Ultrafast singlet excited-state polarization in electronically asymmetric ethyne-bridged bis[(porphinato)zinc(II)] complexes.
Ultrafast singlet excited-state polarization in electronically asymmetric ethyne-bridged bis[(porphinato)zinc(II)] complexes.
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DOI：
10.1021/ja021157p
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发表时间：
2003-02
影响因子：
15
通讯作者：
I. Rubtsov;K. Susumu;G. I. Rubtsov;M. Therien
中科院分区：
文献类型：
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作者：
I. Rubtsov;K. Susumu;G. I. Rubtsov;M. Therien
两个共轭双[（卟啉合）锌（II）]（bis[PZn]）物种，bis[（5，5 '-10，20-双[3，5-双（3，3-二甲基-1-丁氧基）苯基]卟啉合）锌（II）]乙炔（DD）和[（5，-10，20-bis[3，5-bis（3，3-dimethyl-1-butyloxy）phenyl]porphinato）zinc（II）]-[用泵浦-探测瞬态吸收光谱和烧孔技术研究了（5 '，-15'-乙炔基-10 '，20'-双（七氟丙基）卟啉合）锌（Ⅱ）]乙炔（DA）.这两种内消旋-内消旋乙炔桥连的双[PZn]化合物都显示出强烈的近红外（NIR）瞬态S（1）->S（n）吸收和它们最初制备的电子激发Q态的快速弛豫。溶剂化和构象弛豫在DD和DA基态和激发态动力学中起着关键作用;除了这些驱动光谱扩散的过程外，电子激发的DA在2-20 ps的时间尺度上表现出S（1）->S（0）振子强度的3倍减小。DD和DA显示基态和时间依赖性的激发态构象的异质性，烧孔实验表明，这种构象的异质性很大程度上反映了卟啉-卟啉共轭的程度，这是作为颜料-颜料二面角分布的函数而变化。虽然光谱扩散可以看到这两种化合物，旋转动力学驱动的构型平均（τ约30 ps），沿着与一个小的溶剂化的贡献，占基本上所有的光谱变化观察到的电子激发DD。对于DA，补充弛豫过程在激发态动力学中起着关键作用。两个快速溶剂化分量（0.27和1.7 ps）增加DA激发态偶极矩，并伴随降低相应的S（1）-->S（0）跃迁振子强度;这些数据表明，这些效应源自DA S（1）态极化度随时间的变化，而这种变化是由溶剂化和增强的激发态内球结构弛豫所激发的。
The excited-state dynamics of two conjugated bis[(porphinato)zinc(II)] (bis[PZn]) species, bis[(5,5'-10,20-bis[3,5-bis(3,3-dimethyl-1-butyloxy)phenyl]porphinato)zinc(II)]ethyne (DD) and [(5,-10,20-bis[3,5-bis(3,3-dimethyl-1-butyloxy)phenyl]porphinato)zinc(II)]-[(5',-15'-ethynyl-10',20'-bis(heptafluoropropyl)porphinato)zinc(II)]ethyne (DA), were studied by pump-probe transient absorption spectroscopy and hole burning techniques. Both of these meso-to-meso ethyne-bridged bis[PZn] compounds display intense near-infrared (NIR) transient S(1)-->S(n) absorptions and fast relaxation of their initially prepared, electronically excited Q states. Solvational and conformational relaxation play key roles in both DD and DA ground- and excited-state dynamics; in addition to these processes that drive spectral diffusion, electronically excited DA manifests a 3-fold diminution of S(1)-->S(0) oscillator strength on a 2-20 ps time scale. Both DD and DA display ground-state and time-dependent excited-state conformational heterogeneity; hole burning experiments show that this conformational heterogeneity is reflected largely by the extent of porphyrin-porphyrin conjugation, which varies as a function of the pigment-pigment dihedral angle distribution. While spectral diffusion can be seen for both compounds, rotational dynamics driving configurational averaging (tau approximately 30 ps), along with a small solvational contribution, account for essentially all of the spectral changes observed for electronically excited DD. For DA, supplementary relaxation processes play key roles in the excited-state dynamics. Two fast solvational components (0.27 and 1.7 ps) increase the DA excited-state dipole moment and reduce concomitantly the corresponding S(1)-->S(0) transition oscillator strength; these data show that these effects derive from a time-dependent change of the degree of DA S(1)-state polarization, which is stimulated by solvation and enhanced excited-state inner-sphere structural relaxation.