Search Results (21)

A series of cobalt(II) dicyanamide (dca⁻) coordination polymers with substituted pyrazines (pyz) and pyrimidines (pym) as auxiliary ligands have been synthesized and structurally characterized to investigate the influence of the type and substitution pattern of the auxiliary ligand on the dimensionality and topology of the resulting frameworks. As a result of our studies, 13 novel heteroleptic cobalt(II) dicyanamide coordination polymers were obtained, and their crystal structures were determined by single-crystal X-ray diffraction. Eight of the investigated compounds exhibit a single-chain structure composed of [Co(L_pyz/_pym)₂]²⁺ units bridged via double μ_1,5–dca ligands. In two complexes, neutral triple-chain topologies were observed, in which double μ_1,5– and single μ_1,3,5–dca bridges connect two crystallographically independent cobalt(II) ions, both being six-coordinate in tetragonally elongated octahedral environments. Two- and three-dimensional architectures were confirmed only in the case of Co(II) compounds with 2,6–Me₂pyz and 4-NH₂-pym co-ligand, respectively The cobalt(II) complexes described herein have also been compared with dicyanamide-based cobalt(II) systems incorporating pyrazine- and pyrimidine-like ligands. These structural relationships are of high significance for the rational design and synthesis of heteroleptic cobalt(II) dicyanamide systems. Full article

Polyphenolic compounds, such as flavonoids, possess important structural and physico-chemical characteristics that in combination with their biological properties render them an important class of natural compounds with medicinal prospects. Chrysin is a well-known flavone with antioxidant activity and a multitude of other beneficial properties. The potential of flavonoids to coordinate with metal ions leads to derivatives with enhanced biological profile. Within this framework, four novel heteroleptic complexes of cobalt and nickel with chrysin and the aromatic bidentate chelating agents 2,2′-bipyridine and 1,10-phenanthroline were synthesized, as well as physico-chemically and structurally characterized. The in vitro antioxidant efficiency of the synthesized complexes was examined via the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. All complexes showed notable radical scavenging capacity comparable to that of ascorbic acid, providing the incentive for further investigation of their therapeutic potential. Full article

A new complex, tetrakis(1,10-phenanthroline)-bis(succinate)-(µ₂-oxo)-bis(iron(III)) nonahydrate, [Fe₂(Phen)₄(Succinate)₂(μ-O)](H₂O)₉, was synthesized using the slow evaporation method. This study provides a comprehensive characterization of this coordination compound, focusing on its structural, spectroscopic, and thermal properties, which are relevant for applications in catalysis, material science, and chemical engineering processes. Single-crystal X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared (FT-IR), ultraviolet-visible (UV-Vis) spectroscopy, and thermoanalytical analyses were employed to investigate the material properties. Intermolecular interactions were further explored through Hirshfeld surface analysis. XRD results revealed a monoclinic crystal system with the C2/c space group, lattice parameters: a = 12.7772(10) Å, b = 23.0786(15) Å, c = 18.9982(13) Å, β = 93.047(2)°, V = 5594.27(7) ų, and four formulas per unit cell (Z = 4). The crystal packing is stabilized by C–H⋯O, C–O⋯H, C–H⋯π, and π⋯π intermolecular interactions, as confirmed by vibrational spectroscopy. The heteroleptic coordination environment, combining weak- and strong-field ligands, results in a low-spin state with an estimated crystal field stabilization energy of −4.73 eV. Electronic properties indicate direct allowed transitions (γ = 2) with a maximum optical band gap of 2.66 eV, suggesting potential applications in optoelectronics and photochemical processes. Thermal analysis demonstrated good stability within the 25–136 °C range, with three main stages of thermal decomposition, highlighting its potential for use in high-temperature processes. These findings contribute to the understanding of Fe(III)-based complexes and their prospects in advanced material design, catalytic systems, and process optimization. Full article

The N-oxide functional group has been exploited for synthetic strategies and drug design, and it has been utilized in imaging agents. Herein, we present rare examples of neutral heteroleptic cyclometallated Ir(III) compounds that contain an uncoordinated N-oxide functional group. These species, along with others described within, were verified by NMR, EA, HRMS, and single-crystal X-ray analysis. N-oxide-containing Ir(III) species were prepared selectively in high yields > 66% from chloro-bridged Ir(III) dimers with Acipimox, a picolinate-type ligand containing the N-oxide functional group. Non-N-oxide analogs were synthesized in a similar fashion (yields > 77%). Electrochemical comparison (cyclic voltammetry) indicates that the presence of an N-oxide functional group anodically shifts the reduction potential, suggesting that the N-oxide is acting as an electron-withdrawing group in these species. Crystallographic studies were pursued to examine the coordination behavior of these N-oxides compared to their non-oxidized congeners. The Ir(III) complexes with Acipimox indeed leave the N-oxide uncoordinated and exposed on the complexes. The uncoordinated N-oxide group is influential in directing the packing structures of these complexes directly through C-H···O and O···π interactions at the N-oxide. The crystallographic characterization of cationic Ir(III) compounds with uncoordinated nitrogen atoms is also presented. The C-H···N interactions between these complexes form a variety of dimers, finite chains, and continuous chains. Future work will focus on functionalizing the cationic Ir(III) species into their corresponding N-oxide derivatives and rigorously characterizing how the N-oxide functional group impacts the optical properties of transition metal compounds in both cationic and neutral complexes. Full article

In this review, we present a timeline that shows the origin of mixed chelate copper (II) complexes, registered as Mark Title Casiopeínas^®, as the first copper (II) compounds proposed as anticancer drugs in 1988 and 1992. In the late twentieth century, the use of essential metals as anticancer agents was not even considered, except for their antifungal or antibacterial effects; also, copper, as gold salts, was used for arthritis problems. The use of essential metals as anticancer drugs to diminish the secondary toxic effects of Cisplatin was our driving force: to find less toxic and even more economical compounds under the rational design of metal chelate complexes. Due to their chemical properties, copper compounds were the choice to continue anticancer drug development. In this order of ideas, the rational designs of mixed chelate–copper (II) complexes (Casiopeínas, (Cas) homoleptic or heteroleptic, depending on the nature of the secondary ligand) were synthesized and fully characterized. In the search for new, more effective, and less toxic drugs, Casiopeína^® (Cas) emerged as a family of approximately 100 compounds synthesized from coordinated Cu(II) complexes with proven antineoplastic potential through cytotoxic action. The Cas have the general formula [Cu(N–N)(N–O)]NO₃ and [Cu(N–N)(O–O)]NO₃, where N–N is an aromatic substituted diimine (1,10-phenanthroline or 2,2′-bipyridine), and the oxygen donor (O–O) is acetylacetonate or salicylaldehyde. Lately, some similar compounds have been developed by other research groups considering a similar hypothesis after Casiopeína’s discoveries had been published, as described herein. As an example of translational medicine criteria, we have covered each step of the established normative process for drug development, and consequently, one of the molecules (Casiopeína III ia (CasIIIia)) has reached the clinical phase I. For these copper compounds, other activities, such as antibacterial, antiparasitic and antiviral, have been discovered. Full article

A predictable type of coordination is a key property of tripodal ligands. Homo- and heteroleptic lanthanide complexes with tripodal ligands are a representative class of compounds. However, despite the fact that many of them are paramagnetic, their magnetic behavior is poorly studied. This is because their photophysical and catalytic properties are considered more attractive. In the present review, we try to summarize the available structural information and only a few examples of data on magnetic properties in order to draw some conclusions about the prospect of such ligands in the design of quantum molecular magnets involving lanthanide (Ln) ions. We would also like to catch the reader’s attention to the fact that, despite the consideration of a large part of the currently known Ln compounds with tripodal ligands, this review is not exhaustive. However, our goal is to draw the attention of magnetochemists and theoreticians to a whole niche of air-stable Ln complexes that is still out of their field of vision. Full article

A new Co(II) perchlorate complex of the bis-morpholino/benzoimidazole-s-triazine ligand, 4,4′-(6-(1H-benzo[d]imidazol-1-yl)-1,3,5-triazine-2,4-diyl)dimorpholine (BMBIT), was synthesized and characterized. The structure of the new Co(II) complex was approved to be [Co(BMBIT)₂(H₂O)₄](ClO₄)₂*H₂O using single-crystal X-ray diffraction. The Co(II) complex was found crystallized in the monoclinic crystal system and P2₁/c space group. The unit cell parameters are a = 22.21971(11) Å, b = 8.86743(4) Å, c = 24.38673(12) Å and β = 113.4401(6)°. This heteroleptic complex has distorted octahedral coordination geometry with two monodenatate BMBIT ligand units via the benzoimidazole N-atom and four water molecules as monodentate ligands. The hydration water and perchlorate ions participated significantly in the supramolecular structure of the [Co(BMBIT)₂(H₂O)₄](ClO₄)₂*H₂O complex. Analysis of d_norm map and a fingerprint plot indicated the importance of O···H, N···H, C···H, C···O, C···N and H···H contacts. Their percentages are 27.5, 7.9, 14.0, 0.9, 2.8 and 43.5%, respectively. The sensitivity of some harmful microbes towards the studied compounds was investigated. The Co(II) complex has good antifungal activity compared to the free BMBIT which has no antifungal activity. The Co(II) complex has good activity against B. subtilis, S. aureus, P. vulgaris and E. coli while the free BMBIT ligand has limited activity only towards B. subtilis and P. vulgaris. Hence, the [Co(BMBIT)₂(H₂O)₄](ClO₄)₂*H₂O complex has broad spectrum antimicrobial action compared to the free BMBIT ligand. Full article

Six heteroleptic Cu(II) carboxylates (1–6) were prepared by reacting 2-chlorophenyl acetic acid (L¹), 3-chlorophenyl acetic acid (L²), and substituted pyridine (2-cyanopyridine and 2-chlorocyanopyridine). The solid-state behavior of the complexes was described via vibrational spectroscopy (FT-IR), which revealed that the carboxylate moieties adopted different coordination modes around the Cu(II) center. A paddlewheel dinuclear structure with distorted square pyramidal geometry was elucidated from the crystal data for complexes 2 and 5 with substituted pyridine moieties at the axial positions. The presence of irreversible metal-centered oxidation reduction peaks confirms the electroactive nature of the complexes. A relatively higher binding affinity was observed for the interaction of SS-DNA with complexes 2–6 compared to L¹ and L². The findings of the DNA interaction study indicate an intercalative mode of interaction. The maximum inhibition against acetylcholinesterase enzyme was caused for complex 2 (IC₅₀ = 2 µg/mL) compared to the standard drug Glutamine (IC₅₀ = 2.10 µg/mL) while the maximum inhibition was found for butyrylcholinesterase enzyme by complex 4 (IC₅₀ = 3 µg/mL) compared to the standard drug Glutamine (IC₅₀ = 3.40 µg/mL). The findings of the enzymatic activity suggest that the under study compounds have potential for curing of Alzheimer’s disease. Similarly, complexes 2 and 4 possess the maximum inhibition as revealed from the free radical scavenging activity performed against DPPH and H₂O₂. Full article

The possibility of obtaining volatile polynuclear heterometallic complexes containing lanthanides and transition metals bound by methoxy-β-diketonates was studied. New compounds were prepared by cocrystallization of monometallic complexes from organic solvents. Ln(tmhd)₃ were used as initial monometallic complexes (Ln = La, Pr, Sm, Gd, Tb, Dy, Lu; tmhd = 2,2,6,6-tetramethylheptane-3,5-dionate) in combination with TML₂ in various ratios (TM = Cu, Co, Ni, Mn; L: L¹ = 1,1,1-trifluoro-5,5-dimethoxypentane-2,4-dionate, L² = 1,1,1-trifluoro-5,5-dimethoxy-hexane-2,4-dionate, L³ = 1,1,1-trifluoro-5-methoxy-5-methylhexane-2,4-dionate). Heterometallic complexes of the composition [(LnL₂tmhd)₂TM(tmhd)₂] were isolated for light lanthanides Ln= La, Pr, Sm, Gd, and L= L¹ or L². By single crystal XRD, it has been established that heterometallic compounds containing La, Pr, Cu, Co, and Ni are isostructural linear coordination polymers of alternating mononuclear transition metal complexes and binuclear heteroleptic lanthanide complexes, connected by donor–acceptor interactions between oxygen atoms of the methoxy groups and transition metal atoms. A comparison of powder XRD patterns has shown that all heterometallic complexes obtained are isostructural. Havier lanthanides Ln = Tb, Dy, Lu did not form heterometallics. Instead, homometallic complexes Ln(L³)₃ were identified for Ln = Dy, Lu as well as for Ln = La. The thermal properties of the complexes were investigated by TG-DTA and vacuum sublimation tests. The heterometallic complexes were found to be not volatile and decomposed under heating to produce inorganic composites of TM oxides and Ln fluorides. In contrast, Ln(L³)₃ is volatile and may be sublimed in a vacuum. Results of magnetic measurements are discussed for several heterometallic and homometallic complexes. Full article

This review summarizes the data on the synthesis of coordination compounds containing two or more different metal ions based on fluorinated β-diketonates. Heterometallic systems are of high interest in terms of their potential use in catalysis, medicine and diagnostics, as well as in the development of effective sensor devices and functional materials. Having a rich history in coordination chemistry, fluorinated β-diketones are well-known ligands generating a wide variety of heterometallic complexes. In this context, we focused on both the synthetic approaches to β-dicarbonyl ligands with additional coordination centers and their possible transformations in complexation reactions. The review describes bi- and polynuclear structures in which β-diketones are the key building blocks in the formation of a heterometallic framework, including the examples of both homo- and heteroleptic complexes. Full article

Herein, we report the synthesis of a series of heteroleptic magnesium complexes stabilized with the scorpionate ligand tris(2-pyridylthio)methanide (Tptm). The compounds of the general formula [Mg(Tptm)(X)] (1-X; X = Cl, Br, I) were obtained via protonolysis reaction between the proligand and selected Grignard reagents. Attempts to isolate the potassium derivative K(Tptm) lead to decomposition of Tptm and formation of the alkene (C₅H₄N-S)₂C=C(C₅H₄N-S)₂, and this degradation was also modelled using DFT methods. Compound 1-I was treated with K(CH₂Ph), affording the degradation product [Mg(Bptm)₂] (2; Bptm = {CH(S-C₅NH₃)₂}⁻). We analyzed and quantified the steric properties of the Tptm ligand using the structural information of the compounds obtained in this study paired with buried volume calculations, also adding the structural data of HTptm and its CF₃-substituted congener (HTptm^CF3). These studies highlight the highly flexible nature of this ligand scaffold and its ability to stabilize various coordination motifs and geometries, which is a highly desirable feature in the design of novel organometallic reagents and catalysts. Full article

Metal-organic frameworks (MOFs), whose definition has been regularly debated, are a sub-class of coordination polymers (CPs) which may feature both an overall 3D architecture and some degree of porosity. In this context, MOFs based on lanthanides (Ln-MOFs) could find many applications due to the combination of sorption properties and magnetic/luminescent behaviors. Here we report rare examples of 3D Ln-CPs based on anilate linkers, obtained under solvothermal conditions using a heteroleptic strategy. The three compounds of formula [Yb₂(μ-ClCNAn)₂(μ-F₄BDC)(H₂O)₄]·(H₂O)₃ (1), [Er₂(μ-ClCNAn)₂(μ-F₄BDC)(H₂O)₄]·(H₂O)₄ (2) and [Eu₂(μ-ClCNAn)₂(μ-F₄BDC)(H₂O)₆] (3) have been characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and optical measurements. Structural characterization revealed that compounds 1 and 2 present an interesting MOF architecture with extended rectangular cavities which are only filled with water molecules. On the other hand, compound 3 shows a much more complex topology with no apparent cavities. We discuss here the origins of such differences and highlight the crucial role of the Ln(III) ion nature for the topology of the CP. Compounds 1 and 2 now offer a playground to investigate the possible synergy between gas/solvent sorption and magnetic/luminescent properties of Ln-MOFs. Full article

The two ligands 2-(1-(2-(4,6-dimorpholino-1,3,5-triazin-2-yl)hydrazono)ethyl)aniline (DMAT) and 2-(1-(2-(4,6-dimorpholino-1,3,5-triazin-2-yl)hydrazono)ethyl)phenol (DMOHT) were used to synthesize three heteroleptic Cu(II) complexes via a self-assembly technique. The structure of the newly synthesized complexes was characterized using elemental analysis, FTIR and X-ray photoelectron spectroscopy (XPS) to be [Cu(DMAT)(H₂O)(NO₃)]NO₃.C₂H₅OH (1), [Cu(DMOT)(CH₃COO)] (2) and [Cu(DMOT)(NO₃)] (3). X-ray single-crystal structure of complex 1 revealed a hexa-coordinated Cu(II) ion with one DMAT as a neutral tridentate NNN-chelate, one bidentate nitrate group and one water molecule. In the case of complex 2, the Cu(II) is tetra-coordinated with one DMOT as an anionic tridentate NNO-chelate and one monodentate acetate group. The antimicrobial, antioxidant and anticancer activities of the studied compounds were examined. Complex 1 had the best anticancer activity against the lung carcinoma A-549 cell line (IC₅₀ = 5.94 ± 0.58 µM) when compared to cis-platin (25.01 ±2.29 µM). The selectivity index (SI) of complex 1 was the highest (6.34) when compared with the free ligands (1.3–1.8), and complexes 2 (0.72) and 3 (2.97). The results suggested that, among those compounds studied, complex 1 is the most promising anticancer agent against the lung carcinoma A-549 cell line. In addition, complex 1 had the highest antioxidant activity (IC₅₀ = 13.34 ± 0.58 µg/mL) which was found to be comparable to the standard ascorbic acid (IC₅₀ = 10.62 ± 0.84 µg/mL). Additionally, complex 2 showedbroad-spectrum antimicrobial action against the microbes studied. The results revealed it to possess the strongest action of all the three complexes against B. subtilis. The MIC values found are 39.06, 39.06 and 78.125 μg/mL for complexes 1–3, respectively. Full article

Mononuclear heteroleptic complexes [Fe(tpma)(bimz)](ClO₄)₂ (1a), [Fe(tpma)(bimz)](BF₄)₂ (1b), [Fe(bpte)(bimz)](ClO₄)₂ (2a), and [Fe(bpte)(bimz)](BF₄)₂ (2b) (tpma = tris(2-pyridylmethyl)amine, bpte = S,S′-bis(2-pyridylmethyl)-1,2-thioethane, bimz = 2,2′-biimidazoline) were prepared by reacting the corresponding Fe(II) salts with stoichiometric amounts of the ligands. All complexes exhibit temperature-induced spin crossover (SCO), but the SCO temperature is substantially lower for complexes 1a and 1b as compared to 2a and 2b, indicating the stronger ligand field afforded by the N₂S₂-coordinating bpte ligand relative to the N₄-coordinating tpma. Our findings suggest that ligands with mixed N/S coordination can be employed to discover new SCO complexes and to tune the transition temperature of known SCO compounds by substituting for purely N-coordinating ligands. Full article

A series of new low-melting triply charged homoleptic Cr(III)-based ionic liquids of the general formula (RMIm)₃[Cr(NCS)₆] (R = methyl, ethyl, n-butyl, benzyl) is reported. Their syntheses and properties are described in comparison to their singly charged heteroleptic analogues of the general formula (RMIm)[Cr(NCS)₄L₂] (R = methyl, ethyl, n-butyl, benzyl; L = pyridine, γ-picoline). In total, sixteen new Reineckate related salts with large imidazolium cations are described. Out of these, five compounds were crystallized, and their structures determined by single-crystal X-ray structure analyses. They all consisted of discrete anions and cations with octahedrally coordinated Cr(III) ions. In the structures, various hydrogen contacts interconnect the entities to build up hydrogen bonded networks. Thermal investigations showed relatively low melting points for the homoleptic complexes. The compounds with the [Cr(NCS)₆]³⁻ anion melt without decomposition and are stable up to 200 K above their melting points. The complex salts with the [Cr(NCS)₄L₂]⁻ anion, in contrast, start to decompose and lose L molecules (Pyr or Pic) already at the melting point. Full article