Synthesis and photochromic behavior of mono-, and biphotochromic system linked by p-phenylene bridge

Fringa, 2001 Dűrr, 2003 Liu, 2003, Chin. Chem. Lett., 12, 1230 Golden, 1961, J. Chem. Soc., 3741, 10.1039/jr9610003741 Maeda, 1970, Bull. Chem. Soc. Jpn., 43, 429, 10.1246/bcsj.43.429 Chen, 2007, Tetrahedron, 63, 4319, 10.1016/j.tet.2007.03.030 Mahmoodi, 2004, J. Chem. Res., 438, 10.3184/0308234041423772 Kiyani, 2009, Mendeleev Commun., 19, 203, 10.1016/j.mencom.2009.07.010 Mahmoodi, 2004, Bull. Korean Chem. Soc., 25, 1417, 10.5012/bkcs.2004.25.9.1417 Mahmoodi, 2007, J. Chin. Chem. Soc., 54, 635, 10.1002/jccs.200700091 Irie, 2004, Bull. Chem. Soc. Jpn., 77, 195, 10.1246/bcsj.77.1037 Victoria, 2005, Acta Crystallogr., E61, o667 Padwa, 1972, J. Chem. Soc. Chem. Commun., 409, 10.1039/c39720000409 The typical procedure for the synthesis of 1-((4-((3-formyl-1H-indol-1-yl)methyl)phenyl)methyl)-1H-indole-3-carbaldehyde 7 was described as follows: POCl3 (1.8mL, 19.8mmol) was added slowly to dry DMF (9.1mL) at 0°C, after 30min a solution of 8 (2.2g, 6.64mmol) in DMF (46mL) was added drop wise over 1h at 0°C. The mixture was stirred at r.t. for 6h and poured into 5mol/L sodium hydroxide (95.24mL). The mixture heated at 100°C for 30min and allowed to cool. The white precipitate was filtered off. Washed with water and purified by silica gel column chromatography to give a pale yellow solid 2.3g (89%), mp=294°C, IR (KBr): 3100, 3050, 2910, 2750, 2800, 1657, 1610, 1528, 1461, 1400cm−1; 1H NMR (500MHz, DMSO-d6): δ 9.92 (s, 2H), 8.43 (s, 2H), 8.11–8.09 (m, 2H), 7.56–7.54 (m, 2H), 7.29 (s, 4H), 7.26–7.23 (m, 4H), 5.5 (S, 4H); 13C NMR (125MHz, DMSO-d6): δ 185.56, 141.79, 137.79, 137.27, 128.60, 125.65, 124.5, 123.43, 121.95, 118.29, 112.21, 50.25; HRMS m/z (EI) calcd. for C26H20N2O2 392.1525. Found 392.1529; Anal. calcd. for C26H20N2O2: C, 79.57; H, 5.14; N, 7.14; Found: C, 79.56; H, 5.13; N, 7.16.