Intermolecular interactions enhanced second harmony generation of iridium complex for bio-labeling

Abstract

Second harmonic generation (SHG) microscopy avoids the inherent drawbacks of traditional fluorescent probes and brings a major breakthrough in live cell imaging. However, not all ordered non-centrosymmetric matter has the ability to generate SHG signals due to the different modes of intermolecular interaction. Here, we designed a non-centrosymmetric metal iridium complex (Ir-SHG) and obtained single crystals with two different intermolecular interaction modes in red (Ir-R) and yellow (Ir-Y), in which Ir-Y was shown to acquire a significant SHG effect. Interestingly, the SHG imaging of Ir-SHG exhibits high imaging signal-to-ratio (SNR) and brightness, as well as can be used in combination with a large number of fluorophores without signal cross-talk. We believe this work brings new insights into the development of SHG materials for multimodal nonlinear optical imaging.