ABSTRACT
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 â¼550 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 â¼150 times greater than that of α-SiO2.
ABSTRACT
o-Phthalonitrile couples with chelating dioxime on nickel(II), with formation of a dinuclear nickel(II) macrocyclic complex--the first representative of a new class of imine-appended macrocycles.
ABSTRACT
4,7-Dithiadecane-2,9-dione dioxime forms both violet and purple-black nickel(II) complexes with unexpected structural properties, quite unlike the square-planar chelates formed by its dithiaundecane homologue. Their perchlorate salts were isolated and examined crystallographically. The lilac product [Ni{(Dtox)(CH(3)CNH)(2)}](ClO(4))(2) entails a bis(iminoether) ligand formed by coupling of the dioxime with two moles of acetonitrile. The purple-black complex results from further ligand deprotonation, to yield trinuclear, antiferromagnetic [Ni(3)(Dtox)(DtoxH)(2)](ClO(4))(2).CH(3)CN, which maintains its structure in solution. The first one-electron electrochemical oxidation step is relatively facile for the trimer, yielding a Ni(2)(II)Ni(III) complex, whereas for [Ni{(Dtox)(CH(3)CNH)(2)}](ClO(4))(2) a transient Ni(I) species is accessible. Comment is made on those properties (coordination number, donor type, core charge) of nickel(II) coordination spheres that affect the accessibility of the corresponding nickel(I) and nickel(III) forms. [Ni(3)(Dtox)(DtoxH)(2)](ClO(4))(2).CH(3)CN crystallizes in the monoclinic space group P2(1)/n, with cell parameters a = 12.295(2) Å, b = 17.360(2) Å, c = 20.764(2) Å, alpha = 90 degrees, beta = 94.080(10) degrees, gamma = 90 degrees, V = 4420.7(6) Å(3), Z = 4. [Ni{(Dtox)(CH(3)CNH)(2)}](ClO(4))(2) crystallizes in the rhombohedral space group R&thremacr;, with cell parameters a = 32.954(2) Å, b = 32.954(2) Å, c = 13.477(2) Å, alpha = 90 degrees, beta = 90 degrees, gamma = 120 degrees, Z = 18.
