Dinuclear manganese(iii) complexes with bioinspired coordination and variable linkers showing weak exchange effects: a synthetic, structural, spectroscopic and computation study

Abstract

High-resolution HFEPR indicates weak exchange interactions between MnIII ions in agreement with DFT calculations.

Permethylated dinuclear Mn(III) coordination nanostructure with stripe‐ordered magnetic domains

“…The N 2 O 4 coordination site is built up by two nitrogen atoms from Schiff base ligand and two oxygen atoms from bridging di‐carboxylate moiety in equatorial plane, while two apical positions are occupied by the phenolato oxygen atoms of L 2− . The axial bond distances in the range between 1.858(3) and 1.871(3) Å are shorter compared with those for Mn‐N and Mn‐O equatorial distances indicating similar axial compression of coordination polyhedra, as it was observed in already reported mono‐ [ 18,20 ] and dinuclear [ 21 ] complexes . Overall molecular dimensions are of 26.96x17x15 Å.…”

“…As expected, this distance is slightly longer than that in the of structures with vinyl spacer (8.736 Å) and phenylene (10.912 Å) but shorter than in the case of bis‐phenylene (15,103 Å). [ 21 ]…”

“…For the recently reported series of analogous Mn(III) compounds, similar positive D values have been found. [ 21 ] It could be also concluded that the magnetic behavior of these compounds is governed exclusively by the crystal field splitting generated by the donor atoms in the first coordination sphere. As reported in, [ 21 ] due to the large distance between Mn(III) … Mn(III) and the aliphatic nature of the bridging carboxylic ligand, the magnetic interaction between Mn … Mn was neglected.…”

“…Originally, our idea was to replace the acetato co‐ligand in this manganese(III) mononuclear complex, [MnL (OAc)], by other anions, such as SCN [ 20 ] or another carboxylate. [ 21 ] In the latter case unsaturated or aromatic dicarboxylic acids, namely, fumaric, benzene‐1,4‐dicarboxylic acid and biphenyl‐4,4′‐dicarboxylic acids were used, thus leading to the LMn (OOCCH=CHCOO)MnL, LMn (OOCC 6 H 4 COO)MnL, and LMn (OOCC 6 H 4 C 6 H 4 COO)MnL dinuclear derivatives, respectively. The results of the studies revealed the existence of magnetic interactions over relatively long distances (up to about 11 Å).…”

A Synergy and Struggle of EPR, Magnetometry and NMR: A Case Study of Magnetic Interaction Parameters in a Six-Coordinate Cobalt(II) Complex

“…While EPR spectroscopy seems to be an obvious complement to paramagnetic NMR, its potential for complexes showing relatively well-resolved NMR spectra is very limited due to the inverse correlation between nuclear and electronic relaxation rates in the fast motion limit. , Thus, NMR is rarely used simultaneously with EPR spectroscopy in X- and Q-bands or at higher microwave frequencies. , However, the information content extractable from EPR can be significantly increased by shifting EPR excitation frequencies to the THz range where inter-Kramer transitions can be excited even for systems with very large magnetic anisotropies (e.g., single molecule magnets, for which NMR is the method of choice ,, ). This method is applicable even for spin states with very large zero-field splitting (ZFS) that are EPR-silent at conventional EPR frequencies .…”