DFT/TD-DFT Framework of Mixed-Metal Complexes with Symmetrical and Unsymmetrical Bridging Ligands—Step-By-Step Investigations: Mononuclear, Dinuclear Homometallic, and Heterometallic for Optoelectronic Applications

Recently, mono- and dinuclear complexes have been in the interest of scientists due to their potential application in optoelectronics. Herein, progressive theoretical investigations starting from mononuclear followed by homo- and heterometallic dinuclear osmium and/or ruthenium complexes with NCN-cyclometalating bridging ligands substituted by one or two kinds of heteroaryl groups (pyrazol-1-yl and 4-(2,2-dimethylpropyloxy)pyrid-2-yl) providing the short/long axial symmetry or asymmetry are presented. Step-by-step information about the particular part that built the mixed-metal complexes is crucial to understanding their behavior and checking the necessity of their eventual studies. Evaluation by using density functional theory (DFT) calculations allowed gaining information about the frontier orbitals, energy gaps, and physical parameters of complexes and their oxidized forms. Through time-dependent density functional theory (TD-DFT), calculations showed the optical properties, with a particular emphasis on the nature of low-energy bands. The presented results are a clear indication for other scientists in the field of chemistry and materials science.

Mono- and Mixed Metal Complexes of Eu3+, Gd3+, and Tb3+ with a Diketone, Bearing Pyrazole Moiety and CHF2-Group: Structure, Color Tuning, and Kinetics of Energy Transfer between Lanthanide Ions

Three novel lanthanide complexes with the ligand 4,4-difluoro-1-(1,5-dimethyl-1H-pyrazol-4-yl)butane-1,3-dione (HL), namely [LnL3(H2O)2], Ln = Eu, Gd and Tb, were synthesized, and, according to single-crystal X-ray diffraction, are isostructural. The photoluminescent properties of these compounds, as well as of three series of mixed metal complexes [EuxTb1-xL3(H2O)2] (EuxTb1-xL3), [EuxGd1-xL3(H2O)2] (EuxGd1-xL3), and [GdxTb1-xL3(H2O)2] (GdxTb1-xL3), were studied. The EuxTb1-xL3 complexes exhibit the simultaneous emission of both Eu3+ and Tb3+ ions, and the luminescence color rapidly changes from green to red upon introducing even a small fraction of Eu3+. A detailed analysis of the luminescence decay made it possible to determine the observed radiative lifetimes of Tb3+ and Eu3+ and estimate the rate of excitation energy transfer between these ions. For this task, a simple approximation function was proposed. The values of the energy transfer rates determined independently from the luminescence decays of terbium(III) and europium(III) ions show a good correlation.

In vitro kinetic release study of ketoprofen enantiomers from alginate metal complexes

Background To explore the release behavior of ketoprofen enantiomers from alginate-metal-complexes. Five mathematical models of drug release kinetics were investigated. Results Beads of alginate-metal complexes, loaded with racemic ketoprofen, were prepared by the ionotropic method. Divalent (Ca, Ba, Zn) and trivalent (Fe, Al) metals were used in the preparation of single-metal and mixed-metal alginate complexes. In vitro release experiments were carried out in an aqueous phosphate buffer medium at pH = 7.4. The concentrations of ketoprofen released enantiomers were determined using chiral HPLC technique. The obtained data were used to simulate the release kinetic of ketoprofen enantiomers using various mathematical models. The Korsmeyer-Peppas model was the best fit for Ca, Al, and Fe beads. Moreover, alginate-iron beads tend to release the drug faster than all other cases. In contrast, the drug release for alginate-barium complex was the slowest. The presence of barium in alginate mixed-metal complexes reduced ketoprofen release in the case of Fe and Zn, while it increased the release in the case of Al complex. Conclusion In all the studied cases, ketoprofen showed very slow release for both enantiomers over a period exceeded 5 h (10 days in some cases). The release rate modification is possible using different multivalent metals, and it is also feasible by using two different metals for congealing either consecutively or simultaneously.

Syntheses, structural characterization, and thermal behaviour of metal complexes with 3-aminopyridine as co-ligands

Six mixed metal complexes with 3-aminopyridine (3-ampy) as a co-ligand have been synthesized: catena-{[M(μ2-3-ampy)(H2O)4]SO4·H2O} (M=Ni (1) and Co (2)), [Co(3-ampy)4(NCS)2] (3), [Co(3-ampy)2(NCS)2] (4), [Co(3-ampy)4(N3)2] (5) and mer-[Co(3-ampy)3(N3)3] (6), (NCS−=isothiocyanate ion, N3− azide ion), and characterized by physio-chemical and spectroscopic methods as well as single crystal X-ray and powder diffraction. In the isostructural complexes 1 and 2 single μ2-3-ampy links the Ni(II) and Co(II) centers into polymeric chains. The mononuclear Co(II) and Co(III) pseudohalide complexes 3–6 reveal only terminal 3-ampy ligands. The 3-ampy ligands form supramolecular hydrogen bonded systems via their NH2-groups and non-covalent π-π ring-ring interactions via their pyridine moieties. Thermoanalytical properties were investigated for 1–3. Graphic abstract

Synthesis and characterization of novel four heterodimetallic mixed metal complexes of 2,6-pyridinedicarboxylic acid

Four novel hetero dimetallic mixed metal complexes of 2,6-pyridinedicarboxylic acid (H2dipic), [Ni(H2O)5Co(dipic)2] (1), [Co(H2O)5Co(dipic)2][Ni(H2O)5Ni(dipic)2][Co(dipic)(H2O)3] (2), [Cu(H2O)5Ni(dipic)2]2[Co(dipic)(H2O)] (3) and [Ni(H2O)5Cu(dipic)2]2[Co(dipic)(H2O)] (4) have been prepared and characterized by elemental, AAS, spectral (IR and UV-Vis), and thermal analyses, as well as by using magnetic measurement and molar conductivity techniques. The results indicate that metal ions coordinate with 2,6-pyridinedicarboxylate ions (dipic2-) nitrogen atoms and carboxylate oxygen atoms of ligands. The mole ratio of dipic2- and metal ions in the complexes have been determined to be 2:2 (Co, Ni) for 1, 5:5 (3Co, 2Ni) for 2, 5:5 (Co, 2Ni and 2Cu) for 3 and 5:5 (Co, 2Ni and 2Cu) for 4 according to the results of elemental analysis. The structures of 1-4 might be proposed as octahedral ([Cu(dipic)(H2O)] unit for 2 square plane) according to results of spectroscopic analysis. The TG and DTA properties of compounds have been studied. KEY WORDS: 2,6-Pyridinedicarboxylic acid, Mixed metal, Metal complex Bull. Chem. Soc. Ethiop. 2020, 34(2), 313-321 DOI: https://dx.doi.org/10.4314/bcse.v34i2.9

Synthesis, Structures and Magnetism of Mn(II)-Gd(III) Mixed-metal Complexes of 2,6-Dipicolinoylbis (N,N-diethylthiourea)

A novel Mn(II)-Gd(III) mixed-metal complex has been synthesized by one-pot reaction in methanolic solution of GdCl3, Mn(CH3OO)2∙4H2O and the organic ligand 2,6-dipicolinoylbis(N,N-diethylthiourea) (H2L) with 1:2:3 molar ratio. The structure of the complex was elucidated by IR spectroscopy, and single crystal X-ray diffraction, while the magnetic properties were studied by SQUID measurements in the temperature range of 10 ÷ 330 K. The complex is comprised of one Gd3+ ion, two Mn2+ cations, and three dianionic ligands {L}2- with the chemical composition of [GdMn2(L)3](PF6). The magnetic interaction between Mn(II) and Gd(III) is weakly ferromagnetic with J = + 0,027 cm-1.

SYNTHESIS AND RESEARCH OF NEW HETEROMETAL COMPLEXES Cо(II), Ni(II), Cu(II) AND Mn(II) BASED ON V(V) AND 5-(4-PYRIDYL)-1,3,4-OXADIAZOLE-2(3H)-THIONE LUBRICANTS

The oxadiazole derivatives complex compounds with metals are biologically active substances. The aim of the study was to study the interaction of the chlorides of Co (II), Ni (II), Cu (II) and Mn (II) with 5-(4-pyridyl)-1,3,4-oxadiazole-2(3H)–thione, ammonium vanadate. Competitive coordination of donor centers, electronic and geometric structures of the ligand molecule were studied on the basis of the quantum-chemical software package Gaussian09 LanL2DZ. It was shown that 5-(4-pyridyl)-1,3,4-oxadiazole-2(3H)-thione ligand is partially coordinated through a localized nitrogen or sulfur atoms at formation of the complex. А procedure was developed for the synthesis of new mixed-metal complexes. The composition and structure of the synthesized compounds were studied using elemental analysis, termogravimetric and X-ray phase analysis and IR spectroscopy.

Computational Druglikeness Assessment, Synthesis, Characterization and in vitro Biological Activity Evaluation of some Novel Mixed Metal Complexes of 2-(butan-2-ylidene) hydrazinecarbothioamide

Aims and Objectives: The heteronuclear (mixed metal) complexes of Schiff bases have been explored as part of the coordination and bioinorganic chemistry. Five novel mixed metal complexes of (E)-2-(butan-2-ylidene) hydrazinecarbothioamide (2-butanone thiosemicarbazone) were prepared and characterized by different spectroscopic techniques. Molecular docking studies were performed with three proteins for two complexes. The toxicity potential, physicochemical properties and bioactivity scores were also predicted. The complexes were tested against three cell lines and also evaluated for their antibacterial activity. Materials and Methods: The mixed metal complexes were prepared in 1:4 molar ratio of metal salt and ligand. OSIRIS 4.6.1 was used to assess the toxicity whereas Molinspiration 2016.03 was used to calculate the bioactivity scores and other physicochemical properties. Principal Component Analysis (PCA) was performed using the Osiris Property Explorer 4.5.1 for defining and visualizing multidimensional property spaces by assigning dimensions to numerical descriptors. Molecular docking studies were performed with three proteins. The anticancer activity was tested against MCF-7, MDA-MB-231, HepG2 and A549 cell lines using MTT assay whereas antibacterial activity was tested using disc diffusion method. Results and Conclusion: The melting points of the complexes were as high as >3500C, indicating high thermal stability. [CuZn(C5H11N3S)4(SO4)2] exhibited minimum energies against the selected proteins. The bioactivity scores of the complexes were between -0.50 and 0.0. All the prepared complexes showed negative Ames score predicted their non-carcinogenic nature. Against A549 [CuZn(C5H11N3S)4(SO4)2], [CoZn(C5H11N3S)4(SO4)Cl2] and [FeZn(C5H11N3S)4(SO4)2] showed potential in vitro activity. IC50 of these three complexes were 19.69, 37.73 and 38.4 respectively. Against MCF-7, [FeCu(C5H11N3S)4(SO4)2] had IC50 value 53.5. Whereas, against HepG2 [CoZn(C5H11N3S)4(SO4)Cl2] was active having IC50 value 61.8. [CoZn(C5H11N3S)4(SO4)Cl2], [FeCu(C5H11N3S)4(SO4)2] and [FeCo(C5H11N3S)4(SO4)Cl2] were active against S. aureus in the concentration range 2-20 mg/mL. The complexes showed improved biological activity as compared to the monometallic complexes of the same ligand.

Novel Mixed Complexes Derived from Benzoimidazolphenylethanamine and 4-(Benzoimidazol-2-yl)aniline: Synthesis, Characterization, Antibacterial Evaluation and Theoretical Prediction of Toxicity

Benzoimidazolphenylethanamine (BPE) has been synthesized using condensation reaction from o-phenyldiamine and L-phenylalanine. Some metal complexes have been synthesized from 4-(benzoimidazol-2-yl)aniline, benzoimidazolylphenylethanamine and cadmium(II), tin(II), copper(II) and nickel(II) metal in a molar ratio (1:1:1). All new metal complexes were characterized by spectroscopic data of FTIR, UV-visible electronic absorption, X-ray powder diffraction and thermal analysis. Spectra analysis of the mixed metal complexes showed the coordination of ligands to the metal ions via nitrogen atoms. The XRD powder showed that metal complexes have a monoclinic system. The preliminary tested in vitro antibacterial activities of Sn(II) complex was assayed against four bacterial isolates namely Micrococcus luteus, Staphylococcus aureus as Gram-positive, Pseudomonas aerugmosa and Escherichia coli.