▎ 摘　　要

NOVELTY - A graphene nanoribbon precursor comprising polycyclic aromatic hydrocarbon repeat units is new. USE - As graphene nanoribbon precursor for producing graphene nanoribbon (claimed), where the graphene is used in organic electronics e.g. as transparent electrode material or as active material in field-effect transistors. ADVANTAGE - The graphene nanoribbon precursors provide graphene nanoribbons that are defect free with defined structure and armchair edge structure and width of less than 10 nm. DETAILED DESCRIPTION - A graphene nanoribbon precursor comprising polycyclic aromatic hydrocarbon repeat units of formula (I) is new. R1 and R2=H, halo, -OH, -NH2, -CN, -NO2 or a 1-40C hydrocarbyl, which is optionally linear or branched, optionally saturated and mono- or polysubstituted by halo (F, Cl, Br, I), -OH, -NH2, -CN and/or -NO2, where at least one CH2 group is optionally also replaced by -O-, -S-, -C(O)O-, -O-C(O)-, -C(O)-, -NH- or -NR-; R=optionally substituted 1-40C hydrocarbyl radical or optionally substituted aryl, alkylaryl or alkoxyaryl radical. INDEPENDENT CLAIMS are included for the following: (1) a graphene nanoribbon obtainable by cyclodehydrogenation of graphene nanoribbon precursors in solution or on metal surfaces; (2) a process for preparing the graphene nanoribbon precursors; (3) a process for preparing monomers of formula (II) involving: (i) reacting 1,3-di(biphenyl-3-yl)propan-7-one (VII) with 4,4'-dihalobenzyl of formula 1,2-diphenyl-ethane-1,2-dione (substituted on 4 and 4'-positions by X) (IX) by Knoevenagel condensation to give tetraarylcyclopentadienone of formula (VIII); and (ii) reacting the tetraarylcyclopentadienone (VIII) with a tolane of formula (X) by Diels-Alder reaction to give the monomer (II); and (4) a monomer of formula (II) for preparation of graphene nanoribbon precursors by Yamamoto coupling reaction. (Structures (II), (VIII) and (X)) X=halo, trifluoromethylsulfonate or diazonium.