
图图式1 合成路线
Figure 图式1. Synthetic route
荧光小分子在多个方面都有应用,如生物标签、光电池、发光二极管(LED)和光传感器[1~4]等. 芳基胺衍生物是富电子化合物[5],被广泛应用于空穴传输材料和光电子学领域的有机场效应晶体管、有机发光二极管(OLED)[6, 7]、非线性材料[8, 9]和静电复印[10, 11]等. 作为良好的电子供体,吩噻嗪和吩噻嗪基聚合物已被广泛用于薄膜晶体管、光电池、发光二极管和染料敏化太阳能电池(DSSC)等[12]. 理论上,以吩噻嗪或三苯胺为原料可合成新的Donor-Aeceptor (D-A)型空穴传输材料[13]. 咪唑及其衍生物具有光致变色特性[14]、光学特性[15]和电化学性质[16].
本文设计了吩噻嗪(或三苯胺)取代的咪唑衍生物并通过多步反应成功地合成得到了新型有机荧光分子(Scheme 1). 通过改变咪唑环上的取代基,可将产物荧光发射从紫色调谐到蓝色[17]. 产物5具有高荧光量子产率(0.42~0.52),在功能材料方面具有良好的应用前景.
中间体及产物的物理性质及产率见表 1. 由表 1 可知,产物5a~5c (80%~83%)、9a~9b产率相近(80%,88%),说明吩噻嗪骨架和胺上的取代基的空间位阻和电子效应对其影响不大.
Entry | R1 | R2 | Temp./℃ | t/h | Yield/% | m.p./℃ |
2a | C2H5 | — | 100 | 12 | 90 | — |
2b | C4H9 | — | 100 | 12 | 90 | — |
3a | C2H5 | — | 100 | 6 | 62 | — |
3b | C4H9 | — | 100 | 6 | 61 | — |
5a | C2H5 | H | 150 | 6 | 81 | 137~138 |
5b | C4H9 | H | 150 | 6 | 83 | 127~128 |
5c | C2H5 | Ph | 150 | 6 | 80 | 229~231 |
9a | — | H | 150 | 6 | 88 | 153~154 |
9b | — | Ph | 150 | 6 | 80 | 284~286 |
以吩噻嗪、三苯胺、正丁基溴、溴代丁二酰亚胺、醋酸铵、苯胺、苯偶酰类衍生物等为原料,通过取代、Wittig反应、Mannich反应等反应成功合成了吩噻嗪(或三苯胺)取代的咪唑衍生物.
将0.2 mmol化合物5和9溶于100 mL乙醇中得储备液(2×10-4 mol•L-1),用乙醇稀释储备溶液得2× 10-6 mol•L-1工作液. 测得工作液的紫外吸收光谱如图 1所示. 化合物在350~400 nm吸收峰归属于电荷从吩噻嗪或三苯胺转移至咪唑骨架而引起的π-π∗跃迁; 200~300 nm的吸收峰归属于吩噻嗪或三苯胺自身的π-π∗跃迁. 根据紫外可见吸收光谱可计算出这些化合物的π-π∗能隙[18].
λ Solvent | 5a | 5b | 5c | 9a | 9b | |
λAbs/nm | EtOH | 302 | 303 | 291 | 372 | 357 |
353 | 357 | 354 | 363 | 353 | ||
λEm/nm | Toluene | 455 | 455 | 456 | 420 | 423 |
CH2Cl2 | 458 | 459 | 466 | 420 | 427 | |
EtOH | 465 | 462 | 462 | 425 | 424 | |
Φa | 0.42 | 0.47 | 0.52 | 0.48 | 0.49 | |
a The fluorescence quantum yields (Ф) were measured in CHCl3 using quinine sulfate (Ф=0.55) as standard. |
将化合物5的储备液用N,N-二甲基甲酰胺(DMF)稀释为2×10-6mol/L工作液,以340 nm为激发波长,其荧光发射光谱如图 2. 荧光发射光谱为420~450 nm,为蓝光. 同等条件下,具有刚性平面结构的三苯胺取代菲并咪唑衍生物9a与9b的荧光强度远远强于化合物5a~5c,说明平面刚性结构和长共轭体系以及强供电子基是获得强荧光发射的关键因素.
以硫酸奎宁(Ф=0.55)为标准在CHCl3中测定了产物的荧光量子产率(表 2). 由表 2可知,化合物5的荧光量子产率为0.42~0.52,全部大于参比的75%,具有进一步研究价值. 我们还研究了化合物的溶剂效应(表 2),随着溶剂极性的增强,荧光发射波长有轻度红移.
室温下采用循环伏安法,以铂电极为工作电极与辅助电极,饱和甘汞电极为参比电极,在二氯甲烷溶剂中,以四丁基六氟磷酸铵(0.1 mol/L n-Bu4NPF6)为支持电解质测试了化合物5的电化学性质(表 3). 所有化合物都具有一个可逆氧化还原峰,说明体系中存在一个稳定的阳离子自由基(5b的循环伏安图见图 3). 计算所得的HOMO能量(-5.04~-5.25 eV)接近于最广泛使用的空穴传输材料4,4'-双(1-萘基)联苯(NBP) (-5.20,-2.4 eV),说明该系列化合物具有一定的空穴传输性能[19~21]. 同时其较低的LUMO能量(-1.58~-2.07 eV) 和较小的能带间隙(表 3)使得该系列化合物很容易被注入电子[22]. 因此,这些化合物有作为空穴传输和电子传输材料的潜力[23].
Band gapa | 4.03 | 3.70 | 3.71 | 3.97 | 3.91 |
EHOMO/ELUMOa (eV) | -4.91/-1.20 | -4.90/-1.20 | -4.90/-1.20 | -5.16/-1.19 | -5.11/-1.21 |
Egb/eV | 3.37 | 3.23 | 3.50 | 3.25 | 3.18 |
Eoxonsetc/V | 0.64 | 0.67 | 0.68 | 0.83 | 0.85 |
EHOMO/ELUMOd (eV) | -5.04/-1.67 | -5.07/-1.84 | -5.08/-1.58 | -5.23/-1.98 | -5.25/-2.07 |
a DFT/B3LYP calculated values; b Optical energy gaps calculated from the edge of the electronic absorption band; c Oxidation potential in CH2Cl2 (10-3 mol•L-1) containing 0.1 mol•L-1 (n-C4H9)4NPF6 with a scan rate of 100 mV•s-1; d EHOMO was calculated by Eox=4.4 V,and ELUMO=EHOMO-Eg. |
为进一步研究其电子分布,利用高斯03软件[24]计算了其理论模型. 基于密度泛函理论(DFT) (B3LYP; 6-31G∗)计算得到化合物5的HOMO和LUMO分布信息(图 4和图 5). 根据紫外吸收光谱数据所计算得到的带隙与理论计算相符. HOMO/LUMO的能量水平比对应实验数据稍高,可能由于构象变换和溶剂效应引起的,还有待进一步确认. 此外,由于氧化还原过程的可逆性和Eg值的精度相对有限,该电化学过程比较复杂[24].
通过多步反应高产率地制备了一系列基于咪唑骨架的新型有机荧光小分子,采用密度泛函理论计算了该化合物的HOMO和LUMO分布,通过紫外-可见、荧光和电化学法系统分析了其光致发光性能和结构的关系. 化合物5d和5e的强的荧光强度和高荧光量子产率显示其在光学材料的应用潜力.
IR光谱用Varian FTIR-Tensor-27红外光谱仪测定; 核磁共振谱(NMR)(内标为TMS,溶剂为CDCl3)由Bruker Avance DPX-400MHz型核磁共振仪测定; 紫外-可见光谱使用Shimadzu UV-2501PC分光计测定; 荧光光谱使用日立FL-4600荧光分光光度计测定; 高分辨质谱(HRMS)使用Bruker TOF-MS高分辨质谱仪测定; 热性能使用SDT 2960(升温速率为20 ℃/min)测定; 循环伏安法使用Chi 1200 A电化学分析仪测定.
10-乙基-10H-吩噻嗪(2a): 无色油状物,产率90%. 1H NMR (400 MHz,CDCl3) δ: 7.20~7.15 (m,4H),7.01 (d,J=8.4 Hz,2H),6.97~6.94 (m,2H),3.10 (q,J=7.9 Hz,2H),1.10 (t,J=7.6 Hz,3H).
称取10 mmol吩噻嗪和3 mmol四丁基溴化铵加入50 mL圆底烧瓶中,以100 mL 二甲基亚砜(DMSO)为溶剂,剧烈搅拌下加入70 mL 75 mmol氢氧化钾水溶液. 氩气保护下,搅拌、加热至100 ℃,再慢慢滴加溴乙烷或1-溴丁烷12 mmol. 继续搅拌12 h,待降至室温后,将反应液倒入100 mL冰水中,二氯甲烷萃取3次,合并有机相,无水硫酸钠干燥,减压旋转蒸发掉溶剂,柱层析纯化[淋洗液为石油醚],得到白色固体2.
10-丁基-10H-吩噻嗪(2b): 无色油状物,产率90%. 1H NMR (400 MHz,CDCl3): δ 7.20~7.15 (m,4H),7.01 (d,J=8.4 Hz,2H),6.97~6.94 (m,2H),3.86 (t,J=7.6 Hz,2H),1.69~1.65 (m,2H),1.49~1.40 (m,2H),0.87 (t,J=7.6 Hz,3H).
N,N-二苯基-4-(1-苯基-1H-菲并[9,10-d]咪唑-2-基)苯胺(5e): 绿色粉末,产率80%. m.p. 284~286 ℃; 1H NMR (400 MHz,CDCl3) δ: 8.85 (d,J=7.6 Hz,1H),8.77~8.74 (m,1H),8.66 (s,1H),7.57~7.55 (m,4H),7.49~7.47 (m,1H),7.43 (s,1H),7.41 (s,1H),7.38 (s,3H),7.09~7.02 (m,14H),6.88 (d,J=8.8 Hz,2H); 13C NMR (100 MHz,CDCl3) δ: 115.54,116.73,117.45,117.53,117.84,117.89,117.94,118.33,118.39,118.53,118.88,119.49,119.66,119.80,120.27,120.31,121.02,121.18,121.94,122.02,122.14,122.31,122.81,122.99,123.96,124.12,124.19,124.22,124.25,124.34,124.36,124.59,124.85,124.95,132.13,133.72,141.97,143.12,145.63; IR ν: 1587,1473,1456,1332,1282,843,761,685 cm-1; HRMS calcd for C39H27N3 538.2283,found 538.2243.
4-二苯基氨基苯甲醛(7): 黄色粉末,产率60%. m.p. 128~130 ℃; 1H NMR (400 MHz,CDCl3) δ: 9.81 (s,1H),7.34 (t,J=7.4 Hz,4H),7.18 (d,J=7.2 Hz,6H),7.01 (d,J=8.0 Hz,2H).
1 mmol化合物7,1 mmol菲-9,10-二酮,1.5 mmol乙酸铵,1 mmol 胺和10 mL 甲醇混合,150 ℃搅拌. 在反应结束后(通过TLC监测),将混合物用水稀释(15~20 mL). 将粗产物过滤并用水洗涤,然后以95%的乙醇重结晶,得到纯的化合物5d~5e.
将16.8 mmol POCl3与19.5 mmol DMF混合,在0 ℃下搅拌1 h,缓慢加入13.3 mmol化合物6,6 h后,用100 mL水稀释,并用CH2Cl2萃取,将有机层用盐水洗涤,经MgSO4干燥并在真空下浓缩. 原始固体用硅胶柱色谱法[V(石油醚):V(乙酸乙酯)=10:1]纯化,得到黄色固体化合物7.
N-[4-(1H-菲并[9,10-d]咪唑-2-基)苯基]-N-苯基苯胺 (5d): 绿色粉末,产率88%. m.p. 153~154 ℃; 1H NMR (400 MHz,CDCl3) δ: 8.87 (d,J=7.6 Hz,1H),8.77 (d,J=8.4 Hz,1H),8.71 (d,J=8.4 Hz,1H),7.74 (t,J=7.6 Hz,1H),7.67~7.61 (m,4H),7.56~7.54 (m,2H),7.52~7.47 (m,1H),7.44 (d,J=8.8 Hz,2H),7.23 (s,1H),7.16~7.14 (m,1H),7.09~7.07 (m,5H),7.04~7.03 (m,1H),6.94 (d,J=8.4 Hz,2H); 13C NMR (100 MHz,CDCl3) δ: 122.71,123.34,12 3.50,123.61,123.65,123.69,123.71,124.99,125.19,125.22,126.99,127.25,128.31,129.42,129.47,147.14,148.42,148.97,149.09,149.48,150.10; IR ν: 3448,1591,1483,1457,1332,1282,839,751,697 cm-1; HRMS calcd for C33H23N3 462.1934,found 462.1970.
将16.8 mmol POCl3与19.5 mmol DMF混合,在0 ℃下搅拌1 h,缓慢加入13.3 mmol化合物2,6 h后,用100 mL水稀释,并用CH2Cl2萃取,将有机层用盐水洗涤,经MgSO4干燥并在真空下浓缩. 原始固体用硅胶柱色谱法[V(石油醚):V(乙酸乙酯)=10:1]纯化,得到化合物3,黄色油状物,产率61.5%.
10-丁基-10H-3-甲醛吩噻嗪(3b): 黄色油状物,产率61%. 1H NMR (400 MHz,CDCl3) δ: 9.80 (s,1H),7.64 (d,J=8.4 Hz,1H),7.59 (s,1H),7.17 (t,J=7.6 Hz,1H),7.11 (d,J=7.6 Hz,1H),6.99 (d,J=7.6 Hz,1H),3.90 (t,J=7.2 Hz,2H),1.82~1.76 (m,2H),1.50~1.44 (m,2H),0.95 (t,J=7.2 Hz,3H).
10-乙基-10H-3-甲醛吩噻嗪(3a): 黄色油状物,产率62%. 1H NMR (400 MHz,CDCl3) δ: 9.83 (s,1H),7.60 (d,J=7.6 Hz,1H),7.54 (s,1H),7.18 (t,J=7.6 Hz,1H),7.13 (d,J=7.6 Hz,1H),6.97 (d,J=7.6 Hz,1H),3.12~3.10 (m,2H),0.97 (t,J=7.2 Hz,3H).
10-丁基-3-[5-(2-氯苯基)-4-(3,4-二甲氧基苯基)-1H-咪唑-2-基]-10H-吩噻嗪(5b): 绿色粉末,产率83%. m.p. 127~128 ℃; 1H NMR (400 MHz,CDCl3) δ: 7.72 (d,J=8.0 Hz,1H),7.61 (s,1H),7.45~7.40 (m,2H),7.30~7.28 (m,1H),7.26~7.22 (m,2H),7.17~7.09 (m,2H),6.99 (s,1H),6.93~6.89 (m,1H),6.90~6.82 (m,2H),6.75~6.73 (m,1H),3.85~3.83 (m,5H),3.64 (s,3H),1.78~1.81 (m,2H),1.45~1.44 (m,2H),0.94 (t,J=6.4 Hz,3H); 13C NMR (100 MHz,CDCl3) δ: 13.86,20.16,28.90,47.25,55.50,55.79,111.00,115.36,115.49,119.74,120.59,122.60,124.11,124.14,124.24,124.76,124.77,126.94,127.33,127.45,129.41,129.42,129.93,129.99,132.73,145.62,148.02,148.06,148.63; IR ν: 3444,2955,1663,1514,1459,1252,1137,1027,759 cm-1; HRMS calcd for C33H30ClN3O2S 568.1826,found 568.1866.
10-丁基-3-[5-(2-氯苯基)-4-(3,4-二甲氧基苯基)-1-苯基-1H-咪唑-2-基]-10H-吩噻嗪(5c): 绿色粉末,产率80%. m.p. 229~231 ℃; 1H NMR (400 MHz,CDCl3) δ: 7.52~7.50 (m,1H),7.37 (s,1H),7.24 (s,1H),7.17~7.09 (m,3H),7.04 (d,J=6.4 Hz,2H),6.87 (t,J=7.6 Hz,1H),6.81 (d,J=8.0 Hz,1H),6.64~6.42 (m,1H),6.33 (s,1H),3.88~3.85 (m,2H),3.78 (s,3H),3.40 (s,3H),1.36 (t,J=6.4 Hz,3H); 13C NMR (100 MHz,CDCl3) δ: 7.64,36.58,50.13,50.37,105.31,107.67,108.93,109.78,117.20,117.23,117.25,118.65,118.72,119.24,121.38,122.00,122.09,122.47,122.64,1 23.33,123.32,123.59,124.17,124.42,126.54,128.96,129.08,131.51,132.18,139.02,140.44,142.79,142.80; IR ν: 2963,1667,1455,1352,1141,1007,841,759,679 cm-1; HRMS calcd for C37H30ClN3O2S 616.18265,found 616.1877.
3-[5-(2-氯苯基)-4-(3,4-二甲氧基苯基)-1H-咪唑-2-基]-10-乙基-10H-吩噻嗪(5a): 绿色粉末,产率81%. m.p. 137~138 ℃; 1H NMR (400 MHz,CDCl3) δ: 7.70 (d,J=8.0 Hz,1H),7.61 (s,1H),7.48~7.42 (m,2H),7.30 (s,1H),7.17~7.10 (m,2H),6.99 (s,1H),6.94~6.86 (m,3H),6.77 (d,J=8.0 Hz,1H),3.96~3.92 (m,2H),3.85 (s,3H),3.67 (s,3H),1.43 (t,J=6.4 Hz,3H); 13C NMR (100 MHz,CDCl3) δ: 12.94,49.50,55.49,55.78,109.78,109.87,109.97,109.99,110.05,111.00,114.99,115.14,122.58,123.68,124.07,124.10,124.10,124.81,124.83,126.92,126.94,127.35,129.92,129.93,129.96,132.67,132.72,133.99,136.30,144.34,146.41,148.01,148.59,148.62; IR ν: 3441,2933,1654,1510,1463,1252,1137,1027,758 cm-1; HRMS calcd for C31H26ClN3O2S 540.1513,found 540.1648.
1 mmol化合物3,1 mmo 1-(2-氯苯基)-2-(3,4-二甲氧基苯基)乙烷-1,2-二酮,1.5 mmol乙酸铵,1 mmol胺和10 mL甲醇混合,150 ℃搅拌. 在反应结束后(通过TLC监测),将混合物用水稀释(15~20 mL). 将粗产物过滤并用水洗涤,然后以95%的乙醇重结晶,得到纯的化合物5a~5c.
Tang, C. W.; Van, Slyke, S. A. Appl. Phys. Lett. 1987, 51, 913. doi: 10.1063/1.98799
Shi, J.; Tang, C.W. Appl. Phys. Lett. 1997, 70, 1665. doi: 10.1063/1.118664
Kulkami, A.P.; Tonzola, C. J.; Bable, A.; Jenekhe, S. A. Chem. Mater. 2004, 16, 4556. doi: 10.1021/cm049473l
Pu, L. Chem. Rev. 1998, 98, 2405.
Thelakkat, M. Macromol. Mater. Eng. 2002, 287, 442.
Shirota, Y. Mater. Chem. 2000, 10, 21.
Shirota, Y.; Mater. Chem. 2005, 15, 75. doi: 10.1039/B413819H
Song, Y.; Di, C.; Yang, X.; Li, S.; Xu, W.; Liu, Y. J. Am. Chem. Soc. 2006, 128, 15940. doi: 10.1021/ja064726s
Saragi, T. P. I.; Lieker, T. F.; Salbeck, J. Adv. Funct. Mater. 2006, 16, 966. doi: 10.1002/(ISSN)1616-3028
Bordeau, G.; Lartia, R.; Metge, G.; Fiorini-Debuisschert, C.; Charra, F.; Teulade-Fichou, M. P. J. Am. Chem. Soc. 2008, 130, 16836. doi: 10.1021/ja8055112
Bhaskar, A.; Ramakrishna, G.; Lu, Z.; Twieg, R.; Hales, J. M.; Hagan, D. J.; Van, S. E.; Goodson, T. J. Am. Chem. Soc. 2006, 128, 11840. doi: 10.1021/ja060630m
Tian, H. N.; Yang, X. C.; Chen, R. K.; Pan, Y. Z.; Li, L.; Hagfeldt, A., Sun, L. C. Chem. Commun. 2007, 36, 3741.
Guerret, O.; Sole, S.; Gornitzka, H.; Teichert, M.; Trinquier, G.; Bertrand, G. J. Am. Chem. Soc. 1997, 119, 6668. doi: 10.1021/ja964191a
Kawai, S.; Yamaguchi, T.; Kato, T.; Hatano, S.; Abe, J. Dyes Pigm. 2012, 92, 872.
Adam, B. P.; Suzuki, Y.; Ueda, M.; Bielawski, C. W.; Cowley, A. H. J. Am. Chem. Soc. 2011, 133, 5218. doi: 10.1021/ja200602e
Dhirendra, K.; Justin, T. K. R.; Lin, C. C.; Jou, J. H.; Chem.-Asian J. 2013, 8, 2111. doi: 10.1002/asia.201300271
Yousuke, O.; Hironori, K.; Kazuki, U.; Katsuhira, Y. Tetrahedron 2009, 65, 8336.
Hu, N. X.; Xie, S.; Popovic, Z. D.; Wong, B. A.; Hor, M. Synth. Met. 2000, 111, 421.
Yu, G.; Yin, S.; Liu, Y.; Shuai, Z.; Zhu, D. J. Am. Chem. Soc. 2003, 125, 14816. doi: 10.1021/ja0371505
Janietz, S.; Bradley, D. D. C; Grell, M.; Giebeler, C.; Inbaselatan, M.; Woo, E. P. Appl. Phys. Lett. 1998, 73, 2453. doi: 10.1063/1.122479
Pommerehne, J.; Vestweber, H.; Guss, W.; Mahrt, R. F.; Bässler, H.; Porsch, M.; Daub, J. Adv. Mater. 1995, 7, 551.
Kamtekar, K. T.; Wang, C.; Bettington, S.; Batsanov, A. S.; Perepichka, I. F.; Bryce, M. R.; Ahn, J. H.; Rabinal, M.; Petty, M. C. J. Mater. Chem. 2006, 16, 3823. doi: 10.1039/B604543J
Thelakkat, M.; Schmidt, H. W. Adv. Mater. 1998, 10, 219. doi: 10.1002/(ISSN)1521-4095
Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Gill, P. M. W.; Johnson, B. G.; Robb, M. A. Gaussian 03, revision C.01, Pittsburgh, PA, Gaussian, Inc., 2004.
表 1 中间体及产物化合物的物理性质及产率
Table 1. Physical properties and yield of relative compound
Entry | R1 | R2 | Temp./℃ | t/h | Yield/% | m.p./℃ |
2a | C2H5 | — | 100 | 12 | 90 | — |
2b | C4H9 | — | 100 | 12 | 90 | — |
3a | C2H5 | — | 100 | 6 | 62 | — |
3b | C4H9 | — | 100 | 6 | 61 | — |
5a | C2H5 | H | 150 | 6 | 81 | 137~138 |
5b | C4H9 | H | 150 | 6 | 83 | 127~128 |
5c | C2H5 | Ph | 150 | 6 | 80 | 229~231 |
9a | — | H | 150 | 6 | 88 | 153~154 |
9b | — | Ph | 150 | 6 | 80 | 284~286 |
表 2 化合物5和9的光学性能
Table 2. Optical properties of compounds 5 and 9
λ Solvent | 5a | 5b | 5c | 9a | 9b | |
λAbs/nm | EtOH | 302 | 303 | 291 | 372 | 357 |
353 | 357 | 354 | 363 | 353 | ||
λEm/nm | Toluene | 455 | 455 | 456 | 420 | 423 |
CH2Cl2 | 458 | 459 | 466 | 420 | 427 | |
EtOH | 465 | 462 | 462 | 425 | 424 | |
Φa | 0.42 | 0.47 | 0.52 | 0.48 | 0.49 | |
a The fluorescence quantum yields (Ф) were measured in CHCl3 using quinine sulfate (Ф=0.55) as standard. |
表 3 化合物5的电化学性能
Table 3. Electrochemical properties of compound 5
Band gapa | 4.03 | 3.70 | 3.71 | 3.97 | 3.91 |
EHOMO/ELUMOa (eV) | -4.91/-1.20 | -4.90/-1.20 | -4.90/-1.20 | -5.16/-1.19 | -5.11/-1.21 |
Egb/eV | 3.37 | 3.23 | 3.50 | 3.25 | 3.18 |
Eoxonsetc/V | 0.64 | 0.67 | 0.68 | 0.83 | 0.85 |
EHOMO/ELUMOd (eV) | -5.04/-1.67 | -5.07/-1.84 | -5.08/-1.58 | -5.23/-1.98 | -5.25/-2.07 |
a DFT/B3LYP calculated values; b Optical energy gaps calculated from the edge of the electronic absorption band; c Oxidation potential in CH2Cl2 (10-3 mol•L-1) containing 0.1 mol•L-1 (n-C4H9)4NPF6 with a scan rate of 100 mV•s-1; d EHOMO was calculated by Eox=4.4 V,and ELUMO=EHOMO-Eg. |