Synthesis of a novelSn(IV) porphycene. ferrocene triad linked byaxial coordination and solvent polarity effect inphotoinduced charge separation process
Synthesis of a novelSn(IV) porphycene. ferrocene triad linked byaxial coordination and solvent polarity effect inphotoinduced charge separation process
复制标题
新型Sn(IV)卟啉的合成。
DOI：
10.1021/ic902444x
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发表时间：
2010
影响因子：
4.6
通讯作者：
TetsuroMajima
中科院分区：
文献类型：
--
作者：
Daisuk Maeda;Mamoru Fujitsuka;TetsuroMajima
合成了一种新型的二茂铁三元分子trans-bis(ferrocenecarboxylato)(2，3，6，7，12，13，16，17-octaethylporphycenato)tin(IV)，[SnIV(−)(FcCOO)2](2)，并用多种光谱方法对其进行了表征。这是第一个通过两个官能化单元的轴向配位连接到金属分配中心的金属茂三元化合物的例子。稳态荧光测量表明，与相应的二羟基−[SnV(Opc)(OH)2](1)(1)(1，ΦF=0.094；2，ΦF=0.0 1)相比，二茂铁甲酸的配位能有效地猝灭荧光。在乙腈(极性溶剂)和甲苯(非极性溶剂)中，用亚皮秒瞬时吸收光谱直接观察到二茂铁单元到激发态的锡(IV)卟烯的电子转移过程。在乙腈溶液中，在激发后1ps内，在750ps和850nm处观察到属于锡(IV)卟啉阴离子的瞬变物种，随后产生的电荷分离态消失，时间常数为6.9×1011s−1。在甲苯中，生成的电荷分离态衰减为3.90×1011s和9.6×109s−1时间常数。对于在甲苯中观察到的两组分衰变，提出了电荷分离态和三重态之间的显著平衡，因为这两个能级彼此接近。因此，得到了锡(IV)卟烯−二茂铁三元体系中与溶剂极性相关的长寿命电荷分离态。观察到了[SnIV(OEP)(FcCOO)2](4)(其中OEP为2，3，6，7，12，13，16，17-八乙基卟啉配体)在锡(IV)卟啉激发下的电子转移。然而，在乙腈和甲苯中都没有观察到电荷分离和三重态之间的平衡。锡(IV)−卟啉和−卟啉电荷复合过程的不同是由于2的HOMO−LUMO能隙较小，驱动力(−ΔGCS)比4大，导致甲苯中电荷分离态的能级接近三重态。此外，2的驱动力(LUMOGCS)比4大，这归因于分子对称性的降低和大的茂金属π电子骨架导致的LUMO能级的显著稳定。这一结果表明，在光诱导电子转移体系中，卟烯类化合物是一种很好的电子受体。
A novel Sn(IV) porphycene−ferrocene triad molecule,trans-bis(ferrocenecarboxylato)(2,3,6,7,12,13,16,17-octaethylporphycenato)tin(IV), [SnIV(OEPc)(FcCOO)2] (2), was synthesized and fully characterized by various spectroscopic methods. This is the first example of a metalloporphycene triad linked by the axial coordination of two functionalized units to a metallocenter. The steady-state fluorescence measurement indicated the efficient fluorescence quenching by coordination of the ferrocenecarboxylic acid in comparison to the corresponding dihydroxy−Sn(IV) porphycene, [SnIV(OEPc)(OH)2] (1) (1, ΦF= 0.094;2, ΦF= 0.01). The electron transfer process from the ferrocene units to the excited Sn(IV) porphycene was directly observed by subpicosecond transient absorption spectroscopy in acetonitrile (polar solvent) and toluene (nonpolar solvent). In acetonitrile, the transient species attributed to the Sn(IV) porphycene radical anion was observed at 750 and 850 nm within 1 ps after the excitation, and then the generated charge separation state disappeared with a value of 6.9 × 1011s−1for the time constant. On the other hand, the generated charge separation state decayed with two components, 3.9 × 1011and 9.6 × 109s−1time constants, in toluene. For the observed two-component decay in toluene, a significant equilibrium between the charge separation state and the triplet state was proposed because these energy levels are close to each other. Therefore, the solvent-polarity-dependent long-lived charge separation state was obtained in the Sn(IV) porphycene−ferrocene triad system. The electron transfer upon excitation of the Sn(IV) porphyrin of [SnIV(OEP)(FcCOO)2] (4), in which OEP denotes the 2,3,6,7,12,13,16,17-octaethylporphyrin ligand, was observed. However, no equilibrium between the charge separation and the triplet states was observed in both the acetonitrile and toluene. The difference in the charge recombination processes of the Sn(IV)−porphycene and −porphyrin is due to the small HOMO−LUMO gap and the large driving force (−ΔGCS) of2compared to that of4, which resulted in the energy level of the charge separation state close to the triplet state in toluene. Furthermore, the large driving force (−ΔGCS) of2compared to that of4is attributed to the significant stabilization of the LUMO energy level caused by a decrease in the molecular symmetry and a large porphycene π-electron framework. This result indicates that porphycenes are excellent candidates as an electron acceptor in photoinduced electron transfer systems.