Luminescence and Nonlinear Optical Properties in Copper(I) Halide Extended Networks.

The syntheses, structures, and luminescence properties of a series of copper(I) halide coordination polymers, prepared with mono- and bidentate N-heteroaromatic ligands, are reported. These metal-organic coordination networks form [Cu2I2L]n for bidentate ligands (where L = pyrazine (1), quinazoline (2)) and [CuIL]n for monodentate ligands (where L = 3-benzoylpyridine (3) and 4-benzoylpyridine(4)). Both sets of compounds exhibit a double-stranded stair-Cu2I2-polymer, or "ladder" structure with the ligand coordinating to the metal in a bidentate (bridging two stairs) or monodentate mode. The copper bromide analogues for the bidentate ligands were also targeted, [Cu2Br2L]n for L = pyrazine (5) with the same stair structure, as well as compositions of [CuBr(L)]n for L = pyrazine (6) and quinazoline (7), which have a different structure type, where the -Cu-Br- forms a single-stranded "zigzag" chain. These copper halide polymers were found to be luminescent at room temperature, with emission peaks ranging from ∼550 to 680 nm with small shifts at low temperature. The structure (stair or chain), the halide (I or Br), as well as the ligand play an important role in determining the position and intensity of emission. Lifetime measurements at room and low temperatures confirm the presence of thermally activated delayed fluorescence, or singlet harvesting for compounds 1, 2, and 7. We also investigated the nonlinear optical properties and found that, of this series, [CuBr(quinazoline)]n shows a very strong second harmonic generating response that is ∼150 times greater than that of α-SiO2.

Eu(III) and Tb(III) luminescence sensitized by thiophenyl-derivatized nitrobenzoato antennas.

Thiophenyl-derivatized nitrobenzoic acid ligands have been evaluated as possible sensitizers of Eu(III) and Tb(III) luminescence. The resulting solution and solid-state species were isolated and characterized by luminescence spectroscopy and X-ray crystallography. The Eu(III) complex with 2-nitro-3-thiophen-3-yl-benzoic acid, 1, crystallizes in the monoclinic space group C2/c with a = 28.569(3) A, b = 17.7726(18) A, c = 17.7073(18) A, beta= 126.849(2) degrees, and V = 7194.6(13) A3. The Tb(III) complex with this ligand, 2, is isostructural, and its cell parameters are a = 29.755(6) A, b = 18.123(4) A, c = 19.519(4) A, beta= 130.35(3) degrees, and V = 8021(3) A3. Eu(III) crystallizes with 3-nitro-2-thiophen-3-yl-benzoic acid as a triclinic complex, 3, in the space group P1 with a = 11.045(2) A, b = 12.547(3) A, c = 15.500(3) A, alpha = 109.06(3)degrees, beta = 94.79(3) degrees, gamma = 107.72(3) degrees. and V = 1893.5(7) A3. With the ligand 5-nitro-2-thiophen-3-yl-benzoic acid, Eu(III) yields another molecular compound, 4, triclinic P1, with a = 10.649(2) A, b = 14.009(3) A, c = 15.205(3) A, alpha= 112.15(3) degrees, beta = 100.25(3) degrees, gamma = 106.96(3) degrees, and V = 1900.5(7) A3. All compounds dissolve in water and methanol, and the methanolic solutions are luminescent. The solution species have a metal ion-to-ligand ratio of 1:1. The quantum yields have been determined to be in the range of 0.9-3.1% for Eu(III) and 4.7-9.8% for Tb(III). The highest values of these correspond to the most intense luminescence reported for Ln(III) solutions with this type of sensitizer. The lifetimes of luminescence are in the range of 248.3-338.9 micros for Eu(III) and 208.6-724.9 micros for Tb(III). The stability constants are in the range of log 11 = 2.73-4.30 for Eu(III) and 3.34-4.18 for Tb(III) and, along with the energy migration pathways, are responsible for the reported efficiency of sensitization.