Charge-Transfer Triplet Chromophores: Adding Efficiency to Organic Photosensitisers

电荷转移三重态发色团：提高有机光敏剂的效率

• 批准号: EP/W03431X/1
• 负责人: Yi-Lin Wu
• 金额: $ 38.89万
• 依托单位: CARDIFF UNIVERSITY
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FW03431X%2F1
• 关键词: Charge; Transfer; Triplet; Chromophores; Adding

Light-induced chemical transformation is ubiquitous in nature and central to the function of many life processes; photosynthesis of bacterial or plant and phototropism of plant or fungi, among many others, are two examples of longstanding interest and importance. In these events, light-absorbing molecules are photo-excited and store this energy transiently before transferring the excess energy (or electron) to the substrates for subsequent chemical or physical processes. Since the reactive species in the latter process often cannot interact with solar radiation directly, these otherwise inactive components are said to be 'sensitised' by the light-absorbing molecules. The involvement of solar power as the ultimate energy input not only suggests the sustainability of these processes, but also hints at the fact that photoexcitation can supply an ample amount of energy to enable high barrier, energy-demanding process to occur--photocatalytic water splitting to generate hydrogen as solar fuel is one example that attracts much recent attention due to the increasing demands for sustainable chemistry.Inspired by this possibility, the use of photosensitizers under mild conditions for synthetic chemistry, photocatalytic waste/toxin decomposition, photodynamic therapy and photovoltaics has found widespread applications. The selection of photosensitizers, however, is largely dominated by the transition-metal-based materials due to the long lifetime and strong redox power in their excited states. While the development of less toxic organic photosensitizers would enhance the sustainability of this process, along with the energetic and structural diversity, it presents considerable challenges for optimising the favourable kinetic and thermodynamic parameters seen in transition-metal materials. The popularity of metal-based photosensitizers stems primarily from the efficient formation of the triplet excited state, where two electrons in different molecular orbitals have a parallel spin orientation. The difference between the spin configurations in the triplet excited state and the ground state (antiparallel spins, singlet) impedes energy dissipation, thus allowing sufficient time for inter-molecular energy (or electron) transfer from excited photosensitizers to occur.To unlock the full potential of metal-free organic photosensitisers, I present in this project a renovated molecular design based on fundamental quantum chemical considerations. I will introduce a small functional group into commercial dyes to bias the orbital orientation of their high-energy electrons. I will also engineer the electron density across the molecular skeleton such that the electron distribution will be dissimilar between the ground and excited states. These two features would guarantee fast triplet formation with minimal energy loss from the spin flipping process. I will quantitatively analyse the kinetic process after photoexcitation to gauge the energy conversion efficiency of the new photosensitizers in the absence and presence of reactive substrates. Special attention will be paid to ensure energy tuning and high photostability for practical applications. Furthermore, since several spin states of small energy separation are present in these excited photosensitisers, I will elucidate the influence of the nearby energy levels on the spin flipping mechanism. This proposal is built upon my research expertise in the synthetic, analytical, and theoretical aspects of photo- and electrochemically active materials. The outcome of the project will immediately offer new photocatalysis tools to enhance reaction efficiency. The fundamental understanding of the energy conversion mechanism will provide insight into any spin-involving processes, such as electroluminescence, photovoltaics and spintronics.

光诱导的化学转化在自然界中是普遍存在的，并且是许多生命过程的核心功能;细菌或植物的光合作用和植物或真菌的向光性，以及许多其他的，是两个长期感兴趣和重要性的例子。在这些情况下，光吸收分子被光激发，并在将多余的能量（或电子）转移到衬底用于随后的化学或物理过程之前瞬时存储该能量。由于后一过程中的活性物质通常不能直接与太阳辐射相互作用，这些原本不活跃的成分被认为是由光吸收分子“敏化”的。太阳能作为最终能量输入的参与不仅表明了这些过程的可持续性，而且还暗示了光激发可以提供充足的能量以实现高势垒的事实，能源需求的过程--由于对可持续化学的需求不断增加，光催化水分解产生氢气作为太阳能燃料是最近引起广泛关注的一个例子。由于光敏剂的存在，在温和条件下将光敏剂用于合成化学、光催化废物/毒素分解、光动力疗法和光生物学已得到广泛应用。然而，光敏剂的选择在很大程度上由基于过渡金属的材料主导，这是由于它们在激发态下的长寿命和强氧化还原能力。虽然毒性较小的有机光敏剂的发展将提高这一过程的可持续性，沿着能量和结构的多样性，它提出了相当大的挑战，优化过渡金属材料中看到的有利的动力学和热力学参数。基于金属的光敏剂的流行主要源于三重激发态的有效形成，其中不同分子轨道中的两个电子具有平行的自旋取向。在三重激发态和基态（反平行自旋，单重态）的自旋配置之间的差异阻碍能量耗散，从而允许足够的时间从激发photosensitizers分子间的能量（或电子）transfer发生.To解锁的全部潜力的无金属的有机photosensitisers，我在这个项目中提出了一个翻新的分子设计的基础上的基本量子化学的考虑。我将在商业染料中引入一个小的官能团，以偏置其高能电子的轨道方向。我也会设计分子骨架上的电子密度，使基态和激发态之间的电子分布不同。这两个特征将保证快速的三重态形成，同时自旋翻转过程的能量损失最小。我将定量分析光激发后的动力学过程，以衡量新的光敏剂的能量转换效率在反应底物的存在和不存在。将特别注意确保实际应用的能量调谐和高光稳定性。此外，由于这些激发光敏剂中存在几个能量分离较小的自旋态，因此我将阐明附近能级对自旋翻转机制的影响。这个建议是建立在我的研究专长，在合成，分析和理论方面的光和电化学活性材料。该项目的成果将立即提供新的反应器工具，以提高反应效率。对能量转换机制的基本理解将提供对任何涉及自旋的过程的深入了解，例如电致发光，光致发光和自旋电子学。

项目成果

Butterfly-Shaped Dibenz[a,j]anthracenes: Synthesis and Photophysical Properties.

• DOI: 10.1021/acs.orglett.3c02306
• 发表时间: 2023-11-03
• 期刊: Organic letters
• 影响因子: 5.2
• 作者: Wu YY;Wu YL;Lin CL;Chen HC;Chuang YY;Chen CH;Chou CM
• 通讯作者: Chou CM

Why does thionating a carbonyl molecule make it a better electron acceptor?

为什么羰基分子硫代可以使其成为更好的电子受体？

• DOI: 10.1039/d2cp05186a
• 发表时间: 2023
• 期刊: PCCP
• 作者: Wu YL