Methyl- and methoxy-substituted di[1,4]benzodithiio[2,3-b:2,3-e]pyridines as new electron donor compounds: synthesis, molecular structure, electrochemical properties, and EPR studies
作者:B. Bueno、B. Esteve、J. Irurre、E. Brillas、X. Torrelles、J. Rius、A. Alvarez-Larena、J. F. Piniella、C. Alemán、L. Juliá
DOI:10.1039/a900148d
日期:——
Two new derivatives of di[1,4]benzodithiino[2,3-b:2,3-e]pyridine (5) tetrasubstituted with methyl (7) and methoxy (8) groups at the 2,3,9 and 10 positions have been prepared from 2,3,5,6-tetrachloropyridine, by cyclization reaction with the bidentate nucleophiles, 4,5-dimethyl- and 4,5-dimethoxy-benzene-1,2-dithiol. Cyclic voltammograms for the oxidation of both polyheterocyclic compounds 7 and 8 in CH2Cl2 exhibit two consecutive redox couples. The first pairs are due to the equilibria between the initial compounds and their radical cations, while in the second couples, the electrogenerated radical cations are in equilibrium with the corresponding dications. Radical cations of these molecules have been generated in fluid solution, by oxidation of the parent compounds with thallium(III) trifluoroacetate in trifluoroacetic acid in the case of 7, and by irradiation of a CH2Cl2 solution containing trifluoroacetic acid (10%) in the case of 8. Both species were analyzed by electron paramagnetic resonance (EPR). X-Ray analysis of the molecular structures of both 7 and 8 shows a stable chair-shaped conformation with interplanar angles between the phenyl rings and the pyridine ring of 139.9 and 141.4° for 7 and 133.7° for 8.
两种新的二[1,4]苯并硫并[2,3-b:2,3-e]吡啶(5)的衍生物在2、3、9和10位分别用甲基(7)和甲氧基(8)取代,已通过与双齿亲核试剂4,5-二甲基-和4,5-二甲氧基-苯-1,2-二硫的环化反应,从2,3,5,6-四氯吡啶制备而成。两种多杂环化合物7和8在CH2Cl2中的氧化循环伏安图显示出两个连续的氧化还原对。第一个对是由于初始化合物与其自由基阳离子之间的平衡,而第二个对中,电生成的自由基阳离子与相应的双阳离子处于平衡状态。这些分子的自由基阳离子通过将母体化合物与三氟甲酸铊(III)氧化,在三氟乙酸中生成的,在7的情况下,由于在含有10%三氟乙酸的CH2Cl2溶液中辐照而生成的,在8的情况下。这两种物质通过电子顺磁共振(EPR)进行分析。对7和8的分子结构进行的X射线分析显示出一种稳定的椅形构象,苯环与吡啶环之间的面间角分别为7的139.9°和141.4°,8的133.7°。