RESUMEN
We report on the design of 1D MOFs based on a nopinane-annelated organic ligand and Co(II) or Ni(II), the variation of which allows tuning the optical modulation bandwidth. Structural and time-resolved analysis revealed the optical modulation mechanism, the rates and its endurance, thereby enriching the list of sustainable MOFs for tunable optical modulators.
RESUMEN
Zinc(II) and cadmium(II) chlorido complexes with an N,N-chelating nopinane-annelated 4,5-diazafluoren-9-one ligand (LO) were synthesized. While the zinc(II) complex is mononuclear and adopts a tetrahedral ZnN2Cl2 coordination geometry, its cadmium(II) analogue features a 1D polymeric structure due to the bridging coordination of chlorido ligands with Cd2+ ions having an octahedral CdN2Cl4 coordination geometry. The photophysical properties of the oxygen-containing LO ligand and its zinc(II) and cadmium(II) complexes were studied in solution and in the solid state and matched against the properties of its oxygen-free 4,5-diazafluorene congener L and its complexes of the same metal ions. Comprehensive experimental and theoretical studies revealed the impact of the oxygen atom in the ligand core on the luminescence of the ligands and the complexes. For the oxygen-free L ligand and L-based complexes, the structural differences between the S0 and S1 geometries are small, which leads to fluorescence with extraordinarily small Stokes shifts. The emission of these compounds is of locally excited character for L and of mixed locally excited + ligand-to-halide charge transfer character for the L-based complexes. The introduction of the oxygen atom in the ligand core results in a drastic red-shift of the emission band due to short-range charge transfer. The differences between the S0 and S1 geometries are much more pronounced for LO and LO-based compounds than those of their oxygen-free analogues, leading to an order of magnitude larger Stokes shifts. On going from solution to the solid state, LO and its complexes exhibit aggregation-induced emission (AIE) behaviour with photoluminescence quantum yields (PLQYs) reaching tens of percent.
RESUMEN
The reactions of CuX2 (X = Cl, Br) with dipinodiazafluorenes yielded four new complexes [CuX2L1]2 (X = Cl (1), Br (2), L1 = (1R,3R,8R,10R)-2,2,9,9-Tetramethyl-3,4,7,8,9,10-hexahydro-1H-1,3:8,10-dimethanocyclopenta [1,2-b:5,4-b']diquinolin-12(2H)-one) and [(CuX2)2L2]n (X = Cl (3), Br (4), L2 = (1R,3R,8R,10R,1'R,3'R,8'R,10'R)-2,2,2',2',9,9,9',9'-Octamethyl-1,1',2,2',3,3',4,4',7,7',8,8',9,9',10,10'-hexadecahydro-1,3:1',3':8,10:8',10'-tetramethano-12,12'-bi(cyclopenta [1,2-b:5,4-b']diquinolinylidene). The complexes were characterized by IR and EPR spectroscopy, HR-ESI-MS and elemental analysis. The crystal structures of compounds 1, 2 and 4 were determined by X-ray diffraction (XRD) analysis. Complexes 1-2 have a monomeric structure, while complex 4 has a polymeric structure due to additional coordinating N,N sites in L2. All complexes contain a binuclear fragment {Cu2(µ-X)2×2} (X = Cl, Br) in their structures. Each copper atom has a distorted square-pyramidal coordination environment formed by two nitrogen atoms and three halogen atoms. The Cu-Nax distance is elongated compared to Cu-Neq. The EPR spectra of compounds 1-4 in CH3CN confirm their paramagnetic nature due to the d9 electronic configuration of the copper(II) ion. The magnetic properties of all compounds were studied by the method of static magnetic susceptibility. For complexes 1 and 2, the effective magnetic moments are µeff ≈ 1.87 and 1.83 µB (per each Cu2+ ion), respectively, in the temperature range 50-300 K, which are close to the theoretical spin value (1.73 µB). Ferromagnetic exchange interactions between Cu(II) ions inside {Cu2(µ-X)2X2} (X = Cl, Br) dimers (J/kB ≈ 25 and 31 K for 1 and 2, respectively) or between dimers (θ' ≈ 0.30 and 0.47 K for 1 and 2, respectively) were found at low temperatures. For compounds 3 and 4, the magnetic susceptibility is well described by the Curie-Weiss law in the temperature range 1.77-300 K with µeff ≈ 1.72 and 1.70 µB for 3 and 4, respectively, and weak antiferromagnetic interactions (θ ≈ -0.4 K for 3 and -0.65 K for 4). Complexes 1-4 exhibit high catalytic activity in the oxidation of alkanes and alcohols with peroxides. The maximum yield of cyclohexane oxidation products reached 50% (complex 3). Based on the data on the study of regio- and bond-selectivity, it was concluded that hydroxyl radicals play a decisive role in the oxidation reaction. The initial products in reactions with alkanes are alkyl hydroperoxides.
RESUMEN
A synthetic approach to a new group of stable chiral C2-symmetric diimines with the 4,5-diazafluorene core has been developed based on condensation of dipinodiazafluorene with aromatic diamines. The chemical structures of new compounds were proven by spectroscopic methods and X-ray crystallography. All the compounds form solvates with organic solvents (chloroform, benzene, 1,4-dioxane) and water. Specific spectral data of the new compounds are explained using calculated data (DFT). Diimines of the pinodiazafluorene series give colored reactions with transition metal ions and can be regarded as prospective polydentate ligands with interesting luminescent and chiroptical properties.
