Researches on the Molecular Magnetic Complexes of Single,double and Multiple Nitronyl Nitroxide Radicals

Author:Zuo Hao

Supervisor:wang xin yi


Degree Year:2019





Nitronyl nitroxides(NIT)are a kind of stable radicals under ambient conditions and their structures are easy to be modified.Since they can act as paramagnetic bridging ligands,NIT radicals can transfer strong magnetic interactions between the metal ions and the radical ligands.Therefore,NIT radicals with different substituent groups are widely used in the construction of molecular magnetic materials.Current studies of nitronyl nitroxides mostly focus on the monoradicals,while the researches on the nitronyl nitroxide diradicals and polyradicals are still in its infancy.This dissertation mainly centers on the nitronyl nitroxide monoradical,diradical,triradical,tetraradical and their metal complexes.32 new complexes have been designed,synthesized and characterized structurally and magnetically.The results contain the following five parts:In part one,a new bi-tridentate nitronyl nitroxide monoradical NIT-Pm2Py(1)was designed and synthesized.Three three-spin binuclear complexes,2Mn,3Ni and 4Co,were synthesized based on 1.Magnetic studies showed the existence of antiferromagnetic interaction in 1.Also,antiferromagnetic interactions between the metal ions and radicals in 2Mn,3Ni and 4Co were confirmed.Antiferromagnetic interaction between the Mn2+and radical was also obtained by theoretical calculations for 2Mn with the exchange coupling constant J of-25 cm-1.Magnetic dynamics studies revealed the field-induced slow magnetic relaxation in 4cO.In part two,based on ligand 1,we synthesized six two-spin mononuclear complexes 5Gd-10Yb and five three-spin binuclear complexes 11cd-15Er.Magnetic studies showed that the interaction between the Ln3+and radicals in 5Gd-15Er is antiferromagnetic.Magnetic dynamics studies show that frequency-dependent properties were not observed under zero or 1 kOe dc field in complexes 6Tb-9Er and 12Tb-15Er.While lOYb displays the frequency-dependent properties under a 1kOe dc field,indicating the field-induced slow magnetic relaxation in 10Yb.In part three,we synthesized a biradical BNIT-Terpy,one binuclear CoⅡ-NIT complex 17Co,and a family of Ln-radical complexes 18Tb-21Er based on the BNIT-Terpy.Besides,we designed and synthesized a new biradical BNIT-PhPm2Py(16),in order to synthesize tetranuclear metal-radical complexes.Single crystal structure analysis showed that one NIT radical of the BNIT-Terpy ligand in 17CO has been reduced to IM(IM=imino nitroxide).The structural analysis showed that the rare earth ions in 18Tb-21Er are all in a nine-coordinated environment and the coordination geometry is the distorted tricapped trigonal prism(D3h)-Magnetic studies showed the existence of the antiferromagnetic interactions in biradical BNIT-Terpy and 16.Also,antiferromagnetic interactions between the metal ions and radicals in 17Co-21Er were noticed.Unfortunately,the study of ac susceptibility precluded the SMM behavior in all five compounds.In part four,a triradical BTR and its reduced IM form triradical BTIM were synthesized.In addition,we obtained two mononuclear complexes 23Pr and 24Nd based on BTR and three mononuclear complexes 25Ni,26Pr and 27Nd based on BTIM.Besides,we designed and synthesized a new triradical TNIT-Pm2Py(22)in order to synthesize five-spin binuclear metal complexes.Based on 22,two five-spin binuclear Ln-radical complexes 28Pr and 29Nd,and a trinuclear complex 30Co were obtained.Single crystal structure analysis showed that TNIT-Pm2Py in 30Co has been reduced to TIM-Pm2Py.Magnetic studies showed that antiferromagnetic interactions exist in triradical 22.And antiferromagnetic interactions between the metal ions and radicals in 23Pr-24Nd and 26Pr-30Co were found.Unfortunately,all seven compounds are not single-molecule magnets.In part five,we designed and synthesized a new tetraradical TNIT-DPh(31),and obtained a double-layer tetranuclear GdⅢ-NIT complex 32Gd.The tetraradical 31 is only the third nitronyl nitroxide tetraradical reported to date.Compared to the other two reported nitronyl nitroxide tetraradicals and other tetraradicals,31 has more simplified molecular structure and stronger chelating ability.32Gd is the first metal-NIT complex based on the nitronyl nitroxide tetraradical.Week ferromagnetic interaction between the Gd3+ and radicals were confirmed by magnetic studies and theoretical calculations.