Zr Complexes Research Articles

Selective formation of cubic or tetragonal zirconia thin films of transparent, with no use of metal ion stabilizer by heating molecular precursor films under mild conditions

Cubic or tetragonal zirconia thin films of transparent and 100 nm thickness were selectively formed on a quartz glass substrate by heat-treating the molecular precursor films involving Zr(IV) complexes of nitrilotriacetic acid, at 500[Formula: see text]C in air for 1 h. A precursor solution was prepared by a reaction of the ligand and zirconium tetrabutoxide in alcohol under the presence of butylamine. By the addition of H2O2 or H2O into the solution, the spin-coated precursor films were converted to cubic zirconia thin films by the abovementioned procedure. Further, the identical phase was produced also in the case of the electro-sprayed precursor film which was formed by an addition of H2O2 into the solution. On the other hand, the tetragonal zirconia thin film was obtained from a precursor film formed by using a solution dissolving the original Zr(IV) complex of the ligand, without H2O2 nor H2O. The crystal structure of all thin films was determined by using both the X-ray diffraction (XRD) patterns and Raman spectra. Thus, the zirconia thin films of both crystals could be facilely and selectively obtained with no use of hetero-metal ion stabilizers. The XPS spectra of the thin films show that the O/Zr ratio of the cubic phase is 1.37 and slightly larger than tetragonal one (1.29), and also demonstrate that the nitrogen atoms, which may contribute to stabilize these metastable phases at room temperature, of about 5−7 atomic% was remained in the resultant thin films. The adhesion strengths of cubic zirconia thin film onto the quartz glass substrate was 68 MPa and larger than that of tetragonal one, when the precursor films were formed via a spin coating process. The optical and surface properties of the thin films were also examined in relation to the crystal systems.

Incorporation of Boronic Acid Functionality into Isotactic Polypropylene and Its Application as a Cross-Linking Point

Direct copolymerization of propylene and functional monomers using early transition metal catalysts is a prominent synthesis method to render a functionality to polypropylene maintaining high stereoregularity. In this study, we investigated the copolymerization of propylene and alkenylboronic acid moieties using the Zr complex and found that diaminonaphthalene (dan) is a good protective group for the boronic acid. Dan-protected boronic acid scarcely reduced the stereospecificity of the propylene polymerization so that the incorporation of 3.8 mol % comonomer still maintained a high melting point (107 °C). Moreover, deprotection of boronic acid amide proceeded along with the standard purification of polypropylene in acidic methanol. Boronic acid-functionalized isotactic polypropylene showed high Young’s modulus and strength probably because the copolymer was cross-linked upon molding via dehydrotrimerization of the boronic acids. Such cross-link was accelerated by the addition of a secondary amine.

Smartphone-based colorimetric determination of fluoride anions using polymethacrylate optode

We developed a new transparent polymer optode based on polymethacrylate with Zr(IV) and alizarin red complex immobilized into it for digital colorimetric and solid-phase spectrophotometric determination of fluoride anions. The matrix changes its colour from purple to yellow after it contacts fluoride anion. We developed a processing algorithm for coloured images which helps calculate mean value for the RGB colour-coordinate system in a selected optode image and translates it into a fluoride concentration value. The analytical signal of the suggested method has a linearity range of 0.1–30 mg⋅L−1 with the detection limit 0.03 mg⋅L−1. Compared to other methods, the modified polymethacrylate matrix is actually a ready-to-use colorimetric system offering rapid results for drinking water quality control.

Allosteric Guest Binding in Chiral Zirconium(IV) Double Decker Porphyrin Cages.

Chiral zirconium(IV) double cage sandwich complex Zr(1)2 has been synthesized in one step from porphyrin cage H21. Zr(1)2 was obtained as a racemate, which was resolved by HPLC and the enantiomers were isolated in >99.5 % ee. Their absolute configurations were assigned on the basis of X‐ray crystallography and circular dichroism spectroscopy. Vibrational circular dichroism (VCD) experiments on the enantiomers of Zr(1)2 revealed that the chirality around the zirconium center is propagated throughout the whole cage structure. The axial conformational chirality of the double cage complex displayed a VCD fingerprint similar to the one observed previously for a related chiral cage compound with planar and point chirality. Zr(1)2 shows fluorescence, which is quenched when viologen guests bind in its cavities. The binding of viologen and dihydroxybenzene derivatives in the two cavities of Zr(1)2 occurs with negative allostery, the cooperativity factors α (=4 K2/K1) being as low as 0.0076 for the binding of N,N’‐dimethylviologen. These allosteric effects are attributed to a pinching of the second cavity as a result of guest binding in the first cavity.

Development of Group 4 Metal Complexes Bearing Fused-Ring Amido-Trihydroquinoline Ligands with Improved High-Temperature Catalytic Performance toward Olefin (Co)polymerization

The development of homogeneous metal catalysts with high activity and high thermal stability is vital for the synthesis of polyolefin elastomers (POEs) in solution-phase olefin polymerization processes. In this contribution, the stoichiometric reactions of 8-(2,6-(R1)2-4-R2-anilide)-5,6,7-trihydroquinoline (1–3; 1, R1 = iPr, R2 = H; 2, R1 = Me, R2 = H; 3, R1 = Me, R2 = Me) with MMe4 (M = Hf, Zr) afforded metal complexes 1-HfMe3, 2-HfMe3, 3-HfMe3, and 1-ZrMe3 in high yields. Treatment of ligand 1 with Ti(NMe2)4 resulted in the formation of 1-Ti(NMe2)3, which reacted with SiMe2Cl2 to form 1-TiCl3. 1-TiMe3 was obtained by alkylation of 1-TiCl3 with MeMgBr. All metal complexes were characterized by 1H and 13C NMR spectroscopy, and the molecular structures of complexes 1-HfMe3, 2-HfMe3, 1-ZrMe3, and 1-TiMe3 were determined by single-crystal X-ray diffraction, revealing an approximate trigonal-bipyramidal geometry around the metal center in all of the structures. The complexes showed extremely high activity toward ethylene polymerization (up to 13860 kg of PE (mol of M)−1 h–1) and ethylene/1-octene copolymerization (up to 49000 kg of PE (mol of M)−1 h–1) at elevated temperatures (up to 140 °C). The catalytic properties were highly dependent on the appropriate matching of the metal and cocatalyst. In the presence of [Ph3C][B(C6F5)4], the activity of metal complexes with the same ligand was in the order Hf > Zr > Ti; with B(C6F5)3 as the cocatalyst, this order followed Zr > Ti > Hf; using MAO as the cocatalyst, the Ti complex was highly active, while the Hf and Zr complexes were inactive. The Hf and Zr complexes showed both high-molecular-weight capability and high 1-octene incorporation ability. Therefore, high-molecular-weight polyethylene homopolymers and ethylene/1-octene elastomers were successfully prepared, and the 1-octene incorporations of copolymers could be readily tuned from 1.3 to 43.5 mol % depending on different catalysts and polymerization conditions.

Insilico Anti-COVID Study of New-fangled High Polar Zr(IV) Complexes Functionalized with Resacetophenone and NMP Ligands

A significant issue restricting their commercialization is the short dependability of utilitarian biomolecules. These days, enduring immunizations, antiviral specialists, and anti-infection agents without zero results are intriguing examination subjects. In continuation of our pandemic exploration interest focused on the advancement of the keen antiviral specialist for COVID-19 utilizing heterocyclic metal builds. We describe herein synthesis and structural characterization of two new Zr(IV) complexes containing ligands like resacetophenone (T-R-Zr) (I) and N-methyl-2-pyrrolidone (T-NMP-Zr) (II). The absorption character in a neat solvent, in presence of 4.5 % BSA, and the biological interaction of COVID-19 virus through molecular docking have been summarized taking the scope into coordination chemistry directly or indirectly. The two complexes in 4.5% of BSA display both blue and red shift in peaks corresponds to LCT and MLCT transitions. The molecular docking study of the complex with the crystal structure of SARS-Coronavirus-2 (PDB: 6LU7) shows strong polar interaction with various amino acids present in the spike protein. The complex shows excellent binding energies ranges in-7.0 and -4.9 kcal mol-1, respectively. This makes them potential lead compounds for development into candidates against the SARS-Coronavirus-2. The absorption spectral behavior insolvent and in 4.5 % BSA has been found to show the importance of our complex in biological application especially in COVID-19 treatment studies. Furthermore, we investigated the basic energies like potential and steric energy of the complex through Gaussian energy calculations.

Insilico Anti-COVID Study of New-fangled High Polar Zr(IV) Complexes Functionalized with Resacetophenone and NMP Ligands

A significant issue restricting their commercialization is the short dependability of utilitarian biomolecules. These days, enduring immunizations, antiviral specialists, and anti-infection agents without zero results are intriguing examination subjects. In continuation of our pandemic exploration interest focused on the advancement of the keen antiviral specialist for COVID-19 utilizing heterocyclic metal builds. We describe herein synthesis and structural characterization of two new Zr(IV) complexes containing ligands like resacetophenone (T-R-Zr) (I) and N-methyl-2-pyrrolidone (T-NMP-Zr) (II). The absorption character in a neat solvent, in presence of 4.5 % BSA, and the biological interaction of COVID-19 virus through molecular docking have been summarized taking the scope into coordination chemistry directly or indirectly. The two complexes in 4.5% of BSA display both blue and red shift in peaks corresponds to LCT and MLCT transitions. The molecular docking study of the complex with the crystal structure of SARS-Coronavirus-2 (PDB: 6LU7) shows strong polar interaction with various amino acids present in the spike protein. The complex shows excellent binding energies ranges in-7.0 and -4.9 kcal mol-1, respectively. This makes them potential lead compounds for development into candidates against the SARS-Coronavirus-2. The absorption spectral behavior insolvent and in 4.5 % BSA has been found to show the importance of our complex in biological application especially in COVID-19 treatment studies. Furthermore, we investigated the basic energies like potential and steric energy of the complex through Gaussian energy calculations.

Zirconium-catalysed direct substitution of alcohols: enhancing the selectivity by kinetic analysis

Kinetic analysis was used as a tool for rational optimization of catalytic direct substitution of alcohols to enable selective formation of ethers, thioethers, and Friedel–Crafts alkylation products using a moisture-tolerant and commercially available Zr complex.

Homoleptic titanium and zirconium complexes exhibiting unusual Oiminol–metal coordination: application in stereoselective ring-opening polymerization of lactide

The synthesis and characterization of novel homoleptic Ti and Zr complexes with tridentate ONO-type Schiff base ligands and their catalytic activities towards the ring-opening polymerization (ROP) of lactide are reported.

Catalytic Systems Based on Cp2ZrX2 (X = Cl, H), Organoaluminum Compounds and Perfluorophenylboranes: Role of Zr,Zr- and Zr,Al-Hydride Intermediates in Alkene Dimerization and Oligomerization

The activity and chemoselectivity of the Cp2ZrCl2-XAlBui2 (X = H, Bui) and [Cp2ZrH2]2-ClAlEt2 catalytic systems activated by (Ph3C)[B(C6F5)4] or B(C6F5)3 were studied in reactions with 1-hexene. The activation of the systems by B(C6F5)3 resulted in the selective formation of head-to-tail alkene dimers in up to 93% yields. NMR studies of the reactions of Zr complexes with organoaluminum compounds (OACs) and boron activators showed the formation of Zr,Zr- and Zr,Al-hydride intermediates, for which diffusion coefficients, hydrodynamic radii, and volumes were estimated using the diffusion ordered spectroscopy DOSY. Bis-zirconium hydride clusters of type x[Cp2ZrH2∙Cp2ZrHCl∙ClAlR2]∙yRnAl(C6F5)3−n were found to be the key intermediates of alkene dimerization, whereas cationic Zr,Al-hydrides led to the formation of oligomers.

Thermal and potentiometric studies for complexes of Zr and Hf with some barbituric acid derivatives

The complexes of Barbital (Bal), Thiobarbituric acid thione (TBA), Thiobarbituric acid thiol (2-TBA), 2-Thiouracil (TU) with Zr (IV) and Hf (IV) were prepared. The structures and mode of bonding were characterized by elemental analysis, IR and electronic spectroscopy. Thermal analyses of the prepared complexes were done by DTA, TG, DSC techniques. The thermodynamic parameters were evaluated. The change of entropy values, AS#, for all the complexes lie within the range -0.267,-0.299 KjK-1 mol-1. The thermal processes proceed in complicated mechanisms with ordered transition states. In general, the complexes dissociated after losing small molecules such as H2O, Cl2 and CO. The decomposition is usually ended by the metal moiety. The DSC technique explained the effect of temperature on physical properties of some complexes. The glass transition phase doesn`t appear in all the complexes, while the crystallization temperature (Tc) was 780C-322.120C. Potentiometric titration studies calculated the dissociation constants of the ligands, the stability constants of the complexes and the distribution of species at different pH values.

Enhanced adsorption of Cr (VI) from aqueous solution by zirconium impregnated chitosan microspheres: mechanism and equilibrium

ABSTRACT The present paper reports a novel adsorbent that is synthesized with chitosan and zirconium ions through a simple method, for the removal of Cr (VI) ions from solutions. In this study, the effects of solution pH, absorbent dosage, contact time, and initial concentration were evaluated through a series of experiments. The modified chitosan was also characterized by SEM-EDS, FTIR, TG, and XPS. It is found that the Cr (VI) adsorption capacity by Zr-CS of 230.41 mg/g, was achieved at pH 4.5. The adsorption results indicated that the adsorption process was in line with Langmuir isotherm at 25°C. At the same time, the kinetic studies indicated that the adsorption process followed a pseudo-second-order model. Therefore, Zr-CS is a very promising adsorbent for the treatment of chromium-containing wastewater. XPS and element spectrum images, however, showed the difference between the adsorbent before and after Cr (VI) adsorption. According to the data, the adsorption should include electrostatic interaction between protonated amino and Cr (VI) as well as complexation of Zr with Cr (VI). According to the experimental data, it is believed that zirconium-modified chitosan adsorbent is an effective adsorbent for removing chromium ions in the solution.

Solution-Phase Synthesis of a Base-Free Benzoborirene and a Three-Dimensional Inorganic Analogue.

The base-free benzoborirene 1,2-BR-1,2-C6H4 (7) and its three-dimensional inorganic analogue 1,2-BR-1,2-C2B10H10 (13) have been successfully synthesized by Cp2ZrBr2 and LiCl elimination, respectively. The Cl analogue of the key intermediate for the formation of benzoborirene 7 has been isolated and structurally characterized, thus suggesting the reaction pathway via benzyne Zr complex formation, B-Br/Cbenzyne-Zr σ-bond metathesis, and a Cp2ZrBr2 elimination/ring-closing process. The rationality of the reaction pathway has been confirmed by DFT calculations. In addition, the title compounds shared the same reactivity pattern (i.e., 1,3-silyl migration) toward MeIiPr (8), thus allowing for the synthetic approach to the first carborane-substituted iminoborane 14.

Vibrational Spectroscopy of Intermediates and C-H Activation Products of Sequential Zr+ Reactions with CH4.

Vibrational spectra of the entrance channel complexes Zr+(CH4)n(Ar) (n = 1-2) and Zr+(CH4)n (n = 3-4) and the reaction products ZrC3H10+, ZrC4H13+, ZrC4H14+, and ZrC4H15+ in the C-H stretching region (2550-3100 cm-1) are obtained using photofragment spectroscopy. The experimental spectra and simulations based on calculations at the B3LYP/aug-cc-pVTZ level of theory work together to identify the structures of the ions. The n = 1-3 entrance channel complexes show peaks around 2800 and 3000 cm-1 which indicates methane η3 hydrogen coordination, while the n = 4 complex has two peaks around 2800 cm-1 indicative of methane η2 hydrogen coordination. Observation of the low-frequency C-H stretch of an agostic carbene group, as well as the high-frequency H-H stretch, also confirms production of (H2)ZrCH2+(CH4)n-1 (n = 1-2) exit channel complexes. The observed C-H activation products formally correspond to loss of H2 from Zr+(CH4)3 and loss of H, H2, and H2 + H from Zr+(CH4)4. Comparison of experiment and simulations indicates that the activation products are Zr(CH3)2+(CH4), Zr(CH3)3+(CH4), Zr(CH3)2+(CH4)2, and HZrCH2+(CH4)3 and/or ZrCH3+(CH4)3.

Synthesis, Characterization and Biological Activity of a Bidentate NS Schiff Base Containing S-Benzyl Dithiocarbazate and Its Zr(IV), Sn(II) Complexes

Zr (IV) and Sn (II) complexes were prepared with bidentate ligand, benzyl 2-(3-phenylallylidene) hydrazinecarbodithioate, derived from the condensation of S-benzyldithiocarbazate (SBDTC) with cinnamaldehyde and characterized by microanalysis, molar conductance and magnetic measurements, IR, electronic and ESI-MS studies. It was found that the ligand coordinated to the metal center through azomethine nitrogen and thiol sulfur atoms to form octahedral complexes with both the metal ions. The antimicrobial activities of the ligand and its complexes were investigated against the gram-positive and gram-negative bacteria and the fungus strain. The metal complexes showed strong activity than the free ligand.

SBDTC Derived Schiff Base Metal Complexation: Synthesis, Physicochemical, and Spectral Studies with Antibacterial Activity

A Schiff base ligand derived from condensation of S-benzyldithiocarbazate (SBDTC) and salicylaldehyde, and its U(VI), Th(IV) and Zr(IV) complexes have been synthesized. The compounds are characterized by elemental analysis, molar conductance, magnetic moments, UV-Vis, FT-IR and 1H NMR spectra. The Schiff base ligand coordinates via azomethine nitrogen, thiol sulfur and/or the phenolic OH group, and acts as bidentate in case of U(VI) and Zr(IV) ions and tridentate with Th(IV) ion. The U(VI) and Th(IV) complexes are 1 : 2 electrolytes whereas Zr(IV) complex is non-electrolytic. All the compounds have been tested for their antibacterial activity against four pathogenic bacteria, two Gram-negative Escherichia coli and Shigella dysenteriae and two Gram-positive Staphylococcus aureus and Bacillus subtilis using Kanamycin (K-30) as a standard. The U(VI) and Th(IV) complexes exhibit stronger antibacterial activity than the Zr(IV) complex against all tested organisms.

Peroxo Complexes of Th(IV) and Zr(IV) Ions Containing Aspartic Acid and Amine Bases as Potential Biological Agents

Eight new peroxo complexes of the type [MO(O2)(Asp)L] have been synthesized and characterized by conductivity, magnetic moments, UV-Vis, IR, ESI-MS and 1H NMR spectra, TLC, and elemental analyses [M = Th(IV) and Zr(IV), Asp= deprotonated aspartic acid, L = quinoline, isoquinoline, 8-hydroxyquinoline, and 1,10-phenanthroline]. IR spectra indicate that the ligands coordinate to the metal ions via nitrogen of the amino group of aspartic acid and heterocyclic amines, oxygen of the carboxylate group of deprotonated aspartic acid and the peroxo group (O–O). ESI-MS spectral data and magnetic moment values coupled with electronic spectral data suggest an octahedral geometry for all the complexes. The molar conductance values indicate that all the complexes behave as 1 : 2 electrolytes except complexes of 8-hydroxyquinoline that behaves as 1 : 3 electrolytes. Antibacterial activity of the complexes has been tested against four pathogenic bacteria, two Gram-positive Staphylococcus aureus and Bacillus subtilis and two Gram-negative Escherichia coli and Shigella dysenteriae using Kanamycin (K-30) as a standard. The MIC values for complexes hve been measured. Antifungal activity of the complexes has been tested against four pathogenic fungi Aspergillus flavus, Penicillium species, Candida species, and Aspergillus niger using Fluconazole-50 as a standard. The complexes K2[ThO(O2)(Asp)(IQ)] and K2[ZrO(O2)(Asp)(Q)] demonstrate the highest antibacterial activity, and K2[ZrO(O2)(Asp)(1,10-Phen)] exhibits the highest antifungal activity against all the tested pathogens.

Synthesis, Chracterization and Antibacterial Activity of Cd(II) and Zr(IV) Peroxo-complexes

Two new peroxo-complexes of Cd(II) and Zr(IV) ion containing Schiff base (SB) were synthesized and characterized by Thin Layer Chromatography (TLC), Elemental analyses, conductivity, magnetic moment measurements, UV-Vis. and FT-IR spectral studies. The Schiff base ligand derived from cinnamaldehyde and o-aminophenol participated in complexation through a single pot reaction. FT-IR spectra showed that the Schiff base ligand coordinated to the metal ion through nitrogen of azomethine group and oxygen of hydroxyl group & peroxo group (O-O). The molar conductance values indicated the non-electrolytic nature of both the complexes. Antibacterial activity of the complexes was tested against four pathogenic bacteria, two Gram-positive Staphylococcus aureus & Bacillus cereus and two Gram-negative Escherichia coli & Shigella dysenteriae with standard Kanamycin-30. The result showed that Cd(II) complex exhibited more potential antibacterial activity than the Zr(IV) complex against all the tested pathogens.

Zirconium‐Salan Catalyzed Enantioselective α‐Hydroxylation of β‐Keto Esters

AbstractWe report herein the development of enantioselective and scalable α‐hydroxylation of 1‐indanone‐derived β‐keto esters by Zr(IV) complexes bearing readily available C2‐symmetric salan ligands and cumene hydroperoxide as an oxidant, affording synthetically valuable hydroxylation products in high yields (up to 99%) with excellent enantioselectivities (up to 99% ee) under mild reaction conditions. In mechanistic studies, we have shown that (1) a Zr(IV)‐salan complex was generated in situ as the active catalyst responsible for the chiral induction, (2) the transfer of the electrophilic fragment from cumene hydroperoxide to the Zr(IV)‐bound enolate was accompanied by a heterolytic O−O bond cleavage, and (3) the formation of hydrogen bond between the amine hydrogen atom(s) of the salan ligand and the hydroxy group of cumene hydroperoxide was significant for stabilizing the stereocontrolled transition state and improving the enantioselectivity.magnified image

Inverse Chrome Tanning Technology

Conventional chrome tanning technology (CCTT) generates a remarkable quantity of Cr(III)-containing wastewater and solid wastes, which may pose a potential risk to the environment. In this work, an inverse chrome tanning technology (ICTT) was developed based on chrome-free tanning by Al–Zr complexes and highly oxidized starch (AZ–HOS) to minimize Cr(III) discharge. The 7.5% AZ–HOS exhibited sufficient tanning effect and gave wet white a shrinkage temperature of over 80o C. Thus, wet white can be stably stored for one year and possessed high absorption capacity to post-tanning chemicals (85%–90%) because its pI (7.1) was as high as that of wet blue. Terminal chrome tanning with 1.0% chrome tanning agent after post-tanning gave the ICTT crust leather physical and organoleptic properties that are comparable to those of CCTT crust leather. Moreover, the Cr and TOC loads in ICTT wastewater decreased by 99.9% and 42.4%, respectively. Therefore, this work provides a clean and practical tanning system for the sustainable leather industry.