The chemistry of life is founded on light, so is it appropriate to think of light as a chemical substance? Planck's quantization offers a metric analogous to Avogadro's number to relate the number of particles to an effective reaction of single molecules and photons to form a new compound. A rhodamine dye molecule serves as a dehalogenating photocatalyst in a consecutive photoelectron transfer (conPET) process which adds the energy of two photons, with the first photon inducing radical formation and the second photon triggering PET to the substrate molecule. Rather than probing catalytic heterogeneity and dynamics on the single-molecule level, single-photon synthesis is demonstrated: the light quantum constitutes a reactant for the single substrate molecule in a dye–driven reaction. The approach illustrates that molecular diffusion and excited-state internal conversion are not limiting factors in conPET reaction kinetics because of catalyst–substrate preassociation. The effect could be common to photoredox catalysis, removing the conventional requirement of long excited-state lifetimes.

中文翻译：

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单分子光氧化还原催化†

生命的化学是建立在光的基础上的，那么将光视为化学物质是否合适？普朗克的量化提供了类似于阿伏加德罗数的度量标准，可以将粒子数与单个分子和光子的有效反应形成新化合物联系起来。罗丹明染料分子在连续的光电子转移（conPET）过程中用作脱卤光催化剂，该过程将两个光子的能量相加，第一个光子诱导自由基的形成，第二个光子触发PET到底物分子。单光子合成不是在单分子水平上探索催化的异质性和动力学，而是被证明：光量子构成了染料驱动反应中单个底物分子的反应物。该方法表明，由于催化剂与底物的预缔合，分子扩散和激发态内部转化不是conPET反应动力学的限制因素。这种效应可能是光氧化还原催化所共有的，从而消除了传统的长激发态寿命的要求。