Three Novel Thiazole-Arm Containing 1,3,4-Oxadiazole-Based [HS-HS] Fe(II) Dinuclear Complexes

Abstract

Novel synthesis of 2,5-bis[(1,3-thiazol-2-ylmethyl)amino]methyl-1,3,4-oxadiazole (LThiazole) is reported, along with the preparation of three new dinuclear Fe(II) complexes with different counterions [FeII2(μ2-LThiazole)2](BF4)4·2CH3CN (1), [FeII2(μ2-LThiazole)2](ClO4)4 (2) and [FeII2(μ2-LThiazole)2](CF3SO3)4·2CH3CN (3). The obtained complexes were characterized by single-crystal X-ray crystallography, SQUID magnetometry and IR spectroscopy. The structure of the crystalline material was determined at 120 K for 1 and 3. The magnetic properties of all three complexes (1–3) were measured between 2–300 K and clearly show that all three complexes stay in the high-spin state over the measured temperature range.

Synergetic spin singlet–quintet switching and luminescence in mononuclear Fe(ii) 1,3,4-oxadiazole tetradentate chelates with NCBH3 co-ligand

“…Ring-closing was achieved by the use of the three-component system triphenylphosphine, carbon tetrachloride and triethylamine to yield 2-(chloromethyl)-5-(naphthalen-2-yl)-1,3,4-oxadiazole (IV) in low yields. 33,46 In the fifth and final step, L Tetra-ODA was successfully isolated after a nucleophilic reaction of IV and bis( pyridine-2ylmethyl) amine (V) in moderate yields, using potassium carbonate as the base. The obtained L Tetra-ODA was fully characterized using a range of techniques, including 1 H-NMR, 13 C-NMR, 2D-NMR, IR, mass spectrometry and elemental analysis (Fig.…”

“…33 Attempts made to further tune the ligand field by choice of a five-membered thiazole ring in comparison with the six-membered pyridine ring were not successful, and the compounds stayed in HS over the measured temperature range irrespective of the three different counterions used. 46 Other attempts to synthesise mononuclear Fe(II) SCO complexes described in the literature have, to the best of our knowledge, also not been successful so far. Klingele, Letard and co-workers in 2013 reported a mononuclear Fe(II) complex based on a bis-bidentate oxadiazole ligand and NCS co-ligand, and the complex stayed in HS over the measured temperature window.…”

A combined theoretical and experimental approach to determine the right choice of co-ligand to impart spin crossover in Fe(ii) complexes based on 1,3,4-oxadiazole ligands

“…25,28,30 The role of the lattice solvent in spin crossover materials influences various aspects of the SCO behaviour including cooperative effects. 24,25,28,30 Interactions between the solvent and the spin crossover complexes may facilitate or hinder the structural rearrangements required for spin state switching. Understanding and controlling these interactions are essential for the design and optimization of spin crossover materials.…”

“…24 Given the extended pi system of the naphthalic substituent, which is known to be an antenna component in photoactive systems, the luminescence property of the complex, along with the synergistic effects of luminescence and spin crossover behaviour was investigated for this compound. 24 In the present manuscript, the tetradentate binding pocket of the previously reported ligand is kept constant, but the naphthalene moiety of the previously reported analogue is changed to pyridine and phenyl to investigate in more detail the effect of it on the SCO behaviour. The incorporation of pyridine in the ligand backbone also facilitated the synthesis of a new dinuclear Fe(II) complex based on 1,3,4-oxadiazole.…”

Effect of Methoxy Ligand-Substituent and NCE Coligands in Tuning T1/2 of Coordinatively Elastic Fe(II) Spin Crossover Complexes

“…One way of tuning the spin switching temperatures ( T 1/2 ) in metal complexes is through the design of the ligands. Dinuclear Fe­(II) complexes based on 1,3,4-thiadiazole and analogue oxadiazole ligands are studied for SCO in the solid state by some of us − and also by others in the literature . The SCO phenomena is tuned in these systems by changing the ligand field strength by changing the ring sizes for the coordinating side arms from a 6-membered pyridine ring to different 5-membered rings with different heteroatoms (imidazole and thiazole).…”