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

Abstract

Optimized structures, with all real frequencies, of superalkali superhalides (Li(3))(+)(SH)(-) (SH=LiF(2), BeF(3), and BF(4)), are obtained, for the first time, at the B3LYP/aug-cc-pVDZ and MP2/aug-cc-pVDZ computational levels. These superalkali superhalides possess three characteristics that are significantly different from normal alkali halides. 1) They have a variety of structures, which come from five bonding mode types: edge-face, edge-edge, face-face, face-edge, and staggered face-edge. We find that the bonding mode type closely correlates with the Li(3)-SH bond energy. 2) The valence electrons on the Li(3) ring are pushed out by the (SH)(-) anion, and become excess electrons, conferring alkalide or electride characteristics on these Li(3)-SH species, depending on the bonding mode type. 3) The highest occupied molecular orbital of each Li(3)-SH species is a doubly occupied delocalized sigma bonding orbital on the Li(3) ring, which indicates its aromaticity. It is noticeable that the maximum negative nucleus-independent chemical shift value (about -10 ppm) moves out from the center of the Li(3) ring, owing to repulsion by the SH(-) anion. We find that these superalkali superhalides are not only complicated "supermolecules", but are also a new type of alkalide or electride, with aromaticity.

Are trinuclear superhalogens promising candidates for building blocks of novel magnetic materials? A theoretical prospect from combined broken-symmetry density functional theory and ab initio study

“…3,4,9 This important character also leads to great potential of applications in the fields of synthesis, 3 new dopants to increase the electrical conductivity of polymers 1, 3 and production of organic metal, organic superconductors 2-4 as well as nonlinear optical materials. [10][11][12] In fact, some superhalogen anions are commonly found as promising candidates of building blocks in both condensed phase materials and gas phase molecules. 4,6,13 Previous results have proven that increasing the number of ligands will lead to higher EA value.…”

Out-of-plane σ-aromaticity and enhanced π-aromaticity in superatom compounds Li3+N42−M3+ (M=Li, Na and K)

“…From Table 2, the order of vertical ionization energies VIE is 3.49 (1a) < 5.71 (2a) < 5.97 eV (3a) for the sandwich-like structures, VIE increases with increasing the atomic number of M. While the order of VIE is 5.05 (1b) > 4.67 (2b) > 3.94 eV (3b) for the chainlike structures, VIE decreases with increasing the atomic number of M. Attentively, these lower VIEs due to interaction between subunits show that the superatom compounds Li 3 -N 4 -M 3 have electride characteristic [8,16].…”

“…Bergeron et al found an Al 13 cluster can mimic the chemical behavior of halogen [4], and an Al 14 cluster can exhibit electronic features like an alkaline earth atom [5]. It has been further demonstrated that superatoms as building blocks can be combined to form compounds and clusters in both theory and experiment [3][4][5][6][7][8]. Recently, Khanna and co-worker have demonstrated that superatom compounds formed by combining superhalogens (Al 13 ) with superalkalis (K 3 O and Na 3 O) can exhibit novel chemical and electronic features [6].…”

“…Alexandrova and Boldyrev [15] have extended r-aromaticity concept to small clusters including Li 3 + which has in-plane r-aromaticity. In superalkali compound royal crown-shaped Li 3 -N 3 -Be, the Li 3 + ring exhibits out-of-plane r-aromaticity [8,16], not like the isolated aromatic Li 3 + cation.…”

Designing nonlinear optical molecule by incorporating the planar tetracoordinate unit NAl4- or CAl42- into decaborane B10H14

“…Li et al investigated that superatom clusters act as building blocks to form superalkali-(super)halogen compounds BLi 6 -X (X ¼ F, LiF 2 , BeF 3 , BF 4 ) 16 and superalkali superhalides (Li 3 ) þ (SH) À (SH ¼ LiF 2 , BeF 3 and BF 4 ). 17 Besides, a series of small clusters, [18][19][20][21][22][23][24][25][26] that is OAl 4 , NAl 4 À , NAl 3 Si, BAl 3 Si and CAl 2 Si 2 were employed to incorporate into the assembled molecular materials. In 2002, by means of ab initio calculations, Geske and Boldyrev 21 showed that two CAl 4 2À groups remain separated in a dimeric structure ((Na þ ) 2 [CAl 4 2À ]) 2 and proposed the possible existence of the solid ionic salt with the (Na þ ) 2 [CAl 4 2À ] stoichiometry.…”