The entatic state denotes a distorted coordination geometry of a complex from its typical arrangement that generates an improvement to its function. The entatic-state principle has been observed to apply to copper electron-transfer proteins and it results in a lowering of the reorganization energy of the electron-transfer process. It is thus crucial for a multitude of biochemical processes, but its importance to photoactive complexes is unexplored. Here we study a copper complex—with a specifically designed constraining ligand geometry—that exhibits metal-to-ligand charge-transfer state lifetimes that are very short. The guanidine–quinoline ligand used here acts on the bis(chelated) copper(I) centre, allowing only small structural changes after photoexcitation that result in very fast structural dynamics. The data were collected using a multimethod approach that featured time-resolved ultraviolet–visible, infrared and X-ray absorption and optical emission spectroscopy. Through supporting density functional calculations, we deliver a detailed picture of the structural dynamics in the picosecond-to-nanosecond time range.

焓状态表示复杂结构的配合几何形状偏离其典型布置，从而对其功能产生了改善。已经观察到焓态原理适用于铜电子转移蛋白，它导致电子转移过程的重组能降低。因此，它对于许多生化过程至关重要，但是对于光活性复合物的重要性尚待探索。在这里，我们研究了具有特殊设计的约束配体几何形状的铜络合物，该络合物的金属-配体电荷转移态寿命非常短。此处使用的胍基-喹啉配体作用于双（螯合）铜（I）中心，在光激发后仅允许很小的结构变化，从而导致非常快的结构动力学。数据是采用多方法方法收集的，该方法具有时间分辨的紫外可见，红外和X射线吸收以及光发射光谱法。通过支持密度泛函计算，我们提供了皮秒至纳秒级时间范围内结构动力学的详细图片。