Transition-Metal Monofluorophosphate BaM(POF)F (M = Mn, Co, and Ni): Varied One-Dimensional Transition-Metal Chains and Antiferromagnetism.

Four transition-metal monofluorophosphates, with a chemical formula of BaM(POF)F (M = Mn, Co, Ni, and Cu), have been synthesized hydrothermally using phosphoric and fluorophosphoric acids. The structures of BaM(POF)F were intensively investigated by single-crystal and powder X-ray diffraction. Their networks exhibited three-dimensional frameworks formed by -MOF octahedra and POF tetrahedra. BaM(POF)F (M = Mn, Co, and Cu) are isostructural, crystallizing in the monoclinic space group 2/, while BaNi(POF)F adopted an unpredetermined structure, crystallizing in the monoclinic space group 2/. The different arrangements of the same -MOF moieties and POF groups within one-dimensional chains lead to different frameworks in this late-first-row transition-metal series. By a comparison of normalized bond lengths with their normal counterparts, the more elongated octahedral -MOF units in BaCu(POF)F reveal the presence of static Jahn-Teller distortion, uncovering the puzzling reason for the exceptional structure of BaNi(POF)F in the series. BaM(POF)F (M = Mn, Co, and Ni) forms spin chains of M made of coupled dimers or tetramers, showing dominant antiferromagnetic behavior.