₁₂⁻ cluster. Very lately, we show that the CoB₁₆⁻ cluster possesses a highly symmetric Cobalt-centered drum-like structure, with a new record of coordination number at 16. Here we report the CoB₁₈⁻ cluster to possess a unique planar structure, in which the Co atom is doped into the network of a planar boron cluster. PES reveals that the CoB₁₈⁻ cluster is a highly stable electronic system with the first adiabatic detachment energy (ADE) at 4.0 eV. Global minimum searches along with high-level quantum calculations show the global minimum for CoB₁₈⁻ is perfectly planar and closed shell (¹A₁) with C_2v symmetry. The Co atom is bonded with 7 boron atoms in the closest coordination shell and the other 11 boron atoms in the outer coordination shell. The calculated vertical detachment energy (VDE) values match quite well with our experimental results. Chemical bonding analysis by the Adaptive Natural Density Partitioning (AdNDP) method shows the CoB₁₈⁻ cluster is π-aromatic with four 4-centered-2-electron (4c-2e) π bonds and one 19-centered-2-electron (19c-2e) π bond, 10 π electrons in total. This perfectly planar structure reveals the viability of creating a new class of hetero-borophenes and metallo-borophenes by doping metal atoms into the plane of monolayer boron atoms. This gives a new approach to design perspective hetero-borophenes and metallo-borophenes materials with tunable chemical, magnetic and optical properties.

Study of the carbon dioxide dimer has a long history, but there is only one previous observation of an intermolecular vibration [1]. Here we analyze four new combination bands of (CO₂)₂ in the CO₂ ν₃ region ( ∼ 2350 cm⁻¹), observed using tunable infrared lasers and a pulsed slit-jet supersonic expansion. The previous combination band at 2382.2 cm⁻¹was simple to assign [1]. A much more complicated band ( ∼ 2370 cm⁻¹) turns out to involve two upper states, one at 2369.0 cm⁻¹(B_u symmetry), and the other at 2370.0 cm⁻¹(A_u). The spectrum can be nicely fit by including the Coriolis interactions between these states. Another complicated band around 2443 cm⁻¹also involves two nearby upper states which are highly perturbed in so-far unexplained ways (possibly related to tunneling shifts). With the help of new ab initio calculations [2], we assign the results as follows. The 2369.0 cm⁻¹band is the combination of the forbidden A_g intramolecular fundamental (probably [1] at about 2346.76 cm⁻¹) and the intermolecular geared bend (B_u). The 2370.0 cm⁻¹band is the combination of the same A_g fundamental and the intermolecular torsion (A_u). This gives about 22.3 and 23.2 cm⁻¹for the geared bend and torsion. The previous 2382.2 cm⁻¹band [1] is the allowed B_u fundamental (2350.771 cm⁻¹) plus two quanta of the geared bend (B_u), giving 31.509 cm⁻¹for this overtone. The highly perturbed 2442.7 cm⁻¹band is the B_u fundamental plus the antigeared bend (A_g), giving about 91.9 cm⁻¹for the antigeared bend. Finally, the perturbed 2442.1 cm⁻¹band is due to an unknown combination of modes which gains intensity from the antigeared bend by a Fermi-type interaction. Calculated values [2] are: 20.64 (geared bend), 24.44 (torsion), 32.34 (geared bend overtone), and 92.30 cm⁻¹(antigeared bend), in good agreement with experiment. [1] M. Dehghany, A.R.W. McKellar, Mahin Afshari, and N. Moazzen-Ahmadi, Mol. Phys. 108, 2195 (2010). [2] X.-G. Wang, T. Carrington, Jr., and R. Dawes, private communication.

Using a pulsed slit nozzle multipass absorption spectrometer with a tunable quantum cascade laser we investigated van der Waals clusters involving sulfur hexafluoride in the spectral range near the ν₃ stretching vibration. Different sized homocomplexes were generated in a planar supersonic expansion with typically 0,5 % SF₆ diluted in 6 bar He. Firstly, several rotationally resolved parallel and perpendicular bands of (SF₆)₂, at 934,0 and 956,1 cm⁻¹(#1 structure) in agreement with Takami et al.R. D. Urban and M. Takami, J. Chem. Phys. 103, 9132 (1995).ut also one band at 933,6 cm⁻¹(#2 structure) never observed previously, were analyzed in light of a recent theoretical study predicting three nearly isoenergetic isomers of D_2d, C_2h and C₂ symmetry for the dimer. T. Vazhappily, A. Marjolin and K. D. Jordan, J. Phys. Chem. B, DOI: 10.1021 / acs.jpcb.5b09419 (2015).urthermore, some broader bands were detected around 938 and 964 cm⁻¹and assigned to (SF₆)₃ and (SF₆)₄ clusters on the grounds of concentration effects and/or ab initio calculations. Lastly, with 0,5 % rare gas Rg (Rg = Ne, Ar, Kr and Xe) added to the SF₆:He gas mixture, a series of van der Waals (SF₆)₂-Rg hetero-trimers were observed, which display a remarkable linear dependence of the vibrational shift with the polarizability of the rare gas atom provided that the initial SF₆ dimer structure is #2 . In the same time no transitions belonging to the binary complexes SF₆-Rg were found near the ν₃ monomer band. This result suggests a complex thermodynamics within the pulsed supersonic expansion leading to the preponderance of (SF₆)₂-Rg clusters over SF₆-Rg binary systems. r0pt Figure R. D. Urban and M. Takami, J. Chem. Phys. 103, 9132 (1995).b T. Vazhappily, A. Marjolin and K. D. Jordan, J. Phys. Chem. B, DOI: 10.1021 / acs.jpcb.5b09419 (2015).F

As part of a systematic study of the effect of chlorine substitution on the structures of protic acid haloethylene complexes, the structure of the (E)-1-chloro-2-fluoroethylene-hydrogen chloride complex has been investigated using ab initio quantum chemistry calculations and microwave spectroscopy. Although theory predicts a non-planar equilibrium structure for this species, it is only 7 cm⁻¹ lower in energy than the planar geometry connecting the two equivalent minima on either side of the haloethylene plane, and the observed spectrum is consistent with a planar, average structure, likely the result of zero-point averaging. The geometry is very similar to the fluorine binding, vinyl fluoride-hydrogen chloride complex, suggesting that the substitution of chlorine for a hydrogen trans to the fluorine atom has very little effect on intermolecular interactions in this case. On the other hand, vinyl chloride-hydrogen chloride adopts a non-planar, chlorine binding configuration so that alternatively one could say that the presence of fluorine has a large effect on protic acid-chlorine interactions.

As part of a systematic study of the effect of chlorine substitution on the structures of protic acid-haloethylene complexes, the structure of the (Z)-1-chloro-2-fluoroethylene-hydrogen chloride complex has been investigated using ab initio quantum chemistry calculations and microwave spectroscopy. Although theory predicts a non-planar equilibrium structure for this species, it is only 6 cm⁻¹ lower in energy than the planar geometry connecting the two equivalent minima on either side of the haloethylene plane, and the observed spectrum is consistent with a planar, average structure, likely the result of zero-point averaging. The geometry is unlike that of any previously characterized protic acid-haloethylene complex with a bifurcated primary interaction in which the hydrogen of the acid interacts with both the fluorine and the chlorine atoms on the haloethylene and there is no evidence for a secondary interaction involving the electron rich region of the acid. This structure can be contrasted to those of vinyl fluoride-hydrogen chloride (fluorine bound, planar "top-binding," across the double bond), vinyl chloride-hydrogen chloride (chlorine bound, non-planar) and (Z)-1-chloro-2-fluoroethylene-acetylene (chlorine bound, planar "side-binding," at one end of the double bond).

Jet cooled infrared spectrum of the N₂O-CO van der Waals complex was observed in the region of the ν₁ fundamental band of the N₂O monomer (2224 cm⁻¹) and in the CO stretch region (2143 cm⁻¹). These new measurements allowed the predicted less stable isomer, N₂O-OC, to be observed for the first time in both spectral regions. In addition, four combination bands were observed in the CO region. Two of these were assigned to N₂O-CO and the other two to N₂O-OC. Finally, a combination band in the N₂O region was assigned to the most stable isomer. In this talk I will discuss our results for the intermolecular vibrational frequencies and compare these to the recently published experimental values on similar systems CO₂-CO and CO₂-OC S . Sheybani-Deloui, A. J. Barclay, K. H. Michaelian, A. R. W. McKellar, and N. Moazzen-Ahmadi, J. Chem. Phys 143, 121101 (2015).nd to ab initio predictions on this complex M. Venayagamoorthy, T. A. Ford, THEOCHEM 717,111 (2005)

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S . Sheybani-Deloui, A. J. Barclay, K. H. Michaelian, A. R. W. McKellar, and N. Moazzen-Ahmadi, J. Chem. Phys 143, 121101 (2015).a M. Venayagamoorthy, T. A. Ford, THEOCHEM 717,111 (2005) .

About 14 bands of C₃Ar near the 0 4⁻ 0-000 and 0 2⁺ 0-000 bands of the Ã-~X system of C₃ have been recorded by laser-induced fluoresence with a laser resolution of 0.035 cm⁻¹. Bands at 25428 amd 25515 cm⁻¹ are found to be type A, and those at 25431, 25496, and 25519 cm⁻¹ are type C. Bands at 25504 and 25507 cm⁻¹ are too diffuse for rotational analysis. The bands near 25500 cm⁻¹ form part of two progressions with about 10 cm⁻¹ separations, which appear to represent the van der Waals in-plane-bending vibration. A third diffuse feature was observed near the R(3) line of the 25519 cm⁻¹ band. Possible dissociation processes will be discussed.

The rotational spectrum of the weakly bound complex 3,5-difluoropyridine…CO₂ has been observed using pulsed-nozzle Fourier transform microwave spectroscopy. Spectroscopic constants are reported for the parent and the ¹³CO₂ isotopologues. The data indicate a structure in which the nitrogen approaches the carbon of the CO₂ with the C₂ axis of the difluoropyridine perpendicular to the CO₂. The N…C van der Waals bond distance is 2.827(17) Å and the oxygen…ortho-hydrogen distance is 3.045(3) Å. The amplitude of the zero point bending vibrational motion of the difluoropyridine moiety away from the C₂ axis of the complex is estimated from ¹⁴N nuclear hyperfine structure to be 8.8^°. The N…C van der Waals bond length is 0.029 Å  longer than that previously determined for pyridine-CO₂, but is still considerably shorter than the 2.997(1) Å  distance in HCN…CO₂. Density functional theory calculations place the binding energy of the complex at 3.2 kcal/mol.

Infrared spectra in the carbon monoxide CO stretch region ( ≈ 2150 cm⁻¹) are assigned to the previously unobserved O-bonded form of the CO₂-CO dimer (“isomer 2”), which has a planar T-shaped structure like that of the previously observed C-bonded form (“isomer 1”). Results will also be reported for both isomers of the ¹²C¹⁸O₂-substituted form of the dimer. In addition, we have observed two combination bands for each isomer yielding the first experimental determinations of intermolecular frequencies for the planar T-shaped structures. Within both of the fundamental bands, weak “satellite bands” are observed. These are tentatively assigned to the trimer He-CO₂-CO. To the higher side of the fundamental for “isomer 1”, we have observed a weaker b-type band which we have assigned to (CO₂)₂-CO trimer. This trimer has a “pin wheel” structure with C2 symmetry and the derived experimental structural parameters match well with those obtained from ab initio calculations.

r0pt Figure FTMW spectroscopy has long been known to be a powerful tool in characterizing van der Waals complexes.Stewart Novick, Bibliography of Rotational Spectra of Weakly Bound Complexeslong with this, advances in microwave technology and computing have made complicated spin-interaction systems much easier to observe and characterize. One such system, O₂-CO has been observed for the first time on a CP-FTMW spectrometer operational in the 6-18 GHz region. Preliminary observations and calculations indicate a slipped-parallel structure. High level calculations are ongoing, including the construction of a 4D potential energy surface. Rotational assignments, along with any observed fine structure due to the ³Σ ground state of O₂ will be discussed.

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Stewart Novick, Bibliography of Rotational Spectra of Weakly Bound ComplexesA