Magnetic cooling is a highly efficient refrigeration technique with the potential of replacing expensive and rare helium-3 in the field of ultra-low temperature cooling. However, the visualization of a cryogen at an extremely low temperature and in a strong magnetic field is challenging, but it is crucial for the precise positioning and in situ thermal probe measurements in potential practical applications. Here, the activation of a red-emissive Mn(II) ion using 3d/4f chemistry produces a luminescent molecule cooler, [Gd₅Mn₂(L^OMe)₂(OH)₄(Ac)₆(MeOH)₁₀Cl₂]Cl₃·2MeOH (1), with the core of an Mn(II)-anchored heptanuclear [Gd^III₅Mn^II₂] pyramid. The photoluminescence (PL) of the Mn²⁺ emission, with a large Stokes shift (λ_em ∼ 690 nm) from ⁴T₁(⁴G) → ⁶A₁(⁶S), shows not only a sensitive temperature sensing property but also reversible mechanoluminescence (ML). More attractively, these findings reveal a considerable magnetocaloric effect (MCE) coupled with a tunable emission window, opening up new opportunities in the multifunctional applications of PL, ML, and the MCE involving red-light sources, thermometers, and stress imaging. In particular, this provides a novel resolution to design visualized PL coolers.

中文翻译：

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Gd ₅ Mn ₂锥体络合物中的多功能发光磁性低温制冷器†

电磁冷却是一种高效的制冷技术，具有在超低温冷却领域替代昂贵且稀有的He-3的潜力。但是，在极低的温度和强磁场中显示冷冻剂是一项挑战，但是对于潜在的实际应用中的精确定位和原位热探针测量而言，这至关重要。在此，使用3d / 4f化学方法激活红色发射Mn（II）离子产生了发光分子冷却器，[Gd ₅ Mn ₂（L ^OMe）₂（OH）₄（Ac）₆（MeOH）₁₀ Cl ₂ ]。氯₃·2MeOH（1），具有固定在Mn（II）上的七核[Gd ^III ₅ Mn ^II ₂ ]金字塔的核心。的光致发光中的Mn的（PL）²⁺发射，具有大的斯托克斯位移（λ _EM〜690纳米）从⁴ Ť ₁（⁴ G）→ ⁶阿₁（⁶S）不仅显示出敏感的温度感测特性，而且显示出可逆的机械发光（ML）。更有吸引力的是，这些发现揭示了相当大的磁热效应（MCE）和可调的发射窗口，为PL，ML和MCE的多功能应用（包括红光源，温度计和应力成像）开辟了新的机遇。特别是，这为设计可视化PL冷却器提供了一种新颖的解决方案。