A New Series of Chiral Metal Formate Frameworks of [HONH3][MII(HCOO)3] (M=Mn, Co, Ni, Zn, and Mg): Synthesis, Structures, and Properties

We report the synthesis, crystal structures, IR, and thermal, dielectric, and magnetic properties of a new series of ammonium metal formate frameworks of [HONH3][M-II(HCOO)(3)] for M = Mn, Co, Ni, Zn, and Mg. They are isostructural and crystallize in the nonpolar chiral orthorhombic space group P2(1)2(1)2(1), a = 7.8121(2)-7.6225(2) angstrom, b = 7.9612(3)-7.7385(2) angstrom, c = 13.1728(7)-12.7280(4) angstrom, and V = 819.27(6)-754.95(4) angstrom(3). The structures possess anionic metal formate frameworks of 4(9).6(6) topology, in which the octahedral metal centers are connected by the anti-anti formate ligands and the hydroxylammonium is located orderly in the channels, forming strong O/N-H center dot center dot center dot O-formate hydrogen bonds with the framework. HONH3+ with only two non-H atoms favors the formation of the dense chiral 4(9).6(6) frameworks, instead of the less dense 4(12).6(3) perovskite frameworks for other monoammoniums of two to four non-H atoms because of its small size and its ability to form strong hydrogen bonding. However, the larger size of HONH3+ compared to NH4+ resulted in simple dielectric properties and no phase transitions. The three magnetic members (Mn, Co, and Ni) display antiferromagnetic long-range ordering of spin canting, at Neel temperatures of 8.8 K (Mn), 10.9 K (Co), and 30.5 K (Ni), respectively, and small spontaneous magnetizations for the Mn and Ni members but large magnetization for the Co member. Thermal and IR spectroscopic properties are also reported.