Spectrally distinct fluorophores are desired for multiplexed bioimaging. In particular, monitoring biological processes in living mammals needs fluorophores that operate in the ‘tissue-transparent’ near-infrared (NIR) window, that is, between 700 and 1,700 nm. Here we report a fluorophore system based on molecular erbium(III)–bacteriochlorin complexes with large Stokes shift (>750 nm) and narrowband NIR-to-NIR downconversion spectra (full-width at half-maximum ≤ 32 nm). We have found that the fast (2 × 10⁹ s^–¹) and near-unity energy transfer from bacteriochlorin triplets to the erbium(III) ⁴I_13/2 level overcomes the notorious vibrational overtones quenching, resulting in bright and long-lived (1.73 μs) 1,530 nm luminescence in water. We demonstrate the excitation/emission-multiplexed capability of the complexes in the visualization of dynamic circulatory and metabolic processes in living mice, and through skull tracking of cancer cell metastases in mouse brain. This hybrid probe system facilitates robust multiplexed NIR imaging with high contrast and spatial resolution for applications ranging from fluorescence-guided surgery, diagnostics and intravital microscopy.

多重生物成像需要光谱不同的荧光团。特别是，监测活体哺乳动物的生物过程需要在“组织透明”近红外 (NIR) 窗口（即 700 至 1,700 nm 之间）运行的荧光团。在这里，我们报告了一种基于分子铒（III）-菌绿素复合物的荧光团系统，具有大斯托克斯位移（％3E750 nm）和窄带近红外到近红外下转换光谱（半峰全宽≤32 nm）。我们发现，从菌绿素三重态到铒(III) ⁴ I _13/2能级的快速（2 × 10 ⁹ s ^– 1）且接近统一的能量转移克服了臭名昭著的振动泛音猝灭，从而产生明亮且长寿命的光(1.73 μs) 1,530 nm 水中发光。我们展示了复合物在活体小鼠动态循环和代谢过程可视化中的激发/发射复用能力，以及通过小鼠大脑中癌细胞转移的头骨追踪。这种混合探针系统可实现具有高对比度和空间分辨率的强大的多重近红外成像，适用于荧光引导手术、诊断和活体显微镜等应用。