Syntheses, crystal structures, photophysical and theoretical studies of 1,3,2-benzodiazaborolyl-functionalized diphenylacetylenes
作者:Lothar Weber、Daniel Eickhoff、Vanessa Werner、Lena Böhling、Stefanie Schwedler、Anna Chrostowska、Alain Dargelos、Małgorzata Maciejczyk、Hans-Georg Stammler、Beate Neumann
DOI:10.1039/c0dt01410a
日期:——
A series of diphenylacetylenes with one 1,3,2-benzodiazaborolyl end group (BDB) and a second end group X (X = H, OMe, NMe2, SMe, CN and BDB) were synthesized using established 1,3,2-benzodiazaborole methodologies. The 1,3,2-benzodiazaborolyldiphenylacetylenes with X = p-H (4), p-OMe (5), p-NMe2 (6), p-SMe (7) and p-CN (8) end groups are functionalized with cyano groups at the central ring in an ortho-position to the triple bond. Molecular structures of 2, 3, 5, 6 and 7 were determined by X-ray diffraction. These borylated systems show intense blue luminescence in cyclohexane, toluene, chloroform, dichloromethane and tetrahydrofuran, whereas green luminescence was observed in acetonitrile solutions. Thereby Stokes shifts in the range 1700–8600 cm−1 and quantum yields of 0.60–1.00 were observed in cyclohexane solutions. The absorption maxima (308–380 nm) are well reproduced by TD–DFT computations (B3LYP/G-311G(d,p)) and arise from strong HOMO–LUMO transitions. The LUMOs in all the molecules under study are mainly located on the diphenylacetylene bridge, while with the exception of the dimethylamino derivative 6, the HOMO is largely benzodiazaborolyl in character. Thus, the S1←S0 absorption bands are assigned to π(diazaborolyl)–π*(diphenylacetylene) transitions. In contrast to this, in compound 6 the HOMO is mainly represented by the terminal dimethylaminophenyl unit. While calculated ground state dipole moments μg are small (1.1–7.5 D), experimentally determined changes of the dipole moments upon excitation are large (14.8–19.7 D) and reflect a significant charge transfer upon excitation. NLO activities of the rod-structured compounds 2, 4, 6 and 8 are indicated by calculated static first-order hyperpolarizabilities β up to 76.8 × 10−30 esu.
合成了一系列具有一个1,3,2-苯并二氮硼烯末端基团(BDB)和第二个末端基团X(X = H、OMe、NMe2、SMe、CN和BDB)的二苯乙炔。采用成熟的1,3,2-苯并二氮硼烯方法。这些1,3,2-苯并二氮硼烯二苯乙炔(X = p-H (4)、p-OMe (5)、p-NMe2 (6)、p-SMe (7)、p-CN (8))在中央环的邻位三键附近功能化了氰基。通过X射线衍射确定了分子结构2、3、5、6和7。这些硼基化系统在环己烷、甲苯、氯仿、二氯甲烷和四氢呋喃中显示出强烈的蓝色荧光,而在乙腈溶液中观察到绿色荧光。因此,在环己烷溶液中观察到了1700–8600 cm−1的斯托克斯位移和0.60–1.00的量子产率。吸收最大值(308–380 nm)通过TD–DFT计算(B3LYP/G-311G(d,p))得到了良好的复现,并源于强HOMO–LUMO跃迁。所有研究分子的LUMO主要位于二苯乙炔桥上,而除了二甲氨基衍生物6外,HOMO主要具有苯并二氮硼烯的特征。因此,S1←S0吸收带被归因于π(苯并二氮硼烯)–π*(二苯乙炔)跃迁。与此相反,在化合物6中,HOMO主要由末端二甲基氨基苯基单元表示。虽然计算的基态偶极矩μg较小(1.1–7.5 D),但实验测定的激发后偶极矩变化较大(14.8–19.7 D),反映了激发时显著的电荷转移。杆状化合物2、4、6和8的NLO活性通过计算的静态一阶超极化率β最高达到76.8 × 10−30 esu。