Responsive Four‐Coordinate Iron(II) Nodes in FePd(CN)₄

Abstract

Metal node design is crucial for obtaining structurally diverse coordination polymers (CPs) and metal-organic frameworks with desirable properties;h owever,F e II ions are exclusively six-coordinated. Herein, we present ac yanidebridged three-dimensional (3D) CP,F ePd(CN) 4 ,bearing fourcoordinate Fe II ions,which is synthesized by thermal treatment of at wo-dimensional (2D) six-coordinate Fe II CP,F e-(H 2 O) 2 Pd(CN) 4 •4 H 2 O, to remove water molecules.A tomicresolution transmission electron microscopyand powder X-ray and neutron diffraction measurements revealed that the FePd-(CN) 4 structure is composed of atwo-fold interpenetrated PtS topology network, where the Fe II center demonstrates an intermediate geometry between tetrahedral and square-planar coordination. This four-coordinate Fe II center with the distorted geometry can act as athermo-responsive flexible node in the PtS network.

Coordination Geometry Changes in Amorphous Cyanide-Bridged Metal–Organic Frameworks upon Water Adsorption

“…For these three metals, the abrupt water adsorption behavior was attributed to the tetrahedral metal centers in amorphous MNi . Notably, crystalline structures associated with square-planar and tetrahedral centers bridged by cyanide ligands [adopting a network similar to three-dimensional (3D)-sphalerite (PtS) type] have been reported, namely for Fe­[Pd­(CN) 4 ] (FePd) and Zn­[M­(CN) 4 ] (M = Ni, Pd, and Pt) . In particular, one-step water adsorption was also observed for FePd .…”

“…In this case, the adsorption was associated with a reversible single-crystal to single-crystal transformation, from the anhydrous 3D structure with tetrahedral Fe 2+ to 2D layers with octahedral Fe 2+ in Fe­(H 2 O) 2 [Pd­(CN) 4 ]·4H 2 O ( FePd–H 2 O ), involving cleavage and reforming of the cyanide bridges (Figure S6). Thus, the resultant water-induced amorphous-2D structural transitions of MNi plausibly involve similar local coordination geometry changes around the M 2+ centers except for M = Ni. MNi (M = Mn, Fe, and Co) and FePd were obtained as amorphous and crystalline, respectively, under the same preparation condition.…”

“…Fe(H 2 O) 2 [Pd(CN) 4 ]•4H 2 O (FePd−H 2 O), involving cleavage and reforming of the cyanide bridges (FigureS6) 56. Thus, the resultant water-induced amorphous-2D structural transitions of MNi plausibly involve similar local coordination geometry changes around the M 2+ centers except for M = Ni.…”

The ligand field in low-crystallinity metal–organic frameworks investigated by soft X-ray core-level absorption spectroscopy

“…Synthetic procedures, materials and methods, and crystallography M[Ni(CN) 4 ] (MNi, M = Mn, Fe, Co, and Ni) and Ni[Pd(CN) 4 ] (NiPd) were synthesized using a precipitation method. 20,25,26 The details of the sample preparation are provided in the ESI. † The infrared (IR) spectra were collected using a JASCO FT/IR-4200 spectrophotometer.…”

New family of Hofmann-like coordination polymers constructed with imidazole ligands and associated with spin crossover and anisotropic thermal expansions

“…Recently, negative thermal expansion (NTE) behavior in Hofmann-like 2D layer has been investigated. 9,10 However, there are few reports of a coexistence of SCO with anisotropic TE. An ability to consider a combination of lattice expansion (NTE) and rapid lattice contraction (SCO), i.e.…”