Ligand-to-Metal Ratio Controlled Assembly of Tetra- and Hexanuclear Clusters Towards Single-Molecule Magnets

Abstract

A simple template-mediated route, starting from triethalolamine 1, sodium hydride or caesium carbonate, and iron(III) chloride led to the six- and eight-membered iron coronates [Na c [Fe6[N(CH2CH2O)3]6]]+ (2) and [Cs c (Fe8[N(CH2CH2O)3]8]]+ (3). In the reaction of N-methyldiethanolamine 4 (H2L1) or N-(2,5-dimethylbenzyl)iminodiethanol 6 (H2L2) with calcium hydride followed by addition of a solution of iron(III) chloride, the neutral unoccupied coronands [Fe6Cl6(L1)6] (5) and [Fe6Cl6(L2)6] (7) were formed. Subsequent exchange of the chloride ions of 7 by bromide or thiocyanate ions afforded the ferric wheels [Fe6Br6(L2)6] (8) or [Fe6(NCS)6(L2)6] (9), respectively. Titration experiments of solutions of dianion (L1)2- with iron(III) chloride in THF revealed interesting mechanistic details about the self-assembling process leading to 5. At an iron/ligand ratio of 1:1.5 star-shaped tetranuclear [Fe[Fe(L1)2]3] (11) was isolated. However, at an iron/ligand ratio of 1:2, complex 11 was transformed into the ferric wheel 5. It was shown, that the interconversion of 5 and 11 is reversible. Based on the mechanistic studies, a procedure was developed which works for both the synthesis of homonuclear 11 and the star-shaped heteronuclear clusters [Cr[Fe(L1)2]3] (12) and [Al[Fe(L1)2]3] (13). The structures of all new compounds were determined unequivocally by single-crystal X-ray analyses.

Self‐Assembly and Crystal Structure of a Novel Octadecametallic Square Box Composed of 52 Single Components

“…[3] Compared with the complexes generated with triethanolamine, in 1 the lacking m 1 -O ethanolate ligands are replaced by extra chloride donors to achieve charge compensation and octahedral coordination at iron (Scheme 1).…”

Molecular magnetism

“…Iron-6 rings for instance can host alkali ions such as lithium or sodium which allows to modify the parameters of the spin Hamiltonian within some range [16,35]. Another realization of rings is possible using chromium ions as paramagnetic centers.…”

The roles of the allyloxy groups on terephthalate for the formation of three coordination networks

“…This is because the selfassembly process of a MOF is very sensitive to various factors, such as the ligand type, the chemical and geometrical preference of the metal node, and the synthetic conditions, etc. [9][10][11][12][13][14].Using designed ligand with specific configuration and functionality we can comprehensively understand the driving forces of organic ligand and metal node in the course of self-assembly of a MOF with fantastic topology and special functionality [15]. 1,4-benzenedicarboxylic acid (H 2 BDC) with various coordination modes has been widely employed for the synthesis of diverse porous MOFs [1,16], Because of their interesting structural motifs, many H 2 BDC derivatives decorated by amino, hydroxyl and ester groups have been used for the construction of various functional MOFs [17,18].…”

“…This is because the selfassembly process of a MOF is very sensitive to various factors, such as the ligand type, the chemical and geometrical preference of the metal node, and the synthetic conditions, etc. [9][10][11][12][13][14].…”