Synthesis,Structures And Properties Of High-nuclear Cuprofullerenes

High-nuclear complexes have been widely reported for their exquisite structure and excellent properties.Solvothermal synthesis,as a major method for synthesis of coordination complexes,has been also applied to synthesize high-nuclear complexes.However,most of high-nuclear complexes are reported as 0-D clusters,and coordination polymers based on high-nuclear metal clusters as SBUs are rarely reported.Compared with these 0-D cluster complexes,coordination polymers present much higher stability usually.The coordination polymers with metal clusters as SBUs are usually constructed by the coordination of linear or polydentate ligands.As a spherical ligand with 30 C=C bonds,C₆₀ can coordinate with up to 30 metals to form C₆₀@M₃₀ icosidodecahedron,so it can act as a natural template to induce formation of high-nuclear metal cluster complexes.However,the highest nuclearity in the reported Ex MFs（exohedral metallofullerenes）was no more than 6 due to with the multi-coordinated sites of open-shell metals with,high steric-resistance of phosphorous auxiliary ligands and the traditional synthesis conditions,which is seriously mismatched with spherical C₆₀ with 30 coordinated sites.Therefore,it is crucial to search for a new synthesis method.In recent years,our group reported the highest nuclearity C₆₀@Cu₂₄ by utilizing closed-shell Cu（I）with low coordinated sites and fluorocarboxylic acid under solvothermal conditions,which indicated this method is valid for constructing high-nuclear Ex MFs.In this work,a series of complexes 1-10 based on high-nuclear cuprofullerene complexes,including regioisomers,coordination polymers,and interpenetrated/non-interpenetrated MOFs,were obtained under solvothermal conditions,using trifluoroacetic（HL_F）and thiodiglycolate acid（H₂L_S）/4-methylbenzoic acid(HL_mb)/dialdehydes/trialdehydes as the primary and secondary auxiliary ligands.Their regioisomers,topological network,interpenetration/non-interpenetration and luminescence property were discussed,which broadened the field of Ex MFs and laid a foundation for constructing novel high-nuclear Ex MFs.According to rhombicuboctahedron C₆₀@Cu₂₄ constructing by glutaric acid,using HL_F as primary auxiliary ligand,complexes 1-4 with C₆₀@Cu^I₁₈@Cu₆^I,C₆₀@Cu^I₂₄@Cu₈^I triplet core-shell structure were prepared assisted by extra S of H₂L_S similar with glutaric acid and changing the ratio of auxiliary ligands.The inner Cu（I）in complexes 1 and 2 form six unshared vertex canopying Cu₃ units on the C₆₀ equator.Complexes 3 and 4 form C₆₀@M₂₄/C₆₀@M₆ style regioisomers with C₆₀@Cu^I₂₄ reported by our group.Complexes 2 and 4 are 3-D coordination polymers constructed by Cu-Cu and S-Cu.Complex 5 was obtained by utilizing HL_mb.On the basic of complex 5 and C₆₀@Cu₂₄reported by our group,three complexes 6-8 with interpenetrated pcu network were prepared with linear benzaldehyde ligands replacing O bridging Cu（I）.Assisted by prolonging carbon chain of linkers,the numbers of Cu（I）also gradually increased.Complexes 6-8 are C₆₀-MOFs with C₆₀@Cu₁₂,C₆₀@Cu₁₈,C₆₀@Cu₂₄ core-shell structure as SBUs and linear aldehyde ligands as linkers,respectively.The different length of carbon chains also leads to the different numbers and stacking modes of linkers in each framework.In terms of luminescence property,with the increase of the Cu（I）nuclearity,the emission intensity was enhanced in the visible region,but the intensity in the NIR region is less affected.Two trialdehyde ligands were introduced to stop the interpenetration in complex 6-8 bringing from the linear dialdehyde linkers.The results showed that complexes 9 and 10 based on C₆₀@Cu₁₈and C₆₀@Cu₁₂ core-shell structure without interpenetrations were constructed,respectively.Moreover,complex 10 showed better thermal stability than complexes 6-9.The luminescence of complexes 9-10 were analogous to complex 6-8.In short,under solvothermal conditions,we not only realized a series of high-nuclear cuprofullerenes and even their MOFs structures,but also regulated their core-shell structure,regioisomerization,coordination polymerization,interpenetration,and luminescence.This work provided valuable research ideas for the field of Ex MFs,and a new method for preparing novel MOFs.C₆₀-MOFs are also expected to become a novel material.