Molecular wheel to monocyclic ring transition in boron-carbon mixed clusters C2B6⁻ and C3B5⁻.

In this joint experimental and theoretical work we present a novel type of structural transition occurring in the series of C(x)B(8-x)(-) (x=1-8) mixed clusters upon increase of the carbon content from x=2 to x=3. The wheel to ring transition is surprising because it is rather planar-to-linear type of transition to be expected in the series since B(8), B(8)(-), B(8)(2-) and CB(7)(-) are known to possess wheel-type global minimum structures while C(8) is linear.