Magnetic behaviour in metal-organic frameworks—Some recent examples

Abstract

The article describes the synthesis, structure and magnetic investigations of a series of metal-organic framework compounds formed with Mn +2 and Ni +2 ions. The structures, determined using the single crystal X-ray diffraction, indicated that the structures possess two-and three-dimensional structures with magnetically active dimers, tetramers, chains, two-dimensional layers connected by polycarboxylic acids. These compounds provide good examples for the investigations of magnetic behaviour. Magnetic studies have been carried out using SQUID magnetometer in the range of 2-300 K and the behaviour indicates a predominant anti-ferromagnetic interactions, which appears to differ based on the M-O-C-O-M and/or the M-O-M (M = metal ions) linkages. Thus, compounds with carboxylate (Mn-O-C-O-Mn) connected ones, [C 3 N 2 H 5 ][Mn(H 2 O){C 6 H 3 (COO) 3 }], I, [{Mn(H 2 O) 3 }{C 12 H 8 O(COO) 2 }]⋅H 2 O, II, [{Mn(H 2 O)}{C 12 H 8 O(COO) 2 }], III, show simple anti-ferromagnetic behaviour. The compounds with Mn-O/OH-Mn connected dimer and tetramer units in [NaMn{C 6 H 3 (COO) 3 }], IV, [Mn 2 (μ 3 -OH) (H 2 O) 2 {C 6 H 3 (COO) 3 }]⋅2H 2 O, V, show canted-antiferromagnetic and anti-ferromagnetic behaviour, respectively. The presence of infinite one-dimensional -Ni-OH-Ni-chains in the compound, [Ni 2 (H 2 O)(μ 3 -OH) 2 (C 8 H 5 NO 4 ], VI, gives rise to ferromagnet-like behaviour at low temperatures. The compounds, [Mn 3 {C 6 H 3 (COO) 3 } 2 ], VII and [{Mn(OH)} 2 {C 12 H 8 O(COO) 2 }], VIII, have two-dimensional infinite -Mn-O/OH-Mn-layers with triangular magnetic lattices, which resemble the Kagome and brucite-like layer. The magnetic studies indicated canted-antiferromagnetic behaviour in both the cases. Variable temperature EPR and theoretical magnetic modelling studies have been carried out on selected compounds to probe the nature of the magnetic species and their interactions with them.

Two CdII/CoII‐Imidazolate Coordination Polymers: Syntheses, Crystal Structures, Stabilities, and Luminescent/Magnetic Properties

“…Therefore, 2 with an experimental value of μ eff = 4.8 μ B exhibits one independent high spin Co II center. The higher experimental value of μ eff /μ B is consistent with the literature and caused by very high spin–orbit couplings of 3d metal atoms 34–36…”

Tuning the magnetic properties of transition metal MOFs by metal–oxygen condensation control: the relation between synthesis temperature, SBU nuclearity and carboxylate geometry

“…Such a value agrees with that expected for a compound containing non-interacting sixcoordinated Ni 2+ ions. 34 The onset of a maximum at 2.5 K in x9 and the increase of the x99 at 2.5 K, see Fig. 12, indicates the existence of long-range ferromagnetic interactions with a critical temperature T C of 2.5 K. The hysteresis loop obtained at 2 K confirms such magnetic behaviour, see inset of Fig.…”

Synthesis, Structure and Luminescence Properties of a Three‐Dimensional Heterobimetallic Chiral Metal–Organic Framework Based on Sodium(I), Lead(II) and (S)‐5,5′‐Bis(4‐carboxyphenyl)‐2,2′‐bis(diphenylphosphinoyl)‐1,1′‐binaphthyl as Linker

“…Heterobimetallic MOFs and coordination polymers based on Na + and transition‐metal ions such as (Na–Cd),16 (Na–Zn),17 (Na–Y),18 (Na 4 Cu 6 Mn 4 ),19 (Na–Co),20 (Na–Cu),21 (Na–Ag),22 (Fe–Ni–Na and the other alkali metals Li, K, Rb and Cs),23 (Na–Mn),24 and (Na–Pd 3 ),25 with Na + and lanthanoid ions (Ln–Na)26 and even with main‐group metals, for example, (Na–Bi)27 and (Na–Pb),28 have been reported and showed interesting structural and functional features.…”