ABSTRACT
The luminescence properties of two types of heterotrimetallic aluminum-lanthanide-sodium 12-metallacrown-4 compounds are presented here, LnNa(ben)4[12-MCAl(III)N(shi)-4] (LnAl4Na) and {LnNa[12-MCAl(III)N(shi)-4]}2(iph)4 (Ln2Al8Na2), where Ln = GdIII, TbIII, ErIII, and YbIII, MC is metallacrown, ben- is benzoate, shi3- is salicylhydroximate, and iph2- is isophthalate. The aluminum-lanthanide-sodium metallacrowns formed with benzoate are discrete monomers while, upon replacement of the benzoate with the dicarboxylate isophthalate, two individual metallacrowns can be joined to form a dimer. In the solid state, the terbium version of each structure type displays emission in the visible region, and the erbium and ytterbium complexes emit in the near-infrared. The luminescence lifetimes (τobs) and quantum yields have been collected under ligand excitation (QLLn) for both LnAl4Na monomers and Ln2Al8Na2 dimers. Several of these values tend to be shorter (luminescence lifetimes) and smaller (quantum yields) than the corresponding values recorded for the structurally similar gallium-lanthanide monomer and dimer 12-MC-4 molecules. However, the quantum yield value recorded for the visible emitting Tb2Al8Na2 dimer, 43.9%, is the highest value observed in the solid state to date for a TbIII based metallacrown.
ABSTRACT
The two [3.3.1] metallacryptate complexes, namely, poly[[µ3-acetato-hexa-kis-(µ-N,N-di-methyl-formamide)-bis-(N,N-di-methyl-formamide)bis-[salicyl-hydroxi-mato(2-)]hepta-kis-[salicyl-hydrox-im-ato(3-)]hexa-aluminium(III)dysprosium(III)penta-sodium(I)] N,N-di-methyl-formamide tetra-solvate monohydrate], [DyAl6Na5(OAc)(Hshi)2(shi)7(DMF)8]·4DMF·H2O or {[DyAl6Na5(C7H5NO3)2(C7H4NO3)7(C2H3O2)(C3H7NO)8]·4C3H7NO·H2O} n , 1, and poly[[di-µ4-acetato-nona-kis-(µ-N,N-di-methyl-form-amide)-octa-kis-(N,N-di-methyl-formamide)tetra-kis-[sali-cyl-hydroximato(2-)]tetra-deca-kis-[salicyl-hydroximato(3-)]dodeca-aluminium(III)didysprosium(III)deca-sodium(I)] N,N-di-methyl-form-amide 6.335-solvate], [DyAl6Na5(OAc)(Hshi)2(shi)7(DMF)8.5]2·6.335DMF or {[Dy2Al12Na10(C7H5NO3)4(C7H4NO3)14(C2H3O2)2(C3H7NO)17]·6.335C3H7NO} n , 2, where shi3- is salicyl-hydroximate and DMF is N,N-di-methyl-formamide, both consist of an aluminium-based metallacryptand. In 1 and 2, the metallacryptand encapsulates a dysprosium(III) ion in the central cavity, and the resulting metallacryptates are connected to each other via sodium-DMF linkages to generate a two-dimensional sheet. The metallacryptates of 1 and 2 are the three-dimensional analogues of metallacrowns as the metallacryptates contain a metal-nitro-gen-oxygen cyclic repeat unit throughout the complexes. For 1 the building block of the two-dimensional sheet is comprised of only one type of metallacryptate, which is connected to four neighboring metallacryptates via four sodium-DMF linkages. In 2, the building block is a dimeric unit of two metallacryptates. Each dimeric metallacryptate unit is connected to four other dimeric units via six sodium-DMF linkages. The two metallacryptates of each dimeric unit can be considered enanti-omers of each other. In both 1 and 2, chirality is imparted to the metallacryptate due to the Λ and Δ propeller configurations of the four octa-hedral aluminium ions of the metallacryptand shell.
ABSTRACT
The paramagnetic one-dimensional 1H NMR spectra of twelve LnIIINaI(OAc)4[12-MCMnIII(N)shi-4] complexes, where LnIII is PrIII-YbIII (except PmIII) and YIII, are reported. Their solid-state isostructural nature is confirmed in methanol-d4 solution, as a similar pattern in the 1H NMR spectra is observed along the series. Notably, a relatively well-resolved spectrum is reported for the GdIII complex. The chemical shift data are analyzed using the "all lanthanides" method, and the Fermi contact and pseudo-contact contributions are calculated for the lanthanide-induced shift (LIS). For the TbIII-YbIII complexes, the pseudo-contact contributions are typically 1 order of magnitude higher than the Fermi contact contributions; however, for the GdIII complex, the Fermi contact is the main contribution to the paramagnetic chemical shift. For the methyl protons of the axial acetate (-OAc) ligands, the LIS is opposite in sign, with respect to that of the aromatic salicylhydroximate (shi3-) protons, because of structural rearrangements that occur upon dissociation of the NaI cation in solution. The calculated crystal field parameters (BLn) for the TbIII (360 cm-1), DyIII (250 cm-1), HoIII (380 cm-1), ErIII (410 cm-1), TmIII (620 cm-1), and YbIII (380 cm-1) complexes are not constant, likely as a consequence of the inaccuracy of the Bleaney's constants and, to a smaller extent, the small structural changes that occur in solution. Overall, the metallacrown scaffold retains structural integrity and similarity in solution for the entire series; however, small structural features, which do not affect the overall similarity, do likely occur.
ABSTRACT
The synthesis and crystal structure for the title compound, [YNaMn4(C7H4NO3)4(C5H9O2)4(H2O)3.76(C3H7NO)0.24]·8.04C3H7NO·0.62H2O or [Y(III)Na(OTMA)4[12-MCMn(III)N(shi)-4](H2O)3.76(DMF)0.24·8.04DMF·0.62H2O, where OTMA is tri-methyl-acetate, MC is metallacrown, shi(3-) is salicyl-hydroximate, and DMF is N,N-di-methyl-formamide, is reported. The macrocyclic metallacrown consists of an -[Mn(III)-N-O]4- ring repeat unit, and the metallacrown captures one Y(III) ion and one Na(I) ion in the central cavity on opposite faces of the metallacrown. Overall the metallacrown is domed towards the side of the Na(I) ion. Both the Y(III) and Na(I) ions are eight-coordinate, and the tri-methyl-acetate anions bridge the central Y(III) to each ring Mn(III) ion. The ring Mn(III) ions are six-coordinate with a tetra-gonally distorted octa-hedral geometry.
