Effects of the alkyl group in (dialkylamino)perfluorophenazines on the melting point and fluorescence properties
作者:Siddanagouda Biradar、Yasuhiro Shigemitsu、Yasuhiro Kubota、Kazumasa Funabiki、Hiroyasu Sato、Masaki Matsui
DOI:10.1039/c4ra09342a
日期:——
The alkyl groups in 2-(dialkylamino)- and 2,7-bis(dialkylamino)perfluorophenazines drastically affected the melting point and solid-state fluorescence. 2-(Dialkylamino)- and 2,7-bis(dialkylamino) derivatives such as 2-(dioctylamino)-, 2-(didodecylamino)-, and 2,7-bis(dioctylamino)perfluorophenazines were liquid at ambient temperature, whereas shorter and longer dialkylamino derivatives were solid. 2-(Dioctadecylamino)perfluorophenazine exhibited a fluorescence maximum at 581 nm, being significantly blue-shifted compared with the other derivatives, with the most intense fluorescence quantum yield of 0.29 in the crystalline form. This result is attributed to the isolated dimer-type packing coming from long octadecyl groups. 2-(Dimethylamino)perfluorophenazine showed positive fluorescence solvatochromism due to a large dipole moment in the excited state. The computational analysis of (2-(dimethylamino)perfluorophenazine suggests that the red-shift of the fluorescence maximum in the crystalline form, compared with that in solution, mainly comes from π–π interactions with adjacent molecules. The fluorescence lifetime of 2-(dioctadecylamino)perfluorophenazine was significantly longer compared with 2-(dioctadecylamino)phenazine owing to the aromatic C–F bonds.
2-(二烷基氨基)- 和 2,7-双(二烷基氨基)全氟吩嗪中的烷基对熔点和固态荧光有很大影响。2-(二烷基氨基)-和 2,7-双(二烷基氨基)衍生物,如 2-(二辛基氨基)-、2-(十二烷基氨基)-和 2,7-双(二辛基氨基)全氟吩嗪在环境温度下呈液态,而较短和较长的二烷基氨基衍生物则呈固态。2-(双十八烷基氨基)全氟吩嗪在 581 纳米波长处显示出荧光最大值,与其他衍生物相比明显偏蓝,结晶形式的荧光量子产率最高,为 0.29。这一结果归因于长十八烷基产生的孤立二聚体型堆积。由于激发态的偶极矩较大,2-(二甲基氨基)全氟吩嗪显示出正的荧光溶解色度。对(2-(二甲基氨基)全氟吩嗪)的计算分析表明,与溶液中的荧光最大值相比,晶体中的荧光最大值的红移主要来自与相邻分子的π-π相互作用。与 2-(双十八烷基氨基)吩嗪相比,2-(双十八烷基氨基)全氟吩嗪的荧光寿命明显更长,这是由于芳香族 C-F 键的缘故。