Reported are the syntheses, crystal structures, and photophysical properties of 28, novel lanthanide compounds across five structural types, [Ln­(3-NO2Tp)2(NO3)] (1-Ln, Ln = La–Tm, except Pm), [Bu4N]­[Ln­(3-NO2Tp)­(NO3)3] (2-Ln, Ln = Yb, Lu), [Eu­(3-NO2Tp)2Cl­(H2O)]·2 i PrOH (3-Eu), [{Ln­(3-NO2Tp)2}2(μ2-CO3)]·MeOH (4-Ln, Ln = La–Gd, except Pm), and [{Ln­(3-NO2Tp)}4(μ2-OMe)6(μ4-O)] (5-Ln, Ln = Pr–Tb, except Pm) with the 3-nitrotrispyrazolylborate (3-NO2Tp–) ligand. The reaction of methanol or isopropanol solutions of LnX3 (X = Cl, NO3) with the tetrabutyl ammonium salt of the flexidentate 3-NO2Tp– ([Bu4N]­[3-NO2Tp]) yields Ln­(3-NO2Tp) x complexes of various nuclearities as either monomers (1-Ln, 2-Ln, 3-Eu), dimers (4-Ln), or tetramers (5-Ln) owing to the efficient conversion of atmospheric CO2 to CO3 2– (dimers) or ligand controlled solvolysis of lanthanide ions (tetramers). 3-NO2Tp– is an efficient sensitizer for both the visible and near-IR (NIR) emissions of most of the lanthanide series, except thulium. Optical measurements, supported by density functional theory calculations, indicate that the dual visible and NIR Ln3+ emission arises from two intraligand charge transfer (ILCT) transitions of 3-NO2Tp–. This is the first report of lanthanide complexes with a nitro-functionalized pyrazolylborate ligand. The derivatization of the known Tp– ligand results in new coordination chemistry governed by the increased denticity of 3-NO2Tp–, imparting remarkable structural diversity and charge transfer properties to resultant lanthanide complexes.

Nitrated lanthanide trispyrazolylborates, [Ln(4-NO2Tp)3], display Ln3+ luminescence (Ln = Pr, Nd, Sm, Eu, Tb and Dy) while the Nd3+ analogue is a single-ion magnet under a small applied field.

We report the synthesis, crystal structures, photophysical and magnetic properties of 11 novel lanthanide complexes with the asymmetrically functionalized trispyrazolylborate ligand, 4-nitrotrispyrazolylborate, 4-NO2Tp–: [Ln(4-NO2Tp)3] (Ln = La – Dy, except Pm). In depth photophysical characterization of the ligands via luminescence, reflectance and absorption spectroscopic techniques, decay lifetimes, quantum yields supported by time-dependent density functional theory (TD-DFT) and Natural Bond Order (NBO) analysis reveal that n-NO2Tp– ligands are dominated by intra-ligand charge transfer (ILCT) transitions and that second-sphere interactions are critical to the stabilization of the T1 state of n-NO2Tp– ligands and hence their ability to sensitize Ln3+ emission. The luminescence properties of the complexes indicate that 4-NO2Tp– is a poor sensitizer of Ln3+ emission, unlike 3 NO2Tp–. Moreover, the [Nd(4-NO2Tp)3] (crystallized as a hexane solvate) displays single-molecule magnet (SMM) properties, with longer relaxation times and larger barrier than the non functionalized [NdTp3], attributed to the addition of the NO2-group and subsequent rigidification of the molecular structure.

Reported are the synthesis, crystal structures and photophysical properties of twenty-eight, novel lanthanide compounds across five structural types, [Ln(3-NO2Tp)2(NO3)] (1-Ln, Ln = La -Tm, except Pm), [Bu4N][Ln(3-NO2Tp)(NO3)3] (2-Ln, Ln = Yb, Lu), [Eu(3-NO2Tp)2Cl(H2O)]•2 i PrOH (3-Eu), [{Ln(3-NO2Tp)2}2(µ2-CO3)] (4-Ln, Ln = La -Gd, except Pm) and [{Ln(3-NO2Tp)}4(µ2-OMe)6(µ4-O)] (5-Ln, Ln = Pr -Tb, except Pm) with the 3-nitrotrispyrazolylborate (3-NO2Tp -) ligand. Reaction of methanol or isopropanol solutions of LnX3 (X = Cl, NO3) with the tetrabutyl ammonium salt of the flexidentate 3-NO2Tp -, ([Bu4N][3-NO2Tp]) yields Ln(3-NO2Tp)x complexes of various nuclearities as either monomers (1-Ln, 2-Ln, 3-Eu), dimers (4-Ln) or tetramers (5-Ln) owing to the efficient conversion of atmospheric CO2 to CO3 2-(dimers) or ligand controlled solvolysis of lanthanide ions (tetramers). 3-NO2Tpis an efficient sensitizer for both the visible and near-IR (NIR) emissions of most of the lanthanide series, except thulium. Optical measurements, supported by density functional theory calculations, indicate that the dual visible and NIR Ln 3+ emission arises from two intra-ligand charge transfer (ILCT) transitions of 3-NO2Tp -. This is the first 2 report of lanthanide complexes with a nitro-functionalized pyrazolylborate ligand. The derivatization of the known Tpligand results in new coordination chemistry governed by the increased denticity of 3-NO2Tp -, imparting remarkable structural diversity and charge transfer properties to resultant lanthanide complexes.

No abstract