A series of ()-1,2-diaryldigermenes incorporating bulky Eind groups: structural characteristics and absorption properties

• Published in: Dalton transactions : an international journal of inorganic chemistry 2022-12, Vol.51 (48), p.18633-18641
• Main Authors: Yagura, Shogo, Hayakawa, Naoki, Kuroda, Airi, Ota, Kei, Tanishita, Rhota, Urasaki, Genya, Nakahodo, Tsukasa, Nakai, Hidetaka, Hoshino, Manabu, Hashizume, Daisuke, Matsuo, Tsukasa
• Format: Article
• Language: English
• Subjects: Absorption; Angles (geometry); Aromatic compounds; Chromophores; Conjugation; Molecular orbitals; Pi-electrons
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/d2dt03427a

A series of ( E )-1,2-diaryldigermenes, (Eind)ArGe&z.dbd;GeAr(Eind) [Ar = phenyl ( 2 ), thiophen-2-yl ( 3 ), 9,9-dimethyl-2-fluorenyl ( 4 ) and 2,2′-bithiophen-5-yl ( 5 )], supported by the fused-ring bulky 1,1,3,3,5,5,7,7-octaethyl- s -hydrindacen-4-yl (Eind) groups, have been obtained as yellow-orange to red crystalline solids by the reaction of 1,2-dibromodigermene, (Eind)BrGe&z.dbd;GeBr(Eind) ( 1 ), with ArLi. In the crystals of 2-5 , the digermene cores show a flexible nature adopting a trans -bent geometry with the trans -bent angles ( ) between the Ge-Ge vector and the C Eind -Ge-C Ar plane of 34.04(12)° ( 2 ), 38.3(3)° and 38.8(3)° ( 3 ), 33.69(12)° ( 4 ) and 39.30(13)° ( 5 ). In the UV-vis spectra, strong π-π* absorptions have been observed with an absorption maximum at 451 nm ( = 1.3 × 10 4 ) ( 2 ), 455 nm ( = 9.7 × 10 3 ) ( 3 ), 480 nm ( = 1.3 × 10 4 ) ( 4 ) and 497 nm ( = 1.4 × 10 4 ) ( 5 ), retaining the Ge&z.dbd;Ge double bond in solution. The absorption data and DFT calculations provide evidence for the intrinsic π-conjugation between the Ge&z.dbd;Ge chromophore and aromatic rings involving the narrowing of the HOMO-LUMO gaps (Δ E ) with the extension of the carbon π-electron systems. We present the synthesis, structural features and absorption properties of a series of ( E )-1,2-diaryldigermenes supported by the fused-ring bulky Eind groups.