Electronic structure and photophysics of a supermolecular iron complex having a long MLCT-state lifetime and panchromatic absorption
Electronic structure and photophysics of a supermolecular iron complex having a long MLCT-state lifetime and panchromatic absorption
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DOI：
10.1073/pnas.2009996117
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发表时间：
2020-08-25
影响因子：
11.1
通讯作者：
Therien, Michael J.
中科院分区：
文献类型：
--
作者：
Jiang, Ting;Bai, Yusong;Therien, Michael J.
利用地球上丰富的铁基金属配合物作为高性能光敏剂需要长寿命的电子激发的金属-配体电荷转移（MLCT）状态，但这些物种通常遭受飞秒时间尺度的电荷转移（CT）状态淬火的低洼非反应性金属中心（MC）状态。在这里，我们工程师超分子Fe（II）的发色团的基础上的双（三齿配体）金属（11）-乙炔-（卟啉）锌（11）共轭框架，以前显示，引起高度离域的低（MLCT）-M-3状态的其他第VIII族金属（Ru，Os）配合物。电子光谱，电位，和超快泵-探测瞬态动力学数据表明，一个强大的σ-捐助三齿配体和（卟啉）锌（II）部分与低躺pi*-能级的组合，充分不稳定MC状态和稳定超分子MLCT状态，实现Fe（II）的复合物，表达（MLCT）-M-3状态的物理学让人想起他们的重金属类似物。所得的Fe（II）发色团原型FeNHCPZn具有高度极化的Cr状态，其具有显著延长的（MLCT）-M-3寿命（160 ps）、（MLCT）-M-3磷光和周围环境稳定性。密度泛函和基于域的局域对自然轨道耦合簇[DLPNO-CCSD（T）]理论揭示了与电子光谱和激发态动力学数据一致的三重态波函数空间分布，进一步强调了电子激发的FeNHCPZn的戏剧性Fe金属到扩展配体Cr的特征。这种设计通过在整个可见光谱域中重新分配高能量吸收振荡器强度进一步促进强烈的全色吸收率，同时保持用于宽范围光化学的实质性激发态氧化电位-通过FeNHCPZn将电荷光注入染料敏化太阳能电池（DSSC）架构中的SnO 2/FTO电极中的能力突出显示。本文列举的概念提供了替代用于太阳能转换和光致发光应用的传统的基于稀有金属的发射器的机会。
Exploiting earth-abundant iron-based metal complexes as high-performance photosensitizers demands long-lived electronically excited metal-to-ligand charge-transfer (MLCT) states, but these species suffer typically from femtosecond timescale charge-transfer (CT)-state quenching by low-lying nonreactive metal-centered (MC) states. Here, we engineer supermolecular Fe(II) chromophores based on the bis(tridentate-ligand)metal(11)-ethyne-(porphinato)zinc(11) conjugated framework, previously shown to give rise to highly delocalized low-lying (MLCT)-M-3 states for other Group VIII metal (Ru, Os) complexes. Electronic spectral, potentiometric, and ultrafast pump-probe transient dynamical data demonstrate that a combination of a strong sigma-donating tridentate ligand and a (porphinato)zinc(II) moiety with low-lying pi*-energy levels, sufficiently destabilize MC states and stabilize supermolecular MLCT states to realize Fe(II) complexes that express (MLCT)-M-3 state photophysics reminiscent of their heavy-metal analogs. The resulting Fe(II) chromophore archetype, FeNHCPZn, features a highly polarized Cr state having a profoundly extended (MLCT)-M-3 lifetime (160 ps), (MLCT)-M-3 phosphorescence, and ambient environment stability. Density functional and domain-based local pair natural orbital coupled cluster [DLPNO-CCSD(T)] theory reveal triplet-state wavefunction spatial distributions consistent with electronic spectroscopic and excited-state dynamical data, further underscoring the dramatic Fe metal-to-extended ligand Cr character of electronically excited FeNHCPZn. This design further prompts intense panchromatic absorptivity via redistributing high-energy absorptive oscillator strength throughout the visible spectral domain, while maintaining a substantial excited-state oxidation potential for wide-ranging photochemistry-highlighted by the ability of FeNHCPZn to photo-inject charges into a SnO2/FTO electrode in a dye-sensitized solar cell (DSSC) architecture. Concepts enumerated herein afford opportunities for replacing traditional rare-metal-based emitters for solar-energy conversion and photoluminescence applications.