Increased Antiaromaticity through Pentalene Connection in [ n ]Cyclo-1,5-dibenzopentalenes.

Conjugated nanohoops incorporating nonalternant hydrocarbons have altered optoelectronic properties compared to [ n ]cycloparaphenylenes or other purely aromatic hoops. We synthesized [ n ]cyclo-1,5-dibenzopentalenes ( n = 4, 5), in which nonalternant dibenzo[ a , e ]pentalenes are connected through their pentalene units. This leads to an increase in antiaromatic character and low-lying LUMO energies. Calculations show puckered or entangled conformations of the precursor macrocyclic Pt-complexes. Our study proves dibenzopentalene as a versatile nonalternant building block for conjugated nanohoops with modifiable antiaromaticity and optoelectronic properties.