New Mononuclear Cu(II) Complexes and 1D Chains with 4-Amino-4H-1,2,4-triazole

The crystal structures of two mononuclear Cu(II) NH₂trz complexes [Cu(NH₂trz)₄(H₂O)](AsF₆)₂ (I) and [Cu(NH₂trz)₄(H₂O)](PF₆)₂ (II) as well as two coordination polymers [Cu(μ₂-NH₂trz)₂Cl]Cl·H₂O (III) and [Cu(μ₂-NH₂trz)₂Cl] (SiF₆)_0.5·1.5H₂O (IV) are presented. Cationic 1D chains with bridging bis-monodentate μ₂-coordinated NH₂trz and bridging μ₂-coordinated chloride ligands are present in III and IV. In these coordination polymers, the Cu(II) ions are strongly antiferromagnetically coupled with J = −128.4 cm⁻¹ for III and J = −143 cm⁻¹ for IV (H = −J∑S_iS_i+1), due to the nature of the bridges between spin centers. Inter-chain interactions present in the crystal structures were taken into consideration, as well as g factors, which were determined experimentally, for the quantitative modeling of their magnetic properties.     

Synthesis,crystal structure and magnetic properties of a new cyanide-bridged mixed-valence copper(I)/copper(II) clathrate

A unique cyanide-bridge mixed-valence Cu^I/Cu^II clathrate of formula [Cu^I₂(CN)₃][{Cu^II(tren)}₂(μ-CN)](CF₃SO₃)₂ [tren = tris(2-aminoethyl)amine] containing cyanide-bridged [{Cu^II(tren)}₂(μ-CN)]^3 + binuclear cations stacked between anionic honeycomb layered copper(I) cyanide networks, was synthesized and structurally characterized by single crystal X-ray diffraction. Variable-temperature magnetic susceptibility studies showed that the cyanide bridge mediates a strong antiferromagnetic interaction between the copper(II) centers (J = − 160 cm^− 1, the spin Hamiltonian being defined as H = −J S_A⋅S_B).     

Oxidase Reactivity of CuII Bound to N-Truncated Aβ Peptides Promoted by Dopamine

The redox chemistry of copper(II) is strongly modulated by the coordination to amyloid-β peptides and by the stability of the resulting complexes. Amino-terminal copper and nickel binding motifs (ATCUN) identified in truncated Aβ sequences starting with Phe4 show very high affinity for copper(II) ions. Herein, we study the oxidase activity of [Cu–Aβ_4−x] and [Cu–Aβ_1−x] complexes toward dopamine and other catechols. The results show that the Cu^II–ATCUN site is not redox-inert; the reduction of the metal is induced by coordination of catechol to the metal and occurs through an inner sphere reaction. The generation of a ternary [Cu^II–Aβ–catechol] species determines the efficiency of the oxidation, although the reaction rate is ruled by reoxidation of the Cu^I complex. In addition to the N-terminal coordination site, the two vicinal histidines, His13 and His14, provide a second Cu-binding motif. Catechol oxidation studies together with structural insight from the mixed dinuclear complexes Ni/Cu–Aβ_4−x reveal that the His-tandem is able to bind Cu^II ions independently of the ATCUN site, but the N-terminal metal complexation reduces the conformational mobility of the peptide chain, preventing the binding and oxidative reactivity toward catechol of Cu^II bound to the secondary site.     

Unique direct synthesis of cyanide-bridged Fe2Cu2 molecular squares by destruction of sodium nitroprusside

The one-pot reaction of copper powder, sodium nitroprusside, ammonium thiocyanate and 2,2′-bipyridine (bpy) in acetonitrile solution at ambient conditions of air and water yields the novel heterometallic [Fe₂Cu₂(bpy)₆(μ-CN)₄(NCS)₂]₂[Fe(CN)₅(NO)](NCS)₂·5H₂O complex 1, which has been structurally and magnetically characterized. The most prominent feature of this complex is the unique tetranuclear squares comprised [Cu(bpy)NCS]⁺ and [Fe(bpy)₂]²⁺ corners with CN edges. The CuCu and FeFe separations are 6.72 and 7.73 Å, respectively. The variable-temperature magnetic susceptibility study revealed that a very weak antiferromagnetic coupling is active between Cu(II) centers (J_CuCu = −0.37 cm⁻¹).     

FeIII,CuII and ZnII Complexes of the Rigid 9-Oxido-phenalenone Ligand—Spectroscopy,Electrochemistry, and Cytotoxic Properties

The three complexes [Fe(opo)₃], [Cu(opo)₂], and [Zn(opo)₂] containing the non-innocent anionic ligand opo⁻ (opo⁻ = 9-oxido-phenalenone, Hopo = 9-hydroxyphenalonone) were synthesised from the corresponding acetylacetonates. [Zn(opo)₂] was characterised using ¹H nuclear magnetic resonance (NMR) spectroscopy, the paramagnetic [Fe(opo)₃] and [Cu(opo)₂] by electron paramagnetic resonance (EPR) spectroscopy. While the EPR spectra of [Cu(opo)₂] and [Cu(acac)₂] in dimethylformamide (DMF) solution are very similar, a rather narrow spectrum was observed for [Fe(opo)₃] in tetrahydrofuran (THF) solution in contrast to the very broad spectrum of [Fe(acac)₃] in THF (Hacac = acetylacetone, 2,4-pentanedione; acac⁻ = acetylacetonate). The narrow, completely isotropic signal of [Fe(opo)₃] disagrees with a metal-centred S = 5/2 spin system that is observed in the solid state. We assume spin-delocalisation to the opo ligand in the sense of an opo⁻ to Fe^III electron transfer. All compounds show several electrochemical opo-centred reduction waves in the range of −1 to −3 V vs. the ferrocene/ferrocenium couple. However, for Cu^II and Fe^III the very first one-electron reductions are metal-centred. Electronic absorption in the UV to vis range are due to π–π* transitions in the opo core, giving Hopo and [Zn(opo)₂] a yellow to orange colour. The structured bands ranging from 400 to 500 for all compounds are assigned to the lowest energy π−π* transitions. They show markedly higher intensities and slight shifts for the Cu^II (brown) and Fe^III (red) complexes and we assume admixing metal contributions (MLCT for Cu^II, LMCT for Fe^III). For both complexes long-wavelength absorptions assignable to d–d transitions were detected. Detailed spectroelectrochemical experiments confirm both the electrochemical and the optical assignments. Hopo and the complexes [Cu(opo)₂], [Zn(opo)₂], and [Fe(opo)₃] show antiproliferative activities against HT-29 (colon cancer) and MCF-7 (breast cancer) cell lines in the range of a few µM, comparable to cisplatin under the same conditions.     

NO Scavenging through Reductive Nitrosylation of Ferric Mycobacterium tuberculosis and Homo sapiens Nitrobindins

Ferric nitrobindins (Nbs) selectively bind NO and catalyze the conversion of peroxynitrite to nitrate. In this study, we show that NO scavenging occurs through the reductive nitrosylation of ferric Mycobacterium tuberculosis and Homo sapiens nitrobindins (Mt-Nb(III) and Hs-Nb(III), respectively). The conversion of Mt-Nb(III) and Hs-Nb(III) to Mt-Nb(II)-NO and Hs-Nb(II)-NO, respectively, is a monophasic process, suggesting that over the explored NO concentration range (between 2.5 × 10⁻⁵ and 1.0 × 10⁻³ M), NO binding is lost in the mixing time (i.e., ^NOk_on ≥ 1.0 × 10⁶ M⁻¹ s⁻¹). The pseudo-first-order rate constant for the reductive nitrosylation of Mt-Nb(III) and Hs-Nb(III) (i.e., k) is not linearly dependent on the NO concentration but tends to level off, with a rate-limiting step (i.e., k_lim) whose values increase linearly with [OH⁻]. This indicates that the conversion of Mt-Nb(III) and Hs-Nb(III) to Mt-Nb(II)-NO and Hs-Nb(II)-NO, respectively, is limited by the OH⁻-based catalysis. From the dependence of k_lim on [OH⁻], the values of the second-order rate constant k_OH− for the reductive nitrosylation of Mt-Nb(III)-NO and Hs-Nb(III)-NO were obtained (4.9 (±0.5) × 10³ M⁻¹ s⁻¹ and 6.9 (±0.8) × 10³ M⁻¹ s⁻¹, respectively). This process leads to the inactivation of two NO molecules: one being converted to HNO₂ and another being tightly bound to the ferrous heme-Fe(II) atom.     

Initial use of 1,1′-oxalyldiimidazole for inorganic synthesis: Decomposition of the ligand as a means to the preparation of an imidazole- and oxalate(-2)-containing, 1D copper(II) complex

The use of 1,1′-oxalyldiimidazole, (im)COCO(im), for the synthesis of coordination complexes is explored for the first time. The [Cu₂(O₂CMe)₄(H₂O)₂]/(im)COCO(im) reaction system in 96% EtOH yields the new, 1D coordination polymer [Cu(ox)(Him)₂]_n (1), where Him is the neutral imidazole and ox^2? is the oxalate(-2) ligand. A mechanism for the hydrolytic decomposition of the ligand is proposed. Complex 1 comprises neutral, zigzag chains with the η¹:η¹:η¹:η¹:μ (2.1111 using Harris notation) ox^2? ligand bridging two neighboring Cu^II centers; two cis Him groups complete a Jahn–Teller distorted octahedral geometry at the metal. The dc, variable-temperature magnetic susceptibility data for the complex reveal antiferromagnetic Cu^II?Cu^II exchange interactions.     

Solvothermal synthesis of a novel mixed valence Cu(I)/Cu(II) complex containing sulphate, malate and 4,4-bipyridine, [CuCu2(mal)(SO4)(bpy)2 · H2O]n. Unique binding mode of the malate anion

The reaction of CuSO₄ · 5H₂O with 4,4^′-bipyridine and malic acid at 140 °C under solvothermal conditions afforded a mixed valence three-dimensional coordination polymer [Cu^ICu^II₂(mal)(SO₄)(bpy)₂ · H₂O]_n, (1). The building unit consists of a Cu²⁺-dimer in which copper centers are bridged by malate and sulphate anions. SO₄²⁻ anion further connects dimeric unit with the Cu¹⁺ center. Building units are linked by 4,4^′-bipyridine ligands to form double chains, that are interconnected into 3D network through additional sulphate bridge.     

Copper-assisted oxidative coupling of primary alcohol and hydrazone: A novel function model of galactose oxidase

Treatments of the MeOH, EtOH and PrOH solutions of 2-acetylpyridine, hydrazine and Cu^II salts (in molar ratio 2:3:2) afforded respectively the complexes, [Cu^II(HL)(Cl)](SO₃CF₃)H₂O (1), [Cu^II(MeL)(H₂O)](ClO₄)₂ (2) and [Cu^II(EtL)](Cl)](ClO₄) (3) (L = bis-(methyl, 2-pyridyl ketone hydrazonyl)methine), in which the ligands, HL, MeL and EtL are formed in situ from oxidative couplings of alcohols and hydrazones.     

Reaction of N-Acetylcysteine with Cu2+: Appearance of Intermediates with High Free Radical Scavenging Activity: Implications for Anti-/Pro-Oxidant Properties of Thiols

We studied the kinetics of the reaction of N-acetyl-l-cysteine (NAC or RSH) with cupric ions at an equimolar ratio of the reactants in aqueous acid solution (pH 1.4–2) using UV/Vis absorption and circular dichroism (CD) spectroscopies. Cu²⁺ showed a strong catalytic effect on the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) radical (ABTSr) consumption and autoxidation of NAC. Difference spectra revealed the formation of intermediates with absorption maxima at 233 and 302 nm (ε₃₀₂/Cu > 8 × 10³ M⁻¹ cm⁻¹) and two positive Cotton effects centered at 284 and 302 nm. These intermediates accumulate during the first, O₂-independent, phase of the NAC autoxidation. The autocatalytic production of another chiral intermediate, characterized by two positive Cotton effects at 280 and 333 nm and an intense negative one at 305 nm, was observed in the second reaction phase. The intermediates are rapidly oxidized by added ABTSr; otherwise, they are stable for hours in the reaction solution, undergoing a slow pH- and O₂-dependent photosensitive decay. The kinetic and spectral data are consistent with proposed structures of the intermediates as disulfide-bridged dicopper(I) complexes of types cis-/trans-Cu^I₂(RS)₂(RSSR) and Cu^I₂(RSSR)₂. The electronic transitions observed in the UV/Vis and CD spectra are tentatively attributed to Cu(I) → disulfide charge transfer with an interaction of the transition dipole moments (exciton coupling). The catalytic activity of the intermediates as potential O₂ activators via Cu(II) peroxo-complexes is discussed. A mechanism for autocatalytic oxidation of Cu(I)–thiolates promoted by a growing electronically coupled –[Cu^I₂(RSSR)]_n– polymer is suggested. The obtained results are in line with other reported observations regarding copper-catalyzed autoxidation of thiols and provide new insight into these complicated, not yet fully understood systems. The proposed hypotheses point to the importance of the Cu(I)–disulfide interaction, which may have a profound impact on biological systems.     

Switching on the photochemical reactivity in heterodimetallic Os–Ru bipyridyl complexes containing a bis(bidentate) phosphine

For the first time the excited states of the RuP₂N₄ moiety belonging to a new heterodimetallic Os^II–Ru^II bipyridyl complex are successfully designed in order to introduce photochemical reactivity. This dramatic effect is achieved via the use of the sterically demanding bis(bidentate) phosphine cis, trans, cis-1,2,3,4-tetrakis(diphenylphosphino)cyclobutane (dppcb). Thus, the temperature dependence of the luminescence lifetimes ranging from 77 to 298 K for the novel homodimetallic species meso-(ΔΛ/ΛΔ)-[Os₂(dppcb)(bpy)₄](PF₆)₄ (1) and rac-(ΔΔ/ΛΛ)-[Os₂(dppcb)(bpy)₄](PF₆)₄ (2) clearly indicates that the d–d state responsible for photochemistry is not populated. By contrast, the analogous temperature dependence for the new heterodimetallic species ΔΛ/ΛΔ-[Os(bpy)₂(dppcb)Ru(bpy)₂](PF₆)₄ (3) and ΔΔ/ΛΛ-[Os(bpy)₂(dppcb)Ru(bpy)₂](PF₆)₄ (4) unequivocally shows that as a consequence of the population of the d–d state the photochemical reactivity is switched on. Since single crystal X-ray structure analyses are a major clue to the understanding of photophysical and photochemical properties, also the X-ray structures of 1–3 are given.     

A new NiCuCu Ni complex containing doubly end-on azido bridged dicopper(II) and macrocyclic nickel(II) complex ancillary ligands: Synthesis, structure and magnetism

[Cu₂(NiL)₂(N₃)₄] was synthesized by combining “complex as ligand” approach and “pure bridging ligand” approach (H₂L = dimethyl 5,6,7,8,15,16-hexahydro-15-methyl-6,7-dioxodibenzo[1,4,8,11]tetraazacyclotetradecine-13,18-dicarboxylate). The two Cu^II ions are bridged by two end-on azido ligands. ππ and oxamido–carbonyl interactions link the molecules into 1D supramolecular chains. Ferromagnetic interactions exist between the two Cu^II ions.     

Melatonin as a Signaling Molecule for Metabolism Regulation in Response to Hypoxia in the Crab Neohelice granulata

Melatonin has been identified in a variety of crustacean species, but its function is not as well understood as in vertebrates. The present study investigates whether melatonin has an effect on crustacean hyperglycemic hormone (CHH) gene expression, oxygen consumption (VO₂) and circulating glucose and lactate levels, in response to different dissolved-oxygen concentrations, in the crab Neohelice granulata, as well as whether these possible effects are eyestalk- or receptor-dependent. Melatonin decreased CHH expression in crabs exposed for 45 min to 6 (2, 200 or 20,000 pmol·crab⁻¹) or 2 mgO₂·L⁻¹ (200 pmol·crab⁻¹). Since luzindole (200 nmol·crab⁻¹) did not significantly (p > 0.05) alter the melatonin effect, its action does not seem to be mediated by vertebrate-typical MT1 and MT2 receptors. Melatonin (200 pmol·crab⁻¹) increased the levels of glucose and lactate in crabs exposed to 6 mgO₂·L⁻¹, and luzindole (200 nmol·crab⁻¹) decreased this effect, indicating that melatonin receptors are involved in hyperglycemia and lactemia. Melatonin showed no effect on VO₂. Interestingly, in vitro incubation of eyestalk ganglia for 45 min at 0.7 mgO₂·L⁻¹ significantly (p < 0.05) increased melatonin production in this organ. In addition, injections of melatonin significantly increased the levels of circulating melatonin in crabs exposed for 45 min to 6 (200 or 20,000 pmol·crab⁻¹), 2 (200 and 20,000 pmol·crab⁻¹) and 0.7 (200 or 20,000 pmol·crab⁻¹) mgO₂·L⁻¹. Therefore, melatonin seems to have an effect on the metabolism of N. granulata. This molecule inhibited the gene expression of CHH and caused an eyestalk- and receptor-dependent hyperglycemia, which suggests that melatonin may have a signaling role in metabolic regulation in this crab.     

In Vitro Activity of Copper(II) Complexes,Loaded or Unloaded into a Nanostructured Lipid System,against Mycobacterium tuberculosis

Tuberculosis (TB) is an infectious disease caused mainly by the bacillus Mycobacterium tuberculosis (Mtb), presenting 9.5 million new cases and 1.5 million deaths in 2014. The aim of this study was to evaluate a nanostructured lipid system (NLS) composed of 10% phase oil (cholesterol), 10% surfactant (soy phosphatidylcholine, sodium oleate), and Eumulgin^® HRE 40 ([castor oil polyoxyl-40-hydrogenated] in a proportion of 3:6:8), and an 80% aqueous phase (phosphate buffer pH = 7.4) as a tactic to enhance the in vitro anti-Mtb activity of the copper(II) complexes [CuCl₂(INH)₂]·H₂O (1), [Cu(NCS)₂(INH)₂]·5H₂O (2) and [Cu(NCO)₂(INH)₂]·4H₂O (3). The Cu(II) complex-loaded NLS displayed sizes ranging from 169.5 ± 0.7095 to 211.1 ± 0.8963 nm, polydispersity index (PDI) varying from 0.135 ± 0.0130 to 0.236 ± 0.00100, and zeta potential ranging from −0.00690 ± 0.0896 to −8.43 ± 1.63 mV. Rheological analysis showed that the formulations behave as non-Newtonian fluids of the pseudoplastic and viscoelastic type. Antimycobacterial activities of the free complexes and NLS-loaded complexes against Mtb H₃₇Rv ATCC 27294 were evaluated by the REMA methodology, and the selectivity index (SI) was calculated using the cytotoxicity index (IC₅₀) against Vero (ATCC^® CCL-81), J774A.1 (ATCC^® TIB-67), and MRC-5 (ATCC^® CCL-171) cell lines. The data suggest that the incorporation of the complexes into NLS improved the inhibitory action against Mtb by 52-, 27-, and 4.7-fold and the SI values by 173-, 43-, and 7-fold for the compounds 1, 2 and 3, respectively. The incorporation of the complexes 1, 2 and 3 into the NLS also resulted in a significant decrease of toxicity towards an alternative model (Artemia salina L.). These findings suggest that the NLS may be considered as a platform for incorporation of metallic complexes aimed at the treatment of TB.     

Ruthenium Complexes with 2-Pyridin-2-yl-1H-benzimidazole as Potential Antimicrobial Agents: Correlation between Chemical Properties and Anti-Biofilm Effects

Antimicrobial resistance is a growing public health concern that requires urgent action. Biofilm-associated resistance to antimicrobials begins at the attachment phase and increases as the biofilms maturate. Hence, interrupting the initial binding process of bacteria to surfaces is essential to effectively prevent biofilm-associated problems. Herein, we have evaluated the antibacterial and anti-biofilm activities of three ruthenium complexes in different oxidation states with 2-pyridin-2-yl-1H-benzimidazole (L₁ = 2,2′-PyBIm): [(η⁶-p-cymene)Ru^IIClL₁]PF₆ (Ru(II) complex), mer-[Ru^IIICl₃(CH₃CN)L₁]·L₁·3H₂O (Ru(III) complex), (H₂L₁)₂[Ru^IIICl₄(CH₃CN)₂]₂[Ru^IVCl₄(CH₃CN)₂]·2Cl·6H₂O (Ru(III/IV) complex). The biological activity of the compounds was screened against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa strains. The results indicated that the anti-biofilm activity of the Ru complexes at concentration of 1 mM was better than that of the ligand alone against the P. aeruginosa PAO1. It means that ligand, in combination with ruthenium ion, shows a synergistic effect. The effect of the Ru complexes on cell surface properties was determined by the contact angle and zeta potential values. The electric and physical properties of the microbial surface are useful tools for the examined aggregation phenomenon and disruption of the adhesion. Considering that intermolecular interactions are important and largely define the functions of compounds, we examined interactions in the crystals of the Ru complexes using the Hirshfeld surface analysis.     

Transport Turnover Rates for Human OCT2 and MATE1 Expressed in Chinese Hamster Ovary Cells

MATE1 (multidrug and toxin extruder 1) and OCT2 (organic cation transporter 2) play critical roles in organic cation excretion by the human kidney. The transporter turnover rate (TOR) is relevant to understanding both their transport mechanisms and interpreting the in vitro–in vivo extrapolation (IVIVE) required for physiologically-based pharmacokinetic (PBPK) modeling. Here, we use a quantitative western blot method to determine TORs for MATE1 and OCT2 proteins expressed in CHO cells. MATE1 and OCT2, each with a C-terminal V-5 epitope tag, were cell surface biotinylated and the amount of cell surface MATE1 and OCT2 protein was quantified by western analysis, using standard curves for the V5 epitope. Cell surface MATE1 and OCT2 protein represented 25% and 24%, respectively, of the total expression of these proteins in CHO cells. The number of cell surface transporters was ~55 fmol cm⁻² for MATE1 and ~510 fmol cm⁻² for OCT2. Dividing these values into the different J_max values for transport of MPP, metformin, and atenolol mediated by MATE1 and OCT2 resulted in calculated TOR values (±SE, n = 4) of 84.0 ± 22.0 s⁻¹ and 2.9 ± 0.6 s⁻¹; metformin, 461.0 ± 121.0 s⁻¹ and 12.6 ± 2.4 s⁻¹; atenolol, 118.0 ± 31.0 s⁻¹, respectively. These values are consistent with the TOR values determined for a variety of exchangers (NHEs), cotransporters (SGLTs, Lac permease), and uniporters (GLUTs, ENTs).     

SOD mimic activity,DNA binding and in-vitro antibacterial studies of drug based copper(II) complexes

Square pyramidal complexes [Cu^II(PFL)(bpa)Cl]?5H₂O (1) and [Cu^II(LFL)(bpa)Cl]?5H₂O (2) have been synthesized and characterized. Compounds were checked for their in-vitro antimicrobial activity against two Gram^(+ ve) and three Gram^(–ve) bacterial species. Intrinsic binding constant (K_b) of complexes with CT DNA were determined using absorption titration. Viscosity measurement suggests that complexes bind with CT DNA through partial nonclassical intercalative mode. Superoxide dismutase (SOD) like activity of the complexes was also compared with previously reported compounds.     

Well defined CuI(NO), CuI(NO)2 and CuII(NO)X (X = O− and/or NO 2 − ) complexes in CuI-ZSMS prepared by interaction of H-ZSM5 with gaseous CuCl

In this note an exchange procedure of the acidic protons of H-ZSM5 by Cu^I ions through reaction with CuCl in the gas phase is described. In the so obtained Cu^I-ZSM5 exchanged zeolite the Cu^I ions are in well defined configuration and form with NO mono and di-nitrosyl complexes of high structural and spectroscopic quality. The Cu^I(NO)₂ species are transformed at RT into Cu^II(NO)X (X=O^– and/or NO ₂ ^– ) species which could represent an intermediate in NO decomposition.     

Structural,electrical, and optical properties of Ti-doped ZnO films fabricated by atomic layer deposition

High-quality Ti-doped ZnO films were grown on Si, thermally grown SiO₂, and quartz substrates by atomic layer deposition (ALD) at 200°C with various Ti doping concentrations. Titanium isopropoxide, diethyl zinc, and deionized water were sources for Ti, Zn, and O, respectively. The Ti doping was then achieved by growing ZnO and TiO₂ alternately. A hampered growth mode of ZnO on TiO₂ layer was confirmed by comparing the thicknesses measured by spectroscopic ellipsometry with the expected. It was also found that the locations of the (100) diffraction peaks shift towards lower diffraction angles as Ti concentration increased. For all samples, optical transmittance over 80% was obtained in the visible region. The sample with ALD cycle ratio of ZnO/TiO₂ being 20 had the lowest resistivity of 8.874 × 10⁻⁴ Ω cm. In addition, carrier concentration of the prepared films underwent an evident increase and then decreased with the increase of Ti doping concentration.     

One-dimensional copper(II) complex containing alternate single and double end-on azide ligands: Crystal structure and magnetic characterization

A novel one-dimensional azido-bridged coordination polymer of formula [Cu₂(L)₂(H₂O)(N₃)₄]_n (1) has been synthesized and characterized crystallographically and magnetically, where L is 5-methylpyrimidin-2-amine. Complex 1 consists of 1D chain in which the Cu(II) ions with a square pyramidal geometry are alternately bridged by asymmetric single and symmetric double end-on (EO) azido ligands. Magnetic analysis reveals that the dominating ferromagnetic interaction is mediated by the symmetric double azido bridge with the exchange parameter J = 55.17 cm⁻¹.