The first use of the bare 2,2’-bisimidazole(H_(2)bim)ligand in rare earth metal chemistry is presented.A series of symmetric dinuclear complexes[(Cp_(2)^(*)RE)_(2)(μ-bim)]were synthesized from the salt metathesis re...The first use of the bare 2,2’-bisimidazole(H_(2)bim)ligand in rare earth metal chemistry is presented.A series of symmetric dinuclear complexes[(Cp_(2)^(*)RE)_(2)(μ-bim)]were synthesized from the salt metathesis reaction of the lithium salt Li_(2)(bim)with Cp_(2)^(*)RE(BPh_(4))(RE=Y(1),Gd(2),Dy(3);Cp^(*)=1,2,3,4,5-pentamethylcyclopentadienyl).The isostructural complexes 1–3 were unambiguously characterized through elemental analysis,NMR,IR and UV/Vis spectroscopy,single-crystal X-ray diffraction,SQUID magnetometry and density functional theory(DFT)calculations.Intriguingly,the compounds are redox-inactive both on the timescale of chemical and electrochemical experiments.Herein,a rationale for the redox innocence of the bim^(2−) ligand is provided by calculations of the electron affinity and ionization potential,both correlating well with topologically similar structures of comparable complexes.Remarkably,the Dy complex 3 shows open magnetic hysteresis loops up to 5 K which is rare for lanthanide SMMs with bridging diamagnetic entities.AC magnetic susceptibility measurements at zero field revealed slow magnetic relaxation up to 26 K leading to an effective energy barrier to spin reversal of U_(eff)=154(2)cm^(−1) andτ0=5(1)×10^(−8) s.The lanthanides are weakly antiferromagnetically coupled,where the J value for the Gdcongener 2 was determined to be−0.074(2)cm^(−1).展开更多
基金Funding for the single-crystal X-ray diffractometer was provided through the MRI program of the National Science Foundation under Grant No.CHE-1919565.
文摘The first use of the bare 2,2’-bisimidazole(H_(2)bim)ligand in rare earth metal chemistry is presented.A series of symmetric dinuclear complexes[(Cp_(2)^(*)RE)_(2)(μ-bim)]were synthesized from the salt metathesis reaction of the lithium salt Li_(2)(bim)with Cp_(2)^(*)RE(BPh_(4))(RE=Y(1),Gd(2),Dy(3);Cp^(*)=1,2,3,4,5-pentamethylcyclopentadienyl).The isostructural complexes 1–3 were unambiguously characterized through elemental analysis,NMR,IR and UV/Vis spectroscopy,single-crystal X-ray diffraction,SQUID magnetometry and density functional theory(DFT)calculations.Intriguingly,the compounds are redox-inactive both on the timescale of chemical and electrochemical experiments.Herein,a rationale for the redox innocence of the bim^(2−) ligand is provided by calculations of the electron affinity and ionization potential,both correlating well with topologically similar structures of comparable complexes.Remarkably,the Dy complex 3 shows open magnetic hysteresis loops up to 5 K which is rare for lanthanide SMMs with bridging diamagnetic entities.AC magnetic susceptibility measurements at zero field revealed slow magnetic relaxation up to 26 K leading to an effective energy barrier to spin reversal of U_(eff)=154(2)cm^(−1) andτ0=5(1)×10^(−8) s.The lanthanides are weakly antiferromagnetically coupled,where the J value for the Gdcongener 2 was determined to be−0.074(2)cm^(−1).
