Effect of secondary ligands' size on energy transfer and electroluminescent efficiencies for a series of europium(III) complexes, a density functional theory study

In this paper, a quantum chemistry method was used to investigate the effect of different sizes of substituted phenanthrolines on absorption, energy transfer, and the electroluminescent performance of a series of Eu(TTA)(3)L (L = [1,10] phenanthroline (Phen), Pyrazino[2,3-f][1,10]phenanthroline (PyPhen), 2-methylprrazino[2,3-f][1,10] phenanthroline(MPP), dipyrido[3,2-a:2',3'-c]phenazine(DPPz), 11-methyldipyrido[3,2-a:2',3'c]phenazine(MDPz), 11.12-dimethyldipyrido[3,2-a:2',3'-c]phenazine(DDPz), and benzo[i]dipyrido[3,2-a:2',3'-c]phenazine (BDPz)) complexes. Absorption spectra calculations show that different sizes of secondary ligands have different effects on transition characters, intensities, and absorption peak positions.

The Reasons for Ligand-Dependent Quantum Yields and Absorption Spectrum of Four Polypyridylruthenium(II) Complexes with a Tetrazolate-Based Ligand: TDDFT Study

The quantum yield, lifetime, and absorption spectrum of four [Ru(bpy)(2)L](+) [where bpy is 2,2'-bipyridyl; L is represented by the deprotonated form of 2-(1H-tetrazol-5-yl)pyridine (L1) or 2-(1H-tetrazol-5-yl)pyrazine (L2)], as well as their methylated complexes [Ru(bpy)(2)LMe](2+) (RuL1Me and RuL2Me) are closely ligand dependent. In this paper, density functional theory (DFT) and time-dependent DFT (TDDFT) were performed to compare the above properties among these complexes. The calculated results reveal that the replacement of pyridine by pyrazine or the attachment of a CH3 group to the tetrazolate ring greatly increases the pi-accepting ability of the ancillary ligands.

Near-infrared luminescent mesoporous MCM-41 materials covalently bonded with ternary thulium complexes

Two beta-diketones 4,4,4-trifluoro-1-2-thenoyl-1,3-butanedione (Htta) and 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione (Htfnb), which contain trifluoroalkyl chain, were selected as the main sensitizer for synthesizing Tm(L)(3)phen (L = tta, tfnb) complexes. The two near-infrared (NIR) luminescent thulium complexes have been covalently bonded to the ordered mesoporous material MCM-41 via a functionalized 1,10-phenanthroline (phen) group 5-(N,N-bis-3-(triethoxysilyl)propyl)ureyl-1,10-phenanthroline (phen-Si) [The resultant mesoporous materials are denoted as Tm(L)(3)phen-MCM-41 (L = tta, tfnb)]. The Tm(L)(3)phen-MCM-41 (L = tta, tfnb) mesoporous materials were characterized by small-angle Xray diffraction (XRD) and N-2 adsorption/desorption, and they show characteristic mesoporous structure of MCM-41.

A study on the near-infrared luminescent properties of xerogel materials doped with dysprosium complexes

A series of dysprosium complex doped xerogels with the same first ligand (acac = acetylacetone) and different neutral ligands were synthesized in situ via a sol-gel process. The Fourier transform infrared (FTIR) spectra, diffuse reflectance (DR) spectra, and near-infrared (NIR) luminescent properties of dysprosium complexes and dysprosium complex doped xerogels are described in detail. The results reveal that the dysprosium complex is successfully synthesized in situ in the corresponding xerogel. Excitation at the maximum absorption wavelength of the ligands resulted in the characteristic NIR luminescence of the Dy3+ ion, which contributes to the energy transfer from the ligands to the central Dy3+ ion in both the dysprosium complexes and xerogels via an antenna effect.

Novel Near-Infrared Luminescent Hybrid Materials Covalently Linking with Lanthanide [Nd(III), Er(III), Yb(III), and Sm(III)] Complexes via a Primary beta-Diketone Ligand: Synthesis and Photophysical Studies

A series of novel, colorless, and transparent sot-gel derived hybrid materials Ln-DBM-Si covalently grafted with Ln(DBM-OH)(3)center dot 2H(2)O (where DBM-OH = o-hydroxydibenzoylmethane, Ln = Nd, Er, Yb, and Sin) were prepared through the primary beta-diketone ligand DBM-OH. The structures and optical properties of Ln-DBM-Si were studied in detail. The investigation results revealed that the lanthanide complexes were successfully in situ grafted into the corresponding hybrids Ln-DBM-Si. Upon excitation at the maximum absorption of ligands, the resultant materials displayed excellent near-infrared luminescence.

Stabilization of Imidosamarium(III) Cubane by Amidinates

An imidosamarium(III) cubane has been prepared from the reductive cleavage of azobenzene by a divalent samarium bis (amidinate) complex, indicating that the "spectratoe" bis(amidinate) and the resulting imido ligands help to stabilize the cubane framework. The cubane-type imido cluster is a novel unit in lanthanide chemistry.

Near-infrared luminescent xerogel materials covalently bonded with ternary lanthanide [Er(III), Nd(III), Yb(III), Sm(III)] complexes

A beta-diketone ligand 4,4,5,5,5-pentafluoro-1-(2-naphthyl)-1,3-butanedione (Hpfnp), which contains a pentafluoroalkyl chain, was synthesized as the main sensitizer for synthesizing new near-infrared (NIR) luminescent Ln(pfnp)(3)phen (phen = 1,10-phenanthroline) (Ln = Er, Nd, Yb, Sm) complexes. At the same time, a series of lanthanide complexes covalently bonded to xerogels by the ligand 5-(N,N-bis-3-(triethoxysilyl)propyl)ureyl-1,10-phenanthroline (phen-Si) were synthesized in situ via a sol-gel process. [The obtained materials are denoted as xerogel-bonded Ln complexes (Ln = Er, Nd, Yb, Sm).] The single crystal structures of the Ln(pfnp) 3phen complexes were determined.

Theoretical studies on electronic structures, spectra and charge transporting properties of a series of Pt((CN)-N-Lambda)(2) complexes

We report a quantum-chemical study of electronic, optical and charge transporting properties of four platinum (II) complexes, pt((CN)-N-Lambda)(2) ((CN)-N-Lambda=phenylpyridine or thiophenepyridine). The lowest-lying absorptions at 442, 440, 447 and 429 nm are all attributed to the mixed transition characters of metal-to-ligand charge transfer (MLCT) and ligand-centered (LC) pi - pi(*) transition. While, unexpectedly, the lowest-lying phosphorescent emissions at 663, 660, 675 and 742 nm are mainly from metal-to-ligand charge transfer ((MLCT)-M-3) ligand-centered (LC) pi ->pi* transition. Ionization potential (IP), electron affinities (EA) and reorganization energy P (lambda(hole/electron)) were obtained to evaluate the charge transfer and balance properties between hole and electron.

Metal dependent control of cis-/trans-1,4 regioselectivity in 1,3-butadiene polymerization catalyzed by transition metal complexes supported by 2,6-bis[1-(iminophenyl)ethyl]pyridine

Fe(III), Cr(III), Fe(II), Co(II) and Ni(II) chloride complexes supported by 2,6-bis[1-(iminophenyl)ethyl]pyridine have been synthesized and characterized along with single crystal X-ray diffraction. These complexes, in combination with MAO, have been examined in butadiene polymerization. The catalytic activity and regioselectivity are strongly controlled by metal center and cocatalyst (MAO/Co ratio dependent in the case of Co(II) complex). The activity decreases in the order of Fe(III) > Co(II) > Cr(III) approximate to Ni (II) complexes, in consistent with the space around the metal center. Polybutadiene with different microstructure content, from high trans-1,4 units (88-95% for iron(III) and Cr(III)), medium trans-1,4 and cis-1,4 units (55% and 35%, respectively, for iron(II)) to high cis-1,4 units 79% for Co(II) and 97% for Ni(II) call be easily achieved by varying of the metal center.

Atomic force microscopy and surface-enhanced Raman scattering detection of DNA based on DNA-nanoparticle complexes

We report a simple method for the label-free detection of double-stranded DNA using surface-enhanced Raman scattering (SERS). We prepared cetyltrimethylammonium bromide (CTAB)-capped silver nanoparticles and a DNA-nanoparticle complex by adding silver nanoparticles to lambda-DNA solutions. In the present study, the utilization of CTAB-capped silver nanoparticles facilitates the electrostatic interaction between DNA molecules and silver nanoparticles; at the same time, the introduction of DNA avoids adding aggregating agent for the formation of nanoparticle aggregates to obtain large enhancement of DNA, because the DNA acts as both the probe molecules and aggregating agent of Ag nanoparticles.

Thiacalix[4]arene-Supported Planar Ln(4) (Ln = Tb-III, Dy-III) Clusters: Toward Luminescent and Magnetic Bifunctional Materials

This paper reports the syntheses, crystal structures, and luminescent and magnetic properties of four tetranuclear Tb-III (1 and 3) and Dy-III (2 and 4) complexes supported by p-phenylthiacalix[4]arene (H(4)PTC4A) and p-tert-butylthiacalix-[4]arene (H(4)TC4A). All four frameworks can be formulated as [Ln(4)(III)(PTC4A/TC4A)(2)(mu(4)-OH)Cl-3(CH3OH)(2)(H2O)(3)], and some methanol and water solvent molecules are occupied in the interstices. The compounds are featured with a sandwichlike unit constructed by two tail-to-tail calixarene molecules and a planar tetragonal (mu(4)-OH)Ln(4) cluster. The photoluminescent analyses suggest that there is an efficient ligand-to-Ln(III) energy transfer for compounds 1-3 and H(4)PTC4A is a more efficient "antenna" than H(4)TC4A.

Regioselective Bis-Selenation of Allenes Catalyzed by Palladium Complexes: A Theoretical Study

The reaction mechanism of Pd(O)-catalyzed allene bis-selenation reactions is investigated by using density functional methods. The overall reaction mechanism has been examined. It is found that with the bulkier PMe3 ligand, the rate-determining step is the reductive elimination process, while allene insertion and reductive elimination processes are competitive for the rate-determining step with the PH3 ligand, indicating the importance of the ligand effect. For both cis and trans palladium complexes, allene insertion into the Pd-Se bond of the trans palladium complex using the internal carbon atom attached to the selenyl group is prefer-red among the four pathways of allene insertion processes. The formation of sigma-allyl and pi-allyl palladium complexes is favored over that of the sigma-vinyl palladium species. By using methylallene, the regioselectivity of monosubstituted allene insertion into the Pd-Se bond is analyzed.

Synthesis, crystal structures and spectroscopic properties of copper(I) complexes containing beta-dialdiminato supporting ligands

Two mononuclear neutral copper(I) complexes, Cu(L-1)PPh3 (1), Cu(L-2)(PPh3)(2) (2) ([L-1](-) = [{N((C6H3Pr2)-Pr-i-2,6)C(H)}(2)CPh](-); [L-2](-) = [{N(C6H5)C(H)}(2)CPh](-)) have been synthesized and structurally characterized by X-ray crystallography. In complex 1, the copper(I) atom is in a distorted three-coordinate trigonal planar environment, whereas in complex 2 with the less sterically hindered beta-dialdiminato ligand, the copper(I) atom is the centre of a four-coordinate distorted tetrahedron. At room temperature complexes 1 and 2 in a film of PMMA exhibit green emission at 543 and 549 nm with lifetimes of 5.28 and 5.32 ns, respectively.

Oligoaniline-Functionalized terpyridine ligands and their ruthenium(II) complexes: synthesis, spectroscopic property and redox behaviors

A series of oligoaniline-functionalized mono- and bis-topic terpyridine ligands, i.e. C6H5[N(R)C6H4](n)TPY (R = H, butyl, tert-butyloxycarbonyl; n = 1-4; TPY = 2,2':6',2"-terpyridyl) and TPYC6H4[N(R)C6H4](m)TPY (R = H, tert-butyloxycarbonyl; m = 2, 4), and the corresponding monoand bis-nuclear ruthenium(II) complexes have been synthesized and verified. The spectroscopic results indicate that two kinds of pi-pi* transitions from TPY and oligoaniline fragments of ligands strongly shift to lower energy, and the metal-to-ligand charge-transfer transition ((MLCT)-M-1) bands of all obtained complexes are considerably red-shifted (Delta lambda(max) = 22-64 nm) and their intensities become much more intense (approximately 4-6 times), compared with those of the reported complex [Ru(TPY)(2)](2+). Moreover, the spectroscopic properties of the ligands and complexes with longer oligoaniline units (n = 3, 4) are markedly influenced by the external stimulus, such as the oxidation and proton acid doping.

Synthesis, characterization and electrophosphorescent properties of mononuclear platinum(II) complexes based on 2-phenylbenzoimidazole derivatives

The rational design, synthesis and characterization of five phosphorescent platinum complexes [(C boolean AND N) Pt(acac)] [Hacac = acetylacetone, HC boolean AND N = 1-methyl-2-(4-fluorophenyl)benzoimidazole (H-FMBI), 1-methyl-2-phenylbenzoimidazole (H-MBI), 1,2-diphenyl-benzoimidazole (H-PBI), 1-(4-(3,6-di-t-butylcarbazol-9-yl)) phenyl-2-phenylbenzoimidazole (t-BuCz-H-PBI), and 1-(4-(3,6-di-(3,6-di-t-butyl-carbazol-9-yl))carbazol-9-yl) phenyl-2-phenylbenzoimidazole (t-BuCzCz-H-PBI)] have been discussed. The crystal structure of (MBI) Pt(acac) shows a nearly ideal square planar geometry around Pt atom and the weak intermolecular interactions with pi-pi spacing of 3.55 angstrom. All of the complexes emit green phosphorescence from the metal-to-ligand charge-transfer (MLCT) excited state with high quantum efficiency (0.08-0.17) at room temperature.