The Planar CoB₁₈⁻ Cluster as a Motif for Metallo‐Borophenes

Abstract

Monolayer‐boron (borophene) has been predicted with various atomic arrangements consisting of a triangular boron lattice with hexagonal vacancies. Its viability was confirmed by the observation of a planar hexagonal B36 cluster with a central six‐membered ring. Here we report a planar boron cluster doped with a transition‐metal atom in the boron network (CoB18−), suggesting the prospect of forming stable hetero‐borophenes. The CoB18− cluster was characterized by photoelectron spectroscopy and quantum chemistry calculations, showing that its most stable structure is planar with the Co atom as an integral part of a triangular boron lattice. Chemical bonding analyses show that the planar CoB18− is aromatic with ten π‐electrons and the Co atom has strong covalent interactions with the surrounding boron atoms. The current result suggests that transition metals can be doped into the planes of borophenes to create metallo‐borophenes, opening vast opportunities to design hetero‐borophenes with tunable chemical, magnetic, and optical properties.

TGMin: An efficient global minimum searching program for free and surface‐supported clusters

“…To aid in the simulation of PE spectra, a standalone program named AutoPES is also developed. Recent study on PrB 7 − , CoB 18 − , and Ln 2 B 8 − clusters shows that the TGMin‐2 program and the AutoPES program are powerful tools for the global minimum structure search of free and surface‐adsorbed molecules and nanoclusters. With these implementations and improvements, the TGMin‐2 program can become a useful tool for cluster science and heterogeneous catalysis.…”

“…For the boron clusters and metal‐doped boron clusters this observation also holds true: B x − ( x = 3–14) are all symmetric, and one of the two co‐existed lowest‐lying isomers of B 40 − even has a rather high D 2d symmetry . Similarly, CoB 18 − has C 2v and PrB 7 − has C 6v symmetry . When the initial seed structure is close in to the final global minimum isomer, BH‐based algorithms typically will use far less structures before obtaining the global minimum structure.…”

“…TGMin‐2 has been used to determine global minimum structures of several different metal‐doped boron clusters, which have been published or will be published soon . Here, we provide the global minimum search results of PrB 7 − and CoB 18 − as examples of the application of TGMin‐2.…”

“…The CoB 18 − cluster was originally searched by our previous release of TGMin and its global minimum structure was found to be a planar structure with C 2v symmetry and 1 A 1 state, as depicted in Figure …”

“…Until now, several global optimization programs based on the BH algorithm, in conjunction with density functional theory (DFT), tight‐binding DFT (DFTB), or (semi‐) empirical methods have been proposed . Tsinghua Global Minimum (TGMin), developed in 2011, is one of the most successful BH program as TGMin has already helped researchers identify tens of new clusters, including the hexagonal B 36 − cluster, the all‐boron borophenes and borospherenes B 40 − , B 26 − , B 28 − , B 30 − , B 35 − , B 39 − , metallo‐ borophenes, ‐borospherenes, and ‐nanotubes CoB 18 − , MnB 16 − , RhB 18 − , TaB 20 − , as well as the PrB 7 − , LnB 8 Ln (Ln = La, Pr) sandwich complexes, and others . TGMin was also used to identify atmospheric aerosol clusters and surface‐adsorbed species .…”