The Structural and Magnetic Properties of FeII and CoII Complexes with 2-(furan-2-yl)-5-pyridin-2-yl-1,3,4-oxadiazole

Abstract

Two novel coordination compounds containing heterocyclic bidentate N,N-donor ligand 2-(furan-2-yl)-5-(pyridin-2-yl)-1,3,4-oxadiazole (fpo) were synthesized. A general formula for compounds originating from perchlorates of iron, cobalt, and fpo can be written as: [M(fpo)2(H2O)2](ClO4)2 (M = Fe(II) for (1) Co(II) for (2)). The characterization of compounds was performed by general physico-chemical methods—elemental analysis (EA), Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) in case of organics, and single crystal X-ray diffraction (sXRD). Moreover, magneto-chemical properties were studied employing measurements in static field (DC) for 1 and X-band EPR (Electron paramagnetic resonance), direct current (DC), and alternating current (AC) magnetic measurements in case of 2. The analysis of DC magnetic properties revealed a high spin arrangement in 1, significant rhombicity for both complexes, and large magnetic anisotropy in 2 (D = −21.2 cm−1). Moreover, 2 showed field-induced slow relaxation of the magnetization (Ueff = 65.3 K). EPR spectroscopy and ab initio calculations (CASSCF/NEVPT2) confirmed the presence of easy axis anisotropy and the importance of the second coordination sphere.

Cis and Trans Isomers of Fe(II) and Co(II) Complexes with Oxadiazole Derivatives ‐ Structural and Magnetic Properties

“…All ligands were prepared similarly as in our previous work [7] . The four‐step reaction (Scheme 1) begins with the esterification of picolinic acid (PA) in methanol with the addition of sulphuric acid.…”

“…[6] Recently, structural analogues of abpt, namely 2,5-disubstituted-1,3,4-oxadiazoles have drawn our attention, and two novel complexes [M(fpo) 2 (H 2 O) 2 ](ClO 4 ) 2 (M = Fe(II), Co(II)) with unsymmetrical ligand were reported. [7] Magnetic data revealed significant magnetic anisotropy in [Co(fpo) 2 (H 2 O) 2 ](ClO 4 ) 2 and CASSCF/NEVPT2 calculations revealed the influence of the second coordination sphere on parameters of ZFS (E and D). Fe(II) complex remained in the high spin arrangement and Co(II) exhibited field-induced slow relaxation of the magnetization with effective energy barrier U eff = 65.3 K. While in other works Co(II) compounds were examined, many mainly with respect to biological activities and only occasionally for DC magnetic properties, though without accompanying AC measurements.…”

“…All ligands were prepared similarly as in our previous work. [7] The four-step reaction (Scheme 1) begins with the esterification of picolinic acid (PA) in methanol with the addition of sulphuric acid. Methyl picolinate (I) thus obtained is converted into picolinic acid hydrazide (II) in hydrazine hydrate solution in methanol.…”

“…A simple way to influence these parameters comes from the convenient alternation of various co‐ligands, e. g. in last years, we explored the coordination chemistry of 4‐amino‐3,5‐bis(2‐pyridyl)‐1,2,4‐triazole (abpt) and exploited it in the preparation of Fe(II) spin crossover compounds [5] and Co(II) single‐molecule magnets [6] . Recently, structural analogues of abpt, namely 2,5‐disubstituted‐1,3,4‐oxadiazoles have drawn our attention, and two novel complexes [M(fpo) 2 (H 2 O) 2 ](ClO 4 ) 2 (M=Fe(II), Co(II)) with unsymmetrical ligand were reported [7] . Magnetic data revealed significant magnetic anisotropy in [Co(fpo) 2 (H 2 O) 2 ](ClO 4 ) 2 and CASSCF/NEVPT2 calculations revealed the influence of the second coordination sphere on parameters of ZFS ( E and D ).…”

Impact of the central atom and halido ligand on the structure, antiproliferative activity and selectivity of half-sandwich Ru(ii) and Ir(iii) complexes with a 1,3,4-thiadiazole-based ligand

“…The thiadiazole-based compound L1 (2-(furan-2-yl)-5-(pyridin-2-yl)-1,3,4-thiadiazole) used in this work was prepared by a two-step synthetic procedure (Scheme 1), which was inspired by previously published protocols. 39,40…”