Khadria Anjul, de Coene Yovan, Gawel Przemyslaw, Roche Cécile, Clays Koen, Anderson Harry L
Department of Chemistry, Oxford University, Chemistry Research Laboratory, Mansfield Road, Oxford OX1 3TA, UK.
Department of Chemistry, University of Leuven, Celestijnenlaan 200 D, 3001 Leuven, Belgium.
Org Biomol Chem. 2017 Jan 25;15(4):947-956. doi: 10.1039/c6ob02319c.
Pyropheophorbide-a methyl ester (PPa-OMe) has been modified by attaching electron-donor and -acceptor groups to alter its linear and nonlinear optical properties. Regioselective bromination of the terminal vinyl position and Suzuki coupling were used to attach a 4-(N,N-diethylaminophenyl) electron-donor group. The electron-acceptor dicyanomethylene was attached at the cyclic ketone position through a Knoevenagel condensation. Four different derivatives of PPa-OMe, containing either electron-donor or electron-acceptor groups, or both, were converted to hydrophilic bis-TEG amides to generate a series of amphiphilic dyes. The absorption and emission properties of all the dyes were compared to a previously reported push-pull type porphyrin-based dye and a commercial push-pull styryl dye, FM4-64. Electrochemical measurements reveal that the electron donor group causes a greater decrease in HOMO-LUMO gap than the electron-acceptor. TD-DFT calculations on optimized geometries (DFT) of all four dyes show that the HOMO is mostly localized on the donor, 4-(N,N-diethylaminophenyl), while the LUMO is distributed around the chlorin ring and the electron-acceptor. Hyper-Rayleigh scattering experiments show that the first-order hyperpolarizabilities of the dyes increase on attaching either electron-donor or -acceptor groups, having the highest value when both the donor and acceptor groups are attached. Two-photon excited fluorescence (TPEF) and second harmonic generation (SHG) images of the bis-TEG amide attached dyes in lipid monolayer-coated droplets of water-in-oil reveal that the TPEF and SHG involve transition dipole moments in different orientations.
焦脱镁叶绿酸-a甲酯(PPa-OMe)已通过连接供电子基团和受电子基团进行修饰,以改变其线性和非线性光学性质。利用末端乙烯基位置的区域选择性溴化反应和铃木耦合反应连接一个4-(N,N-二乙氨基苯基)供电子基团。通过克诺文纳格尔缩合反应将受电子基团二氰基亚甲基连接在环酮位置。将四种不同的PPa-OMe衍生物(含有供电子基团或受电子基团,或两者都有)转化为亲水性双-TEG酰胺,以生成一系列两亲性染料。将所有染料的吸收和发射特性与先前报道的推挽型卟啉基染料和市售推挽型苯乙烯基染料FM4-64进行了比较。电化学测量表明,供电子基团导致的最高已占分子轨道-最低未占分子轨道能隙减小比受电子基团更大。对所有四种染料的优化几何结构进行含时密度泛函理论(TD-DFT)计算表明,最高已占分子轨道主要定域在供体4-(N,N-二乙氨基苯基)上,而最低未占分子轨道分布在二氢卟吩环和受电子基团周围。超瑞利散射实验表明,连接供电子基团或受电子基团时,染料的一阶超极化率都会增加,当同时连接供体和受体基团时超极化率最高。在油包水脂质单层包覆液滴中,对连接双-TEG酰胺的染料进行双光子激发荧光(TPEF)和二次谐波产生(SHG)成像,结果表明TPEF和SHG涉及不同取向的跃迁偶极矩。