Slow Magnetic Relaxation, Antiferromagnetic Ordering, and Metamagnetism in Mn^II(H₂dapsc)‐Fe^III(CN)₆ Chain Complex with Highly Anisotropic Fe‐CN‐Mn Spin Coupling

Abstract

Reactions of [Mn(H2dapsc)Cl2]⋅H2O (dapsc=2,6‐ diacetylpyridine bis(semicarbazone)) with K3[Fe(CN)6] and (PPh4)3[Fe(CN)6] lead to the formation of the chain polymeric complex {[Mn(H2dapsc)][Fe(CN)6][K(H2O)3.5]}n⋅1.5n H2O (1) and the discrete pentanuclear complex {[Mn(H2dapsc)]3[Fe(CN)6]2(H2O)2}⋅4 CH3OH⋅3.4 H2O (2), respectively. In the crystal structure of 1 the high‐spin [MnII(H2dapsc)]2+ cations and low‐spin hexacyanoferrate(III) anions are assembled into alternating heterometallic cyano‐bridged chains. The K+ ions are located between the chains and are coordinated by oxygen atoms of the H2dapsc ligand and water molecules. The magnetic structure of 1 is built from ferrimagnetic chains, which are antiferromagnetically coupled. The complex exhibits metamagnetism and frequency‐dependent ac magnetic susceptibility, indicating single‐chain magnetic behavior with a Mydosh‐parameter φ=0.12 and an effective energy barrier (Ueff/kB) of 36.0 K with τ0=2.34×10−11 s for the spin relaxation. Detailed theoretical analysis showed highly anisotropic intra‐chain spin coupling between [FeIII(CN)6]3− and [MnII(H2dapsc)]2+ units resulting from orbital degeneracy and unquenched orbital momentum of [FeIII(CN)6]3− complexes. The origin of the metamagnetic transition is discussed in terms of strong magnetic anisotropy and weak AF interchain spin coupling.

[MII(H2dapsc)]-[Cr(CN)6] (M = Mn, Co) Chain and Trimer Complexes: Synthesis, Crystal Structure, Non-Covalent Interactions and Magnetic Properties

“…The application of an external constant magnetic field leads to the suppression of interchain AF coupling and causes a metamagnetic transition. Such transitions have been observed in other heterospin as well as homospin compounds with interchain AF ordering [ 52 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 ].…”

“…The main difference between them is another solvent composition and the presence of disorder in the K + site in 7 . The chain complex {[Mn(H 2 dapsc)][Fe(CN) 6 ][K(H 2 O) 3.5 ]} n ·1.5 n H 2 O ( 8 ) [ 52 ] also has similar unit cell parameters but higher symmetry ( P 2 1 / n ) because the pair of K + ions in 8 are bridged by two water molecules related by inversion symmetry instead of water/ethanol in 1 and 2 or water/methanol in 7 .…”

“…The presence of labile ligands in the axial positions of the PBP complexes makes them attractive building blocks for the construction of low-dimensional heteronuclear compounds by replacing these ligands with bridging cyanometallates or the PBP complexes with cyanide apical groups [ 17 , 23 , 24 , 37 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ]. Up to date, tri-, penta-, and decanuclear SMMs and coordination polymeric SCMs have been obtained along the way.…”

“…Earlier, we studied the reactions of [Mn(H 2 dapsc)Cl 2 ]·H 2 O (dapsc=2,6-diacetylpyridine bis(semicarbazone), Scheme 1 ) with K 3 [Mn(CN) 6 ] and K 3 [Fe(CN) 6 ] and obtained the chain polymeric complexes {[Mn(H 2 dapsc)][Mn(CN) 6 ][K(H 2 O) 2.75 (MeOH) 0.5 ]} n ·0.5 n (H 2 O) and {[Mn(H 2 dapsc)][Fe(CN) 6 ][K(H 2 O) 3.5 ]} n ·1.5 n H 2 O, which revealed single-chain magnet (SCM) behavior [ 50 , 52 ].…”

New Cyanido-Bridged Heterometallic 3d-4f 1D Coordination Polymers: Synthesis, Crystal Structures and Magnetic Properties

“…In this paper, we report on a new family of 1D coordination polymers, which are assembled from [LnL] 3+ and [M(CN) 6 ] 3− ions (L = bis-semicarbazone ligand, M = Fe, Co). The pentadentate bis-semicarbazone ligand, L (Scheme 1), was previously used for the synthesis of both 3d-3d/3d-4d cyanido-bridged discrete [34] and polymeric structures [35][36][37][38][39][40][41].…”