Xu-Hui Zhu

Triboluminescence and crystal structures of europium(III) complexes

Abstract The triboluminescence of four europium complexes [Eu(TTA) 4 ]Y (TTA: 2-thenoyltrifluoroacetone; complex 1 , Y1: 1,2-dimethylpyridinium; complex 2 , Y2: 1,2,6-trimethylpyridinium; complex 3 , Y3: N -methylisoquinolium; complex 4 , Y4: 4-aminopyridinium) was observed. The triboluminescent spectra of 1 – 4 and the crystal structures of 1 , 3 and 4 were determined. The triboluminescence maxima are all similar to those of their photoluminescence, indicating identical emitting species. The triboluminescent activity of 1 may be correlated with its non-centrosymmetric space group. The disorder of the thienyl rings and CF 3 groups in centrosymmetric 3 and 4 may be responsible for their triboluminescent activities.

Syntheses and metal complexes of a quadridentate NNSS ligand derived from S-benzyl dithiocarbazate (H2L) and crystal structure of the complex CuL

Abstract The quadridentate N2S2 Schiff base ligand, H2L, prepared by the condensation of S-benzyl dithiocarbazate with 1,4-bis (2′-formylphenyl)-1,4-dioxabutane in a 2:1 molar ratio, reacts with divalent metal ions to form the neutral metal complexes, ML (M=Ni, Cu, Zn). The complexes have been characterized by physico-chemical techniques and the single crystal X-ray structure of the Cu (II) complex shows the geometry around the metal atom to be distorted square planar. The monomeric units are weakly associated into dimers via a long Cu–S interaction [2.9519 (8) A].

[4-(4-Methylphenyl)-3,5-bis(2-pyridyl)-4H-1,2,4-triazole]bis(triphenylphosphine)silver(I) perchlorate

The coordination geometry of silver(I) in the title compound, [Ag(C 19 H 15 N 5 )(C 18 H 15 P) 2 ]ClO 4 , is distorted tetrahedral. The pyridyl groups, the substituted benzene ring and the 1,2,4-triazole moiety do not share a common plane. The perchlorate ion is highly disordered and is involved in C-H...O hydrogen bonding.

Unambiguous cis-coordination of mono- and bi-dentate Lewis bases to Ni(SN)2 Schiff-base complexes derived from S-alkyl dithiocarbazate

The bidentate Schiff-base ligand, HL1, prepared by condensation of equivalent molar amount of o-nitrobenzaldehyde with S-benzyl dithiocarbazate, yielded the neutral square-planar complex, NiL12 (1) in the presence of Ni(OAc)2·4H2O. Addition of pyridine to (1) and phenanthroline (phen) to NiL (3) afforded the adducts NiL12(py)2·1.5H2O (2) and NiL(phen) (4), respectively, where H2L is a known quadridentate (NS)2 ligand. Single crystal X-ray analysis of (2) and (4) showed that the pyridine rings and phen occupy cis-positions in the octahedral adducts. In both cases, one N–Ni bond in the parent Ni(NS)2 complexes is severely perturbed, thus facilitating cis-addition of the Lewis bases. The present results together with those reported previously show that cis-addition is preferred in the addition reaction of Ni(NS)2 Schiff-base complexes derived from S-alkyl dithiocarbazate. Addition of pyridine and 2,2′-bipyridine to NiL (3) is also discussed.

CRYSTAL STRUCTURES AND TRIBOLUMINESCENT ACTIVITIES OF SAMARIUM(III) COMPLEXES

Abstract The triboluminescence spectra and crystal structures of 1,2-dimethylpyridinium tetrakis(2-thenoyltrifluoroacetonato)samarium(III) (1) and 1,2,6-trimethylpyridinium tetrakis(2-thenoyltrifluoroacetonato)samarium(III) (2) were determined. The triboluminescent maximums are similar to those of the photoluminescence. Complex 1 is centrosymmetric and the triboluminescent emission may correlate with the disorder of all S atoms, all CF3 groups and the cation. The triboluminescent activity of complex 2 may correlate with its noncentrosymmetric space group. Complex 1 crystallizes in the monoclinic space group P21/a with cell parameters a = 19.874(2) Å, b = 22.922(2)Å, c = 21.188(1)Å, β = 108.126(6)°, V = 9173(1)Å3; Z = 8; R = 0.0758 and Rw = 0.1315. Complex 2 crystallizes in the monoclinic space group Pn with cell parameters a = 11.2808(6)Å, b = 11.0199(5)Å c c = 18.4336(9)Å, β = 108.126(6)° V = 2285.28(19)Å3; Z = 4; R = 0.0347 and Rw = 0.0900. All the structures were refined by full-matrix least squares methods.

CRYSTAL STRUCTURE AND THERMAL ANALYSIS OF A 4,4′-BIPY-BRIDGED BINUCLEAR ZINC(II) COMPLEX, 2[R2NCS2]2 · Zn(4,4′-BIPY) (R=PIPERIDYL)

Abstract The crystal structure of the title complex 2[R2NCS2]2 · Zn(4,4′-bipy) (R = Piperidyl), 1, revealed that it consists of dimers made up from two crystallographically independent molecules. Each zinc atom in 1 forms a 5-coordinate pseudo-square-based pyramidal arrangement (with four Zn-S and one Zn-N interactions). Bondlengths to Zn with the coordinating atoms are comparable to those in other Zn(II) dithiocarbamate complexes. The piperidine ring has a chair conformation. To allow improved packing, the title complex molecules form an approximately linear arrangement extending along both a and b. TGA showed that 1 is decomposed in two close steps to produce ZnS as identified by residual weight. The complex 1 crystallizes in the monoclinic space group C2/c with cell parameters: a = 22.021(5), b = 22.215(3), c = 17.537(2) Å, β = 93.49(2)°, V = 8563(3) Å3 and Z = 8. The structure was refined by full-matrix least-squares methods to R = 0.067, Rw = 0.114.

Crystal structures, molecular packing and picosecond optical limiting properties of quadridentate Schiff base divalent metal complexes derived from S-benzyl dithiocarbazate

The neutral divalent metal complexes ML [H2L=1,4-bis(2′-formylphenyl)-1,4-dioxabutane bis(S-benzyl dithiocarbazate); M=Ni, Pd and Zn] show strikingly different crystal packing patterns. In NiL, C32H28O2N4S4Ni the geometry around the metal atom is shown to be distorted square planar with a shortest Ni(1)···S(1A) (ethereal sulfur) contact of 3.547(2) A in neighboring molecules. The coordination configuration about PdL, C32H28O2N4S4Pd, is square planar with a closest Pd(1)···S(1A) (thiolato) contact of 3.674(1) A in neighboring molecules. The molecular packing of PdL in the unit cell is different from that of NiL, but like a previously reported structure of CuL. Unlike NiL and PdL the molecular structure of ZnL, C32H28O2N4S4Zn, has a C2 crystallographic axis and the monomer is woven into a polymeric structure by weak intermolecular S(thiolato)···H interactions of 2.836 A. The picosecond optical limiting properties of ML [M=Cu(II), Ni(II), Pd(II) and Zn(II)] were investigated. The limiting threshold for PdL is ca. 0.9 J cm−2, comparable to that of C60 when an aperture is placed in front of the transmission detector, and ca. 2.0 J cm−2 without an aperture. The observed optical limiting effects are attributed to both nonlinear absorption and nonlinear refraction processes.

Crystal Structure and Triboluminescence Spectrum of A μ2-(ONC5H5) Bridging Dinuclear Europium(III) Complex

The crystal structure and triboluminescence spectrum of a μ2-(ONC5H5) bridging dinuclear europium(III) complex, Eu2(TTA)6(PyO)2 where HTTA=2-thenoyltrifluoroacetone, PyO=pyridine N-oxide, are reported. It is centrosymmetric and two Eu(III) atoms are bridged by two pyridine oxide oxygen atoms. The Eu……Eu distance is 4.2137(9) Å. The triboluminescence maximum is similar to that of the photoluminescence and the disorder of the thienyl rings and CF3 groups may be responsible for its triboluminescent activity. The complex crystallizes in the triclinic space group P&1macron; with cell parameters a = 12.239(1), b = 12.614(2), c = 14.048(2) Å, α = 110.31(1), β = 112.05(1), γ = 99.23(1)°, V = 1776.6(4) Å 3 and Z = 2. The strcutre was refined by full-matrix least squares methods to R = 0.0451 and R w = 0.01170.

Bis[2-(phenylazo)imidazole-N]silver(I) nitrate methanol solvate

The title compound, bis(2-phenyldiazenyl-1H-imidazole-N)silver(I) nitrate methanol solvate, [Ag(C 9 H 8 N 4 ) 2 ]NO 3 .CH 3 OH, is a monomeric complex linearly coordinated by two N atoms from two different imidazole rings, with Ag-N bond distances of 2.138 (3) and 2.147 (3) A, and an N-Ag-N bond angle of 174.9 (1)°. The crystal packing is stabilized by weak intramolecular N-H...O and O-H...O hydrogen bonds and an intermolecular N-H...O hydrogen bond involving the nitrate anion and the methanol solvent.

Bis­[S-methyl 3-(2-bromo­benzyl­idene)­di­thio­cab­aza­to-N3,S]­platinum(II)

The Schiff base ligand in the title complex, [Pt(C9H8BrN2S2)2], is deprotonated from its tautomeric thiol form and coordinated to PtII via the mercapto S and β–N atoms. The configuration about PtII is a perfect square-planar, with two equivalent Pt—N [2.023 (3) A] and Pt—S [2.293 (1) A] bonds. The phenyl ring is twisted against the coordination moiety Pt1/N1/N1′/S2′/S2 by 31.8 (2)°, due to the steric hindrance induced by ortho-substituted bulky Br atom.