Min-Dong Chen

Photoluminescence properties of dinuclear lanthanide complexes in visible and near-infrared region

Several dinuclear lanthanide complexes of Ln2(HTH)6TPPHZ (Ln=Eu, Sm, Er, Nd, Yb, Ho; TPPHZ=Tetrapyrido (3,2-a:2′,3′-c:3′,2″-h:2′″,3′″-j) phenazine; HTH=4,5,5,6,6,6-heptafluroro-1-(2-thienyl)hexane-1,3-dione were synthesized and their photoluminescence properties were investigated. After ligand-mediated excitation, all the complexes showed the characteristic luminescence of the corresponding Ln(III) ions in the visible and NIR regions attributed to energy transfer from the ligands to the metal center. For Eu2(HTH)6TPPHZ complex, the quantum efficiency was calculated as 9.6% with the major 5D0 lifetime (477.86 μs) by the equation ϕ=τobs/τR, where τobs was observed luminescence lifetime and τR was radiative (or natural) lifetime (5 ms), and 14.9% with air-equilibrated aqueous [Ru(bpy)3](II)·2Cl− solution as a standard sample (ϕstd=2.8%), in CH2Cl2 solution at room temperature.

Adducts of aqua complexes of Ln3+ with a di-hydroxylated symmetrical octamethyl-substituted cucurbituril: potential applications for isolation of heavier lanthanides

The interaction of a series of lanthanide cations (Ln3+) with a di-hydroxylated symmetrical octamethyl-substituted cucurbituril {(OH)2OMeQ[6]} has been investigated. Single-crystal X-ray diffraction analysis has revealed that the interaction results in the formation of adducts of (OH)2OMeQ[6] with aqua complexes of lanthanide cations ([Ln(H2O)8]3+), Ln = Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu in (OH)2OMeQ[6]–Ln(NO3)3–H2O systems. However, no solid crystals were obtained from systems containing La, Ce, Pr, Nd and Sm. X-ray diffraction analysis has revealed that although the solid adducts fall into two isomorphous groups, there are no significant differences in the interactions between (OH)2OMeQ[6] and [Ln(H2O)8]3+ complexes and in the corresponding supramolecular assemblies. Thermodynamic parameters for the interaction between (OH)2OMeQ[6] and [Ln(H2O)8]3+ complexes based on isothermal titration calorimetry experiments show two periods corresponding to the above two systems, with the lighter lanthanide cations preferring to remain in solution and the heavier lanthanide cations forming crystalline solids. Energy dispersive spectroscopy (EDS) has shown that the interaction of OMeQ[6] with lanthanide cations could provide a means of isolating heavier lanthanide cations from their lighter counterparts.

Preparation, crystal structure and luminescence of lanthanide coordination polymers with 2,2′-dimethyl-4,4′-bipyridine-N,N′-dioxide

Four coordination polymers of the bidentate ligand 2,2′-dimethyl-4,4′-bipyridine-N,N′-dioxide (L), [La(L)(NO3)3(H2O)] n (1), {[Gd2(L)3(NO3)6]·6H2O} n (2), {[Sm(L)2(H2O)4]·3ClO4·2L·4H2O} n (3) and {[Nd(L)2(H2O)4]·3ClO4·2L·4H2O} n (4) have been synthesized by the diffusing solvent mixture method. Results of X-ray diffraction analysis reveal that 1, with a Ln/L stoichiometry of 1:1, displays a rare 3-D three-fold interpenetrating diamondoid framework, while 2 has a Ln/L stoichiometry of 1:1.5 and exhibits a polycatenane network with a {82,10} topology and large channels accommodated by water. Complexes 3 and 4, with Ln/L stoichiometry of 1:2, have 3-D two-fold interpenetrating diamondoid structures and large voids. Nonlinear optical property of 2 and luminescence of 3 were also investigated.

Syntheses and photoluminescence properties of rhenium(I) complexes based on dipyrido[3,2-a:2′,3′-c]phenazine derivatives with carbazole moiety

Four rhenium(I) complexes ReL1–ReL4 based on dipyrido[3,2-a:2′,3′-c]phenazine (L1) and derivatives L2-L4 ligands (L2: 10,13-dibromodipyrido[3,2-a:2′,3′-c]phenazine, L3: 10-bromo-13-carbazolyl-dipyrido[3,2-a:2′,3′-c]phenazine, L4: 10,13-dicarbazolyldipyrido[3,2-a:2′,3′-c]phenazine) were synthesized and characterized. The Re(I) complexes ReL1–ReL4 show photoluminescent emissions at 556, 582, 637 and 662 nm, respectively, assigned to d (Re)→ ∗ (diimine) MLCT phosphorescence in CH2Cl2 solution. The carbazole containing complexes ReL3 and ReL4, as compared to ReL1, exhibit higher luminescence. These observations imply that modification of diimine rhenium(I) carbonyl complexes with carbazole moiety would lead to efficient phosphorescent properties.

Study on the reactions of zinc carboxylate complexes with copper(II) or cobalt(II) ions

Reaction of zinc carboxylate, [Zn(pc)(Phen)(H2O)]2·6H2O (1; H2pc = 4-hydroxyphthalic acid), with Cu(NO3)2 or Co(NO3)2 is investigated. By immersion of single crystals of 1 into aqueous solutions of Cu(NO3)2 and Co(NO3)2, respectively, metal ion exchange induced single-crystal to single-crystal (SCTSC) transformation products, [Cu0.63Zn0.37(pc)(Phen)(H2O)]2·6H2O (2) and [Co0.69Zn0.31(pc)(Phen)(H2O)]2·6H2O (3), could be obtained. As heterogeneous catalysts, central metal ion-exchanged products 2 and 3 show high catalytic efficiency in the green oxidative polymerization of 2,6-dimethylphenol (DMP) to poly(1,4-phenylene ether) in the presence of H2O2 as oxidant in water under mild conditions with reuse without significant loss of activity through three runs, which suggests that these catalysts are efficient, mild, and easily recyclable for the oxidative coupling of DMP. Our results indicate that central metal ion exchange might be a powerful and effective method to modify properties of crystalline materials by varying the central metal ions under moderate conditions. Graphical Abstract By immersion of selected big single crystals of [Zn(pc)(Phen)(H2O)]2·6H2O (1; H2pc = 4-hydroxyphthalic acid) into aqueous solutions of Cu(NO3)2 and Co(NO3)2, respectively, two central metal ion exchange induced SCTSC transformation products, [Cu0.63Zn0.37(pc)(Phen)(H2O)]2·6H2O (2) and [Co0.69Zn0.31(pc)(Phen)(H2O)]2·6H2O (3), can be obtained. As heterogeneous catalysts, central metal ion-exchanged products 2 and 3 showed high catalytic efficiency in the green oxidative polymerization of DMP. Our results indicate that central metal ion exchange might be regarded as a powerful and effective method to modify properties of crystalline materials only by varying central metal ions under moderate conditions.