[Ba 4 Cl] Cations Directed Perovskite-like Polar Metal Formate Frameworks {[Ba 4 Cl][M 3 (HCO 2 ) 13 ]} n (M = Mn, Co, and Mg): Microwave-Assisted Synthesis, Structures, and Properties.

Novel 3D metal formate frameworks {[Ba 4 Cl][M 3 (HCO 2 ) 13 ]} n (M = Mn for 1 , Co for 2 , and Mg for 3 ) were successfully assembled via microwave-assisted synthesis. The complexes are rare coordination polymers crystallized at space group P 4 cc with the polar point group C 4 v . In the structure, the M II ions are bridged by two types of anti - anti formate in forming a 3D pcu framework, and additional formates coordinate to the unsaturated sites of the M II ions in the framework, giving an anionic M-formate net. Ba 4 Cl clusters take the cavities of the net as charge balance, in which the chloride ion deviates from the center of the barium ions. The asymmetric Ba 4 Cl structure is transmitted throughout the crystal resulting in polar structure, which is further confirmed by nonlinear optical and piezoelectric test. Nonlinear optical activity tests of 1 and 3 show SHG signals 0.32 and 0.28 times that of KDP, while 2 has a piezoelectric coefficient d 33 of 6.8 pC/N along polar axis. Magnetic studies reveal antiferromagnetic coupling between M II ions in 1 and 2 . Spin canting was found only in 2 with anisotropic Co II ions, and 2 is a canted antiferromagnetically with T N = 5 K. Further field-induced spin flop was also found in 2 with a critical field 0.9 T.