title: Conjugation in and optical properties of 1-R-1,2-diphospholes and 1-R-phospholes.
abstract: The strength of conjugation between the diene moieties of 1-R-1,2-diphospholes and 1-R-phospholes and exocyclic phenyl groups of these P-heteroles has been quantitatively characterized by the use of Raman activities of the bands of the phenyl substituents. It is shown that conjugation in both types of phospholes is very similar to the conjugation of phenyl groups with the diene system of cyclopentadiene. Introduction of substituents (-OMe, -C(═O)H, -NO2, -NMe2, and -CH═CH2) in the para-position of the phenyl groups of 1-R-1,2-diphospholes extends π-delocalization of exocyclic groups into the electronic system of the 1,2-diphosphole ring, producing bathochromic shifts of the absorption bands up to 63 nm. In contrast, hypsochromic shifts up to 40 nm can be achieved by introduction of SnMe3 or SiMe3 groups at the phosphorus(III) atom of the 1,2-diphosphole and concomitant increase of aromaticity of the P-heterole. Conjugation shifts the "centre of gravity" of the whole electronic absorption spectrum, whereas positions of separate absorption bands are not simply dependent on conjugation lengths.
authors.affiliation: A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Centre of the Russian Academy of Sciences , Arbuzov str. 8, 420088 Kazan, Russia.
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Katsyuba
authors.forename: Timur I
authors.initials: TI
authors.lastname: Burganov
authors.forename: Elena E
authors.initials: EE
authors.lastname: Zvereva
authors.forename: Almaz A
authors.initials: AA
authors.lastname: Zagidullin
authors.forename: Vasily A
authors.initials: VA
authors.lastname: Miluykov
authors.forename: Peter
authors.initials: P
authors.lastname: Lönnecke
authors.forename: Evamarie
authors.initials: E
authors.lastname: Hey-Hawkins
authors.forename: Oleg G
authors.initials: OG
authors.lastname: Sinyashin