A series of Hdmh mononuclear dysprosium complexes, namely [Dy(dmh)3(MeOH)] (1), [Dy(dmh)3(2,2′-bpy)]2 (2), and [Dy(dmh)3(phen)] (3), and analogue complexes of complex 2 [Lu(dmh)3(2,2′-bpy)]2 (4) (Hdmh = 2,6-dimethyl-3,5-heptanedione, 2,2′-bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline), have been isolated by reaction of Hdmh and LnCl3·6H2O with 2,2′-bpy/phen auxiliary ligands. X-ray crystallographic analysis reveals that all complexes 1–4 are mononuclear complexes. Complex 1 is seven-coordinated by three dmh ligands and one methanol. Complexes 2, 3 and 4 are all eight-coordinated by three dmh ligands and one 2,2′-bpy or phen. Magnetic studies indicate that complexes 2 and 3 exhibit slow relaxation at zero field but complex 1 does not. Strikingly, complex 2 exhibits mainly single slow relaxation under zero dc field and double slow relaxation under optimized dc field. In contrast, complex 3 exhibits double slow relaxation under zero dc field and single slow relaxation under optimized dc field. The origins of the double slow relaxation modes of complex 2 have been verified by dilution sample of complex 4.

•One-dimensional composite nanofibers has been successfully synthesized by electrospinning.•The origin of the enhanced luminescent properties of Eu(TFI)3TPPO/PVP has been investigated.•The interaction between Eu(TFI)3TPPO and PVP is studied.A new one-dimensional luminescent composite nanofiber of Eu(TFI)3TPPO/PVP (TFI = 2-(2,2,2-trifluoroethyl)-1-indone, TPPO = triphenylphosphine oxide, PVP = Poly(vinyl pyrrolidone) has been successfully prepared by electrospinning. The unique microstructure, thermal stability, and luminescent characteristics of the composite nanofibers have been revealed by high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), fluorescence microscope (FM), fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible spectroscopy (UV–Vis), thermogravimetric analysis (TGA), and fluorescence spectrophotometer (FS). The origin of the enhanced luminescent properties of composite nanofibers has been identified by Judd-Ofelt analysis. The experimental results suggest that PVP plays an essential role on the interaction between the Eu(TFI)3TPPO precursor and neighboring chain segments of PVP, leading to the increased polarization degree of Eu3+ ions and significantly enhanced the electronic dipole allowed transitions of Eu3+ ions, which further enhances the luminescent efficiency of composite nanofiber of Eu(TFI)3TPPO/PVP.Download high-res image (344KB)Download full-size image

Two types of sixteen complexes 1–16, namely, {[Ln(TFBDC)1.5(H2O)]·2H2O}n [Ln = Pr (1) and Nd (2)] and {[Ln(TFBDC)1.5(H2O)2]·H2O}n [Ln = Ce (3), Pr (4), Nd (5), Sm (6), Eu (7), Gd (8), Tb (9), Dy (10), Ho (11), Er (12), Yb (13) and Lu (14)], {[Dy0.281Eu0.719(TFBDC)1.5(H2O)2]·H2O}n (15) and {[Gd0.871Eu0.103Tb0.026(TFBDC)1.5(H2O)2]·H2O}n (16), were isolated by the reaction of LnCl3·6H2O with 2,3,5,6-tetrafluoroterephthalic acid (H2TFBDC). X-ray crystallographic analysis revealed that 1 and 2 exhibit 3D network structures and complexes 3–14 feature 2D network structures formed via three different coordination modes of the ligand. Luminescence spectra revealed that these complexes exhibit broad-spectrum luminescence from the visible to the near-infrared (NIR) region. Unexpectedly, complex 1 exhibits a unique NIR luminescence pattern and the longest lifetime among reported molecular praseodymium complexes. White-light emission was realized via three approaches using the single-component complex 6 (Sm), the two-component complex 15 (Eu and Dy) and the three-component complex 16 (Eu, Tb and Gd). Complex 9 exhibits high sensitivity and selectivity in its luminescence response to benzaldehyde, which provides a promising luminescent sensor for the detection of benzaldehyde.

Four new lanthanide coordination complexes incorporating with the flexible ligands 3-(3-(pyridin-4-yl)-1,2,4-oxadiazol-5-yl) propanoic carboxylate (NaL1) and 3-(3-pyridin-3-yl-[1,2,4]oxadiazol-5-yl)-propionic carboxylate (NaL2), namely, [Ln(L)2(NO3)(H2O)2] [Ln = La (1) and Dy (2)], [LnL3H2O] [Ln = La (3) and Pr (4)] have been isolated. X-ray crystallographic analysis indicates that 1 and 2 are isostructural with two dimension network structure as well as complexes 3 and 4 are isostructural with one dimension chain structure.

Two discrete salen type homo-multinuclear Yb3 and Yb4 complexes, namely, [Yb3L3(OAc)3]·3CH3OH·H2O (1) and [Yb4L2(OAc)4(μ3-OH)2(H2O)2](ZnCl4)·3CH3OH (2) (H2L = N,N′-bis(2-oxy-3-methoxybenzylidene)-1,2-phenylenediamine) have been synthesized by reactions of H2L and different ytterbium salts. X-ray crystallographic analysis reveals that complex 1 exhibits a triple-decker Yb3 sandwich structure with a ratio of H2L:Yb = 1:1, while complex 2 exhibits a defect-dicubane Yb4 core with a ratio of H2L:Yb = 1:2. The NIR luminescence of complexes 1 and 2 have been investigated and discussed.

Three new salen-type 3d–4f heteronuclear metal complexes incorporating with the semi-rigid ligand N,N′-bis(2-hydroxy-3-methoxybenzylidene)-1,2-diaminocyclohexane (H2L), namely, [(CuClL)LaCl2(CH3OH)3]·H2O (1), [(CuClL)DyCl2(CH3OH)2] (2) and [(CuClL)2GdCl2(CH3OH)2] (3), have been isolated. X-ray crystallographic analysis indicates that 1 and 2 possess the typical heterodinuclear structures, while, complex 3 has a trinuclear structure. In 1–3, the Cu2+ ion is in the N2O2 cavity of the ligand and the lanthanide ions are to the O2O2 set of the ligand. The coordination numbers of the lanthanide ions are reduced from 9 to 8 along with lanthanide contraction. These results further enrich the structures of salen type 3d–4f heteronuclear complexes.

Three novel N,N′-bis(2-hydroxy-3-methoxybenzylidene)-1,3-diaminopropane dimeric lanthanide complexes, namely, [{H2L}Sm(NO3)3]2·H2O (1), [{H2L}Gd(NO3)3]4·CH3OH (2), [{H2L}Lu(NO3)3]4·H2O (3) (H2L = N,N′-bis(2-hydroxy-3-methoxybenzylidene)-1,3-diaminopropane) and three new N,N′-bis(2-hydroxy-3-methoxybenzylidene)-1,3-diaminopropane 3d-Gd heterodinuclear complexes, namely, [{LCo}(CH3COO)(CH3COOH)Gd(NO3)2] (4), [{LNi(MeOH)2}Gd(NO3)3]·2MeOH (5) and [{(L)Zn(HNO3)}Gd(NO3)3]·NO3·H3O·MeOH (6) have been synthesized and isolated. X-ray crystallographical analysis reveals that complexes 1–3 are isomorphic with unique dimeric topology. Complexes 4–6 are of discrete 3d–4f dinuclear cores. Magnetic properties of complexes 2 and 4–6 are systematically investigated. Complexes 4 and 5 are ferromagnetic, while 2 and 6 are antiferromagnetic.Novel N,N′-bis(2-hydroxy-3-methoxybenzylidene)-1,3-diaminopropane lanthanide complex with unique dimeric topology and antiferromagnetic coupling between the Gd(III) ions.

Three Salen-like gadolinium complexes, namely, mononuclear (4f) complex [{H2L}Gd(NO3)3] (1), heterodinuclear (3d–4f) complex [{LCu}Gd(NO3)3]·0.25H2O (2) and dimeric heterotrinuclear (3d–4f–3d′) complex [{LCu}Gd(H2O)3{Fe(CN)6}]2·6H2O (3) [H2L = N,N′-ethylene-bis(3-methoxysalicylideneimine)] have been synthesized by stepwise reactions. X-ray diffraction analysis reveals that 1 is of a discrete structure in which H2L coordinates to gadolinium ion through O2O2 moiety. Then, addition of Cu(Ac)2·H2O to the mononuclear lanthanide complex yields expected heterodinuclear (3d–4f) complexes [{LCu}Gd(NO3)3]. 3 features a unique 1D ladder-like topology structure through the intermolecular double links of Cu–N bonds. The measurement of variable-temperature magnetic susceptibility reveals that complex 1 exhibits antiferromagnetic interaction while 2 and 3 exhibit ferromagnetic interaction between spin carriers. The correlations between the structure and magnetism are described and discussed.

An array of TCNQ (TCNQ = 7,7,8,8-tetracyano-p-quinodimethane) lanthanide complexes, namely, [Ln2(TCNQ)4(H2O)10(EtOH)2][2TCNQ]·xH2O [Ln = La (1, x = 5), Pr (2, x = 3)], [Ln2(TCNQ)4(H2O)10][2TCNQ]·yH2O [Ln = Gd (3, y = 6), Dy (4, y = 5)] and [Ln(TCNQ)2(H2O)6][TCNQ]·H2O·MeOH [Ln = Er (5), Lu (6)], have been synthesized by salt-elimination reactions. X-ray crystallographic analysis indicates that 1–6 are discrete ion complexes. Cations of 1–4 adopt a dimer structure, while cations of 5 and 6 display a monomer structure. The magnetic study proposes that an antiferromagnetic interaction between TCNQ radicals exists in 1–6. The depopulation of the Stark levels for 2 and 5 leads to a continuous decrease in χmT when the samples are cooled from 300 K to 2 K. The desolvated 3, namely, 3a exhibits a unique magnetic conversion from the magnetic disordering to the magnetic ordering at 4 K. 4 shows a ferromagnetic coupling between paramagnetic centers.

Reaction of Ln(NO3)3·6H2O with H2L [H2L=N,N′-bis(salicylidene)propane-1,2-diamine] gives rise to five new coordination polymers, viz. [Pr(H2L)(NO3)3(MeOH)]n (1) and [Ln(H2L)1.5(NO3)3]n [Ln=La (2), Eu (3), Sm (4) and Gd (5)]. Crystal structural analysis reveals that H2L effectively functions as a bridging ligand forming one-dimensional (1D) chain and two-dimensional (2D) open-framework polymers. Solid-state fluorescence spectra of 3 and 4 exhibit typical red fluorescence of Eu(III) and Sm(III) ions at room temperature while 2 emits blue fluorescence of ligand H2L. The lowest triplet level of ligand H2L was calculated on the basis of the phosphorescence spectrum of 5. The energy transfer mechanisms in the lanthanide polymers were described and discussed.Five coordination polymers were synthesized. Given is the perspective view of a H2L bridged hexametal ring along the c axis for 2 (La), excitation and emission spectra of 3 (Eu) and 4 (Sm) in the solid state.

Treatments of p-ferrocenylbenzoate [p-NaOOCH4C6Fc, Fc=(η5-C5H5)Fe(η5-C5H4)] with Ln(NO3)3·nH2O afford seven p-ferrocenylbenzoate lanthanide complexes {[Ln(OOCH4C6Fc)2(μ2-OOCH4C6Fc)2(H2O)2](H3O)}n [Ln=Ce (1), Pr (2), Sm (3), Eu (4), Gd (5), Tb (6) and Dy (7)]. X-ray crystallographic analysis reveals that the isomorphous complexes {[Ce(OOCH4C6Fc)2(μ2-OOCH4C6Fc)2(H2O)2](H3O)}n (1) and {[Pr(OOCH4C6Fc)2(μ2-OOCH4C6Fc)2(H2O)2](H3O)}n (2) form a unique 1D double-bridged infinite chain structure bridged by μ2-OOCH4C6Fc groups. Each Ln(III) ion adopts a dodecahedron coordination environment with eight coordinated oxygen atoms from two terminal monodentate coordinated FcC6H4COO− units, two terminal monodentate coordinated H2O molecules and four μ2-−OOCH4C6Fc units. The luminescent spectra reveal that only 4 and 6 exhibit characteristic emissions of lanthanide ions, Eu(III) and Tb(III) ions, respectively. The variable-temperature magnetic properties of 5 and 7 suggest that a ferromagnetic coupling between spin carriers may exist in 5.Seven p-ferrocenylbenzoate lanthanide coordination polymers were synthesized. Given is the perspective view of a unique 1D double-bridged infinite chain structure of 1, excitation and emission spectra of 6 and plots of χmT vs. T and χm−1 vs. T of 5.

Reactions of H2L [H2L = N,N′-bis(3-methoxysalicylidene)propane-1,2-diamine] and Ln(NO3)3 · 6H2O give rise to two different mononuclear 4f complexes, namely, {[(H2L)La(NO3)3(MeOH)] · H2O}n (1) and [(H2L)Nd(NO3)3] (2). Further additions of Cu(Ac)2 · H2O to the mononuclear 4f complexes yield expected heterodinuclear Cu-4f complexes [LCu(Me2CO)Ln(NO3)3] (3, Ln = Nd; 4, Ln = Eu; 5, Ln = Dy). Complex 1 is a unique 1D polymeric chain structure, and 2 is one of the few structurally characterized discrete hexadentate salen-type mononuclear 4f complexes. Complexes 3–5 are similar to their analogues. However, they are prepared by a reversed synthetic route in contrast to their isomorphic complexes. Electrochemical behavior of heterodinuclear Cu-4f complexes 3–5 has been examined by cyclic voltammetry in acetonitrile. The redox potential of heterodinuclear Cu-4f complexes 3–5 shows significant anodic shift comparing to that of mononuclear copper complex (LCu). A tendency of anodic shift was observed in a sequence of 3 < 4 < 5. This results from the modulating effect of coordination geometry around Cu(II) ion on redox potential.A stepwise synthesis of mononuclear 4f and heterodinuclear Cu-4f complexes has been investigated through structural determination of the intermediates and the final products. Electrochemical behavior of heterodinuclear Cu-4f complexes shows significant anodic shift comparing to that of mononuclear copper complex (LCu).

The stepwise synthesis of mononuclear (4f) and heterodinuclear (3d–4f) Salen-like complexes has been investigated through structural determination of the intermediate and final products occurring in the process. In the first step, reactions of ligand H2L and Ln(NO3)3 · 6H2O give rise to three mononuclear lanthanide complexes Ln(H2L)(NO3)3 [H2L = N,N′-ethylene-bis(3-methoxysalicylideneimine), Ln = Nd (1), Eu (2) and Tb (3)], in which N,N′-ethylene-bis(3-methoxysalicylideneimine) acts as tetradentate ligands with the O2O2 set of donor atoms capable of effective coordination. These species are fairly stable and have been isolated. Then, addition of Cu(Ac)2 · H2O to the mononuclear lanthanide complex yields expected heterodinuclear (3d–4f) complexes Cu(L)Ln(NO3)3 · H2O [Ln = Nd (4) and Eu (5)] where the Cu(II) ion is inserted to the inner N2O2 cavity. Luminescent analysis reveals that complex 3 exhibits characteristic metal-centered fluorescence of Tb(III) ion. However, the characteristic luminescence of both Sm(III) and Eu(III) ions is not observed both in solution and solid state of the complexes.The stepwise synthesis of mononuclear (4f) and heterodinuclear (3d–4f) Salen-like complexes has been investigated. In the first step, reaction of ligand H2L and Ln(NO3)3 · 6H2O gives rise to three mononuclear lanthanide complexes Ln(H2L)(NO3)3 [H2L = N,N′-ethylene-bis(3-methoxysalicylideneimine), Ln = Nd (1), Eu (2) and Tb (3)]. Then, addition of Cu(Ac)2 · H2O to the mononuclear lanthanide complex yields expected heterodinuclear (3d–4f) complexes Cu(L)Ln(NO3)3 · H2O [Ln = Nd (4) and Eu (5)]. Luminescent properties of the complexes have been discussed.

An array of TCNQ (TCNQ = 7,7,8,8-tetracyano-p-quinodimethane) lanthanide complexes, namely, [Ln2(TCNQ)4(H2O)10(EtOH)2][2TCNQ]·xH2O [Ln = La (1, x = 5), Pr (2, x = 3)], [Ln2(TCNQ)4(H2O)10][2TCNQ]·yH2O [Ln = Gd (3, y = 6), Dy (4, y = 5)] and [Ln(TCNQ)2(H2O)6][TCNQ]·H2O·MeOH [Ln = Er (5), Lu (6)], have been synthesized by salt-elimination reactions. X-ray crystallographic analysis indicates that 1–6 are discrete ion complexes. Cations of 1–4 adopt a dimer structure, while cations of 5 and 6 display a monomer structure. The magnetic study proposes that an antiferromagnetic interaction between TCNQ radicals exists in 1–6. The depopulation of the Stark levels for 2 and 5 leads to a continuous decrease in χmT when the samples are cooled from 300 K to 2 K. The desolvated 3, namely, 3a exhibits a unique magnetic conversion from the magnetic disordering to the magnetic ordering at 4 K. 4 shows a ferromagnetic coupling between paramagnetic centers.

Two types of sixteen complexes 1–16, namely, {[Ln(TFBDC)1.5(H2O)]·2H2O}n [Ln = Pr (1) and Nd (2)] and {[Ln(TFBDC)1.5(H2O)2]·H2O}n [Ln = Ce (3), Pr (4), Nd (5), Sm (6), Eu (7), Gd (8), Tb (9), Dy (10), Ho (11), Er (12), Yb (13) and Lu (14)], {[Dy0.281Eu0.719(TFBDC)1.5(H2O)2]·H2O}n (15) and {[Gd0.871Eu0.103Tb0.026(TFBDC)1.5(H2O)2]·H2O}n (16), were isolated by the reaction of LnCl3·6H2O with 2,3,5,6-tetrafluoroterephthalic acid (H2TFBDC). X-ray crystallographic analysis revealed that 1 and 2 exhibit 3D network structures and complexes 3–14 feature 2D network structures formed via three different coordination modes of the ligand. Luminescence spectra revealed that these complexes exhibit broad-spectrum luminescence from the visible to the near-infrared (NIR) region. Unexpectedly, complex 1 exhibits a unique NIR luminescence pattern and the longest lifetime among reported molecular praseodymium complexes. White-light emission was realized via three approaches using the single-component complex 6 (Sm), the two-component complex 15 (Eu and Dy) and the three-component complex 16 (Eu, Tb and Gd). Complex 9 exhibits high sensitivity and selectivity in its luminescence response to benzaldehyde, which provides a promising luminescent sensor for the detection of benzaldehyde.