Experimental consideration of covalent‐bonding interactions in stacks of singlet biradicals having Kekulé structures

Kekulé singlet biradicals stabilized by phenalenyl rings afford one‐dimensional stacks in the solid state, in which covalent‐bonding interactions exist not only within a molecule but also between molecules. Through the covalent‐bonding interactions spreading over the stack, the lowest‐energy absorption band shifts to a lower‐energy region in the solid state relative to the solution band, and an electro‐conductive property in a single component state is also observed.