Over the past few years our group has been interested in the syntheses of highly conjugated arenediynes to examine their thermal and photochemical reactivity.  We recently reported the synthesis of 1,2-bis(naphthalen-1-ylethynyl)benzene, which was found to undergo a novel tandem [2+2] photodimerization upon irradiation at 350 nm.  To further explore this chemistry we have prepared related symmetrical arenediynes bearing 2-methoxynaphthalen-1-yl, 4-methoxynaphthalen-1-yl, phenanthren-9-yl, anthracen-9-yl and are working towards preparing pyren-1-yl derivatives.  With increased conjugation, red shifts are observed in the absorption spectra of these symmetrical arenediynes compared to their parent polycyclic aromatic hydrocarbon along with intense emission upon excitation at 300 or 350 nm.  Upon irradiation at 350 nm, 4-methoxynaphthalen-1-yl and phenanthren-9-yl derivatives undergo this novel photodimerization while introduction of substituents at the naphthyl 2 position (as in 2-methoxynaphthalen-1-yl and anthracen-9-yl) inhibit [2+2] photodimerization.

Syntheses, electronic properties and photochemical reactivity of symmetrical arylethynyl arenediynes

243rd National Meeting (2012)

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