The self-assembly of lanthanide(3+)ions with pyrazine N,N′-dioxide(pzdo)and bis(triphenylphosphine)iminium(PPN+)salts of diamagnetic octacyanidometallates of MoIV and WIV results in one-dimensional(PPN)[LnIII(pzdo)2(...The self-assembly of lanthanide(3+)ions with pyrazine N,N′-dioxide(pzdo)and bis(triphenylphosphine)iminium(PPN+)salts of diamagnetic octacyanidometallates of MoIV and WIV results in one-dimensional(PPN)[LnIII(pzdo)2(MeOH)0.3(H2O)3.7][MIV(CN)8]·7.7H2O·2MeOH(Ln=Er and Yb;M=Mo and W)coordination networks.They are constructed of zigzag metal–organic{LnIII(μ-pzdo)}n chains with terminal[MIV(CN)8]4−metalloligands attached to the LnIII centres.Both Er-and Yb-containing frameworks exhibit field-induced slow magnetic relaxation originating from the field-dependent equilibrium between quantum tunnelling of magnetization and the direct process along with the temperature-dependent Raman and Orbach relaxation processes.Transition metal substitution on[MIV(CN)8]4−sites modifies the intrinsic magnetic anisotropy of lanthanides,as depicted by the subtle change of thermal energy barriers of Orbach relaxation in Er-based systems,while it significantly affects Raman relaxation due to the modulated phonon mode scheme.All reported compounds exhibit strong visible light absorption due to a series of electronic transitions of pzdo ligands and[M(CN)8]4−ions and the appearance of low energy anion–π charge transfer band involving pzdo and octacyanidometallates.These charge transfer states were utilized in achieving the sensitized near-infrared photoluminescence of Er^(Ⅲ) and Yb^(Ⅲ) centers;thus,the energy transfer process is strongly dependent on the nature of the metal centre in the[M^(Ⅳ)(CN)8]4−ion.The W(Ⅳ)-pzdo system is a good sensitizer for Er^(Ⅲ),while the Mo(Ⅳ)-pzdo unit is better for Yb^(Ⅲ) emission which can be rationalized in terms of the positions of energy levels of their respective donor states.Therefore,we report NIR emissive Er^(Ⅲ) and Yb^(Ⅲ) single-molecule magnets with tunable magnetic and optical properties,uncovering the crucial role of octacyanidometallates and their anion–π interactions with pzdo ligands.展开更多
基金financed by the National Science Centre,Poland,within the OPUS-15 project,grant no.2018/29/B/ST5/00337supported by the Japan Society for the Promotion of Science,the Grant-in-Aid for Specially Promoted Research,grant no.15H05697.
文摘The self-assembly of lanthanide(3+)ions with pyrazine N,N′-dioxide(pzdo)and bis(triphenylphosphine)iminium(PPN+)salts of diamagnetic octacyanidometallates of MoIV and WIV results in one-dimensional(PPN)[LnIII(pzdo)2(MeOH)0.3(H2O)3.7][MIV(CN)8]·7.7H2O·2MeOH(Ln=Er and Yb;M=Mo and W)coordination networks.They are constructed of zigzag metal–organic{LnIII(μ-pzdo)}n chains with terminal[MIV(CN)8]4−metalloligands attached to the LnIII centres.Both Er-and Yb-containing frameworks exhibit field-induced slow magnetic relaxation originating from the field-dependent equilibrium between quantum tunnelling of magnetization and the direct process along with the temperature-dependent Raman and Orbach relaxation processes.Transition metal substitution on[MIV(CN)8]4−sites modifies the intrinsic magnetic anisotropy of lanthanides,as depicted by the subtle change of thermal energy barriers of Orbach relaxation in Er-based systems,while it significantly affects Raman relaxation due to the modulated phonon mode scheme.All reported compounds exhibit strong visible light absorption due to a series of electronic transitions of pzdo ligands and[M(CN)8]4−ions and the appearance of low energy anion–π charge transfer band involving pzdo and octacyanidometallates.These charge transfer states were utilized in achieving the sensitized near-infrared photoluminescence of Er^(Ⅲ) and Yb^(Ⅲ) centers;thus,the energy transfer process is strongly dependent on the nature of the metal centre in the[M^(Ⅳ)(CN)8]4−ion.The W(Ⅳ)-pzdo system is a good sensitizer for Er^(Ⅲ),while the Mo(Ⅳ)-pzdo unit is better for Yb^(Ⅲ) emission which can be rationalized in terms of the positions of energy levels of their respective donor states.Therefore,we report NIR emissive Er^(Ⅲ) and Yb^(Ⅲ) single-molecule magnets with tunable magnetic and optical properties,uncovering the crucial role of octacyanidometallates and their anion–π interactions with pzdo ligands.
