Capability to control macroscopic molecular properties with external stimuli offers the possibility to exploit molecules as switching devices of various types. However, application of such molecular‐level switching has often been limited by its speed and thus efficiency. Herein, we demonstrate ultrafast, photoinduced polarization switching in the crystal of a [CrCo] dinuclear complex by ultrafast pump–probe spectroscopy in the visible and mid‐infrared regions. The photoinduced polarization switching was found to have a time constant of 280 fs, which makes the [CrCo] complex crystal the fastest polarization‐switching material realized using the metastable state. Moreover, the pump–probe data in the visible region reveal the pronounced appearance of coherent nuclear wavepacket motion with a frequency as low as 22 cm⁻¹, which we attribute to a lattice vibrational mode. The pronounced non‐Condon effect for its resonance Raman enhancement implies that this mode couples the relevant electronic states, thereby facilitating the ultrafast polarization switching.

中文翻译：

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[CrCo]双核络合物晶体中的飞秒偏振转换。

通过外部刺激来控制宏观分子特性的能力提供了利用分子作为各种类型的开关装置的可能性。但是，这种分子级转换的应用通常受到其速度和效率的限制。在本文中，我们通过可见光和中红外区的超快泵浦-探针光谱学证明了[CrCo]双核络合物晶体中的超快光诱导极化转换。发现光致偏振转换的时间常数为280 fs，这使得[CrCo]复晶体成为使用亚稳态实现的最快的偏振转换材料。此外，可见光区域的泵浦探测数据还揭示了相干核波包运动的明显表现，其频率低至22 cm ^-1，我们将其归因于晶格振动模式。其共振拉曼增强的明显的非康登效应意味着该模式耦合了相关的电子状态，从而促进了超快的极化切换。