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

Org Lett. 2022 Feb 4;24(4):983-988. doi: 10.1021/acs.orglett.1c03900. Epub 2022 Jan 14.

Abstract

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.