Square-planar Research Articles

Cyclopalladated complexes with pincer-like ONC-donor N-(4-R-benzoyl)-N′-(9-phenanthrylidene)hydrazines: Regioselective peri‑palladation of the 9-phenanthryl group

Two series of cyclopalladates [Pd(HL1–5)Cl] (1–5) and [Pd(L1–5)(PPh3)] (6–10) with the Schiff bases N-(4-R-benzoyl)-N′-(9-phenanthrylidene)hydrazines (H2Ln, where n = 1–5 for R = H, Cl, OMe, NO2 and NMe2, respectively and 2 Hs represent the amide and the ortho or peri H-atom of the 9-phenanthryl group) are reported. All the complexes were characterized by mass spectrometric and spectroscopic (IR, UV–Vis and fluorescence) measurements. Molecular structures of two Schiff bases (H2L1 and H2L4) and three representative complexes from each series [Pd(HL1,3,5)Cl] (1, 3 and 5) and [Pd(L1,2,4)(PPh3)] (6, 7 and 9) were confirmed by single crystal X-ray crystallographic studies. In each of the two types of complexes (HLn)– or (Ln)2– acts as ONC-donor pincer-like ligand. In [Pd(HL1,3,5)Cl], the metal center is in square-planar ONCCl environment assembled by amide-O, azomethine-N and 9-phenanthryl peri‑C coordinating (HL1,3,5)– and the Cl-atom. On the other hand, in [Pd(L1,2,4)(PPh3)], (L1,2,4)2– coordinate through amidate-O, azomethine-N and 9-phenanthryl peri‑C and the P-atom of PPh3 satisfies the fourth coordination site to form a square-planar ONCP coordination geometry around the metal center. The mass spectrometric and infrared and electronic spectroscopic characteristics of all the complexes are complementary to their molecular structures. All the Schiff bases and the complexes are emissive in solution. Theoretical calculations were carried out with a representative complex to comprehend the regioselective peri‑palladation of the 9-phenanthryl fragment of the tridentate ligand.

New Copper Complexes with Antibacterial and Cytotoxic Activity.

The discovery of a new non-toxic metal complex with biological activity represents a very active area of research. Two Cu+2 complexes, [Cu4(L1)4(OH)4(DMF)2(H2O)] (C1) (HL1 = N-(5-ethyl-[1,3,4]-thiadiazole-2-yl)-benzenesulfonamide) and [Cu(L2)2(phen)(H2O)] (C2) (HL2 = N-(5-(4-methylphenyl)-[1,3,4]-thiadiazole-2-yl)-naphtalenesulfonamide), with two new ligands were synthesized. The X-ray crystal structures of the complexes were determined. In both complexes, Cu+2 is five-coordinated, forming a CuN2O3 and CuN4O chromophore, respectively. The ligands act as monodentate, coordinating the metal ion through a single Nthiadiazole atom; for the two complexes, the molecules from the reaction medium (phenantroline, dimethylformamide and water) are also involved in the coordination of Cu+2. The complexes have a distorted square pyramidal square-planar geometry. The compounds were characterized by FT-IR and UV-Vis spectroscopy. Using the microdilution method, the antibacterial activity of the complexes was determined against four Gram-positive and two Gram-negative bacteria, with Gentamicin as the positive control. Cytotoxicity studies were carried out on two tumor cell lines (HeLa, DLD-1) and on a normal cell line (HFL1) using the MTT method and Cisplatin as a positive control. Flow cytometric assessment of apoptosis induced by the complexes on the three cell lines was also performed. Both complexes present in vitro biological activities but complex C2 is more active.

Pressure-Induced Superconductivity in the Charge-Density-Wave Compound LaTe2–x Sb x (x = 0 and 0.4)

Magnetic CeTe2 achieving superconductivity under external pressure has received considerable attention. The intermingling of 4f and 5d electrons from Ce raised the speculation of an unconventional pairing mechanism arising from magnetic fluctuations. Here, we address this speculation using a nonmagnetic 4f-electron-free LaTe2 as an example. No structural phase transition can be observed up to 35 GPa in the in situ synchrotron diffraction patterns. Subsequent high-pressure electrical measurements show that LaTe2 exhibits superconductivity at 20 Gpa with its T c (4.5 K) being two times higher than its Ce-counterpart. Detailed theoretical calculations reveal that charge transfer from the 4p orbitals of the planar square Te–Te network to the 5d orbitals of La is responsible for the emergence of superconductivity in LaTe2, as confirmed by Hall experiments. Furthermore, we study the modulation of q CDW by Sb substitution and find a record high K in LaTe1.6Sb0.4. Our work provides an informative clue to comprehend the role of 5d–4p hybridization in the relationship between charge density wave (CDW) and superconductivity in these RETe2 (RE = rare-earth elements) compounds.

Synthesis and Biological Activities of Luminescent 5,6-Membered Bis(Metallacyclic) Platinum(II) Complexes.

Four couples of 5,6-membered bis(metallacyclic) Pt(II) complexes with acetylide and isocyanide auxiliary ligands have been prepared and characterized. The structures of (-)-2 and (-)-3 are confirmed by single-crystal X-ray diffraction, showing a distorted square-planar coordination environment around the Pt(II) nucleus. Both solutions and solid samples of all complexes are emissive at RT. Acetylide-coordinated Pt(II) complexes have a lower energy emission than those isocyanide-coordinated ones. The emission spectra of N^N'*C-coordinated Pt(II) derivatives show a lower energy emission maximum relative to N^C*N'-coordinated complexes with the same auxiliary ligand. Moreover, the difference between cyclometalated N^N'*C and N^C*N' ligands exerts a more remarkable effect on the emission than the auxiliary ligands acetylide and isocyanide. Cytotoxicity and cell imaging of luminescent 5,6-membered bis(metallacyclic) Pt(II) complexes have been evaluated.

SYNTHESISAND ANTIMICROBIAL STUDIES OF SCHIFF BASE DERIVED FROM2-THENOYLTRIFLUOROACETONE AND 4-AMINOANTIPYRINEAND ITSCo(II), Fe(III), Ni(II) AND Cu(II) COMPLEXES

A new ligand, 3-[2-(1, 5-dimethyl-3-oxo-2-phenyl-2, 3-dihydro-1H-pyrazol-4-yl) hydrazinylidene]-2-thenoyltrifluoroacetone (HPDP) was prepared by diazotization of 4-aminoantipyrine and coupling of the obtained diazonium salt with 2-thenoyltrifluoroacetone. It’s Co(II), Fe(III), Cu(II), Ni(II) complexes were synthesized by refluxing the ligand(HPDP) with the metal chlorides in absolute ethanol for 6 hrs. Obtained compounds were characterized by means of melting point, conductivity, elemental analysis UV-Visible, FT-IR, 1H and 1 3C NMR.The molar conductivity values indicated that,[Fe(PDP)(H2O)Cl2], [Co(PDP)Cl2(OH2)], [Cu(HPDP)Cl2], [Ni(PDP)Cl2(OH2)] complexes were electrolytes when compared with CuSO4 and KCl salts respectively. The chloride analysis determination revealed the presence of chloride ions inside the coordination sphere of all the complexes. The Uv-Vis, IR, 1H and 13CNMR data of the complexes suggest square-planar geometry around Co (II), Cu (II), Ni (II) and octahedral geometry around Fe (III) ions. The ligand is tridentate and the complexes crystalized as M (HPDP). The ligand coordinated through the carbonyl oxygens and nitrogen atom of the azomethine –C=N group. The antimicrobial screening of the ligand and complexes with B.subtilis, E.coli, and P.mirabilis,S. aureus, S. intermediusS. typhi and S. pneumoniae showed more activities for the complexes than the ligand in comparison with standard drugs (Ampicillin and Ciprofloxacin), this implies that the synthesized compounds have potency for possible use as antbacterial agents against resistant strains.

Heterotridentate Organomonophosphines in Pt(η3-P1C1C2)(Y) and Pt(η3-P1C1N1)(Y) Derivatives—Structural Aspects

This paper covers Pt(II) complexes of the compositions Pt(η3-P1C1C2)(Y) (Y = NL or I) and Pt(η3-P1C1N1)(Y), Y = OL, NL, CL, Cl or Br). These complexes crystallized in four crystal classes: monoclinic (9 examples), triclinic (3 examples), orthorhombic (3 examples), and tetragonal (2 examples). The structural parameters (Pt-L, L-Pt-L) are analyzed and discussed with attention to the distortion of square-planar geometry about the Pt(II) atoms and trans-influence. These data are compared and discussed with those of Pt(η3-P1N1N2)(Y), Pt(η3-P1N1X1)(Y), (X1=O1, C1, S1, Se1), Pt(η3-N1P1N2)(Cl), Pt(η3-S1P1S2)(Cl), Pt(η3-P1S1Cl1)(Cl), and Pt(η3-P1Si1N1)(OL) types. Each heterotridentate ligand creates two metallocyclic rings with a common central ligating atom. These η3-ligands form twenty-three types of metallocycles and differ by the number and type of the atoms involved in the metallocyclic rings.

Complexes of 1,10-phenanthroline-mono-N-oxides with copper(II) and nickel(II) in aqueous solution and solid phase

Thorough equilibrium and spectroscopic studies are reported on the complexes formed between copper(II) or nickel(II) and derivatives of phenanthroline-mono-N-oxides (1,10-phenanthroline-1-N-oxide (phenO), 2,9-dimethyl-1,10-phenanthroline-1-N-oxide (DMPO) and 3,4,7,8-tetramethyl-1,10-phenanthroline-1-N-oxide (TMPO)). PhenO exhibits excellent metal binding ability, both copper(II) and nickel(II) form bis complexes in which the ligands coordinate to the metal ions via the (N,O) donor set. In the case of copper(II), a square-pyramidal complex forms, where the phenO-s coordinate at the corners of the square and the remaining site is occupied by the water molecule. The bis complex formed between nickel(II) and phenO possesses square-planar geometry in solution, however, the Ni(II) ion exhibits a distorted octahedral geometry in solid phase. DMPO forms relatively stable complexes with copper(II), but the coordination of this ligand to nickel(II) could not be confirmed. Because of precipitate formation in the entire studied pH range (pH = 2.0 – 11.0), well defined complexes could not be identified in the copper(II) – TMPO system. In contrast, this ligand forms stable water soluble nickel(II) complexes. The noted selectivity of these ligands in complex formation reactions is explained by considering the plasticity of copper(II), the rigid, square-planar geometry of nickel(II) and the enhanced steric repulsion of the methyl substituents of DMPO.

DFT insight into metals and ligands substitution effects on reactivity of phenoxy-imine catalysts for ethylene polymerization

The reaction mechanism of ethylene (ET) polymerization catalyzed by the phenoxy-imine (FI) ligands using DFT calculations was studied. Among five possible isomers, isomer A which has an octahedral geometry and a (cis-N/trans-O/cis-Cl) arrangement is the most stable pre-reaction Ti-FI dichloride complex. The isomer A can be activated by MAO to form the active catalyst and the active form was used for the study of the mechanism for Ti-FI. The second ethylene insertion was found to be the rate-determining step of the catalyzed ethylene polymerization. To examine the effect of group IVB transition metals (M = Ti, Zr, Hf) substitutions, calculated activation energies at the rate-determining step (EaRDS) were compared, where values of EaRDS of Zr < Hf < Ti agree with experiments. Moreover, we examined the effect of substitution on (O, X) ligands of the Ti-phenoxy-imine (Ti-1) based catalyst. The results revealed that EaRDS of (O, N) > (O, O) > (O, P) > O, S). Hence, the (O, S) ligand has the highest potential to improve the catalytic activity of the Ti-FI catalyst. We also found the activation energy to be related to the Ti-X distance. In addition, a novel Ni-based FI catalyst was investigated. The results indicated that the nickel (II) complex based on the phenoxy-imine (O, N) ligand in the square-planar geometry is more active than in the octahedral geometry. This work provides fundamental insights into the reaction mechanism of M − FI catalysts which can be used for the design and development of M − FI catalysts for ET polymerization.

Calix[4]pyrrolato-germane-(thf)2: Unlocking the Anti-van't Hoff-Le Bel Reactivity of Germanium(IV) by Ligand Dissociation.

Anti-van't Hoff-Le Bel configured p-block element species possess intrinsically high reactivity and are thus challenging to isolate. Consequently, numerous elements in this configuration, including square-planar germanium(IV), remain unexplored. Herein, we follow a concept to reach anti-van't Hoff-Le Bel reactivity by ligand dissociation from a rigid calix[4]pyrrole germane in its bis(thf) adduct. While the macrocyclic ligand assures square-planar coordination in the uncomplexed form, the labile thf donors provide robustness for isolation on a multigram scale. Unique properties of a low-lying acceptor orbital imparted to germanium(IV) can be verified, e.g., by isolating an elusive anionic hydrido germanate and exploiting it for challenging bond activations. Aldehydes, water, alcohol, and a CN triple bond are activated for the first time by germanium-ligand cooperativity. Unexpected behaviors against fluoride ion donors disclose critical interferences of a putative redox-coupled fluoride ion transfer during the experimental determination of Lewis acidity. Overall, we showcase how ligand lability grants access to the uncharted chemistry of anti-van't Hoff-Le Bel germanium(IV) and line up this element as a member in the emerging class of structurally constrained p-block elements.

A Conformationally Restricted Gold(III) Complex Elicits Antiproliferative Activity in Cancer Cells.

Diamine ligands are effective structural scaffolds for tuning the reactivity of transition-metal complexes for catalytic, materials, and phosphorescent applications and have been leveraged for biological use. In this work, we report the synthesis and characterization of a novel class of cyclometalated [C^N] Au(III) complexes bearing secondary diamines including a norbornane backbone, (2R,3S)-N2,N3-dibenzylbicyclo[2.2.1]heptane-2,3-diamine, or a cyclohexane backbone, (1R,2R)-N1,N2-dibenzylcyclohexane-1,2-diamine. X-ray crystallography confirms the square-planar geometry and chirality at nitrogen. The electronic character of the conformationally restricted norbornane backbone influences the electrochemical behavior with redox potentials of -0.8 to -1.1 V, atypical for Au(III) complexes. These compounds demonstrate promising anticancer activity, particularly, complex 1, which bears a benzylpyridine organogold framework, and supported by the bicyclic conformationally restricted diaminonorbornane, shows good potency in A2780 cells. We further show that a cellular response to 1 evokes reactive oxygen species (ROS) production and does not induce mitochondrial dysfunction. This class of complexes provides significant stability and reactivity for different applications in protein modification, catalysis, and therapeutics.

Research on Metal Foreign Object Detection Method in Wireless Charging System of Electric Vehicle Based on Array Detection Coil

In order to eliminate the potential safety hazard that arises when metal foreign objects intervene in the wireless charging area of electric vehicles, this paper proposes that a metal foreign object detection method be applied to the wireless charging system of electric vehicles based on the optimal design of the array detection coil. Firstly, the equivalent circuit model of the metal foreign object detection system is established, then the principle of the foreign object detection system is analyzed, and the scale factor β is introduced as the optimization index of the detection coil. Secondly, the change of the scale factor β with the circuit parameters is analyzed and the appropriate circuit parameters are compared and selected. Thirdly, on the basis of the planar square spiral coil, Ansys Maxwell finite element simulation software is used to optimize its structural parameters, combination mode, and resonant circuit, as well as design the anti-series and anti-parallel enhanced detection coil sets with the decoupling and elimination of detection blind spots. Finally, the feasibility of the proposed detection method of metal foreign objects is verified by experiments. The results show that the two array detection coil sets can detect small-sized common metal foreign objects such as paper clips and the proposed double-layer reinforced structure can significantly improve the detection sensitivity of the system.

Persistence of a Delocalized Radical in Larger Clusters of Hydrated Copper(II) Hydroxide, CuOH+(H2O)3-7.

The structures, vibrational spectra, and electronic properties of copper hydroxide hydrates CuOH+(H2O)3-7 were investigated with quantum chemistry computations. As a follow-up to a previous analysis of CuOH+(H2O)0-2, this investigation examined the progression as the square-planar metal coordination environment was filled and as solvation shells expanded. Four-, five-, and six-coordinate structures were found to be low-energy isomers. The delocalized radical character, which was discovered in the small clusters, was found to persist upon continued hydration, although the hydrogen-bonded water network in the larger clusters was found to play a more significant role in accommodating this spin. Partial charges indicated that the electronic structure includes more Cu2+···OH- character than was observed in smaller clusters, but this structure remains decidedly mixed with Cu+···OH· configurations and yields roughly half-oxidation of the water network in the absence of any electrochemical potential. Computed vibrational spectra for n = 3 showed congruence with spectra from recent predissociation spectroscopy experiments, provided that the role of the D2 tag was taken into account. Spectra for n = 4-7 were predicted to exhibit features that are reflective of both the mixed electronic character and proton-/hydrogen-shuttling motifs within the hydrogen-bonded water network.

Supramolecular Control of the Oxidative Addition as a Way To Improve the Catalytic Efficiency of Pincer-Rhodium (I) Complexes.

1 H NMR studies using a cationic complex with a pyridine-di-imidazolylidene pincer ligand of formula [Rh(CNC)(CO)]+ revealed that this compound showed high binding affinity with coronene in CH2 Cl2 . The interaction between coronene and the planar RhI complex is established by means of π-stacking interactions. This interaction has a strong impact on the electron-donating strength of the pincer CNC ligand, which is increased significantly, as demonstrated by the shifting of the ν(CO) stretching bands to lower frequencies. The addition of coronene increases the reaction rate of the nucleophilic attack of methyl iodide on the rhodium (I) pincer complex, and also has a positive effect on the performance of the complex as a catalyst in the cycloisomerization of 4-pentynoic acid. These findings highlight the importance of supramolecular interactions for tuning the reactivity and catalytic activity of square-planar metal complexes.

Crystal structure of bis-{S-octyl-3-[(thio-phen-2-yl)methyl-idene]di-thio-carbazato-κ2N3,S}nickel(II).

In the title complex, [Ni(C14H21N2S3)2], the nickel(II) atom is located on a crystallographic inversion center and exhibits a square-planar coordination environment, being coordinated by two negatively charged N,S-chelating ligands in a trans configuration. In the crystal, the non-H atoms of the complex are practically coplanar (r.m.s. deviation of fitted atoms = 0.135 Å), and the angle between the thienyl and the chelating rings is 6.7 (1)°. The mol-ecules stack at a distance of 3.623 (2) Å along the b-axis direction.

Synthesis and Characterization of 4-amino-N'-[(1E)-1-(2-hydroxy-6-methyl-4-oxo-4H-pyran-3-yl)ethylidene]benzohydrazide and its Cu(II), Ni(II), Zn(II) and Mn(II) Complexes

New benzohydrazone compound, 4-amino-N'-[(1E)-1-(2-hydroxy-6-methyl-4-oxo-4H-pyran-3-yl)ethylidene] benzohydrazide (HL1) and its Cu(II), Ni(II), Zn(II) and Mn(II) complexes were synthesized. The structures of HL1 and its complexes were elucidated by elemental analysis and IR, UV-Vis, 1H and 13C NMR spectroscopy and mass spectrometry. The infrared spectral data of the complexes revealed that HL1 coordinated with the metal ions through azomethine nitrogen, enolic oxygen and amide carbonyl oxygen atoms, hence, HL1 behaves as a monobasic tridentate ligand. UV-Vis data revealed that Zn(II) and Mn(II) complexes adopted octahedral geometry, while Cu(II) and Ni(II) complexes had five-coordinate and square-planar geometries respectively. The mass spectra data and elemental analysis values are in accordance with the calculated values for the suggested molecular formula of the complexes, a confirmation of the 1:1 ligand to metal stoichiometry in case of Cu(II) complex and 2:1 ligands to metal stoichiometry in case of the other complexes.

Cluster Variation for Spatially Distributed Heterogeneous Systems

Fundamentals of cluster variation (CV) are developed for locally heterogeneous spatially distributed systems. The theory is based on the principles of homogeneous CV in which all variants of the location of the basis cluster on a heterogeneous lattice are additionally considered when it is translated over the system. The structure of the statistical sum of homogeneous CV is shown to remain upon moving to a heterogeneous or homogeneous spatially distributed lattice. However, cofactors of the statistical sum, which previously corresponded to homogeneous clusters, must now consider all arrangements of heterogeneous sites inside each cluster. The general approach is to use a layered structure of the transitional region with variable density between vapor and fluid on a planar square lattice. Explicit expressions for a heterogeneous statistical sum of the transitional region are given on the basis of a 3 × 3 cluster. Using a 2 × 2 cluster, it is shown how an explicit equation for the equilibrium particle distribution in the transitional region can be obtained from the heterogeneous statistical sum. A gradual increase in the size of the m × n basis cluster in the transitional region converges to the exact solution.

Cluster Variation for Spatially Distributed Heterogeneous Systems

Fundamentals of cluster variation (CV) are developed for locally heterogeneous spatially distributed systems. The theory is based on the principles of homogeneous CV in which all variants of the location of the basis cluster on a heterogeneous lattice are additionally considered when it is translated over the system. The structure of the statistical sum of homogeneous CV is shown to remain upon moving to a heterogeneous or homogeneous spatially distributed lattice. However, cofactors of the statistical sum, which previously corresponded to homogeneous clusters, must now consider all arrangements of heterogeneous sites inside each cluster. The general approach is to use a layered structure of the transitional region with variable density between vapor and fluid on a planar square lattice. Explicit expressions for a heterogeneous statistical sum of the transitional region are given on the basis of a 3 × 3 cluster. Using a 2 × 2 cluster, it is shown how an explicit equation for the equilibrium particle distribution in the transitional region can be obtained from the heterogeneous statistical sum. A gradual increase in the size of the m × n basis cluster in the transitional region converges to the exact solution.

Copper(II) o-Iminophenolate Complexes Based on Catecholaldimines

The exchange reactions of 4,6-di-tert-butylpyrocatechols containing in position 3 different N‑aryliminomethyl groups (aryl is p-halophenyl; halogen is fluorine (I), chlorine (II), bromine (III), and iodine (IV); p-tolyl (V)) with copper(II) acetate in a molar ratio of 2 : 1 afford planar square copper(II) o‑iminophenolate complexes of the general formula [(R-CatH)2Cu], where R is the aryl substituent in the Ar–N=CH group. The molecular structures of complexes I, III, and V in the crystalline state are determined by X-ray diffraction (XRD) (CIF files CCDC nos. 2227448 (I), 2226727 (III), and 2227449 (V)). The electrochemical properties of compounds I–V are studied by cyclic voltammetry.

Synthesis, crystal structure, and thermal behavior of Pt-based heterometallics [PtPy4](FcCOO)2 and trans-[PtPy2(FcCOO)2

Novel square-planar Pt-based heterometallic complexes with ferrocenecarboxylic acid were prepared in two steps from (tetrapyridine)platinum diacetate [PtPy4](OAc)2. The crystal structure of [PtPy4](FcCOO)2 and [PtPy2(FcCOO)2] was established by single crystal X-ray diffraction. Subsequent thermal transformation of a trinuclear compound [PtPy2(FcCOO)2] to a bimetallic Pt–Fe phase was studied by XAFS techniques.

Crystal structure and Hirshfeld surface analysis of bis-{(Z)-N'-[(E)-(furan-2-yl)methyl-idene]carbamo-hydrazono-thio-ato}nickel(II) methanol disolvate.

In the title complex, [Ni(C6H6N3OS)2]·2CH3OH, the NiII atom is coordinated by the S and N atoms of two N'-[(Z)-(furan-2-yl)methyl-idene]carbamohydrazono-thioic acid ligands in a distorted square-planar geometry. The two mutual ligands bound to NiII are also connected by C-H⋯S inter-actions, while the H atoms of the NH2 group of the ligands form R 4 4(8) motifs with the O atoms of the solvent ethyl alcohol mol-ecules. At the same time, the OH groups of the solvent ethyl alcohol mol-ecules form parallel layers to the (011) plane by the O-H⋯N inter-actions with the ligand N atom that is not bonded to the NiII atom.. The layers are connected by van der Waals inter-actions. A Hirshfeld surface analysis indicates that the most important contacts are H⋯H (37.7%), C⋯H/H⋯C (14.6%), O⋯H/H⋯O (11.5%) and S⋯H/H⋯S (10.6%).