Population and coherence dynamics in large conjugated porphyrin nanorings.
Population and coherence dynamics in large conjugated porphyrin nanorings.
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DOI：
10.1039/d2sc01971j
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发表时间：
2022-08-24
期刊：
影响因子：
8.4
通讯作者：
中科院分区：
文献类型：
--
作者：
在光合作用中，大自然利用排列在超分子环中的发色团的独特电子特性来有效地收集光。在合成的超分子环结构中，卟啉纳米结构引起了相当大的关注，因为它们与自然发生的光收集结构相似，但提供了控制环大小和无序程度的能力。本文采用宽带飞秒瞬态吸收光谱技术，利用泵浦脉冲与非均匀加宽吸收光谱的高能量侧或低能侧共振，研究了大型卟啉纳米颗粒中的居群动力学以及基态和激发态振动相干性。研究了一系列由10 - 40个卟啉单元组成的全共轭炔桥化纳米环。发现了与泵浦波长相关的快速光谱演化。当在吸收光谱的高能区或低能区分别激发大的卟啉纳米粒子时，受激辐射迅速上升或衰减。这种动力学与非均匀加宽基态系综上的跃迁偶极矩变化的假设是一致的。观察到的动力学表明纳米环构象和振荡器强度的相互作用。在两种泵浦条件下均观察到子ps时域上的振荡动力学。对激发波长相关的瞬态光谱以及振荡的振幅和相位演变的综合分析允许分配在基态或激发态电子势能表面上演变的振动波包。尽管卟啉纳米结构支持高度离域的电子波函数，其相干长度跨越数十个发色团，但测量到的振动相干仍然局限于单体上。对跳动的主要贡献被分配到卟啉核心上的两种振动模式：Zn-N拉伸模式和骨架甲基/吡啶C-C拉伸和面内弯曲模式。对由10 ~ 40个重复单元组成的锌卟啉纳米结构，观察到由非均匀加宽、基态和激发态核波包引起的泵浦波长依赖的超快激发态动力学。
In photosynthesis, nature exploits the distinctive electronic properties of chromophores arranged in supramolecular rings for efficient light harvesting. Among synthetic supramolecular cyclic structures, porphyrin nanorings have attracted considerable attention as they have a resemblance to naturally occurring light-harvesting structures but offer the ability to control ring size and the level of disorder. Here, broadband femtosecond transient absorption spectroscopy, with pump pulses in resonance with either the high or the low energy sides of the inhomogeneously broadened absorption spectrum, is used to study the population dynamics and ground and excited state vibrational coherence in large porphyrin nanorings. A series of fully conjugated, alkyne bridged, nanorings constituted of between ten and forty porphyrin units is studied. Pump-wavelength dependent fast spectral evolution is found. A fast rise or decay of the stimulated emission is found when large porphyrin nanorings are excited on, respectively, the high or low energy side of the absorption spectrum. Such dynamics are consistent with the hypothesis of a variation in transition dipole moment across the inhomogeneously broadened ground state ensemble. The observed dynamics indicate the interplay of nanoring conformation and oscillator strength. Oscillatory dynamics on the sub-ps time domain are observed in both pumping conditions. A combined analysis of the excitation wavelength-dependent transient spectra along with the amplitude and phase evolution of the oscillations allows assignment to vibrational wavepackets evolving on either ground or excited states electronic potential energy surfaces. Even though porphyrin nanorings support highly delocalized electronic wavefunctions, with coherence length spanning tens of chromophores, the measured vibrational coherences remain localised on the monomers. The main contributions to the beatings are assigned to two vibrational modes localised on the porphyrin cores: a Zn–N stretching mode and a skeletal methinic/pyrrolic C–C stretching and in-plane bending mode. Pump wavelength-dependent, ultrafast excited state dynamics arising from inhomogeneous broadening and ground and excited state nuclear wavepackets were observed for a series of Zn porphyrin nanorings made of 10 to 40 repeating units.
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影响因子：
2.9
作者：
Baskin, JS;Yu, HZ;Zewail, AH
通讯作者：
Zewail, AH
影响因子：
5.7
作者：
Brazard, Johanna;Bizimana, Laurie A.;Turner, Daniel B.
通讯作者：
Turner, Daniel B.
影响因子：
2.9
作者：
Fitzpatrick, Colin;Odhner, Johanan H.;Levis, Robert J.
通讯作者：
Levis, Robert J.
DOI：
10.1021/acs.jpca.0c10807
发表时间：
2021-04-01
期刊：
The journal of physical chemistry. A
影响因子：
--
作者：
Arpin PC;Turner DB
通讯作者：
Turner DB
影响因子：
8.6
作者：
Camargo, Franco V. de A.;Grimmelsmann, Lena;Heisler, Ismael A.
通讯作者：
Heisler, Ismael A.