Rational synthetic design of well-defined Pt(bisethynyl)/Zn(porphyrin) oligomers for potential applications in photonics
作者:Guillaume Langlois、Shawkat M. Aly、Claude P. Gros、Jean-Michel Barbe、Pierre D. Harvey
DOI:10.1039/c0nj00819b
日期:——
Well-defined oligomers of 1, 2, 3 and 4 units built upon the very soluble bis-1,15-(1,4-ethynylbenzene)-3,7,13,17-tetramethyl-2,8,12,18-tetrakis(n-hexyl) zinc(II) porphyrin ligand and the trans-bis(tri-n-butylphosphine)platinum(II) linker, with acetylene or trimethylsilane as end groups, has been prepared in the presence of a dichloromethane/diethylamine mixture (1 : 1 v/v) and CuX (X = Cl, I) at room temperature, analogue to a Sonogashira coupling. The new monodisperse organometallic oligomers were characterized by 1H, 31P NMR, UV-visible spectroscopies and MALDI-TOF mass spectrometry. The methyl groups placed at the 3,7,13,17-positions induces the locking of the C6H4 fragment in a perpendicular conformation with respect to the zinc(II) porphyrin chromophore, hence removing conjugation as corroborated by the almost total absence of spectral shift of the Soret and Q-bands upon increasing the number of units. Despite this feature, exciton coupling in the Soret band is noted at both room temperature and 77 K. The photophysical parameters, fluorescence lifetimes and quantum yields are practically constant going from the monomer, dimer and tetramer, and as a function of the monitored fluorescence wavelength, all indicating that the excitonic behavior (excitation energy delocalization) is minimal, which is consistent with the weak exciton coupling constants and the lack of conjugation of the π-system. The synthetic methodology can provide longer well-defined oligomers as the presented products were still very soluble even when the number of unit was 4.
以非常易溶的双-1,15-(1,4-
乙炔基
苯)-3,7,13,17-四
甲基-2,8,12,18-四(正己基)
锌(II)
卟啉配体和反式双(三
正丁基膦)
铂(II)连接体为
基础,由 1、2、3 和 4 个单元组成的定义明确的低聚物、在
二氯甲烷/
二乙胺混合物(1 : 1 v/v)和 CuX(X = Cl,I)的存在下,在室温下制备出类似于 Sonogashira 偶联的新单散有机物。新的单分散有机
金属低聚物通过 1H、31P NMR、紫外-可见光谱和
MALDI-TOF 质谱进行了表征。置于 3、7、13、17 位的
甲基促使
C6H4 片段锁定在与
卟啉锌(II)发色团垂直的构象上,从而消除了共轭作用,这一点可以从单位数量增加时几乎完全没有索雷特和 Q 波段光谱偏移得到证实。从单体、二聚体到四聚体,光物理参数、荧光寿命和量子产率实际上都是恒定的,而且与监测的荧光波长有关,所有这些都表明激子行为(激发能量
脱ocalization)是最小的,这与π-系统的弱激子耦合常数和缺乏共轭是一致的。这种合成方法可以提供更长的定义明确的低聚物,因为即使单位数为 4,所呈现的产品仍然非常易溶。