The design of coordination sites around lanthanide ions has a strong impact on the sensitization of their luminescent signal. An imidodiphosphonate anionic binding site is attractive as it can be functionalized with "remote" sensitizer units, such as phenoxy moieties, namely, HtpOp, accompanied by an increased distance of the lanthanide from the ligand high-energy stretching vibrations which quench the luminescence signal, hence providing flexible shielding of the lanthanide. We report the formation and isolation of Ln(tpOp)3 complexes where Ln = Er, Gd, Tb, Dy, Eu, and Yb and the Y(tpOp)3 diamagnetic analogue. The complexes are formed from reaction of KtpOp and the corresponding LnCl3•6H2O salt either by titration and in situ formation or by mixing and isolation. All complexes are seven-coordinated by three tpOp ligand plus one ethanol molecule, except for Yb(tpOp)3 which has no solvent coordinated. Phosphorus NMR shows characteristic shifts to support the coordination of the lanthanide complexes. The complexes display visible and near-infrared luminescence with long lifetimes even for the near-infrared complexes which range from 3.3 μs for Nd(tpOp)3 to 20 μs for Yb(tpOp)3. The ligand shows more efficient sensitization than the imidodiphosphinate analogues for all lanthanide complexes with a notable quantum yield of the Tb(tpOp)3 complex at 45%. We attribute this to the properties of the remote sensitizer unit and its positioning further away from the lanthanide, eliminating quenching of high energy C−H vibrations from the ligand shell. Calculations of the ligand shielding support the photophysical properties of the complexes. These results suggest that these binding sites are promising in the further development of the lanthanide complexes in optoelectronic devices for telecommunications and new light emitting materials.
Introducing
both tetrazine radical and azido bridges afforded two
air-stable square complexes [MII
4(bpztz•–)4(N3)4] (MII = Zn2+, 1; Co2+, 2; bpztz = 3,6-bis(3,5-dimethylpyrazolyl)-1,2,4,5-tetrazine),
where the metal ions are cobridged by μ1,1-azido
bridges and tetrazine radicals. Magnetic studies revealed strong antiferromagnetic
metal–radical interaction with a coupling constant of −64.7
cm–1 in the 2J formalism in 2. Remarkably, 2 exhibits slow relaxation of
magnetization with an effective barrier for spin reverse of 96 K at
zero applied field.
Two Co(ii) [2 × 2] grid-like clusters containing both pyridazine and azido bridges were reported to exhibit overall intramolecular ferromagnetic coupling and field-induced single-molecule magnet behavior with the effective energy barriers up to 56 K.
Supramolecular self-assembly synthetic strategy provides a valid tool to obtain polynuclear Fe(II) complexes containing effective communications between the metal centers and achieve distinct spin crossover behaviour. Despite great success in...
A new nitronyl nitroxide radical L (L = 2-(4-(5methyl-carbonyl-3-pyriyl)benzoxo)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) containing N−O groups and the pyridyl nitrogen group was designed and synthesized as a multidentate ligand to obtain compounds with interesting structures and magnetic properties from 3d or 3d-4f precursors. The reaction of Cu(hfac) 2 and/or Gd(hfac) 3 •2H 2 O (hfac = hexafluoroacetylacetonate) with L resulted in a rare S = 13/2 high spin ground state Cu II complex [(Cu(hfac) 2 ) 7 (L) 6 ] (1) and a Cu II − Gd III chain complex [Gd(hfac) 3 Cu(hfac) 2 (L) 2 ] n •0.5CH 2 Cl 2 (2). Single crystal X-ray diffraction studies indicate that the N−O groups of the L radicals are all axially bound to Cu II ions in complex 1, which result in the ferromagnetic exchange between Cu II and radicals and an S = 13/2 high spin ground state. While adding Gd(hfac) 3 units to the system of Cu(hfac) 2 and L radical, a one dimension chain structure is obtained, and there are ferromagnetic Gd III -radical interactions and antiferromagnetic radical−radical coupling in the chain.
Two Ni(II) molecular metallacycles of [Ni4(bpz*tz•)4(N3)4] (1) and [Ni3(bpzPhtz•)3(pzPh(Cl)tz•)3]•1.3CH3OH•9.3H2O (2) (bpz*tz = 3,6-bis(3,5-dimethyl-pyrazolyl)-1,2,4,5-tetrazine; bpzPhtz = 3,6-bis(3-phenyl-pyrazolyl)-1,2,4,5-tetrazine; pzPh(Cl)tz = 3-bis(3-phenyl-pyrazolyl)-6-Cl-1,2,4,5-tetrazine) were reported. The single-crystal X-ray diffraction study reveals that 1 displays...
On page 96, left column, second full paragraph, in line 9, C 131 H 100 Cl 2 Cu 2 F 60 Gd 2 N 12 O 40 is incorrect. The correct notation is C 65.5 H 50 ClCuF 30 GdN 6 O 20 .On page 98, left column, last paragraph, 18.09 cm 3 K mol −1 (in line 3) and 17.26 cm 3 K mol −1 (in line 4) are incorrect. The correct notations are 9.05 cm 3 K mol −1 and 9.01 cm 3 K mol −1 , respectively.On page 98, left column, last paragraph, 17.26 cm 3 K mol −1 and 29.51 cm 3 K mol −1 (in line 9) are incorrect. The correct notations are 9.05 cm 3 K mol −1 and 14.76 cm 3 K mol −1 , respectively.On page 98, right column, last paragraph in line 18, 2f-3d is incorrect. The correct notation is 2p-3d.
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