Oligo(ethynylene-<i>p</i>-phenylen)ic and Benzilic Spacers for the Modular Construction of Organometallic NLO-Phores

Abstract

Abstract The preparation and characterization of oligo(ethynylene-p-phenylene)s, R-(C ─ C-p-C6H4-) n R'(C8n H4n RR′ n = 2–4) 1-13, and 4,4′-diethynylbenzils, R-C ─ C-(p-C6H4)-CO-CO-(p-C6H4-)C ─ C-R′ 14–18 is reported. An economic strategy from easily accessible precursors towards extended 1,4-phenyleneacetylenes is presented with the synthetic sequence essentially based on repeated Pd/Cu-catalyzed Hagihara coupling of haloarenes with terminal ethynes. The linear and rigid hydrocarbon modules 2,4,6,7 and 4,4′-diethynylbenzil have been chosen as spacers with inherent synthetic potential and satisfy equal structural confinements in principle. Functionalization with metallocenes, particularly ferrocene 14–18 and ruthenocene 11,12,18 and with ethynyltriphenyl borate 13 yields molecular structures with distinctive advantages for the field of nonlinear optics. Monosubstituted derivatives have been prepared as well as homo-and heteronuclear bimetallic species. Anionic rigid rod representatives supplement preceding cationic cobaltocenium derivatives. The salt character of the latter materials appears strikingly favorable to molecular solids with controllable aggregation.