The Ga(84)R(20)(4-) [R = N(SiMe(3))(2)] species, which represents the largest metalloid cluster entity structurally characterized so far, has been electronically and topologically modified: Via changing the redox potential of the reaction solution, crystals different from those containing the Ga(84)R(20)(4-) anion can be isolated, featuring similar Ga(84)R(20)(3-) entities. An accurate crystal structure analysis via synchrotron radiation is presented, which might be the first step toward an understanding of the metallic conductivity and superconductivity of the Ga(84)R(20)(4-) cluster compound, physical properties which are singular in the field of metalloid clusters so far.

The new spin cluster [MnII4MnIII3(teaH)3(tea)3](ClO4)2×3MeOH realizes a topological structure of mixed-valence manganese clusters which is especially favorable for a high-spin ground state. The magnetic properties of the spin cluster are studied numerically by exact diagonalization of the spin Hamiltonian. By magnetic susceptibility two exchange constants are found: J1/kB = − 1.28 K and J2/kB = + 4.25 K, which lead to a S = 11 high-spin ground state. Electron spin resonance (ESR) measurements at three frequencies 95, 190 and 285 GHz confirm the large spin of the ground state and reveal an Ising anisotropy of the ground state which is characterized by the spin Hamiltonian H = α(Sz)2 + β(Sz)4 with α/h.c. = − 0.08 cm−1 and β = − 2.1 × 10−4 cm−1. Ac-susceptibility shows thermally activated relaxation of the magnetization for temperatures above T = 1 K with an activation energy of ΔE/kB = − 19.5 K and a relaxation time of τ0 ≈ 10−8 s.

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