Coordinative Compounds Based on Unsaturated Carboxylate with Versatile Biological Applications

This review presents an overview of the biological applications of coordinative compounds based on unsaturated carboxylates accompanied by other ligands, usually N-based heterocyclic species. The interest in these compounds arises from the valuable antimicrobial and antitumor activities evidenced by some species, as well as from their ability to generate metal-containing polymers suitable for various medical purposes. Therefore, we describe the recently discovered aspects related to the synthesis, structure, and biological activity of a wide range of unsaturated carboxylate-containing species and metal ions, originating mostly from 3d series. The unsaturated carboxylates encountered in coordinative compounds are acrylate, methacrylate, fumarate, maleate, cinnamate, ferulate, coumarate, and itaconate. Regarding the properties of the investigated compounds, it is worth mentioning the good ability of some to inhibit the development of resistant strains or microbial biofilms on inert surfaces or, even more, exert antitumor activity against resistant cells. The ability of some species to intercalate into DNA strands as well as to scavenge ROS species is also addressed.

Synthesis and crystal structure of poly[(μ3-2-(2-carboxylatophenyl)-1H-benzo[d]imidazole-5-carboxylato-κO,O′:O′;:O″, O″′)-(μ2-1-(4-(1Himidazol-1-yl)phenyl)-1H-imidazole-κ2N:N′)cadmium(II)], C27H18CdN6O4

C27H18CdN6O4, triclinic, P 1 ‾ $P‾{1}$ (no. 2), a = 10.2994(8) Å, b = 10.7795(7) Å, c = 11.0038(7) Å, α = 89.778(5)°, β = 78.046(6)°, γ = 83.049(6)°, Z = 2, V = 1186.11(14) Å3, R gt (F) = 0.0402, wR ref (F 2) = 0.0809, T = 293 K.

Synthesis and crystal structure of catena-poly[aqua-bis(nitrato-κ 2 O:O′)- (μ 2-((1 H-imidazol-1-yl)methyl)benzene-κ 2 N,N′)-H2O-κ 2O]cadmium(II), C14H16N6O7Cd

C14H16N6O7Cd, monoclinic, P21/c (no. 14), a = 12.7095(3) Å, b = 17.4705(4) Å, c = 8.5763(3) Å, β = 93.292(10)°, Z = 4, V = 1901.15(9) Å3, R gt (F) = 0.0263, wR ref (F 2) = 0.1047, T = 296(2) K.

Synthesis, structure, fluorescence, electrochemical, and antioxidant studies of a new silver(I) complex with 2,6-bis(N-methylbenzimidazol-2-yl)pyridine

A new silver(I) complex of the type [Ag2(mbbp)2](pic)2·DMF·CH3OH [mbbp = 2,6-bis( N-methylbenzimidazol-2-yl)pyridine] is synthesized and analyzed using a range of spectroscopic and crystallographic techniques. This compound contains cationic Ag2(mbbp)2 dimers, in which the crossed eight-shaped structure is formed by two mbbp ligands bridging two silver(I) centers and Ag–Ag bonds. Two-dimensional supramolecular networks of the silver(I) complex are connected by π···π interactions and hydrogen bonds. Hirshfeld analyses are performed to support the aforementioned intermolecular interactions. The effect of π···π stacking interactions on the fluorescence properties of the complex is investigated. Cyclic voltammetry indicates two irreversible redox processes. In addition, an antioxidant assay in vitro demonstrates that the silver(I) complex displays excellent scavenging activity toward hydroxyl radicals.

Aryl variation and anion effect on CT-DNA binding and in vitro biological studies of pyridinyl Ag(I) complexes

Synthesis and spectroscopic characterization of five ligands ((E)-2-((pyridin-2-ylmethylene)amino)phenol L1, 2-(pyridin-2-yl)benzo[d]thiazole L2, (E)-N-(2-fluorophenyl)-1-(pyridin-2-yl)methanimine L3, (E)-1-(pyridin-2-yl)-N-(p-tolyl)methanimine L4 and (E)-1-(pyridin-2-yl)-N-(thiophen-2-ylmethyl)methanimine L5 along with fifteen silver(I) complexes of L1 - L5, with a general formula [AgL₂]⁺X^- (L = Schiff base and X = NO₃^-, ClO₄^- or CF₃SO₃^-) is reported. The structures of complexes [Ag(L4)₂]NO₃, [Ag(L5)₂]NO₃, [Ag(L3)₂]ClO₄, [Ag(L4)₂]ClO₄ and [Ag(L5)₂]CF₃SO₃ were determined unequivocally by single crystal X-ray diffraction analysis. Calf-thymus deoxyribonucleic acid (CT-DNA), bovine serum albumin (BSA) binding studies, antioxidant, and antibacterial studies were performed for all complexes. Complexes [Ag(L2)₂]NO₃, [Ag(L5)₂]NO₃, [Ag(L1)₂]ClO₄ and [Ag(L3)₂]ClO₄ whose ligands have an OH^- and F^- as substituents or with a thiophene or thiazole moiety showed better antibacterial activities with lower minimum inhibitory concentration (MIC) values compared to the standard ciprofloxacin, against most of the bacterial strains tested. Similarly, complexes [Ag(L1)₂]NO_3,[Ag(L2)₂]NO_3,[Ag(L3)₂]NO₃ and [Ag(L5)₂]NO₃ with the NO₃^- anion, [Ag(L1)₂]ClO₄ and [Ag(L2)₂]ClO₄ with ClO₄^- anion, and [Ag(L5)₂]CF₃SO₃ with CF₃SO₃^- anion showed higher activities for antioxidant studies. Complexes [Ag(L4)₂]ClO₄ and [Ag(L4)₂]CF₃SO₃ with the Methyl substituent and CF₃SO₃^- as the anion, displayed high antioxidant activities in FRAP (ferric reducing antioxidant power) than the standard ascorbic acid. Spectroscopic studies of all the complexes revealed their moderate to high interaction with calf thymus DNA via an intercalation mode. In addition, the relatively moderate interaction of most of the complexes with BSA was through a static quenching mechanism.

Tuned structure and DNA binding properties of metal complexes based on a new 4-acylpyrazolone derivative

The structure and DNA binding performance of three transition metal compounds based on a new pyrazolone ligand were tuned effectively by changing both metal cations and anions.

Synthesis and crystal structure of poly[(μ2-nitrato-κ4O,O′:O′,O′′)-nitrato-κO-(μ2-1,4-bis((1H-imidazol-1-yl)methyl)benzene-κ2N:N′)cadmium(II)], C14H14N6O6Cd

C14H14CdN6O6, monoclinic, P21/c (no. 14), a = 11.2983(5) Å, b = 9.2539(4) Å, c = 17.0604(7) Å, β = 105.398(1)°, Z = 4, V = 1719.69(13) Å3, Rgt(F) = 0.0321, wRref(F2) = 0.1060, T = 193(2) K.

Unprecedented Dinuclear CuII N,O-Donor Complex: Synthesis, Structural Characterization, Fluorescence Property, and Hirshfeld Analysis

An unprecedented dinuclear CuII complex, [Cu2(L2)2], derived from a salamo-like chelating ligand H2L2, was produced by the cleavage of a newly synthesized, half-salamo-like ligand HL1 (2-[O-(1-ethyloxyamide)]oxime-3,5-dichloro-phenol). This was synthesized and characterized by elemental analyses, IR, UV–Vis and fluorescent spectra, single crystal X-ray diffraction analysis, and Hirshfeld surface analysis. X-ray crystallographic analysis indicated that the two CuII (Cu1 and Cu2) ions bore different (N2O3 and N2O2) coordination environments, the penta-coordinated Cu1 ion possessed a slightly twisted tetragonal pyramid geometry with the τ value τ = 0.004, and the tetra-coordinated Cu2 ion showed a slightly twisted square planar geometry. Interestingly, one oxime oxygen atom participated in the coordination reported previously. Moreover, an infinite two-dimensional layered supramolecular network was formed. Compared with HL1, the CuII complex possessed the characteristic of fluorescence quenching.

Fluorescence Properties and Density Functional Theory Calculation of a Structurally Characterized Heterotetranuclear [ZnII2–SmIII2] 4,4′-Bipy-Salamo-Constructed Complex

A new heterotetranuclear complex, [{Zn(L)Sm(NO3)3}2(4,4′-bipy)]·2CH3OH, was synthesized via an unsymmetrical single salamo-like ligand H2L: 6-methoxy-6′-ethoxy-2,2′-[ethylenedioxybis(azinomethyl)]diphenol, with Zn(OAc)2·2H2O, Sm(NO3)3·6H2O, and 4,4′-bipyridine by the one-pot method. The [ZnII2–SmIII2] complex was validated via elemental analysis, powder X-ray diffraction (PXRD) analysis, infrared spectroscopy, and ultraviolet–visible (UV–Vis) absorption spectroscopy. The X-ray single crystal diffraction analysis of the [ZnII2–SmIII2] complex was carried out via X-ray single-crystal crystallography. The crystal structure and supramolecular features were discussed. In addition, while studying the fluorescence properties of the [ZnII2–SmIII2] complex, the density functional theory (DFT) calculation of its structure was also performed.

An Unexpected Trinuclear Cobalt(II) Complex Based on a Half-Salamo-Like Ligand: Synthesis, Crystal Structure, Hirshfeld Surface Analysis, Antimicrobial and Fluorescent Properties

An unexpected trinuclear Co(II) complex, [Co3(L2)2(μ-OAc)2(CH3OH)2]·2CH3OH (H2L2 = 4,4′-dibromo-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol) constructed from a half-Salamo-based ligand (HL1 = 2-[O-(1-ethyloxyamide)]oxime-4-bromophenol) and Co(OAc)2·4H2O, has been synthesized and characterized by elemental analyses, infrared spectra (IR), UV-Vis spectra, X-ray crystallography and Hirshfeld surface analysis. The Co(II) complex contains three Co(II) atoms, two completely deprotonated (L2)2− units, two bridged acetate molecules, two coordinated methanol molecules and two crystalline methanol molecules, and finally, a three-dimensional supramolecular structure with infinite extension was formed. Interestingly, during the formation of the Co(II) complex, the ligand changed from half-Salamo-like to a symmetrical single Salamo-like ligand due to the bonding interactions of the molecules. In addition, the antimicrobial activities of HL1 and its Co(II) complex were also investigated.

Synthesis, crystal structure, fluorescence and antioxidant properties of a binuclear Ag(I) complex based on the SPPh3 ligand

The binuclear silver(I) complex [Ag2(η2-SPPh3)2(SPPh3)2](BF4)2 has been synthesized. Crystal analysis shows the coordination sphere around Ag(I) can be described as a three-coordinated slightly distorted planar triangular configuration with both monodentate and monoatomic bidentate bridging coordination modes for the SPPh3 ligand. The fluorescence properties of free SPPh3 and the Ag(I) complex have been studied in the solid state. The Ag(I) complex shows quasi-reversible Ag+/Ag pairs in its electrochemistry and has significant antioxidant activity against hydroxyl radicals.

Crystal structure of bis[2-(((3-aminopropyl)imino)methyl)-4-nitro-phenolato-κ3N,N′,O]nickel(II), C20H24N6NiO6

C20H24N6NiO6, triclinic, P1̄ (no. 2), a = 5.3944(6) Å, b = 10.1144(12) Å, c = 10.9297(12) Å, α = 65.236(3)°, β = 81.959(3)°, γ = 79.882(3)°, Z = 1, V = 531.61(11) Å3, Rgt(F) = 0.0262, wRref(F2) = 0.0649, T = 173(2) K.

A New Half-Salamo-Based Homo-Trinuclear Nickel(II) Complex: Crystal Structure, Hirshfeld Surface Analysis, and Fluorescence Properties

A new homo-trinuclear Ni(II) half-salamo-based complex [Ni3(L)2(μ-OAc)2(OAc)2(CH3OH)2]·2CH3OH was synthesized via the reaction of a tridentate ligand HL (2-[O-(1-ethyloxyamide)]oxime-4-bromophenol) and Ni(OAc)2·4H2O, and characterized using elemental analyses, IR spectra, UV-Vis absorption spectra, X-ray crystallography, and Hirshfeld analysis. Interestingly, single-crystal X-ray analysis showed that the two acetate molecules were bonded simultaneously with the Ni(II) atoms by mono-dentate chelating and bidentate bridging coordination modes, respectively, and the resulting hexa-coordinate geometries were ultimately formed. Furthermore, the Hirshfeld analysis of the complex was studied. Compared with HL, the complex fluorescence intensity was significantly lowered, indicating that the Ni(II) ions have fluorescence quenching characteristics.

Crystal structure of 5,5′-dimethoxy-2,2′-[1,1′-(ethylenedioxydinitrilo)diethylidyne]diphenol, C20H24N2O6

C20H24N2O6, triclinic, P1̄, a = 7.1389(5) Å, b = 9.4977(7) Å, c = 14.6456(10) Å, α = 105.118(3)°, β = 101.188(2)°, γ = 94.739(3)°, Z = 2, V = 931.08(11) Å3, R gt(F) = 0.0564, wR ref(F 2) = 0.1646, T = 153(2) K.

Cu(I) complexes regulated by N-heterocyclic ligands: Syntheses, structures, fluorescence and electrochemical properties

Three mononuclear Cu(I) complexes, namely, [Cu(2-PBO)(PPh₃)₂]·ClO₄·2CH₂Cl₂ (1), [Cu(3-PBO)(PPh₃)₂(ClO₄)]·CH₂Cl₂ (2) and [Cu(PBM)(PPh₃)₂]·ClO₄ (3) (2-PBO = 2-(2'-Pyridyl)benzoxazole, 3-PBO = 2-(3'-Pyridyl)benzoxazole, PBM = 2-(2'-Pyridyl)benzimidazole, PPh₃ = triphenylphosphine) have been synthesized and characterized by elemental analyses, IR, ¹H NMR, ¹³C NMR, X-ray single crystal diffraction and thermal analysis. Photoluminescent investigation shows that complexes 1-3 exhibit distinct tunable light green (512 nm)-to-yellow (557 nm) photoluminescence by varying the N-heterocyclic ligands. Three complexes show intense 2-PBO-based yellow, 3-PBO-based light green and intense PBM-based bright green luminescence upon irradiation with a standard UV lamp (λ_ex = 254 nm) at room temperature. Moreover, the electrochemical properties of 1-3 have been investigated by cyclic voltammetry. The results suggest the frontier molecular orbits and the HOMO-LUMO energy gaps of these cuprous complexes are effectively adjusted through the introduction of different N-heterocyclic ligands, thus achieving the selective luminescence of the cuprous complexes.

Crystal structure of (6,6′-(((((2-aminoethyl)azanediyl)bis(ethane-2,1-diyl))bis(azanylylidene))bis(methanylylidene))bis(2,4-dichlorophenolato)-κ6 N,N′,N′′,N′′′,O,O′)cadmium(II) – ethanol – water (1/1/1), C22H28CdCl4N4O4

C22H28CdCl4N4O4, monoclinic, C2/c (no. 15), a = 18.5053(5) Å, b = 13.0864(4) Å, c = 23.0284(9) Å, β = 102.367(3)°, V = 5447.4(3) Å3, Z = 8, R gt(F) = 0.0457, wR ref(F 2) = 0.1306, T = 290.7(2) K.

A new modification of [Ag4Br4(PPh3)4]: synthesis, structure and properties

A new modification of the homometallic silver(I) cluster [Ag4Br4(PPh3)4] has been prepared and characterized by elemental analysis, UV/Vis and IR spectroscopy, and X-ray crystallography. The tetramer shows a polycyclic structure with a chair conformation. The bromine atoms adopt μ 2- and μ 3-bridging modes. The shortest Ag–Ag distance in the cluster is 3.159(2) Å, which indicates significant Ag–Ag interactions. A supramolecular structure is arranged by hydrogen bonds (C–H···Br). Cyclic voltammograms of the cluster indicate a quasi-reversible Ag+/Ag couple. The fluorescence properties of the ligand and the Ag(I) cluster were studied in the solid state. The emission peaks of the Ag(I) cluster are attributed to ligand-centered luminescence.

Synthesis and crystal structure of bis(μ2-acetato-κ2 O:O′)-di(ethanol)-bis{μ2-5-(N,N′-diethylamine)-5′-methoxyl-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenolato-κ6 O:O,N,N,O′:O′}trinickel(II) – ethanol – acetonitrile (1/2/2), C58H86Ni3N8O18

C58H86Ni3N8O18, triclinic, P1̅ (no. 2), a = 11.4561(8) Å, b = 13.1859(8) Å, c = 13.5063(11) Å, α = 109.620(7)°, β = 101.234(7)°, γ = 114.469(6)°, V = 1611.1(2) Å3, Z = 1, R gt(F) = 0.0518, wR ref(F 2) = 0.1315, T = 173.69(10) K.