σ-Aromaticity and σ-Antiaromaticity in Alkali Metal and Alkaline Earth Metal Small Clusters

Abstract

We extended the aromaticity concept to small σ-aromatic alkali metal and alkaline earth metal clusters. We performed ab initio calculations (B3LYP/6-311+G* and CCSD(T)/6-311+G*) on a selected group of triatomic and tetraatomic metal clusters. We have shown that the introduction of aromaticity and antiaromaticity in Li3 + and Li3 - ions, respectively, can be used to explain their relative stability and their structure. For the tetratomic 6σ-electron Li2Mg2 species we predicted that the cyclic σ-aromatic structures of Li2Mg2 are more stable than the classical linear Li−Mg−Mg−Li structure, thus showing the importance of the aromaticity in metal clusters. We believe that the further advancing of the aromaticity concept into metal clusters will be a useful tool in understanding chemical bonding in these species.

Novel Superalkali Superhalogen Compounds (Li3)+(SH)−(SH=LiF2, BeF3, and BF4) with Aromaticity: New Electrides and Alkalides

“…This delocalized s bonding system has two electrons, satisfying the 4n + 2 electron counting rule, and indicating the s-aromatic nature [12] of the Li 3 + cation in each Li 3 ÀSH species. Li 3 ÀSH compounds are aromatic.…”

“…Li 3 O, Li 4 N), where L is an alkali metal atom. [10,11] In 2003, Alexandrova and Boldyrev [12] introduced s-aromaticity into the Li 3 + cation, and rationalized the low IP value (4.08 AE 0.05 eV) [13] of its neutral counterpart Li 3 radical. They also pointed out that Li 3 can be considered to be a superalkali, because its IP value is appreciably lower than that of the Li atom (5.390 eV).…”

“…They also pointed out that Li 3 can be considered to be a superalkali, because its IP value is appreciably lower than that of the Li atom (5.390 eV). [12] Li 3 is a special superalkali. It has three valence electrons from the three Li atoms, but loses just one to form In this study, we chose Li 3 as the superalkali, and LiF 2 , BeF 3 , and BF 4 as the superhalogens to assemble a new class of superalkali-superhalogen compound.…”

Die σ‐aromatischen Cluster [Zn3]+ und [Zn2Cu] – kleinste molekulare Bausteine für Messing

“…[3] Die Struktur des Metallacyclus am globalen Minimum ist ebenfalls ein reguläres Dreieck, das Resonanzstabilisierung aufweist, die Ringstromdichte stützt jedoch keine s-Aromatizität. [4] 2012 wurde der ligandenstabilisierte Goldcluster [(LAu) 3 ] + (L = 1,3-Bis(2,6-diisopropylphenyl)imidazol-2-yliden) isoliert (Abbildung 1). [5] + (Ar = C 6 H 4 F); [7] 4 ]w eist eine Cu-ZnBindungslänge von 2.498(2) a uf (gegenüber der in 2 5% länger).…”

Structural Dependence of Magnetic Shielding Properties in Al<SUB>4</SUB>Li<SUB>4</SUB> Clusters

“…The concept of aromaticity used to explain the additional stability of organic conjugated ring molecules was expanded to inorganic systems by the discovery of aromaticity in organometallic, [1][2][3] all-metal clusters, [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and recently transition-metal-containing clusters with aromaticity. [21][22][23] Interest in this field has been increased by the finding of an antiaromatic all-metal cluster.…”