Synthesis, structure and magnetic property of a new organo-templated mixed-valent iron(ii, iii) borophosphate

Abstract

A new layered iron borophosphate (C4N3H 16)(C4N3H15)0.5[Fe 2B4P7O26(OH)4] (denoted FeBPO-CJ28), with a novel B/P ratio of 4/7 and mixed-valent iron(ii, iii) was prepared under mild hydrothermal conditions in the presence of diethylenetriamine (DETA) as the template. Its crystal structure was determined by single-crystal X-ray diffraction (triclinic, P1 (No. 2), a = 8.9568(3) , b = 9.8717(3) , c = 17.9905(5) , α = 102.510(2)°, β = 92.343(2)°, γ = 100.403(2)°, V = 1522.10(8) 3, and Z = 2). The structure comprises unprecedented anionic double layers 2∞{[Fe 2B4P7O26(OH)4] 4-} with one-dimensional 8-ring channels along the [110] direction, which are made up of FeO6, BO4, PO4 and HPO4 polyhedral units. Such double layers parallel to the ab plane are connected by inter-layer hydrogen bonds forming the three-dimensional (3D) supramolecular open framework with pseudo 10-ring channels along the [110] direction. Protonated DETA cations locate in the 8-ring channels and pseudo 10-ring channels to compensate the negative charge of the anionic framework. The structure is featured by a new fundamental building unit (FBU) [B 4P7O26(OH)4], which is the largest one of the borophosphate anionic partial structures. The compound is further characterized by powder XRD, ICP, CHN, TGA and Mössbauer spectroscopy analysis. The magnetic measurement reveals that FeBPO-CJ28 exhibits ferrimagnetic behavior below 9.6 K with a hysteresis loop at 2 K (HC = 2800 Oe, MR = 0.21 B). © 2009 The Royal Society of Chemistry.