Heteroligand Complexes Research Articles

ТЕРМОДИНАМИКА КОМПЛЕКСООБРАЗОВАНИЯ И СТРУКТУРА КОМПЛЕКСОВ ЦИНКА(II) С ГИСТИДИНОМ И 2-МЕТИЛДИПИРИДОХИНОКСАЛИНОМ

The complex formation in the zinc(II) - 2-methyldipyrido-[3,2-f:2',3'-h]-quinoxaline (MeDPQ), zinc(II) - L-histidine (HisH) and zinc(II) - 2-methyldipyrido-[3,2-f:2',3'-h]-quinoxaline - L-histidine systems at 37.0 °C on the 0.15 mol dm-3 NaCl background has been investigated by the pH-potentiometry method. A total of 10 complex forms were characterized. Based on the analysis of the complex formation constants and DFT calculations at the B3LYP/TZVPP level, taking into account the solvent effect within the C-PCM model, the structures of Zn(MeDPQ)(HisH)2+, Zn(MeDPQ)(His)+, and Zn(MeDPQ)(His)(OH) complexes were modeled. The higher stability of the homoligand complexes Zn(His)+, Zn(HisH)(His)+, Zn(His)2 and extra-stabilization in the formation constants of the heteroligand complexes Zn(MeDPQ)(HisH)2+ and Zn(MeDPQ)(His)+ were discovered, which was confirmed by the DFT calculations. Higher values of equilibrium constants of the mentioned homoligand forms are explained by coordination to the central nitrogen atom of the imidazole fragment of histidine. Extra-stabilization of heteroligand forms occurs due to d-π-interaction with electron density transfer from π-donor orbitals of oxygen atoms of the carboxy groups of amino acids through the central ion to π-acceptor orbitals of MeDPQ. It is emphasized that the studied zinc(II) complexes, both in binary and ternary systems, can have high biological activity, in particular, due to the nucleophilic attack of the coordinated hydroxide anion on proteins and other biomaterials. This opens up the prospect of using such zinc(II) complexes in medicine. In particular, the studied complexes may exhibit anticancer activity.

Luminescent Media Based on Heteroligand Lanthanide Complexes and Lyotropic Mesophases for Bioimaging Application

New terbium and europium heteroligand complexes with substituted 1,2,3-triazole – bis-1,3-(4-methylcarboxyl-1,2,3-triazol-1-yl)xylylene have been synthesized. A study of luminescent properties showed that the complexes exhibit high optical characteristics. The luminescence efficiency of [Tb(AcAc)2(TR)(H2O)2], increases by 13 % compared to the monoligand complex [Tb(AcAc)3(H2O)2]. In order to create biocompatible systems, an approach for the solubilization of hydrophobic complexes by incorporating them into the lyomesophase structure of P123/DMSO has been developed. According to polarization optical microscopy, the hybrid system containing 0.2 % of the [Tb(AcAc)3(H2O)2] complex shows a lamellar mesophase. Fluorescence microscopy study showed that the [Eu(TTA)2(TR)(H2O)2] complex is efficiently adsorbed on the surface of the Paramecium caudatum microorganism and exhibits red luminescence allowing visualization of biological objects.

Synthesis, structure of luminescence complexes and metalopolymers of Dy(III) and influence of the nature of substitutes on their emission

The new complexes of Dy (III) other β-diketones containing unsaturated, alkyl- and aryl- substituents were obtainted. Their heteroligand complexes with phenanthroline were synthesized. Quantum-chemical calculations of ligand molecules and metal complexes were performed. The main energy characteristics of ligand molecules were calculated: enthalpy of formation, total energy of the molecule and bond lengths, electronic population parameters of ligands. Metal polymers based on synthesized complexes were obtained by the method of radical polymerization. The composition and structure of synthesized complexes and metal polymers are established. It is shown that during polymerization the coordination environment of the central ion remains unchanged. The spectral-luminescent characteristics of the synthesized compounds were studied. The peculiarities of the influence of substituents in the diketonate fragment on the luminescent properties of metal complexes have been established. It is shown that the emission intensity of powdered samples depends on their morphology and dispersion.

Heteroleptic Cobalt Complexes with Abnormally Coordinated N-Heterocyclic Carbene

The reaction of cobalt pivalate [Co(Piv)2]n and in situ generated N‑heterocyclic carbene IPrPh (1,3-bis(2,6-diisopropylphenyl)-2-phenylimidazol-4-ylidene) affords heteroligand complexes [Co2(Piv)4-(IPrPh)2] (I), [Co2(Piv)2.8(OtBu)1.2(IPrPh)2] (II), and [Co3(μ3-O)(Piv)4(IPrPh)2] (III). The structures of complexes II·C6H14 and III are determined by X-ray diffraction (XRD) (CIF files CCDC nos. 2216724 and 2216725, respectively). Exchange spin-spin interactions between the magnetic Со2+ ions in the synthesized compounds are estimated by quantum chemical calculations.

Heteroleptic Cobalt Complexes with Abnormally Coordinated N-Heterocyclic Carbene

The reaction of cobalt pivalate [Co(Piv)2]n and in situ generated N‑heterocyclic carbene IPrPh (1,3-bis(2,6-diisopropylphenyl)-2-phenylimidazol-4-ylidene) affords heteroligand complexes [Co2(Piv)4-(IPrPh)2] (I), [Co2(Piv)2.8(OtBu)1.2(IPrPh)2] (II), and [Co3(μ3-O)(Piv)4(IPrPh)2] (III). The structures of complexes II·C6H14 and III are determined by X-ray diffraction (XRD) (CIF files CCDC nos. 2216724 and 2216725, respectively). Exchange spin-spin interactions between the magnetic Со2+ ions in the synthesized compounds are estimated by quantum chemical calculations.

Spectral-luminescent characteristics of coordination compounds and metal polymers of Yb(III)

New mono- and heteroligand (with phenanthroline or dipyridyl) metal complexes of ytterbium (III) with 2-methyl-5-biphenylpentene-1-3,5-dione were synthesized in this work. Homo- and copolymers of ytterbium complex with methyl methacrylate or styrene were obtained by the method of radical polymerization. Coordination compounds were investigated by IR spectroscopy, diffuse reflectance spectroscopy, thermal and luminescence analyses. It was determined that the -diketone molecules are bidentate-cyclically coordinated to the central atom, and the coordination sphere of the monoligand complex is supplemented by two water molecules, which in the case of heteroligand complexes (HLC) are replaced by phenanthroline or dipyridyl molecules. An increase in thermal stability of heteroligand complexes and metallopolymers was observed compared to the metallocomplex. The spectral properties of the synthesized compounds were studied and it was established that the structure of the coordination node of the elementary link of polymer macromolecules does not change during the polymerization process. It was shown that all the studied samples exhibited 4f-luminescence in the near-infrared region of the spectrum, while the lowest relative luminescence intensity was characteristic of ytterbium (III) homopolymer and copolymers, and the highest values were shown by heteroligand complexes with phenanthroline, which allows us to propose them as precursors of luminescent materials.

More-Is-Better Strategy for Constructing Homoligand Polypyridyl Ruthenium Complexes as Photosensitizers for Infrared Two-Photon Photodynamic Therapy

Photodynamic therapy (PDT) uses a combination of photosensitizers (PSs), light sources, and reactive oxygen species (ROS) to damage only the desired target and keep normal tissues from being hurt. The dark cytotoxicity (chemotoxicity) of PSs, leading to whole-body damage in the absence of irradiation, is a major limiting factor in PDT. How to simultaneously increase ROS generation and decrease dark cytotoxicity is an essential challenge that must be resolved in PS research. In this study, a series of homoligand polypyridyl ruthenium complexes (HPRCs) containing three singlet oxygen (1O2)-generating ligands (L) in a single molecule ([Ru(L)3]2+) have been constructed. Compared to the heteroligand complexes [Ru(bpy)2(L)]2+ where bpy is 2,2'-bipyridine, the 1O2 quantum yield under infrared two-photon irradiation and the DNA photocleavage effect of the HPRCs are significantly enhanced with two more ligands L. The intraligand triplet excited states transition played an important role in the activation of oxygen. The HPRCs target the mitochondria but not the nuclei, generating 1O2 intracellularly under irradiation of visible or infrared light. Ru1 exhibits high phototoxicity and low dark cytotoxicity toward human malignant melanoma cells in vitro. Moreover, HPRCs have minimal cytotoxicity to human normal liver cells, suggesting their potential as antitumor PDT reagents with more security. This study may provide inspiration for the structural design of potent PS for PDT.

Heteroligand Iron(V) Complexes Containing Porphyrazine, trans-Di[benzo]porphyrazine or Tetra[benzo]porphyrazine, Oxo and Fluoro Ligands: DFT Quantum-Chemical Study

By using quantum chemical calculation data obtained by the DFT method with the B3PW91/TZVP and OPBE/TZVP levels, the possibility of the existence of three Fe(V) complexes, each of which contains in the inner coordination sphere porphyrazine/trans-di[benzo]porphyrazine/tetra[benzo]porphyrazine (phthalocyanine), oxygen (O2-) and fluorine (F-) ions, was shown. Key geometric parameters of the molecular structure of these heteroligand complexes are given; it is noted that FeN4 chelate nodes, and all metal-chelate and non-chelate cycles in each of these compounds, are practically planar with the deviation from coplanarity, as a rule, by no more than 0.5°. Furthermore, the bond angles between two nitrogen atoms and an Fe atom are equal to 90°, or less than this by no more than 0.1°, while the bond angles between donor atoms N, Fe, and O or F, in most cases, albeit insignificantly, differ from this value. Nevertheless, the bond angles formed by Fe, O and F atoms are exactly 180°. It is shown that good agreement occurs between the structural data obtained using the above two versions of the DFT method. NBO analysis data for these complexes are presented; it is noted that, according to both DFT methods used, the ground state of the each of three complexes under consideration may be a spin quartet or spin doublet. Additionally, standard thermodynamic parameters of formation (standard enthalpy ∆fH0, entropy S0 and Gibbs's energy ∆fG0) for the macrocyclic compounds under consideration are calculated.

DFT Method Used for Prediction of Molecular and Electronic Structures of Mn(VI) Macrocyclic Complexes with Porhyrazine/Phthalocyanine and Two Oxo Ligands.

By using the data of the DFT quantum chemical calculation in the OPBE/TZVP and B3PW91/TZVP levels, the possibility of the existence of a manganese(VI) heteroligand complex containing porphyrazine or its tetra[benzo] derivative (phthalocyanine) and two oxygen (O2-) ligands, which is still unknown for this element, is shown. The parameters of the molecular structure, multiplicity of the ground state, NBO analysis data and standard thermodynamic parameters (enthalpy ΔH0f, entropy S0f and Gibbs's energy ΔG0f of formation) of each of these metal macrocyclic compounds are presented. Additionally, it is noted that, based on the totality of structural data obtained by the above versions of the DFT method, the existence of a similar complex of manganese with di[benzo] derivative of porhyrazine and two oxygen (O2-) ligands seems doubtful.

Complex structures, formation thermodynamics and substitution reaction kinetics in the copper(II) – glycylglycyl-l-tyrosine – l/d-histidine systems

Complex formation thermodynamics in the copper(II) – glycylglycyl-l-tyrosine (GGY∙H) and copper(II) – glycylglycyl-l-tyrosine – l/d-histidine (HisH) systems (25.0 °C, 1.0 M KNO3) was investigated by pH-potentiometric titration and spectrophotometry methods in a wide pH range (2–11). As a result five homoligand and six heteroligand complexes were discovered for the first time. Parameters of individual absorption spectra and ESR spectra of the heteroligand copper(II) complexes were first evaluated. Structures of complexes were optimized by DFT computations on the B3LYP/TZVPP level with accounting solvent effect by the C-PCM model and with dispersion correction (D3BJ). Based on the experimental data and the results of quantum chemical computations, it was suggested that there is a d-π interaction between the aromatic system of tyrosine and copper(II) in homoligand complexes with a metal/ligand ratio of 1:1. The stereoselective effect in the formation of Cu(GGY)(His) form having higher stability of complex with l-histidine relative to d-histidine was revealed and explained in terms of trans-influence and π-π-stacking interactions, that was confirmed by quantum-chemical calculations. Using stopped-flow technique with spectrophotometric detection, the kinetics of glycylglycyl-l-tyrosine substitution by l/d-histidine was investigated and three-step scheme of the ligand replacement was proposed. The stereoselective effect in substitution of the glycylglycyl-l-tyrosine by histidine with faster process for d-His− than to l-His− form was detected and explained on the basis of the formation of heteroligand intermediates.

The cluster structure of crystalline phases according to TGA/DTA and XPS data in isodimorphic substitution series [Cu x Ni(1−x){N(CH2PO3)3}]Na4·nH2O (x = 0 … 1)

Abstract The cluster structure, thermochemical behavior, and some mechanisms of thermal decomposition of the crystalline products in the isodimorphic substitution series Cu x Ni(1−x)NTP (x = 0 … 1) have been studied by simultaneous the thermal gravimetric analysis and differential thermal analysis (TGA/DTA) and X-ray photoelectron spectroscopy (XPS). The complexes NiNTP and Cu1/8Ni7/8NTP with a monoclinic crystal structure are the most thermo-stable and characterized by one-step decomposition at 400–440 °C with the formation of metal phosphides and phosphates. The complexes Cu3/8Ni5/8NTP–Cu3/4Ni1/4NTP with the triclinic crystal lattice and the trigonal-bipyramidal coordination of metal atoms decompose in two steps. Firstly, the formation of a heteroligand complex with imino-bis-methylenephosphonic and methylphosphonic acids takes place at 245 °C. Secondly, the complex decomposes at 270–380 °C. The monometallic complex CuNTP decomposes almost completely at 280–300 °C.

Ternary nickel(II) complexes with histidine and glycylglycylglycine in solution

Potentiometric, calorimetric and photometric studies of mixed-ligand complexes of nickel(II) ion with histidine (His) or glycine (Gly) and glycylglycylglycine (GGG) have been carried out in aqueous solution at 298.15 K and ionic strength I = 0.5 (KNO3). The existence in solution of a number of heteroligand complexes of the compositions NiHisGGGHn (n = -2, -1, 0, 1), NiHis2HnGGG (n = 0, 1), as well as NiGlyGGGHn (n = -2, -1, 0) and NiGly2GGG (charges are omitted). Direct calorimetric measurements made it possible to obtain reliable values of heat effects of mentioned above processes. Possible coordination modes of tripeptide and amino acid residues in mixed-ligand complexes are discussed on the basis of comparative analysis of thermodynamic data on complex formation.

Synthesis, Structural, Molecular Docking, DFT, Vibrational Spectroscopy, HOMO-LUMO, MEP Exploration, antibacterial and antifungal activity of new Fe(III), Co(II) and Ni(II) hetero-ligand complexes

Three new FeLphen, CoLphen and NiLphen hetero-ligand were synthesized, characterized and theoretically investigated. The new complexes were based on phenylalanine (Hphen) and 1-{(E)-[(4-methylphenyl)imino]methyl}-2-naphthol Schiff-base (HL). The results showed interesting structural variety as octahedral for FeLphen ([Fe(L)(phen)(Cl)(H2O)]), CoLphen ([Co(L)(phen)(H2O)2]) and tetrahedral for NiLphen ([Ni(L)(phen)]). The molecular properties, geometric optimization, vibrational, frontier molecular orbital, and energy evaluation of the new complexes were characterized theoretically using density functional theory (DFT) approach. The calculations were performed to find out the most reliable cis/trans (Chloride and/or H2O) and the (HL/Hphen) orientations around the Fe(III)/Co(II) and Ni(II) center. The calculations revealed that trans-H2O/Cl-cis-NHL/NHphen & cis-H2O/H2O-cis-NHL/NHphen and cis-NHL/NHphen were the most stable orientations for the FeLphen, CoLphen and NiLphen, respectively. Furthermore, the antibacterial and antifungal activity of the titled compounds was in vitro screened. The results showed that the metal complexes exhibited higher pathogenic effect than the free ligands against the selected microbes. Molecular docking investigation against 2VF5, 4FXQ, and 3cku, was carried out to provide deep insights into their role in inhibiting the growth of pathogenic microbes. Comparative analysis elucidated higher antibacterial and antifungal activity of the titled compounds compared with literature survey.

Heteroligand complexes of chromium, manganese, and iron with trans-dibenzoporphyrazine and two oxo ligands: DFT calculations

Heteroligand complexes of chromium, manganese, and iron with trans-dibenzoporphyrazine and two oxo ligands: DFT calculations

New heteroligand complex of cobalt with phthalocyanine, oxo and fluoro ligands: DFT consideration

Based on the results of a quantum chemical calculation using the DFT method in the OPBE/TZVP and B3PW91/TZVP levels, the possibility of the existence of a cobalt heteroligand complex containing in the inner coordination sphere tetra[benzo]derivative of porphyrazine (phthalocyanine), oxide (O[Formula: see text] and fluoride (F[Formula: see text] ions, with possible oxidation state of Co(V) that is non-characteristic for the given 3[Formula: see text]-element, has been shown. The data on the structural parameters, multiplicity of the ground state, NBO analysis data and standard thermodynamic parameters of formation (standard enthalpy [Formula: see text], entropy [Formula: see text] and Gibbs’s energy [Formula: see text] for the indicated complex have been presented. At the same time, it has been noted that the porphyrazine itself as well as di[benzo]porphyrazine, do not form such metalcomplexes.

Nickel macrocyclic complexes with porphyrazine and some [benzo]substituted, oxo and fluoro ligands: DFT analysis

By using quantum chemical calculation data obtained by the DFT method with the OPBE/TZVP and B3PW91/TZVP levels, the principal possibility of the existence of three heteroligand complexes of nickel, each of which was shown to contain in the inner coordination sphere either porphyrazine or di[benzo]- and tetra[benzo]porphyrazine, oxygen (O[Formula: see text] and fluorine (F[Formula: see text] ions. The data on the geometric parameters of the molecular structure of these complexes are presented; which shows that NiN4 chelate nodes, all metal-chelate and non-chelate cycles in each of these complexes, are strictly planar. The bond angles between two donor nitrogen atoms and a nickel atom are equal to 90[Formula: see text], while the bond angles between donor atoms N, Ni, and O or F, in most cases, albeit insignificantly, differ from this value. Nevertheless, the bond angles formed by Ni, O and F atoms are exactly 180[Formula: see text]. NBO analysis data for these complexes are presented; it was noted that the ground state of all these complexes was a spin doublet. It has been shown that a good agreement between the data obtained using the above two versions of the DFT method occurs. Also, standard thermodynamic parameters of formation (standard enthalpy [Formula: see text], entropy [Formula: see text] and Gibbs’s energy [Formula: see text] for the macrocyclic compounds under consideration were calculated.

Synthesis and luminescent properties of heteroleptic lanthanide complexes with oxybenzo[

The heteroligand complexes CpLn(BQ)2(DME) (BQ = 10-oxybenzo[h]quinoline, Cp = cyclopentadienyl, Ln = La (1), Nd (2), Sm (3), Gd (4)) were synthesised by the reaction of Cp3Ln with (BQ)H. The complexes of La, Nd and Sm were structurally characterised. In the case of ytterbium the reaction affords Cp2Yb(BQ)(DME) (5) and homoligand binuclear complex Yb2(BQ)6 (6) iregardless of the molar ratio of initial reagents. Upon UV excitation all the complexes gave rise to fluorescence of ligands in the visible region. The photoluminescent spectrum of compound 1 also contains a phosphorescent band with a lifetime longer than 10 ms. The complexes of Nd, Sm and Yb along with ligand emission display metal-centered luminescent f–f transitions.

Chemical Characterization and Biological Evaluation of New Cobalt(II) Complexes with Bioactive Ligands, 2-Picolinehydroxamic Acid and Reduced Schiff Base N-(2-Hydroxybenzyl)alanine, in Terms of DNA Binding and Antimicrobial Activity.

Five new heteroligand cobalt(II) complexes with 2-picolinehydroxamic acid and reduced Schiff base, N-(2-hydroxybenzyl)alanine, were formed in an aqueous solution over a wide pH range. The coordination properties of ligands towards the metal ion were determined using a pH-metric method, and then the speciation model was confirmed by UV–Vis studies. A stacking interaction between the Schiff base phenol ring and the 2-picolinehydroxamic acid pyridine ring was found to improve the stability of the heteroligand species, indicating more effective coordination in mixed-ligand complexes than in their respective binary systems. The antimicrobial properties of heteroligand complexes were determined against Gram-negative and Gram-positive bacteria, as well as fungal strains. The formulation demonstrated the highest bacteriostatic and bactericidal activity (3.65 mM) against two strains of Gram-negative Helicobacter pylori bacteria and towards Candida albicans and Candida glabrata; this is important due to the potential co-existence of these microorganisms in the gastric milieu and their role in the development of gastritis. The binary complexes in the cobalt(II)—2-picolinehydroxamic acid system and 2-picolinehydroxamic acid were not cytotoxic against L929 mouse fibroblasts, neither freshly prepared solutions or after two weeks’ storage. By comparison, the heteroligand complexes within the range 0.91–3.65 mM diminished the metabolic activity of L929 cells, which was correlated with increased damage to cell nuclei. The concentration of the heteroligand species increased over time; therefore, the complexes stored for two weeks exhibited stronger anticellular toxicity than the freshly prepared samples. The complexes formed in an aqueous solution under physiological pH effectively bound to calf thymus DNA in an intercalative manner. This DNA-binding ability may underpin the antimicrobial/antifungal activity of the heteroligand complexes and their ability to downregulate the growth of eukaryotic cells.

Microextrusion printing of gas-sensitive planar anisotropic NiO nanostructures and their surface modification in an H2S atmosphere

The formation of NiO nanosheets (average CSR size is 10.4 nm) through the hydrothermal method using a heteroligand complex of composition [Ni(C5H7O2)2-x(C4H9O)x] as a precursor was studied. Using the obtained oxide nanopowder and pneumatic microextrusion printing, NiO coating was applied to the surface of a specialized Pt/Al2O3/Pt chip, and chemosensor properties were investigated in the detection of various gases. It was determined that when CO, NH3, H2, and NO2 were detected, the conductivity of the NiO coating changed from p- to n-type with increasing temperature. Using XPS, XRD, and Raman spectroscopy, it was found that upon exposure to H2S, the surface of NiO coating partially undergoes irreversible chemical modification with the formation of nickel sulfide, resulting in a significant change in the sensory properties of the coating. It was shown that the formed receptor material exhibits the greatest response when detecting H2S, and the proposed approach, combining hydrothermal synthesis and printing technology, is promising for the creation of modern components of resistive gas sensors.

Copper macrocyclic complex with trans-di[benzo]-porphyrazine and two oxo ligands: DFT quantum-chemical design

Based on the results of a quantum chemical calculation using the DFT method in the OPBE/TZVP and B3PW91/TZVP, the possibility of the existence of a copper heteroligand complex with trans-di[benzo]derivative of 3,7,11,15-tetraazaporphine (trans-di[benzo]porphyrazine) and two oxygen (O[Formula: see text] ions that is still unknown for this element was shown. In addition, the data on the structural parameters, the multiplicity of the ground state, NBO analysis and standard thermodynamic parameters of formation (standard enthalpy [Formula: see text], entropy [Formula: see text] and Gibbs’s energy [Formula: see text] for this complex are presented.