Biradical character in the ground state of [Mn@Si₁₂]⁺: a DFT and CASPT2 study

Abstract

Both density functional theory and multi-configurational ab initio (CASPT2) calculations are used to explore the potential energy surface of the hexagonal prismatic cluster [Mn@Si12](+). Unlike isoelectronic Cr@Si12, the ground state is a biradical, with triplet and open-shell singlet states lying very close in energy. The results are discussed in the context of recent experimental studies using infra-red multiple photon dissociation spectroscopy and X-ray MCD spectroscopy.

Revitalizing Spin Natural Orbital Analysis: Electronic Structures of Mixed‐Valence Compounds, Singlet Biradicals, and Antiferromagnetically Coupled Systems

“…To put this “orbitalwise biradical index” to the ultimate test, we have applied our analysis to [MnSi 12 ] + , a molecule that was reported to have five α electrons on the metal center and five β electrons on the cage. We first note that there is one interesting feature of this example not possessed by the aforementioned examples of singlet biradicals, that is, all canonical orbitals from the UDFT calculation still respect molecular symmetry.…”

Experimental and theoretical 2p core-level spectra of size-selected gas-phase aluminum and silicon cluster cations: chemical shifts, geometric structure, and coordination-dependent screening

“…80 It might be particular useful to elucidate the degree of valence electron delocalization, which should have a pronounced effect on electron binding energies and core-level excitation energies via charge screening, 43,81 but also on the quenching of local magnetic moments. 80,[82][83][84][85]…”

Quantum chemical models for the absorption of endohedral clusters on Si(111)-(7 × 7): a subtle balance between W–Si and Si–Si bonding

“…The presence of the vacant but almost entirely non-bonding metal d z 2 orbital renders this 16-electron cluster highly electron deficient, to the extent that the ground state of valence isoelectronic [Mn@Si 12 ] + is in fact a biradical where this orbital is singly occupied. 29 In the context of surface binding, the vacant d z 2 orbital provides a facile pathway for the formation of covalent bonds to the silicon surface. One final point of relevance to the discussion is the unsaturation of the Si-Si bonds that make up the Si 12 framework.…”