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Updated: Mar 14, 2026
Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
Published on: June 10, 2021
Strong Cooperative Spin Crossover in 2D and 3D FeII-MI,II Hofmann-Like Coordination Polymers Based on
Francisco Javier Valverde-Muñoz1, Maksym Seredyuk1,2, M Carmen Muñoz3
1Institut de Ciència Molecular (ICMol), Departament de Química Inorgànica, Universitat de València , C/Catedrático José Beltrán Martínez, 2, Paterna 46980, Valencia, Spain.
Abstract:
Self-assembling iron(II), 2-fluoropyrazine (Fpz), and [MII(CN)4]2- (MII = Ni, Pd, Pt) or [AuI(CN)2]- building blocks have afforded a new series of two- (2D) and three-dimensional (3D) Hofmann-like spin crossover (SCO) coordination polymers with strong cooperative magnetic, calorimetric, and optical properties. The iron(II) ions, lying on inversion centers, define elongated octahedrons equatorially surrounded by four equivalent centrosymmetric μ4-[MII(CN)4]2- groups. The axial positions are occupied by two terminal Fpz ligands affording significantly corrugated 2D layers {Fe(Fpz)2([MII(CN)4]}. The Pt and Pd derivatives undergo thermal- and light-induced SCO characterized by T1/2 temperatures centered at 155.5 and 116 K and hysteresis loops 22 K wide, while the Ni derivative is high spin at all temperatures, even at pressures of 0.7 GPa. The great stability of the high-spin state in the Ni derivative has tentatively been ascribed to the tight packing of the layers, which contrasts with that of Pt and Pd derivatives in the high- and low-spin states. The synthesis and structure of the 3D frameworks formulated {Fe(Fpz)[Pt(CN)4]}·1/2H2O and {Fe(Fpz)[Au(CN)2]2}, where Fpz acts as bridging ligand, which is also discussed. The former is high spin at all temperatures, while the latter displays very strong cooperative SCO centered at 243 K accompanied by a hysteresis loop 42.5 K wide. The crystal structures and SCO properties are compared with those of related complexes derived from pyrazine, 3-fluoropyridine, and pyridine.
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