Open-Framework Manganese(II) and Cobalt(II) Borophosphates with Helical Chains: Structures, Magnetic, and Luminescent Properties

Abstract

Two borophosphates, (NH)M(HO)(BPO)·yHO with M = Mn (I) and Co (II), synthesized hydrothermally crystallize in enantiomorphous space groups P622 and P622 with a = 9.6559(3) and 9.501(3) Å, c = 15.7939(6) and 15.582(4) Å, and V = 1275.3(1) and 1218.2(8) Å for I and II, respectively. Both compounds feature helical chains composed of vertex-sharing tetrahedral PO and BO groups that are connected through O atoms to transition-metal cations, Mn and Co, respectively. For the two crystallographically distinct transition-metal cation sites present in the structure, this results in octahedral coordination with different degrees of distortion from the ideal symmetry. The crystal-field parameters, calculated from the corresponding absorption spectra, indicate that Mn and Co ions are located in a weak octahedral-like crystal field and suggest that the Co-ligand interactions are more covalent than the Mn-ligand ones. Luminescence measurements at room temperature reveal an orange emission that red-shifts upon lowering of the temperature to 77 K for I, while II is not luminescent. The luminescence lifetimes of I are 33.4 μs at room temperature and 1.87 ms at 77 K. Both compounds are Curie-Weiss paramagnets with negative Weiss constants and effective magnetic moments expected for noninteracting Mn and Co cations but no clear long-range magnetic order above 2 K.

Corrosion of Heritage Objects: Collagen‐Like Triple Helix Found in the Calcium Acetate Hemihydrate Crystal Structure

“…Substances with helical structures are regarded as promising candidates for excellent mechanical, electrical and optical properties . Most helical materials that have been synthesized have very complex constitutions . For simple LiP, a double helix structure was predicted but has not been experimentally proven yet .…”

Korrosion von Kulturgut: Entdeckung einer kollagenartigen Tripelhelix in der Kristallstruktur von Calciumacetat‐Hemihydrat

“…Substanzen mit helikalen Strukturen werden als vielversprechende Kandidaten für herausragende mechanische, elektrische und optische Eigenschaften angesehen . Die meisten synthetischen helikalen Verbindungen haben sehr komplexe Konstitutionen . Für einfaches LiP wurde eine Doppelhelix‐Struktur vorhergesagt, aber bisher experimentell nicht nachgewiesen .…”

Chain caesium borophosphates with B:P ratio 1:2: synthesis, structure relationships and low-temperature thermodynamic properties

“…The representative with Fe 2+ /Fe 3+ cations, (NH 4 ) 0.75 Fe[B-P 2 O 8 ]Á(H 2 O) 0.25 , revealed electrochemical responses and is potentially promising as Na/Na-ion battery cathodes (Tao et al, 2015). Magnetic property investigations performed for the Co 2+ , Mn 2+ and Fe 2+,3+ analogues did not show a clear indication of long-range magnetic ordering up to 2 K (Li et al, 2017;Yilmaz et al, 2000Yilmaz et al, , 2005Tao et al, 2015;Huang et al, 2001).…”

“…In this case, in order to achieve charge balance the 'host' structure can trap the additional M 2+ cations (Engelhard, 2000;Schä fer et al, 2002), which are connected to MO 6 octahedra, to form metal clusters. Thus a series of compounds with non-stoichiometric formulae were obtained (Li et al, 2017;Schä fer et al, 2002;Huang et al, 2001;Yilmaz et al, 2005).…”

“…Recent studies have shown that members of the (Menezes et al, 2019). (NH 4 ) 0.50 Mn 1.25 [BP 2 O 8 ]Á(H 2 O) 2.30 exhibits luminescent properties: there is a change from orange to red emission by lowering the temperature from room temperature to 77 K (Li et al, 2017). Another compound, NH 4 Cd(H 2 O) 2 [BP 2 O 8 ]Á0.72H 2 O, emits amaranthine fluorescence when excited by UV light of 365 nm (Ge et al, 2005).…”