Balam-Villarreal J A, López-Mayorga B J, Gallardo-Rosas D, Toscano R A, Carreón-Castro M P, Basiuk V A, Cortés-Guzmán F, López-Cortés J G, Ortega-Alfaro M C
Instituto de Ciencias Nucleares, UNAM, Circuito Exterior, Ciudad Universitaria, Coyoacán C.P. 04510, Ciudad de México, Mexico.
Instituto de Química UNAM, Circuito Exterior, Ciudad Universitaria, Coyoacán C.P. 04510, Cuidad de México, Mexico.
Org Biomol Chem. 2020 Feb 26;18(8):1657-1670. doi: 10.1039/c9ob02410g.
A new family of push-pull biphenyl-azopyrrole compounds 3b-g and 4b-d was efficiently obtained via a Suzuki cross-coupling reaction between 2-(4'-iodophenyl-azo)-N-methyl pyrrole (1a) or 3-(4'-iodophenyl-azo)-1,2,5-trimethyl pyrrole (2a) and 4'-substituted phenyl boronic acids in excellent yields. The influence of the π-biphenyl backbone and pyrrole pattern substitution was correlated with their optical properties. Solvatochromic studies via UV-visible spectrophotometry revealed that the inclusion of a 4'-nitro-biphenyl fragment favors a red-shift of the main absorption band in these azo compounds compared with their non-substituted analogues. Likewise, optical band-gaps were estimated by means of electronic absorption spectra and correlated with TD-DFT studies. The pyrrole pattern substitution and the π-conjugated backbone exhibit a clear influence on their thermal isomerization kinetics at room temperature. In all cases, biphenylazo-pyrrole compounds lead to the formation of J-type aggregates in binary MeOH : H2O solvents. Under these conditions, compounds 3b-c undergo a water-assisted cis-to-trans isomerization at room temperature.
通过2-(4'-碘苯基偶氮)-N-甲基吡咯(1a)或3-(4'-碘苯基偶氮)-1,2,5-三甲基吡咯(2a)与4'-取代苯基硼酸之间的铃木交叉偶联反应，高效地获得了一个新的推拉型联苯-偶氮吡咯化合物家族3b-g和4b-d，产率极高。π-联苯主链和吡咯模式取代的影响与其光学性质相关。通过紫外-可见分光光度法进行的溶剂化显色研究表明，与未取代的类似物相比，包含4'-硝基-联苯片段有利于这些偶氮化合物中主吸收带的红移。同样，通过电子吸收光谱估计光学带隙，并与TD-DFT研究相关联。吡咯模式取代和π-共轭主链对其在室温下的热异构化动力学有明显影响。在所有情况下，联苯偶氮吡咯化合物在二元甲醇∶水溶剂中导致J型聚集体的形成。在这些条件下，化合物3b-c在室温下发生水辅助的顺式到反式异构化。
