Synthesis, Structures, and Magnetic Properties of Three 3D Coordination Polymers Based on M₄O₄ Cubanes (M = Mn^II, Fe^II, Co^II)

Abstract

Three new isostructural coordination polymers, namely, [M 4 (μ 3 -OMe) 4 (nic) 4 ] n [M = Mn II (1), Fe II (2), and Co II (3); Hnic = nicotinic acid], have been solvothermally synthesized and magnetically characterized. Single-crystal X-ray diffraction study reveals that compounds 1-3 are three-dimensional frameworks, which are constructed through {M 4 (μ 3 -OMe) 4 } cubane-like building blocks and bridging nicanions. Variable-temperature magnetic susceptibility measurements [a] State Key 4029indicate that they all show antiferromagnetic behavior with different intracubane coupling constants. Complex 1 exhibits spin-frustration behavior, and was fitted with a two-J model in the temperature range of 2-300 K, which gives J 1 = -0.92 and J 2 = -2.23 cm -1 . Complexes 2 and 3 were fitted with the same model in the temperature range of 30-300 K and 40-300 K to give the exchange coupling constants J 1 = -2.49, J 2 = 4.84 cm -1 and J 1 = -4.18, J 2 = 5.44 cm -1 , respectively.

Surface and Structural Investigation of a MnOx Birnessite‐Type Water Oxidation Catalyst Formed under Photocatalytic Conditions

“…Eur.J.2015, 21,1 4218-14228 www.chemeurj.org bearing MOF,M n 4 (m 3 -OMe) 4 (nic) 4 (Mn 4 -MOF,n ic = nicotinate), to an active MnO x material. [13] Amber crystals of as-synthesized Mn 4 -MOF were obtainedu sing the reported synthesis method (Figures 1a andc )a nd phase purity was confirmed by PXRD ( Figure 2a). The as-made crystals wereg round and added to av isible-light driven water oxidation assay containing [Ru(bpy) 3 ] 2 + photosensitizer and Na 2 S 2 O 8 sacrificial oxidant in pH 7N aHCO 3 buffer.O 2 evolution was monitored using aC lark-typee lectrode and four white LEDs as the light source (see Figure S1 in the Supporting Information for luminescence profile).…”

Magnetic properties of coordination clusters with {Mn4} and {Co4} antiferromagnetic cores

“…Many M 4 O 4 cubane complexes are reported in the literature, for M = Co and Mn. However, their magnetic properties have been investigated only in four cases 22–25 showing a switching or an enhancement of the magnetic coupling by changing the inner core. In [M 4 (dpd-H) 4 (OAc) 3 (OH 2 ) 1 ] + and [M 4 (dpd-H) 4 (OAc) 2 {N(CN) 2 } 2 ] (dpd-H 2 = di-2-pyridylketone in gem-diol form), the overall magnetic coupling shifts from antiferromagnetic for manganese( ii ) centers to ferromagnetic for cobalt( ii ).…”

“…22,23 In [M 4 (cit) 4 ] 8− (cit = citrate) and [M 4 (nic) 4 (OMe) 4 ] (nic = nicotinate) the coupling is antiferromagnetic for both ions, but the coupling is larger for manganese in the former case 24 and for cobalt in the latter. 25 Additionally, while Mn II centers are adequately described by the spin magnetic moment (spin-only model), Co II centers in octahedral or pseudo-octahedral environments are characterized by significant orbital moments, leading to spin–orbit coupling (SOC) effects that are expected to significantly affect more complex devices.…”