Harnessing low-valent metal centers through non-bonding orbital interactions

The synthesis, characterization, and computational analysis of a series of low-valent, In(I) complexes bearing the bis(imino)pyridine scaffold, {Ar'N=CPh}(2)(NC(5)H(3)), is reported. A stepwise steric reduction of the aryl groups on the imine substituents around the coordination site, (Ar' = 2,5-(t)Bu(2)C(6)H(3), 2,6-(i)Pr(2)C(6)H(3), 2,6-(CH(3)CH(2))(2)C(6)H(3)) is explored through the spectroscopic and crystallographic examination of complexes [{Ar'N=CPh}(2)(NC(5)H(3))]In(+)(OTf)(-) (1-3). Compounds 1-3 displayed long In-N and In-OTf distances indicating only weak or no coordination. Application of the ligand with Ar' = 2,6-(CH(3))(2)C(6)H(3) led to an In(III) bis(imino)pyridine complex, [{2,6-Me(2)C(6)H(3)N=CPh}(2)(NC(5)H(3))]In(OTf)(2)Cl 4 with coordinated ligand, chloride, and triflate groups. Computational analysis of the interactions between the In cation and the ligands (orbital populations, bond order, and energy decomposition analysis) point to only minimal covalent interactions of the In(I) cation with the ligands. Although it features three N donor centers, the bis(imino)pyridine ligand provides little ligand-to-metal donation. A thorough electronic structure analysis revealed a correlation of compound stability with the reduced contribution of the In(I) 5s lone electron pair to the highest occupied molecular orbital (HOMO) of the cation. This effect, originating from non-bonding orbital interactions between the metal and the ligand, is more prominent in sterically crowded environments. The discovery of this correlation may help in designing new low-valent complexes.     

Ligating properties of a potentially tetradentate Schiff base [(CH3)2NCH2CH2N=CHC6H3(OH)(OMe)] with zinc(II), cadmium(II), cobalt(II), cobalt(III) and manganese(III) ions: synthesis and structural studies

A series of Zn(II), Cd(II), Co(II), Co(III) and Mn(III) complexes with the Schiff base [(CH3)2NCH2CH2N=CHC6H3(OH)(OMe)], LH, derived from 2-dimethylaminoethylamine and o-vanillin, has been synthesised and structures of all the products have been established by X-ray crystallography. In the cases of zinc and cadmium, dimeric complexes [Zn(LH)2(NCS)] [Zn2(L)(mu(1,1)-CH3COO)(NCS)3] (1), [Cd2(L)2(Cl)2] (2) and [Cd2(L)2(NCS)2] (3), and for cobalt and manganese, monomeric complexes [Co(LH)2(NCS)]2 [Co(NCS)4] (4), [Co(LH)2(NCS)]ClO4 (5), [Co(L)(N3)(o-vanillinate)] x 0.5 MeOH (6) and [Mn(LH)2(MeOH)2](ClO4)3 (7), are formed with various terminal ligands. All the complexes have been characterised by elemental analysis and IR spectra. UV-Vis and NMR spectroscopy, magnetic, and electrochemical studies, were also carried out where feasible. The Schiff base functions as a bi-, tri- or tetra-dentate chelating agent and coordinates via the protonated or deprotonated phenolic oxygen, amine and imine nitrogens, and only in case of 1 with the methoxy oxygen atoms, to the metal ion leading to the formation of mono- or bi-metallic complexes.     

The doubly oxidized, antiaromatic tetraphenylporphyrin complex [Li(TPP)][BF4

[reaction: see text] Oxidation of dilithium tetraphenylporphyrin, Li(2)(TPP), yields the doubly oxidized porphyrin complex [Li(TPP)][BF(4)]. Free TPP appears to be unstable. The crystal structure of [Li(TPP)][BF(4)] reveals that the 16-atom C-N inner ring of the porphyrin consists of alternating single and double bonds. NMR spectroscopy and nucleus-independent chemical shift (NICS) calculations, in addition to the distortion from planarity observed in the crystal structure, indicate that the 16 pi-electron inner C-N ring of the porphyrin is antiaromatic.     

The effects of sodium in ITO by pulsed laser deposition on organic light-emitting diodes

The depth profile of ITO on glass was measured by the time-of-flight secondary ion mass spectroscopy (TOFSIMS) which revealed high sodium (Na) ion concentration at the ITO surface as well as at the ITO–glass interface as a result of out diffusion with substrate heating. Effects of Na ions on the performance of organic light-emitting diode (OLED) were studied by etching away a few tens of nanometers off the ITO surface with a dilute aquaregia solution of HNO₃:HCl:H₂O. A single-layer, molecularly doped ITO/(PVK+TPD+Alq₃)/Al OLEDs were fabricated on bare and etched ITO samples. Although the removal of a 10-nm layer of ITO surface increased the voltage range, brightness, and lifetime, it was insufficient to correlate these improvements with solely to the Na ion reduction without considering the surface roughness.     

Effects of laser fluence on the structural properties of pulsed laser deposited ruthenium thin films

Ruthenium (Ru) has received great interest in recent years for applications in microelectronics. Pulsed laser deposition (PLD) enables the growth of Ru thin films at low temperatures. In this paper, we report for the first time the characterization of pulsed laser deposited Ru thin films. The deposition processes were carried out at room temperature in vacuum environment for different durations with a pulsed Nd:YAG laser of 355-nm laser wavelength, employing various laser fluences ranging from 2 J/cm² to 8 J/cm². The effect of the laser fluence on the structural properties of the deposited Ru films was investigated using surface profilometry, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Ru droplets, some spherical in shape and some flattened into round discs were found on the deposited Ru. The droplets were correlated to ripple formations on the target during the laser-induced ejection from the target. In addition, crystalline Ru with orientations of (100), (101), and (002) was observed in the XRD spectra and their intensities were found to increase with increasing laser fluence and film thickness. Grain sizes ranging from 20 nm to 35 nm were deduced using the Scherrer formula. Optical emission spectroscopy (OES) and energy-dispersive X-ray spectroscopy (EDS) show that the composition of the plume and the deposited Ru film was of high purity.     

Co-delivery of antigen and a lipophilic anti-inflammatory drug to cells via a tailorable nanocarrier emulsion

Nanotechnology promises new drug carriers that can be tailored to specific applications. Here we report a new approach to drug delivery based on tailorable nanocarrier emulsions (TNEs), motivated by a need to co-deliver a protein antigen and a lipophilic drug for specific inhibition of nuclear factor kappa B (NF-κB) in antigen presenting cells (APCs). Co-delivery for NF-κB inhibition holds promise as a strategy for the treatment of rheumatoid arthritis. We used a highly surface-active peptide (SAP) to prepare a nanosized emulsion having defined surface properties predictable from the SAP sequence. Incorporating the lipophilic drug into the oil phase at the time of emulsion formation enabled its facile packaging. The SAP is depleted from bulk during emulsification, allowing simple subsequent addition of the drug-loaded oil-in-water emulsion to a solution of protein antigen. Decoration of emulsion surface with antigen was achieved via electrostatic deposition. In vitro data showed that the TNE prepared this way was internalized and well-tolerated by model APCs, and that good suppression of NF-κB expression was achieved. This work reports a new type of nanotechnology-based carrier, a TNE, which can potentially be tailored for co-delivery of multiple therapeutic components, and can be made using simple methods using only biocompatible materials.     

Structural inhomogeneity and piezoelectric enhancement in ZnO nanobelts

In this work, piezoelectricity of individual ZnO nanobelts grown along the [0?1????0] direction is studied using piezoresponse force microscopy (PFM). It is found that the effective piezoelectric coefficient of these NBs, $d_{33}^{\mathrm{eff}}$ , is increasing from 2.7?pm/V at 30?kHz to 44?pm/V at 150?kHz. The results were explained by the Debye model, where structural inhomogeneity in our NBs was shown to be responsible for piezoelectric enhancement.     

Synthesis and Structural Comparison for a Series of Cr(II) (iodo) NacNac Complexes

Abstract  A series of complexes of the form [bis(2,6-diisopropylphenyl)pentane-2,4-ketiminato](iodo)(solvent) chromium were synthesized and structurally characterized (solvent = tetrahydrofuran, acetonitrile, α-picoline). The tetrahydrofuran adduct crystallized in the P2₁/n space group with the crystal cell parameters a = 17.628(6) ?, b = 10.218(3) ?, c = 20.646(7) ?, β = 109.209(4)°, V = 3512(2) ?³ and Z = 4. The acetonitrile adduct crystallized in the P2₁/c space group with the crystal cell parameters a = 16.104(7) ?, b = 11.965(5) ?, c = 18.201(8) ?, β = 116.091(6)°, V = 3150(2) ?³ and Z = 4. The α-picoline adduct crystallized in the C2/c space group with the crystal cell parameters a = 39.982(9) ?, b = 11.637(2) ?, c = 16.560(4) ?, β = 108.085(4)°, V = 7325(3) ?³ and Z = 8. For each compound, the coordination around each chromium center is square planar with varying degrees of distortion. Graphical Abstract  A series of Cr(II) complexes of the form LCrI(S) (where L = nacnac = β-diketiminate; S = solvent) were synthesized and structurally characterized.      

2,4-Pentane <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-Bis(2,6-Diisopropylphenyl) ketiminato cobalt (II) (trimethylsilyl)methylene

Abstract  

The title compound [^MeL^iPrCoCH₂Si(CH₃)₃ ^MeL^iPr = 2,4-pentane-N,N′-bis(2,6-diisopropylphenyl) ketiminato] possesses trigonal planar geometry and crystallizes in monoclinic space group P2₁/n with crystal cell parameters a = 10.6155(14) ?, b = 21.279(3) ?, c = 14.8057(19) ?, β = 97.196(2)°, V = 3,318.1(7) ?³, and Z = 4. The title compound is the second reported three coordinated 13 valence electron Co(II) alkyl complex and the first such complex reported with an asymmetrically bonded alkyl group. The steric effects are discussed in comparison of known similar structures of Fe, Co, and Zn.