Synthesis,Structure And Properties Of Coordinated Complexes Of Ni(Ⅱ) And Mn(Ⅱ)Based On Methylurea Ligands

Nickel sulfate hexahydrate crystal(NiSO4·6H2O,NSH),as the most commonly used one of Ultraviolet Light Filters(ULFs),has been widely used in optic science,chemistry,communication,military and other fields.However,NSH crystal starts to dehydrate when the temperature reaches 73 ℃,which greatly limits its potential applications in some fields,especially under high-temperature conditions.In this study,we made a pronounced enhancement in its heat endurance by replacing all six water ligands with organic ones,methylurea,which has a stronger coordination capacity and binding tendency to divalent metal ions.In this study,five complexes Ni(C2H6N2O)6SO4,Mn0.33Ni0.67(C2H6N2O)6SO4,Mn0.75Ni0.25(C2H6N2O)6 SO4,Mn0.9Ni0.1(C2H6N2O)6SO4 and Co0.5Ni0.5(C2H6N2O)6SO4 were synthesized and single crystals with large sizes were obtained from aqueous solution by evaporating solvent method.Cell parameters,bond lengths and angles,hydrogen bonds and other structural information of the above crystals were confirmed by X-ray single crystal diffractometer.These crystals belong to the trigonal system,R-3c space group.The incorporation of Mn2 + and Co2 + increases the cell parameters and bond lengths between central metal ions and coordination O atoms.Hydrogen bonds between N-H...O atoms of adjacent ligands in molecules enhance the stability of complexes.The positions of experimental diffraction peaks are consistent with those of the simulated ones based on the single-crystal diffraction data,indicating the high purity of the as-synthesized samples.TGA measurements show excellent stability below 200 ℃,indicating the effectivity of ligands substitution.UV-Vis spectra revealed that,compared with NSH,the transmission peaks of the above crystals have a slight bathochromic-shift.The transmittance in UV band increased as the raising proportion of Mn2+.As the absorption of Co2+ at 500 nm,the transmittance in visible region is obviously lower,making it eligible to filter off more light than NSH.Crystal plane indices were indexed.The angles between different crystal planes and crystal edges of adjacent planes were calculated by programming on the basis of unit cell parameters and space group,and were compared with the results of photomicrographs.The results of the analysis are in good agreement with those obtained by X-ray crystal orientation apparatus.The dislocation etch pits in(0 0 0 1)planes of crystals were observed by metallographic microscope.The symmetries showed by these each pits were identical with those of macroscopic crystals.Spiral growth patterns on {0 1-14} planes of Mn0.90Ni0.10(C2H6N2O)6SO4 crystal were observed by atomic force microscopy(AFM).The height of growth step is equal to interplanar crystal spacing.