Fe(III) clusters built with tripodal alcohol ligands

Reaction of the tripodal ligand 1,1,1-tris(hydroxymethyl)ethane (H3thme) with a variety of Fe(III) precursors under both ambient and solvothermal conditions has led to the isolation of a number of new complexes ranging in nuclearity from 4 to 16. These include the rhomb or diamond-like clusters [Fe4(thme)2Cl4(O2CR)2(R′OH)2] (1, R = Me, R′ = Et; 2, R = Ph, R′ = Me; 3, R = CMe3, R′ = Me); the related nonanuclear and undecanuclear clusters [Fe9O4(O2CCMe3)13(thme)2] (4) and [NEt4][Fe11O4(O2CPh)10(thme)4(dmhp)2Cl4] (5) (dmhp = 4,6-dimethyl-2-hydroxypyrimidine) and the octametallic and hexadecametallic wheels [Fe8(O2CR)12(thme)4] (6, R = Ph; 7, R = CMe3) and [Fe16(EtO)4(O2CPh)16(Hthme)12](NO3)4 (8). Magnetic studies reveal the presence of dominant antiferromagnetic interactions between the Fe centres in all eight complexes which results in the presence of small spin ground states for complexes 1–4 and 6–8. For 5 however, these stabilise an S = 11/2 spin ground state with an axial zero-field splitting parameter of D = −0.46 cm−1. Single crystal hysteresis loops in magnetisation versus external magnetic field measurements show the temperature and sweep rate dependence indicative of single-molecule magnetism behaviour.

Use of the tripodal ligand H3thme has led to the isolation of a number of new Fe(III) clusters ranging in nuclearity from 4 to 16. Magnetic studies reveal that the [Fe11] complex shown is a single-molecule magnet.Figure optionsDownload as PowerPoint slide