Mixed Valency in a 3D Semiconducting Iron–Fluoranilate Coordination Polymer

Abstract

A pair of coordination polymers of composition (NBu)[M(fan)] (fan = fluoranilate; M = Fe and Zn) were synthesized and structurally characterized. In each case the compound consists of a pair of interpenetrating three-dimensional, (10,3)-a networks in which metal centers are linked by chelating/bridging fluoranilate ligands. Tetrabutylammonium cations are located in the spaces between the two networks. Despite the structural similarity, significant differences exist between (NBu)[Fe(fan)] and (NBu)[Zn(fan)] with respect to the oxidation states of the metal centers and ligands. For (NBu)[Fe(fan)] the structure determination as well as Mössbauer spectroscopy indicate the oxidation state for the Fe is close to +3, which contrasts with the +2 state for the Zn analogue. The differences between the two compounds extends to the ligands, with the Zn network involving only fluoranilate dianions, whereas the average oxidation state for the fluoranilate in the Fe network lies somewhere between -2 and -3. Magnetic studies on the Fe compound indicate short-range ordering. Electrochemical and spectro-electrochemical investigations indicate that the fluoranilate ligand is redox-active in both complexes; a reduced form of (NBu)[Fe(fan)] was generated by chemical reduction. Conductivity measurements indicate that (NBu)[Fe(fan)] is a semiconductor, which is attributed to the mixed valency of the fluoranilate ligands.

Square Grid Metal–Chloranilate Networks as Robust Host Systems for Guest Sorption

“…The magnetic properties of chloranilate‐bridged framework materials are currently of great interest– not only for those containing diamagnetic can 2− bridges but also, particularly, those containing radical can 3− bridges of the semiquinone type found in d‐block anilato families such as [Fe 2 (can) 3 ] 2− , the latter forming a 6,3‐ hexagonal network structure ,. The present 2D 4,4‐network is an attractive system to explore magnetic properties, including magnetic exchange, as each Ln III centre is bridged by four can 2− groups to neighbouring Ln III centres.…”

Chameleonic layered metal–organic frameworks with variable charge-ordered states triggered by temperature and guest molecules

“…42,48 The observed electronic conductivity in 1-d at room temperature was comparable with that in previously reported honeycomb layers. 41,49 During the heating process, the thermal variations of s k proles showed an unusual incoherent feature with two-step inections at around T 1/2b and T 1/2c (Fig. 8b).…”

Zirconium metal–organic frameworks incorporating tetrathiafulvalene linkers: robust and redox-active matrices for in situ confinement of metal nanoparticles

“…They have attracted considerable research interest in the elds of gas storage, 1,2 separations, 2,3 energy storage, 4 catalysis 5 and chemical sensing. 6 While many MOFs remain inert under application conditions, recent studies have highlighted their redox activity potential arising from metal ions, [7][8][9][10][11][12][13][14][15] organic linkers, [16][17][18][19][20][21][22][23][24][25] or the guest molecules. 18,26 Redox-active MOFs represent a unique class of switchable solid materials in which the different redox states with distinct physical properties can be achieved by redox modulation.…”