Rationalizing and functionalizing stannaspherene: Very stable stannaspherene “alloys”

Abstract

It is illustrated here by ab initio calculations based on density functional theory and other high level methods that the high stability of the icosahedral Sn(12) (2-) dianion known as stannaspherene, reflects stability toward ionization rather than cohesion. This could be also connected with novel fluxional rearrangements and paths of Sn(12) (1-) leading eventually to Sn(12) (2-) involving charge transfer. In view of the very similar structural and electronic properties with the corresponding isovalent borane (B(12)H(12))(2-), it is demonstrated that stannaspherene can be further rationalized and functionalized on the basis of an isolobal analogy between group 14 clusters and isovalent boranes, carboranes, and bisboranes. Such analogy is of the same nature with analogous isolobal and isovalent similarities between silicon, hydrogenated silicon-carbon clusters and deltahedral boranes and carboranes, which the present author, scoptically and synoptically, has described as the "boron connection." It is predicted and verified theoretically: First, that the isovalent Bi(2)Sn(10) and Sb(2)Sn(10) clusters, considered as the microscopic analogs of tin-bismuth alloys, are very stable (more stable than stannaspherene itself) very symmetric and isolobal to Sn(12) (2-); and second, that embedded clusters of the form M@Sn(12) (2-), M@Bi(2)Sn(10), M=Pt,Pd are very stable and highly symmetrical (I(h) and D(5d) respectively) with large highest occupied-lowest unoccupied molecular orbital gaps and very large embedding energies of the order of 5-6 eV. It is furthermore predicted that Pt@Sn(12) (2-) and Pt@Bi(2)Sn(10) can be synthesized in view of their higher stability compared to Pt@Pb(12) (2-) which has already been synthesized. The marginal energy difference of 0.03 eV between the meta- and the para-isomer of Bi(2)Sn(10) indicates a fluxional behavior with respect to Bi-Sn interchange which should be related with the Sn(12) (1-) fluxionality leading eventually to Sn(12) (2-). This rearrangement is also associated with a strange aromatic behavior. The same type of Bi-Sn fluxionality is also encountered in higher energy structures. Due to the "inert pair effect" in tin, the validity of the isolobal analogy is much stronger and fully valid compared to isovalent species based on germanium or silicon, such as Ge(12) (2-), Bi(2)Ge(10), and Ge(10)C(2)H(2) and Si(12) (2-), Bi(2)Si(10), and Si(10)C(2)H(2). The present ideas are in full agreement with available experiments and suggest even further functionalization of stannaspherene, analogous to metaloboranes, metalocarboranes, and stannaboranes with several potential applications.

Structural reciprocity effect in binary silicon–bismuth clusters

“…Recently, Sun et al [15] have examined experimentally and theoretically neutral and anionic clusters of the form Bi n Si m 0, À1 (and similarly for Bi-Ge and Bi-Sn clusters) with n + m 6 6; while more recently Li et al [19] and Zdetsis [20] have studied dibismuthic clusters of the form Bi 2 Si 5 and Bi 2 Si nÀ2 (with n = 3-12) respectively. Dibismuthic clusters of the form Bi 2 Sn 10 have been also studied by the present author [20] in the context of the 'boron connection' isolobal analogy [20][21][22][23]. This analogy allows the structural and electronic correlation between [19][20][21][22][23] Si n 2À , (B n H n ) 2À dianions, C 2 B nÀ2 H n,…”

“…Dibismuthic clusters of the form Bi 2 Sn 10 have been also studied by the present author [20] in the context of the 'boron connection' isolobal analogy [20][21][22][23]. This analogy allows the structural and electronic correlation between [19][20][21][22][23] Si n 2À , (B n H n ) 2À dianions, C 2 B nÀ2 H n,…”

“…[15,18]). Yet, there have been only few studies on binary Bi-Si (or Bi-Ge, or Bi-Sn) clusters, until recently [15,[19][20][21]. Recently, Sun et al [15] have examined experimentally and theoretically neutral and anionic clusters of the form Bi n Si m 0, À1 (and similarly for Bi-Ge and Bi-Sn clusters) with n + m 6 6; while more recently Li et al [19] and Zdetsis [20] have studied dibismuthic clusters of the form Bi 2 Si 5 and Bi 2 Si nÀ2 (with n = 3-12) respectively.…”

“…2Bi isoelectronic substitution involving 5 valence electrons. The same substitution is behind the schematical formation of bisboranes from boranes or carboranes [19][20][21]. The advantage of invoking such isoelectronic and isolobal analogies is the exploitation of the well known and well tested powerful structural and stability principles, as well as electron counting rules developed for boranes and carboranes [24][25][26][27], in the study of such (seemingly very different) molecular systems.…”

Functionalizable magnetic/luminous silicon/bismuth core/shell nanocrystalline particles

“…[20]) even today, and so is the Si/Bi interface, which leads us to the core/shell Si/Bi nanocrystalline structures. As a zero th order-zero th size 'bottom up' approach to this subject can be considered the recent study of binary of Si/Bi clusters by the present author [26,27], which has revealed many interesting effects on these clusters such as fluxional behavior, similar to organometallic carboranes [28][29][30][31][32] and 'structural reciprocity' [27] with respect to the Bi ? Si substitution.…”