Cyclotrimerization of 9,10‐dibromo‐9,10‐dihydrodibenzo[3,4:7,8]cycloocta[1,2‐l]phenanthrene with potassium tert‐butoxide in the presence of a transition‐metal catalyst afforded two polycyclic aromatic hydrocarbon stereoisomers consisting of three cyclooctatetraene (COT) moieties connected via a central benzene ring. Both isomeric tri[8]annulenes were obtained selectively through the choice of the catalyst: The α,α,α‐form (Ru catalyst) displayed a threefold symmetrywith the COT subunits forming the side walls of a (chiral) molecular cup. In the thermodynamically more stable α,α,β‐isomer (Pd catalyst), one of the three boat‐shaped COTs was flipped over and faced the opposite molecular hemisphere with respect to the central benzene ring as evidenced by crystal structure analysis. Both title compounds are small segments of “cubic graphite”, an elusive carbon allotrope.

We describe the on-surface dehalogenative homocoupling of benzylic bromides, namely bis-bromomethyl-and bis-gem-(dibromomethyl) naphthalene as a potential route to either hydrocarbon dimers or conjugated polymers on Au(111). While bis-gem-(dibromomethyl) naphthalene affords different dimers with naphthocyclobutadiene as the key intermediate, bis-bromomethyl naphthalene furnishes a poly(o-naphthylene vinylidene) as a non-conjugated polymer which undergoes dehydrogenation toward its conjugated derivative poly(o-naphthylene vinylene) upon mild annealing. A combination of scanning tunneling microscopy, non-contact atomic force microscopy and density functional theory calculations provides deep insights into the prevailing mechanisms.

Chrysenea nd its bisbenzannulated homologue, naphtho[2,3-c]tetraphene,w ere synthesized through a PtCl 2-catalyzed cyclization of alkynes, which also furnished corresponding biaryls subsequentt oaGlaser couplingr eaction of the startinga lkynes.T he optoelectronic properties of 5,5'-bichrysenyl and 6,6'-binaphtho[2,3-c]tetraphene were compared to their chrysene-based "monomers". Oxidative cyclodehydrogenations of bichrysenyl andi ts higher homologue towardsl arge nanographenes were also investigated.