A heteroleptic diradical Cr(iii) complex with extended spin delocalization and large intramolecular magnetic exchange.

The reaction of 2,2 '-dibromo-biphenyl on a Ag(111) surface leads to the formation of planar acenes with a high-regioselectivity rather than nonplanar saddle-shaped tetraphenylene as the typical product in solution chemistry. The regioselective aryl-aryl coupling reaction is attributed to the hydrogen repulsion between the reactants on the confined two-dimensional surface.