Accessing the near-infrared spectral region with stable, synthetic, wavelength-tunable bacteriochlorins
作者:Masahiko Taniguchi、David L. Cramer、Anil D. Bhise、Hooi Ling Kee、David F. Bocian、Dewey Holten、Jonathan S. Lindsey
DOI:10.1039/b717803d
日期:——
The near-infrared (NIR) spectral region has been comparatively under-utilized for diverse materials and medical applications owing to the lack of chromophores that afford stability, solubility, synthetic malleability, and tunable photophysical features. Bacteriochlorins are attractive candidates in this regard; however, preparation via modification of naturally occurring bacteriochlorophylls or reduction of porphyrins or chlorins has proved cumbersome. To overcome such limitations, a dibromobacteriochlorin (BC-Br3Br13) was prepared de novo by the acid-catalyzed condensation of an 8-bromodihydrodipyrrin-acetal. BC-Br3Br13 bears (1) a geminal dimethyl group in each reduced ring to block adventitious dehydrogenation, and (2) bromo groups at the 3- and 13-positions for further chemical modifications. BC-Br3Br13 was subjected to four types of Pd-mediated coupling reaction (Suzuki, Stille, Sonogashira, dehalogenation) to give bacteriochlorins bearing substituents at the 3- and 13-positions (phenyl, vinyl, acetyl, phenylethynyl), and a benchmark bacteriochlorin lacking such substituents. The 3,13-divinylbacteriochlorin was transformed to the 3,13-diformylbacteriochlorin. Depending on the substituents at the 3- and 13-positions, the position of the long-wavelength absorption maximum (Qy(0,0) band) lies between 713 and 771 nm, the fluorescence emission maximum lies between 717 and 777 nm, and the fluorescence quantum yield ranges from 0.15 to 0.070. The ability to introduce a wide variety of functional groups via Pd-mediated coupling reactions and the tunable absorption and emission spectral properties suggest that synthetic bacteriochlorins are viable candidates for a wide variety of photochemical applications.
由于缺乏具有稳定性、溶解性、合成延展性和可调光物理特性的发色团,近红外光谱区在各种材料和医疗应用方面的利用率相对较低。在这方面,细菌氯素是很有吸引力的候选物质;然而,事实证明,通过改性天然存在的细菌氯素或还原卟啉或氯素来制备细菌氯素是很麻烦的。为了克服这些限制,我们通过酸催化缩合 8-溴二氢二吡咯啉缩醛,从新制备了一种二溴细菌氯素(BC-Br3Br13)。BC-Br3Br13 (1) 在每个还原环上都带有一个二甲基基团,以阻止偶然脱氢;(2) 在 3 位和 13 位上带有溴基团,用于进一步化学修饰。BC-Br3Br13 经过四种 Pd 介导的偶联反应(铃木反应、斯蒂尔反应、Sonogashira 反应、脱卤反应),得到了在 3-位和 13-位上带有取代基(苯基、乙烯基、乙酰基、苯乙炔基)的细菌氯化物,以及一种缺少此类取代基的基准细菌氯化物。3,13-二乙烯基细菌氯素转化为 3,13-二甲酰基细菌氯素。根据 3-位和 13-位取代基的不同,长波长吸收最大值(Qy(0,0) 带)的位置在 713 到 771 纳米之间,荧光发射最大值在 717 到 777 纳米之间,荧光量子产率在 0.15 到 0.070 之间。通过 Pd 介导的偶联反应引入各种官能团的能力以及可调的吸收和发射光谱特性表明,合成的细菌氯化物是各种光化学应用的可行候选物质。