Calculation Driven Synthesis of an Excellent Dihydropyrene Negative Photochrome and its Photochemical Properties

详细信息    查看全文

• 作者：Khurshid Ayub ; Rui Li ; Cornelia Bohne ; Richard Vaughan Williams ; Reginald H. Mitchell
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：March 23, 2011
• 年：2011
• 卷：133
• 期：11
• 页码：4040-4045
• 全文大小：830K
• 年卷期：v.133,no.11(March 23, 2011)
• ISSN：1520-5126

文摘

The photochromic properties of dihydropyrenes have been substantially improved by making use of density functional theory (DFT) activation barrier calculations, which suggested that the di-isobutenylcyclophanediene 15鈥?/b> should have a significant barrier to thermal isomerization to the dihydropyrene (DHP) 15, which itself should resist isomerization involving migration of the internal groups to the rearranged dihydropyrene 9 (X = 鈭扖H鈺怌(Me)₂). As a result of these calculations, the synthesis of the colorless cyclophanediene (CPD) 15鈥?/b> was undertaken and achieved from the dinitrile 28 in four steps in 37% overall yield %. The cyclophanediene 15鈥?/b> thermally isomerized to the dihydropyrene 15 at 100 掳C with t_1/2 = 4.5 h, giving an extrapolated 20 掳C t_1/2 of 16 y, consistent with the DFT calculations. No evidence for [1,5]-sigmatropic rearrangement in to 9 (X = 鈭扖H鈺怌(Me)₂) was observed on heating to 130 掳C. The ring-opening isomerization quantum yields (_open) for DHP 15 in to CPD 15鈥?/b> were determined in cyclohexane to be 0.12 卤 0.01, which is three times greater than for the benzoDHP 1. Friedel鈭扖rafts naphthoylation of 15 gave 70% of purple 32, which in toluene showed the largest photochemical ring-opening isomerization quantum yields (_open) of 0.66 卤 0.02 for any known dihydropyrene, nine times greater than 1 in toluene. The thermal closing of 32鈥?/b> to 32, although faster than for 15鈥?/b>, gave a useful extrapolated t_1/2 of 2 y at 20 掳C.