Synthesis, optical properties and crystal structure of (E,E)-1,3-(3,4:9,10-dibenzododeca-1,11-diene-5,7-diyne-1,12-di­yl)benzene

The de­hydro­benzannulene (E,E)-1,3-(3,4:9,10-dibenzododeca-1,11-diene-5,7-diyne-1,12-di­yl)benzene, C(26)H(16), was successfully synthesized via photocatalyst-assisted stereoselective reductive de­sulfonyl­ation of 1,3-bis­{1-phenyl­sulfonyl-2-[2-(tri­methyl­silylethyn­yl)phen­yl]ethen­yl}benzene, C(44)H(42)O(4)S(2)Si(2), and subsequent desilylative cyclization of the resulting (E,E)-bis-silyl-protected dienyne, C(32)H(34)Si(2). The structure of the de­hydro­benzannulene thus obtained was confirmed by single-crystal X-ray analysis; three benzene rings are connected to one another by a 1,3-butadiynylene and a pair of ethenylene arrays. Although the π-system expanded efficiently in the de­hydro­benzannulene, it was observed that the butadiynylene and ethenylene arrays were strained, showing smaller [171.3 (2)–172.6 (2) °] and larger bond angles [122.5 (2)–131.9 (2)°] than the conventional bond angles, respectively. In CHCl(3), the de­hydro­benzannulene showed the longest absorption band at 377 nm. When irradiated by UV light, it emitted fluorescence at 468 nm (Φ(F) = 0.26) and 504 nm (Φ(F) = 0.24) in CHCl(3) and in the powdered state, respectively.