Singlet oxygen (1O2) is an important reactive oxygen species in the lowest excited state, playing a crucial role in various fields such as chemistry, biochemistry, and environmental chemistry [[1], [2], [3], [4], [5], [6]]. Photodynamic therapy (PDT) is a new tumor treatment technique developed in the late 1970s [7], and 1O2 plays a key role in the PDT technique of cancers diseases because it is produced by the activation of photosensitizers and can destroy malignant cells [[8], [9], [10], [11], [12]]. However, due to the short lifetime of 1O2 itself, its highly sensitive detection in living cells and tissues currently remains a challenge [[13], [14], [15]]. The fluorescence method, combined with confocal microscopic imaging technology is the only “visible and real-time quantitative detection method” for 1O2 in living cells and tissues [[16], [17], [18]]. Wang et al. [19], Lamb et al. [20], Nam and You et al. [21] have developed a series of organic fluorescent probes that can detect 1O2.

The anthryl group has been shown to be one of the most suitable and sensitive group for the recognition of 1O2 [22,23]. Majima et al. designed the anthryl modified organic fluorescent probe to detect 1O2 [[24], [25], [26]]. When the probe interacted with 1O2 to produce anthracene peroxides, the fluorescence intensity surged by 17 times. Compared to other reactive oxygen species (ROS), this probe exhibits good selectivity for 1O2 and has been used for imaging for 1O2 generated during PDT. The lanthanide ions are recognized for their remarkable properties, including a significant Stokes shift, extended lifetimes, and narrow-band emission, so the 1O2 luminescent probes based on Eu(III) complex have high selectivity, high sensitivity, long lifetime and good biocompatibility, making them less susceptible to interference from background fluorescence, and can be used in bio-related research and biomedical fields. Yuan et al. successfully constructed two luminescence probes for Eu(III) and Tb(III), also based on anthryl peroxidation for the detection of 1O2 [[27], [28], [29], [30]].

In recent years, CPL technologies have attracted great attention in polarized light detection due to their high specificity, and the development of CPL probes has been dominated by high-emitting lanthanide(III) complexes and are widely used in sensor technology due to their long lifetime. Vivid photoluminescence can be distinguished with short-lived autofluorescence [[31], [32], [33]]. The CPL probe mechanism is usually used to adjust the change in the glum value. There are many reports on the detection of 1O2 based on chemical reactions [34], fluorescence and luminescence, but there are currently no reports on the detection of 1O2 using CPL. The background interference of ordinary fluorescent probes is stronger and the signal-to-noise ratio of the images is higher [35]. The CPL probe only collects the circularly polarized light triggered by the target, other non-polarized light is automatically filtered out, greatly improving the spatial resolution and selectivity. In addition, CPL probes also can overcome the intrinsic fluorescence and light scattering of competing biological substances [36]. Therefore, the development of probes based on CPL confocal microscopy imaging technology will provide an effective method for determining 1O2 with high selectivity and sensitivity [37].

On the basis of above points, herein, we present the design of a pair chiral β-diketones ligands (LR/S) that features a stable configurational chirality, derived from R/S-binaphthol. This ligand incorporates two symmetric anthracene functional groups linked by a chiral binaphthol axis. The complex (NEt4)2[Eu2(LS)4] is weakly luminescent due to the strong quenching of anthryl groups to the luminescence of β-diketonate−Eu(III) moiety, but can specifically react with 1O2 to afford the endoperoxide (NEt4)2[Eu2(EP-LS)4], to enable the luminescence of the Eu(III) complex to be restored. Therefore, the complex exhibits a rapidly turn-on luminescence response to 1O2 through the [4 + 2] cycloaddition reaction. At the same time, the glum of (NEt4)2[Eu2(LS)4] also increased during the luminescence imaging.