We present an investigation on the structures and chemical bonding of two Bi-doped boron clusters BiBn− (n = 4, 5) using photoelectron spectroscopy and theoretical calculations. The electron affinities of BiB4 and BiB5 are measured to be 2.22(2) eV and 2.61(2) eV, respectively. Well-resolved photoelectron spectra are obtained and used to compare with theoretical calculations to verify the structures of BiB4− and BiB5−. Both clusters adopt planar structures with the Bi atom bonded to the periphery of the planar Bn moiety. Chemical bonding analyses reveal that the Bn moiety maintains σ and π double-aromaticity. The Bi atom is found to induce relatively small structural changes to the Bn moiety, very different from transition metal-doped boron clusters.
Re©B8– and Re©B9–: New Members of the Transition-Metal-Centered Borometallic Molecular Wheel Family
Transition-metal-centered monocyclic boron wheel clusters (M©Bnq) represent a family of interesting borometallic compounds with double aromaticity. A variety of early and late transition metal atoms have been found to form such structures with high symmetries and various Bn ring sizes. Here we report a combined photoelectron spectroscopy and quantum chemistry theoretical study of two M©Bn– clusters from the middle of the transition metal series: Re©B8– and Re©B9–. Global minimum structure searches reveal that ReB8– adopts a pseudo-C8v structure, while ReB9– is a perfect-planar D9h molecular wheel. Chemical bonding analyses show that both clusters exhibit and double aromaticity and obey the electronic design principle for metal-centered borometallic molecular wheels. The central Re atom are found to possess unusually low oxidation states of +I in Re©B8– and +II in Re©B9–, i.e. the Re atom behaves similarly to late transition-metal elements (Ru, Fe, Co, Rh, Ir) in the M©Bn– molecular wheels. These two clusters become new members of the family of transition-metal-centered monocyclic borometallic molecular wheels, which may be viable for chemical syntheses with appropriate ligands.
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- Award ID(s):
- 1763380
- NSF-PAR ID:
- 10096586
- Date Published:
- Journal Name:
- The journal of physical chemistry. A
- Volume:
- 123
- ISSN:
- 1089-5639
- Page Range / eLocation ID:
- 5317-5324
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Single-layer MoS2is a direct-gap semiconductor whose band edges character is dominated by the d-orbitals of the Mo atoms. It follows that substitutional doping of the Mo atoms has a significant impact on the material’s electronic properties, namely the size of the band gap and the position of the Fermi level. Here, density functional theory is used along with the G0W0method to examine the effects of substituting Mo with four different transition metal dopants: Nb, Tc, Ta, and Re. Nb and Ta possess one less valence electron than Mo does and are therefore p-type dopants, while Re and Tc are n-type dopants, having one more valence electron than Mo has. Four types of substitutional structures are considered for each dopant species: isolated atoms, lines, three-atom clusters centered on a S atom (c3s), and three-atom clusters centered on a hole (c3h). The c3h structure is found to be the most stable configuration for all dopant species. However, electronic structure calculations reveal that isolated dopants are preferable for efficient n- or p-type performance. Lastly, it is shown that photoluminescence measurements can provide valuable insight into the atomic structure of the doped material. Understanding these properties of substitutionally-doped MoS2can allow for its successful implementation into cutting-edge solid state devices.
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/doi: 10.1021/acs.jpca.9b03942
