Rh‐Catalyzed [2 + 2 + 2] Cycloaddition of Linked Bis(Diynes) Ar‐C≡C‐C≡C‐(CH 2 ) 3 ‐C≡C‐C≡C‐Ar With Quinones: Synthesis and Photophysical Properties of Bis(Arylethynyl)‐Naphthoquinones and Anthraquinones

ABSTRACT Herein, we report the Rh‐catalyzed [2 + 2 + 2] cycloaddition of linked bis(diynes) Ar‐C≡C‐C≡C‐(CH 2 ) 3 ‐C≡C‐C≡C‐Ar with quinones for the rapid and efficient assembly of rigid structures containing bis(arylethynyl)naphthoquinones or anthraquinones using microwave radiation. The photophysical properties of the products were investigated, including absorption, emission, transient absorption (TA) spectroscopy, and singlet oxygen luminescence studies. However, the quinones did not exhibit photoluminescence or detectable singlet oxygen luminescence. Computational analysis via density functional theory (DFT) was performed to elucidate the electronic and structural factors influencing their behavior. Moreover, reductive methylation of one of the bis(arylethynyl)naphthoquinones ( 3aa ) generated the fluorescent bis(methoxy) naphthalene derivative 4aa ( Φ f = 0.53). However, 4aa underwent photooxidation in air under sunlight via reaction with 1 O 2 , which it sensitized, leading to ring opening of the bis(methoxy)arene ring.