9-Phenylxanthen-9-ylium and 9-Phenylthioxanthen-9-ylium Ions: Comparison of<i>o</i>- and<i>p</i>-Substitutions in the 9-Phenyl Group by Cyclic Voltammetry and Visible Spectra
作者:Tatsuo Erabi、Masahiro Asahara、Masahumi Miyamoto、Keisuke Goto、Masanori Wada
DOI:10.1246/bcsj.75.1325
日期:2002.6
9-Arylxanthen-9-ylium (3a–i) and 9-arylthioxanthen-9-ylium (4a,b,e–i) perchlorates [aryl = 2,4,6-(MeO)3C6H2 (a), 2,6-(MeO)2C6H3 (b), 2-MeOC6H4 (c), 4-MeOC6H4 (d), 3-Br-2,6-(MeO)2C6H2 (e), 2,4,6-Me3C6H2 (f), 2-MeC6H4 (g), 4-MeC6H4 (h), C6H5 (i)] were prepared by the reactions of 9-arylxanthen-9-ols or 9-arylthioxanthen-9-ols with perchloric acid. Their LUMO and HOMO levels were estimated from the redox potential (E0) in cyclic voltammetry and λmax in the UV–visible spectra measured for a 1,2-dichloroethane solution, and were compared with those of 9-aryl-1,8-dimethoxyxanthen-9-ylium ions (8b,i). We found that 1) both the LUMO and HOMO levels varied almost in the same order of substituent on the 9-phenyl group; 2) the MeO-group on the 9-phenyl group was more effective to raise both the HOMO and LUMO levels than the Me-group; 3) the HOMO levels of 3 and 4 were more sensitive than the LUMO levels to the change in the 9-aryl group; 4) p-substitution by MeO- or Me-groups was more effective to raise the HOMO and LUMO levels than o-substitution; 5) the presence of two o-MeO groups was more effective to raise the HOMO and LUMO levels than one o-MeO group; 6) a m-bromination of 9-aryl group in 3b or 4b greatly lowered both LUMO and HOMO levels, as observed for 3e or 4e; 7) both the HOMO and LUMO levels of 8b and 8i were higher than those of 3b and 3i, respectively; 8) the LUMO level of 3b was higher than that of 8i, the isomer.
9- 芳基氧杂蒽-9-基 (3a-i) 和 9- 芳基硫杂蒽-9-基 (4a,b,e-i) 高氯酸盐 [芳基 = 2,4,6-(MeO)3C6H2 (a)、2,6-(MeO)2C6H3 (b)、2-MeOC6H4 (c)、4-MeOC6H4 (d)、3-Br-2、6-(MeO)2C6H2 (e)、2,4,6-Me3C6H2 (f)、2-MeC6H4 (g)、4-MeC6H4 (h)、C6H5 (i)]是由 9-芳基氧杂蒽-9-醇或 9-芳基硫杂蒽-9-醇与高氯酸反应制备的。根据循环伏安法测得的氧化还原电位(E0)和在 1,2 二氯乙烷溶液中测得的紫外可见光谱中的λmax 值估算了它们的 LUMO 和 HOMO 水平,并将其与 9-芳基-1,8-二甲氧基氧杂蒽-9-鎓离子(8b,i)的 LUMO 和 HOMO 水平进行了比较。我们发现:1)9-苯基上的 LUMO 和 HOMO 水平几乎按照相同的取代基顺序变化;2)9-苯基上的 MeO 基团比 Me 基团更能提高 HOMO 和 LUMO 水平;3) 与 LUMO 水平相比,3 和 4 的 HOMO 水平对 9-芳基的变化更为敏感;4) 与 o 取代相比,MeO 或 Me 取代更有效地提高了 HOMO 和 LUMO 水平;5) 两个 o-MeO 基团的存在比一个 o-MeO 基团更有效地提高了 HOMO 和 LUMO 水平;6) 与 3e 或 4e 一样,3b 或 4b 中 9- 芳基的 m-bromination 大大降低了 LUMO 和 HOMO 水平;7) 8b 和 8i 的 HOMO 和 LUMO 水平分别高于 3b 和 3i;8) 3b 的 LUMO 水平高于同分异构体 8i。