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We present the results of a combined experimental and computational study of the structures of gas-phase M+(N2O)n (M = Li, Al) complexes. Infrared spectra were recorded in the region of the N2O asymmetric (N = N) stretch using photodissociation spectroscopy employing the inert messenger technique. Unlike in our previous studies on M+(N2O)n (M = Cu, Ag, Au and M = Co, Rh, Ir) complexes, N– and O–bound isomers in this case are near isoenergetic and are not distinguished spectroscopically at this resolution. In the case of Li+ complexes, there is, however, evidence for the presence of bound N2 moieties, indicating the presence of inserted, OLi+N2(N2O)n–type structures. The weak N2 band lies to the blue of the signature of molecularly N– and O–bound ligands and is well–reproduced in the simulated spectra of energetically low-lying structures computed from density functional theory. No such inserted isomers are observed in the case of Al+(N2O)n complexes whose infrared spectra can be understood on the basis of molecularly-bound N2O ligands. The differences in M+(N2O)n structures observed for these closed–shell, ns2, metal centres relative to other metal cations are discussed in terms of the likely bonding motifs. [ABSTRACT FROM AUTHOR]

A combined spectroscopic and computational study of gas-phase Au+(CH4)n (n = 3-8) complexes reveals a strongly-bound linear Au+(CH4)2 core structure to which up to four additional ligands bind in a secondary coordination shell. Infrared resonance-enhanced photodissociation spectroscopy in the region of the CH4a1 and t2 fundamental transitions reveals essentially free internal rotation of the core ligands about the H4C-Au+-CH4 axis, with sharp spectral features assigned by comparison with spectral simulations based on density functional theory. In separate experiments, vibrationally-enhanced dehydrogenation is observed when the t2 vibrational normal mode in methane is excited prior to complexation. Clear infrared-induced enhancement is observed in the mass spectrum for peaks corresponding 4u below the mass of the Au+(CH4)n=2,3 complexes corresponding, presumably, to the loss of two H2 molecules. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • CO 2 complexes efficiently with NbO 2 + and TaO 2 + relevant to sequestration by MOFs. • DFT simulations allow clear structural determination of MO 2 (CO 2) n + complexes. • Possible M–O–CO 2 type features observed in larger complexes. • No evidence of oxalate structures in CO 2 complexation to NbO 2 + or TaO 2 +. Abstract We report the results of an infrared photodissociation spectroscopy study to determine the structures of gas–phase NbO 2 (CO 2) n + and TaO 2 (CO 2) n + (n = 1–7) ion–molecule complexes. The experimental spectra, recorded in the region of the CO 2 asymmetric stretch using the inert messenger technique, are interpreted in terms of energetically low–lying structures calculated from density functional theory. Together, experiment and simulation provide important new information on CO 2 –binding relevant to prototypical metal–oxide frameworks. Key findings include strong binding of the first two CO 2 ligands to the MO 2 + species and clear evidence for a first solvation shell at n = 4. Some features characteristic of a possible CO 3 ("carbonate") moiety are found in spectra for n ≥ 3 but oxalate structures, observed in some similar systems, appear to be too high in energy to be observed experimentally. CO 2 activation, reactivity and sequestration have long been of interest to Prof Helmut Schwarz, in whose honour this special issue is published on the occasion of his 75th birthday. [ABSTRACT FROM AUTHOR]

The structures of gas-phase M+(CO2)n (M = Co, Rh, Ir; n = 2-15) ion-molecule complexes have been investigated using a combination of infrared resonance-enhanced photodissociation (IR-REPD) spectroscopy and density functional theory. The results provide insight into fundamental metal ion-CO2 interactions, highlighting the trends with increasing ligand number and with different group 9 ions. Spectra have been recorded in the region of the CO2 asymmetric stretch around 2350 cm-1 using the inert messenger technique and their interpretation has been aided by comparison with simulated infrared spectra of calculated low-energy isomeric structures. All vibrational bands in the smaller complexes are blue-shifted relative to the asymmetric stretch in free CO2, consistent with direct binding to the metal center dominated by charge-quadrupole interactions. For all three metal ions, a core [M+(CO2)2] structure is identified to which subsequent ligands are less strongly bound. No evidence is observed in this size regime for complete activation or insertion reactions [ABSTRACT FROM AUTHOR]

The structures of small gas-phase PtnO2m+(n=1–6, m= 1, 2) cluster cations have been investigatedin a combined infrared multiple photon dissociation (IRMPD) spectroscopyand density functional theory (DFT) study. On the basis of the infraredspectra obtained, it is concluded that in most clusters oxygen isbound dissociatively, preferring 2-fold bridge binding motifs, sometimescombined with singly coordinated terminal binding. Comparison of theoxide cluster structures with those of bare cationic platinum clustersreported previously reveals major structural changes induced in theplatinum core upon oxygen binding. For some cluster sizes the presenceof the Ar messenger atom(s) is found to induce a significant changein the observed cluster structure. [ABSTRACT FROM AUTHOR]