Issue 17, 2016

σ-Aromatic cyclic M3+ (M = Cu, Ag, Au) clusters and their complexation with dimethyl imidazol-2-ylidene, pyridine, isoxazole, furan, noble gases and carbon monoxide

Abstract

The σ-aromaticity of M3+ (M = Cu, Ag, Au) is analyzed and compared with that of Li3+ and a prototype σ-aromatic system, H3+. Ligands (L) like dimethyl imidazol-2-ylidene, pyridine, isoxazole and furan are employed to stabilize these monocationic M3+ clusters. They all bind M3+ with favorable interaction energy. Dimethyl imidazol-2-ylidene forms the strongest bond with M3+ followed by pyridine, isoxazole and furan. Electrostatic contribution is considerably more than that of orbital contribution in these M–L bonds. The orbital interaction arises from both L → M σ donation and L ← M back donation. M3+ clusters also bind noble gas atoms and carbon monoxide effectively. In general, among the studied systems Au3+ binds a given L most strongly followed by Cu3+ and Ag3+. Computation of the nucleus-independent chemical shift (NICS) and its different extensions like the NICS-rate and NICS in-plane component vs. NICS out-of-plane component shows that the σ-aromaticity in L bound M3+ increases compared to that of bare clusters. The aromaticity in pyridine, isoxazole and furan bound Au3+ complexes is quite comparable with that in the recently synthesized Zn3(C5(CH3)5)3+. The energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital also increases upon binding with L. The blue-shift and red-shift in the C–O stretching frequency of M3(CO)3+ and M3(OC)3+, respectively, are analyzed through reverse polarization of the σ- and π-orbitals of CO as well as the relative amount of OC → M σ donation and M → CO π back donation. The electron density analysis is also performed to gain further insight into the nature of interaction.

Graphical abstract: σ-Aromatic cyclic M3+ (M = Cu, Ag, Au) clusters and their complexation with dimethyl imidazol-2-ylidene, pyridine, isoxazole, furan, noble gases and carbon monoxide

Supplementary files

Article information

Article type
Paper
Submitted
16 oct. 2015
Accepted
20 nov. 2015
First published
20 nov. 2015

Phys. Chem. Chem. Phys., 2016,18, 11661-11676

Author version available

σ-Aromatic cyclic M3+ (M = Cu, Ag, Au) clusters and their complexation with dimethyl imidazol-2-ylidene, pyridine, isoxazole, furan, noble gases and carbon monoxide

S. Pan, R. Saha, S. Mandal and P. K. Chattaraj, Phys. Chem. Chem. Phys., 2016, 18, 11661 DOI: 10.1039/C5CP06282A

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