La₃B₁₄⁻: an inverse triple-decker lanthanide boron cluster

We report the observation of the first inverse triple-decker complex in a tri-lanthanide-doped boron cluster. Photoelectron spectroscopy of La₃B₁₄⁻ reveals well-resolved photodetachment transitions. Quantum chemical studies show that the most stable structure of the La₃B₁₄⁻ cluster exhibits a tilted La–B₈–La–B₈–La inverse triple-decker structure with two conjoined B₈ rings sharing a pair of B atoms due to strong inter-layer B–B bonding. The tilted structure enhances both B–B and B–La bonding, resulting in a highly stable inverse triple-decker structure. Theoretical calculations further show that multi-decker conjoined structures are viable as a new class of 1D lanthanide boron nanostructures.