Icosahedron [Cl12]12- Templated Gigantic Gd158Co38 Nanocluster with the Largest Ln158 Core for Magnetic Cooling

The synthesis of large nano-sized cluster-molecules is a goal that synthesists and structural scientists have been pursuing, as well as a huge challenge. Herein, the largest 3d-4f metal clusters Cl 12 @Gd 158 Co 38 and Br 12 @Gd 158 Co 38 until now are obtained through the “multi-anions-template” strategy, with a protein-sized metal frame (ca. 4.3 × 3.6 × 3.5 nm 3 ). Different from the mixed distribution of 3d and 4f metals and the hollow structure in the previous giant 3d-4f clusters, for the dense core-shell structure Cl 12 @Gd 158 Co 38 and Br 12 @Gd 158 Co 38 , the Ln 158 core with the highest Ln nuclearity number is induced by icosahedra-shaped templates [Cl 12 ] 12- or [Br 12 ] 12- , while 3d metals (Co) are distributed on its periphery. Their appearances point out a new structure type of non-open giant Ln-based clusters (metal number > 100) and provide an ideal model for studying the multi-level assembly of complex macromolecules. Additionally, Cl 12 @Gd 158 Co 38 shows the largest magnetic entropy change (- ∆ S mmax = 46.95 J kg -1 K -1 under 2.0 K and ΔH = 7 T) among reported high-nuclearity 3d-4f clusters.

Ongoing progress in synthetic strategy (such as anion template, mixed-ligand, building blocks strategy, etc. [21][22][23][24][25][26] ) has enabled the preparation of giant Ln(4f)-exclusive clusters (such as {Ln 104 } 27  illustrated that the exploration of giant 4f-containing clusters is almost the tip of the iceberg, mainly due to various and complicated coordination modes of lanthanide ions, huge uncertainty in synthesis 36 . Compared to 4f-exclusive clusters, it proves that 3d-4f clusters seem to have better synthetic controllability and may have both the advantages of different metals and potential synergistic effects. On the basis of the mentioned above synthetic methods, Kong, Zheng, and Xu et al. fabricated a series of high-nuclearity 3d-4f clusters [21][22][23][24][25][26] . Unfortunately, 3d-4f compounds with more than 100 metal ions were only realized in the Ni-Ln system and featured the similar metal arrangement and open hollow structure types, which were frequently based on the multi-dentate ligand iminodiacetic acid (H 2 IDA) 24,37 . Recently, Zheng's group constructed a wheel {Gd 102 Ni 36 } high-nuclearity cluster without H 2 IDA ligand, through utilizing SO 4 2− -templates and Ni-complexes as protected groups located at the outer vertices of the cluster 30 . The emergence of this cluster suggests that giant Ni-Ln nano-clusters can also perform the wheel structure, which seems to echo the wheel-shaped {Gd 140 } 28 . Attempting at assembly 3d and 4f ions into giant clusters featured novel and charming con gurations differing from the above two kinds of forms, is promising and challenging.
Relative to the extensive research on the synthesis and properties of Ni-Ln, other high-nuclearity 3d-Ln clusters are less studied, owing to the di culty of synthesis 38-39 . Co ions with the high spin ground state and excellent catalysis have been widely studied [40][41][42][43][44]

Results
Structure analysis. Single-crystal X-ray diffraction (SCXRD) demonstrates that the structure of Cl 12 @Gd 158 Co 38 is similatr to Br 12 @Gd 158 Co 38 , here only Cl 12 @Gd 158 Co 38 as example to be discussed in detail. Cl 12 @Gd 158 Co 38 crystallizes in the trigonal crystal system, R-3 space group. The cationic core of Cl 12 @Gd 158 Co 38 constitutes of six Cl 12 @Gd 27 Co 7 (CO 3 ) 15 (OAc) 4 (µ 3 -OH) 40  It is worth noting that a large series of CO 3 2− anions as important templates and linkers among metal ions, deriving from the decomposition of organic ligands, exhibit a rich variety of coordination modes ( Fig. S3), re ecting the complexity of the nanocluster structure, and the adaptability of the anion templates. Meanwhile, the main ligand MIDA 2− also shows unusual and diverse coordination modes (Fig.  S4). For example, high chemical a nity of N atom from organic ligands tends to coordinate with 3d ions 38 , but N atoms in this work are also linked with 4f ions.

Methods
Material and Instrumentation. All materials were of merchant origin and were used rsthand. The Perkin-Elmer 2400 elemental analyzer was used to perform Elemental analyses (EA; C, H and N). Under room temperature enviromrnt, powder X-ray diffraction (PXRD) was documented (collected in the range of 3 − 50°.) on a Bruker D8X diffractometer furnished with monochromatized Cu-K α under λ = 1.5418 Å radiation. Infrared spectra (IR) was recorded (from 4000 to 400 cm − 1 ) by pressed KBr pellets with a Nicolet Impact 410 FTIR spectrometer. TGA (thermogravimetric analysis and differential scanning calorimeter measurement) was recorded among 25 to 900°C in a owing nitrogen environment with a heating degree of 10 K·min − 1 via the NETZSCH STA409 thermogravimetric analyzer. The ZSX Primus II was used to analuze the X-ray uorescence (XRF) spectrometry. The Hitachi S-4800 scanning electron microscope was carried out to analyze the SEM images and energy dispersive spectrometer (EDS), with a stimulative voltage of 20 kV. The direct current magnetic data (temperature of 1.8-300 K), and the magnetisation isothermal measurements ( eld with 0-7 T) were obtained on MPMS-XL7 SQUID magnetometer. Experimental susceptibilities were revisional for the diamagnetism estimated Pascal's tables and for products holder by antecedently calibration. The KRATOS AXIS SUPRA™ spectrometer, out tted with a monochromatized Al Kα source, wsa used to record X-ray photoelectron spectroscopy (XPS). The charge effect was trued via using the binding energy of C1s (284.8 eV) to weaken the sample charging in uence. Supplementary information is available in the online version of the paper. Reprints and permissions information is available online at www.nature.com/reprints. Correspondence and requests for materials should be addressed to Y. Xu.  pale blue (Gd from Gd48Co32), turquoise (Gd), lime (Gd12), orange, Co. Atomic color codes: green, Gd; orange, Co; bright green, Cl.

Supplementary Files
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