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Updated: Aug 26, 2025
Author Spotlight: Experimental Approaches for the Synthesis of Low-Valent Metal-Organic Frameworks from Multitopic Phosphine Linkers
Published on: May 12, 2023
Structural evolution from preorganized mononuclear triazamacrocyclic metalloligands to polynuclear metallocages and
Bi-Liu Lan1, Ai-Yi Luo1, Bing Shao1
1School of Chemistry and Pharmacy of Guangxi Normal University, State Key Laboratory for Chemistry and Molecular Engineering of Medicinal Resources, Guilin 541004, P. R. China. zhangzhong@mailbox.gxnu.edu.cn.
Abstract:
The reaction of a macrocyclic ligand 1,4,7-triazacyclononane-1,4,7-tripropionic acid (tacntpH3) with Ni(II)/Co(II) sources in the presence or absence of lanthanide cations yielded a series of doubly mononuclear ionic complexes (H3O+)[LnIII(H2O)8][NiII(tacntp)]4 (1-NiLn, Ln = La, Ce, Yb) and a mononuclear Co(III) complex [CoIII(tacntp)]·4H2O (2-Co) incorporating transition metal centers enveloped by both an azamacrocycle ring and pendant carboxylate groups. Either of the two preorganized mononuclear species [MII/III(tacntp)]-/0 was taken as a tripodal 3d metalloligand for the further assembly of modular architectures. Two pentanuclear metallocage-[Ln(NO3)6]3- complexes [NiII5(tacntp)2(H2O)12][LnIII(NO3)6]Cl·2H2O (3-NiLn, Ln = La, Ce), one nonanuclear metallocage [NiII9(tacntp)4(H2O)18](ClO4)6·10H2O (4-Ni), and two types of 2D layered heterometallic 3d-4f coordination networks ((H3O+)[NiII2YbIII(tacntp)2](ClO4)2·3H2O (5-NiYb) and [CoIII2TbIII(tacntp)2(H2O)3](ClO4)·Cl2·5H2O (6-CoLn, Ln = La, Eu, Tb, Dy)) differing largely in their weaving architecture were controllably prepared via the precise regulation of multiple reaction parameters. Furthermore, the time-dependent evolution of metalloligand-derived species was tracked via electrospray ionization-mass spectrometry, to elucidate the modular assembly pathway for the nonanuclear Ni(II) metallocage 4-Ni. Analysis of the structural details and the assembly procedures of the modular architectures revealed that the pH, metalloligand size, and the type of metal bound to the metalloligand considerably influence the structural evolution from mononuclear metalloligands to cage-like and polymeric coordination architectures. Magnetic property studies disclosed that pendant syn-anti carboxylate groups favor a weak ferromagnetic exchange between the adjacent Ni(II) ions within the metallocages of 3-NiLa and 4-Ni but facilitate an antiferromagnetic coupling between the alternating Ni(II) and Yb(III) centers in 5-NiYb.
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