Coordination versus Solvation in Al⁺(benzene)_nComplexes Studied with Infrared Spectroscopy

Abstract

Singly charged aluminum-benzene cation complexes are produced by laser vaporization in a pulsed supersonic expansion. The Al(+)(benzene)n (n = 1-4) ions are mass selected and investigated with infrared laser photodissociation spectroscopy. Density functional theory (DFT) is employed to investigate the structures, energetics and vibrational spectra of these complexes. Spectra in the C-H stretching region exhibit sharp multiplet bands similar to the pattern known for the Fermi triad of the isolated benzene molecule. In the fingerprint region, strong bands are seen corresponding to the ν19 C-C ring motion and the ν11 out-of-plane hydrogen bend. The hydrogen bend is strongly blue-shifted compared to this vibration in benzene, whereas the ν19 carbon ring distortion is only slightly shifted to the red. Computed structures and energetics, together with experimental fragmentation and vibrational patterns, indicate a primary coordination of three benzene molecules around the central Al(+) cation. The n = 4 complex contains one second-sphere solvent molecule.

Lanthanum-mediated dehydrogenation of 1- and 2-butynes: Spectroscopy and formation of La(C4H4) isomers

“…Spectroscopic characterization of metal-hydrocarbon radicals or ions formed in gas phase reactions has recently attracted considerable attention. Metal ion-hydrocarbon species are largely investigated by infrared or ultravioletvisible photodissociation or photoelectron spectroscopy, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] whereas metal atom-hydrocarbons are mainly studied by photoexcitation or photoionization techniques. [21][22][23][24][25][26][27][28][29][30][31][32] In principle, spectroscopic measurements could offer detailed information about metal-ligand bonding, molecular structures, and electronic states.…”

IRMOF‐8: Theoretical evaluation of aluminum doping on hydrogen, methane, and hydrogen sulfide adsorption

“…[ 111–113 ] An Al + ‐benzene DFT study shows that the interaction is mostly through cation‐ π electrostatic interactions (charge‐induced dipole), [ 107 ] rather than the covalent bonding that dominates in the case of transition metal‐benzene complexes. [ 107 ] The binding energy of Al + ‐benzene was found to be 30.00 kcal mol −1 at B3LYP/6‐311+G(d,p) and at a distance of 3.005 Å from the center of benzene ring [ 107 ] and 2.756 Å at MP2/6‐311+G*. [ 103 ] Wiberg and Mayer bond orders give values between 0.4 to 0.5 and 0.8 to 0.9 for the AlC bond, respectively.…”

“…Several studies have been reported for the interaction of Al and transition metals with benzene. [102][103][104][105][106][107][108][109][110] This interaction of aluminum with the MOF ring is large based on the literature for the Al-π interaction and compared to the case of Al + -benzene. The experimental binding energy for Al + -benzene is 35.20 kcal mol −1 .…”

Formation of Al + (C 6 H 6 ) 13 : The Origin of Magic Number in Metal–Benzene Clusters Determined by the Nature of the Core

“…[42][43][44][45] The difference between the electronic configurations of Al + and V + has been shown to account for their altered coordination number of 3 and 2, respectively, in benzene complexes. 46,47 To observe the stability of the Al + Bz n and V + Bz n clusters, we employed the optional DUV-LIMS to identify clusters, based on their intramolecular noncovalent Bz-Bz or Bz with metal ions (Al + or V + ) interactions. 48,49 We obtained high-resolution mass spectra of benzene clusters up to 30 molecules, on which we introduced Al + or V + by laser ablation of the corresponding metal target by way of molecular beam expansion.…”