Di- and tetranuclear heterometallic 3d–4f cobalt(II)–lanthanide(III) complexes derived from a hexadentate bisoxime: Syntheses, structures and magnetic properties

Heterobimetallic 3d-4f complexes supported by a Schiff-base tripodal ligand

Complexes featuring multiple metal centres are of growing interest regarding metal-metal cooperation and its tuneability. Here the synthesis and characterisation of heterobimetallic complexes of a 3d metal (4: Mn, 5: Co) and lanthanum supported by a (1,1,1-tris[(3-methoxysalicylideneamino)methyl]ethane) ligand is reported, as well as discussion of their electronic structure via electron paramagnetic resonance (EPR) spectroscopy, electrochemical experiments and computational studies. Competitive binding experiments of the ligand and various metal salts unequivocally demonstrate that in these heterobimetallic complexes the 3d metal (Mn, Co) selectively occupies the κ6-N3O3 binding site of the ligand, whilst La occupies the κ6-O6 metal binding site in line with their relative oxophilicities. EPR spectroscopy supported by density functional theory analysis indicates that the 3d metal is high spin in both cases (S = 5/2 (Mn), 3/2 (Co)). Cyclic voltammetry studies on the Mn/La and Co/La bimetallic complexes revealed a quasi-reversible Mn2+/3+ redox process and poorly-defined irreversible oxidation events respectively.

Lanthanide and Ladder-Structured Polysilsesquioxane Composites for Transparent Color Conversion Layers

Ladder-type polysilsesquioxanes (LPSQs) containing phenyl as a high refractive index unit and cyclic epoxy as a curable unit were found to be excellent candidates for a transparent color conversion layer for displays due to being miscible with organic solvents and amenable to transparent film formation. Therefore, the LPSQs were combined with luminescent lanthanide metals, europium Eu(III), and terbium Tb(III), to fabricate transparent films with various emission colors, including red, orange, yellow, and green. The high luminescence and transmittance properties of the LPSQs-lanthanide composite films after thermal curing were attributed to chelating properties of hydroxyl and polyether side chains of LPSQs to lanthanide ions, as well as a light sensitizing effect of phenyl side chains of the LPSQs. Furthermore, Fourier-transform infrared (FT-IR) and X-ray photoelectron spectroscopy and nanoindentation tests indicated that the addition of the nanoparticles to the LPSQs moderately enhanced the epoxy conversion rate and substantially improved the wear resistance, including hardness, adhesion, and insusceptibility to atmospheric corrosion in a saline environment. Thus, the achieved LPGSG-lanthanide hybrid organic-inorganic material could effectively serve as a color conversion layer for displays.

Experimental and theoretical insights into Co-Ln magnetic exchange and the rare slow-magnetic relaxation behavior of [CoII2Pr]2+ in a series of linear [CoII2Ln]2+ complexes

We herein report a series of near-linear trinuclear complexes [Co₂Ln(HL)₄(NO₃)](NO₃)₂ (where HL = (2-methoxy-6-[(E)-2'-hydroxymethyl-phenyliminomethyl]-phenolate) with Ln(III) = La (1), Ce (2), Pr (3)). For the comparative study, we have also included the recently reported analogous complexes of Gd(III), Tb(III), and Dy(III) (complexes 4-6) with the same H₂L ligand. The experimental nature of the dc magnetic susceptibilities profile and an empirical approach revealed that the magnetic exchange interaction between Co(II) and Ln(III) having <4f⁷ (complexes 2 and 3) is antiferromagnetic while the dominant interaction between Co(II) and Ln(III) having ≥4f⁷ (complexes 4-6) is ferromagnetic. Dynamic magnetic relaxation studies on complexes 1-3 revealed the field induced single-molecule magnetic (SMM) behavior of 1 and 3 with effective energy barriers of 10.65 K and 15.03 K respectively, for magnetic relaxation. To the best of our knowledge, 3d-Pr(III) based zero or field induced SMMs have not been reported to date. CASSCF/SO-RASSI/SINGLE_ANISO based ab initio calculations on the X-ray structures of complexes 1-6, followed by POLY_ANISO simulations, estimated the magnetic exchange coupling constants J_Co-Ln and J_Co-Co and also rationalized our experimental findings for the dynamic magnetic properties.

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 ‾ $P&#x203e;{1}$ (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 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.

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.

Synthesis and Fluorescence Properties of a Structurally Characterized Hetero-Hexanuclear Zn(II)-La(III) Salamo-Like Coordination Compound Containing Auxiliary Ligands

A hetero-hexanuclear Zn(II)-La(III) coordination compound, [{(ZnL)2La}2(bdc)2](NO3)2 (H2bdc = terephthalic acid) has been synthesized with a symmetric Salamo-like bisoxime, and characterized by elemental analyses, IR, UV-Vis, fluorescent spectroscopy, and single-crystal X-ray diffraction analysis. All of the Zn(II) ions are pentacoordinated by N2O2 donator atoms from the (L)2− unit and one oxygen atom from one terephthalate anion. The Zn(II) ions adopt trigonal bipyramidal geometries (τZn1 = 0.61, τZn2 = 0.56). The La(III) ions are decacoordinated in the Zn(II)-La(III) coordination compound and has a distorted bicapped square antiprism geometry. Meanwhile, the photophysical property of the Zn(II)-La(III) coordination compound was also measured and discussed.

Homo- and heterometallic Cu(II)-M(II) (M = Ca, Sr and Ba) bis(salamo)-based complexes: Syntheses, structures and fluorescent properties

Four homo/heterometallic complexes [Cu₃(L)(μ₂-OAc)₉(CH₃OH) ₉]·3CHCl₃ (1), [Cu₂(L)Ca(μ₂-NO₃)₉] (9), [{Cu₂(L)Sr(μ₂-NO₃)₉}₉]·CH₃CH₂OH (11) and [Cu₂(L)Ba(μ₂-OAc)₉(OAc)] (14), containing an acyclic naphthalenediol-based ligand H₄L, were synthesized and characterized by elemental analyses, IR, UV-Vis, fluorescence spectra, TG-DTA and X-ray crystallography. The complex 1 was obtained by the reaction of H₄L with 11 equivalents of Cu(OAc) ₉·2H₂O. The heterometallic complexes 9, 11, 14 were acquired by the reaction of H₄L with 9 equivalents of Cu(OAc)₉·2H₂O or Cu(NO₃)₉·2H₂O and 1 equivalent of M(OAc)₉ (M = Ca, Sr and Ba). Owing to the different coordination cavities of the N₂O₂ and O₆ of the completely deprotonated (L)^14- unit, the crystal structures showed the N₂O₂ sites were occupied by Cu(II) atoms, alkaline earth metal(II) atoms occupied the O₆ site of the ligand (L)^14- unit, respectively. Furthermore, the fluorescence properties and TG-DTA analyses were discussed.

Exploration and application of a highly sensitive bis(salamo)-based fluorescent sensor for B4O72- in water-containing systems and living cells

A highly selective fluorescent sensor H4L based on a bis(salamo)-type compound with two N2O2 chelating moieties as ionophore was successfully developed. Sensor H4L was found to have excellent selectivity for B4O72- over many other anions (Br-, CI-, CN-, CO32-, HCO3-, H2PO4-, HSO4-, NO3-, OAc-, S2O3-, SCN-, SO42-, Hcy (homocysteine) and H2O2), and it exhibited an approximately 150-fold enhancement of the fluorescence response to B4O72- in Tris-HCl buffer (DMF/H2O = 9:1, v/v, pH = 7) solutions. Significantly, its fluorescence intensity was enhanced in a linear fashion with increasing concentrations of B4O72-. The detection limit of sensor H4L towards B4O72- was 8.61 × 10-7 M. The test strips could conveniently, efficiently and simply detect B4O72- ions in Tris-HCl buffer (DMF/H2O = 9:1, v/v, pH = 7) solutions. Furthermore, sensor H4L showed excellent membrane permeability in living cells, and it was successfully used to monitor intracellular B4O72- by confocal luminescence imaging.

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 6-carboxy-1-(3,5-dicarboxyphenyl)-1H-benzo[d]imidazol-3-ium-5-carboxylate dihydrate, C18H12N2O8

C18H12N2O8, triclinic, P1̄ (no. 2), a = 8.4592(10) Å, b = 9.8442(11) Å, c = 11.2565(12) Å, α = 66.892(3)°, β = 86.069(3)°, γ = 81.658(4)°, V = 852.97(17) Å3, Z = 2, R gt(F) = 0.0609, wR ref(F 2) = 0.1557, T = 153(2) K.

Synthesis and Fluorescence Properties of Structurally Characterized Heterobimetalic Cu(II)⁻Na(I) Bis(salamo)-Based Complex Bearing Square Planar, Square Pyramid and Triangular Prism Geometries of Metal Centers

A novel heterotrinuclear complex [Cu₂(L)Na(µ-NO₃)]∙CH₃OH∙CHCl₃ derived from a symmetric bis(salamo)-type tetraoxime H₄L having a naphthalenediol unit, was prepared and structurally characterized via means of elemental analyses, UV-Vis, FT-IR, fluorescent spectra and single-crystal X-ray diffraction. The heterobimetallic Cu(II)–Na(I) complex was acquired via the reaction of H₄L with 2 equivalents of Cu(NO₃)₂·2H₂O and 1 equivalent of NaOAc. Clearly, the heterotrinuclear Cu(II)–Na(I) complex has a 1:2:1 ligand-to-metal (Cu(II) and Na(I)) ratio. X-ray diffraction results exhibited the different geometric behaviors of the Na(I) and Cu(II) atoms in the heterotrinuclear complex; the both Cu(II) atoms are sited in the N₂O₂ coordination environments of fully deprotonated (L)⁴⁻ unit. One Cu(II) atom (Cu1) is five-coordinated and possesses a geometry of slightly distorted square pyramid, while another Cu(II) atom (Cu2) is four-coordination possessing a square planar coordination geometry. Moreover, the Na(I) atom is in the O₆ cavity and adopts seven-coordination with a geometry of slightly distorted single triangular prism. In addition, there are abundant supramolecular interactions in the Cu(II)–Na(I) complex. The fluorescence spectra showed the Cu(II)–Na(I) complex possesses a significant fluorescent quenching and exhibited a hypsochromic-shift compared with the ligand H₄L.

Synthesis and Fluorescence Properties of a New Heterotrinuclear Co(II)-Ce(III)Complex Constructed from a bis(salamo)-Type Tetraoxime Ligand

[Co₂(L)Ce(OAc)₃(CH₃CH₂OH)]·1.5CH₃OH∙0.5CH₂Cl₂, a heterotrinuclear Co(II)-Ce(III) bis(salamo)-type complex with a symmetric bi(salamo)-type ligand H₄L and an acyclic naphthalenediol moiety, was designed, synthesized and characterized by elemental analyses, FT-IR, UV-Vis and fluorescence spectroscopy and X-ray crystallography. The X-ray crystallographic investigation revealed the heterotrinuclear complex consisted of two Co(II) atoms, one Ce(III) atom, one (L)^4‒ unit, three μ₂-acetate ions, one coordinated ethanol molecule, one and half crystallization methanol molecule and half crystallization dichloromethane molecule. Two Co(II) atoms located in the N₂O₂ coordination spheres, are both hexacoordinated, with slightly distorted octahedral geometries. The Ce(III) atom is nine-coordinated and located in the O₆ cavity possesses a single square antiprismatic geometry. In addition, supramolecular interactions exist in the Co(II)-Ce(III) complex. Two infinite 2D supramolecular structures are built via intermolecular O-H···O, C-H···O and C-H···π interactions, respectively.

A Reversible Bis(Salamo)-Based Fluorescence Sensor for Selective Detection of Cd2+ in Water-Containing Systems and Food Samples

A novel, simple, highly selective, and sensitive fluorescence chemosensor for detecting Cd2+ that was constructed from a bis(salamo)-type compound (H₄L) with two N₂O₂ chelating moieties as ionophore was successfully developed. Sensor H₄L could show fluorescence turn-on response rapidly and significant selectivity to Cd2+ over many other metallic ions (Cu2+, Ba2+, Ca2+, K⁺, Cr3+, Mn2+, Sr2+, Co2+, Na⁺, Li⁺, Ni2+, Ag⁺, and Zn2+), and a clear change in color from colorless to yellow that can be very easily observed via the naked eyes in the existence of Cd2+, while other metallic ions do not induce such a change. Interestingly, its fluorescent intensity was increased sharply with the increased concentration of Cd2+. The detection limit of sensor H₄L towards Cd2+ was down to 8.61 × 10-7 M.

Structurally Characterized Solvent-Induced Homotrinuclear Cobalt(II) N2O2-Donor Bisoxime-Type Complexes

Four new solvent-induced Co(II) complexes with chemical formulae [{CoL(μ2-OAc)(MeOH)}2Co] (1), [{CoL(μ2-OAc)(EtOH)}2Co] (2), [{CoL(μ2-OAc)(Py)}2Co] (3) and [{CoL(μ2-OAc)(DMF)}2Co] (4) (H2L = 4-nitro-4′-chloro-2,2′-[(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol) have been synthesized and characterized by elemental analyses, FT–IR, UV–Vis spectra and single-crystal X-ray diffraction. Each of the prepared complexes, crystallizing in the space groups P–1 (1 and 4), P21/n (2) and P21/c (3), consists of three Co(II) atoms, two completely deprotonated (L)2− units, two μ2-acetato ligands and two coordinated solvent molecules. Although the four complexes 1–4 were synthesized in different solvents, it is worthwhile that the Co(II) atoms in the four complexes 1–4 adopt hexa–coordinated with slightly distorted octahedral coordination geometries, and the ratio of the ligand H2L to Co(II) atoms is 2:3. The complexes 2–4 possess a self-assembled infinite 1D, 2D and 1D supramolecular structures via the intermolecular hydrogen bonds, respectively. Magnetic measurement was performed in the complex 3.

A highly selective fluorescent chemosensor for CN- based on a novel bis(salamo)-type tetraoxime ligand

The optical properties of a novel chemosensor for cyanide anions based on a symmetric bis(salamo)-type ligand (H₃L) were investigated by UV-Vis and fluorescence spectroscopy in MeOH/H₂O (1:1 v/v) solution. Sensor H₃L can selectively sense CN^- based on prominent color changes among other anions. The chemosensor exhibits an apparent fluorescence enhancement at 482nm to CN^- which because cyanide ions interact with CN bonds. Combining the corrected Benesi-Hildebrand formula, the binding constant of the formed host-guest complex was calculated as 2.42×10⁵M^-1. Meanwhile, the detection limit of the sensor toward CN^- was 8.91×10^-7M. It is worth noting that the designed sensor can be used for rapid detection of cyanide anions in basic pH range, and has great practical value.

Crystal structure of tetrakis(methanol-κO)bis{3-((4-methoxy-2-oxidobenzylidene)amino)-2-oxo-2H-chromen-4-olato-κ3 O,N,O′}bicobalt(II), C38H38Co2N2O14

C38H38Co2N2O14, monoclinic, P21/n (no. 14), a = 9.7459(5) Å, b = 7.9026(7) Å, c = 24.0622(15) Å, β = 100.260(5)°, Z = 2, V = 1823.6(2) Å3, R gt(F) = 0.0576, wR ref(F 2) = 0.1201, T = 293(2) K.

Crystal structure of diaqua-bis(N,N-dimethylformamide-κ1 O)-bis{3-((5-chloro-2-oxidobenzylidene)amino)-2-oxo-2H-chromen-4-olato-κ4 N,O,O′:O′}dinickel(II), C38H34Ni2Cl2N4O12

C38H34Ni2Cl2N4O12, monoclinic, C2/c (no. 15), a = 17.867(3) Å, b = 9.170(6) Å, c = 24.651(5) Å, β = 110.837(2)°, Z = 4, V = 3775(3) Å3, R gt(F) = 0.0323, wR ref(F 2) = 0.1078, T = 293(2) K.

Crystal structure of dimethanol-bis{3-(((2-oxidonaphthalen-1-yl)methylene)amino)-2-oxo-2H-chromen-4-olato-κ3 O,N:O′}dizinc(II), C42H30Zn2N2O10

C42H30Zn2N2O10, monoclinic, P21/c (no. 14), a = 8.5451(9) Å, b = 11.6897(12) Å, c = 18.4893(19) Å, β = 100.733(3)°, Z = 2, V = 1814.6(3) Å3, R gt(F) = 0.0404, wR ref(F 2) = 0.1029, T = 296(2) K.

Crystal structure of bis{5-(diethylamino)-2-(((2-oxo-2H-chromen-6-yl)imino)methyl)phenolato-κ2 O,N}cobalt(II), C40H38CoN4O6

C40H38CoN4O6, monoclinic, C2/c (no. 15), a = 25.848(2) Å, b = 9.7537(5) Å, c = 13.8302(11) Å, β = 93.760(7)°, Z = 4, V = 3479.3(4) Å3, R gt(F) = 0.0770, wR ref(F 2) = 0.1824, T = 293 K.

Synthesis and crystal structure tetrakis(μ2-methanolato)-dimethanol-bis(μ2-2-acetyl-1,3-bis(3,5-dichloro-2-oxidophenyl)propane-1,3-bis(olato)-κ5 O 1,O 2,O 3:O 3,O 4,O 5), tetramanganese(III), C40H40Cl8Mn4O16

C40H40Cl8Mn4O16, triclinic, P1̅, a = 9.2586(5) Å, b = 11.6798(10) Å, c = 12.3267(8) Å, α = 70.237(7)°, β = 75.557(5)°, γ = 81.358(6)°, V = 1211.65(16) Å3, Z = 1, R gt(F) = 0.0333, wR ref(F 2) = 0.0906, T = 294 K.

Crystal structure of bis{5-(diethylamino)-2-(((2-oxo-2H-chromen-6-yl)imino)methyl)phenolato-κ2 O,N}copper(II), C40H38CuN4O6

C40H38CuN4O6, monoclinic, P21/c (no. 14), a = 10.590(4) Å, b = 7.273(3) Å, c = 23.345(9) Å, β = 102.347(7)°, Z = 2, V = 1756.5(12) Å3, R gt(F) = 0.0682, wR ref(F 2) = 0.2373, T = 296 K.

Crystal structure of triethylammonium bis{3-(((3-oxidonaphthalen-1-yl)methylene)amino)-2-oxo-2H-chromen-4-olato-κ3 O,N,O′}manganese(III), C46H38MnN3O8

C46H38MnN3O8, triclinic P1̅ (no. 2), a = 8.9705(6) Å, b = 12.0309(8) Å, c = 18.4209(13) Å, α = 96.303(2)°, β = 103.884(2)°, γ = 101.636(2)°, Z = 2, V = 1864.0(2) Å3, R gt(F) = 0.0496, wR ref(F 2) = 0.1274, T = 296 K.

Crystal structure of tetrakis(methanol-κO)-bis{μ2-3-((4-methoxy-2-oxidobenzylidene)amino)-2-oxo-2H-chromen-4-olate-κ4O,N;O′:O′}dizinc(II), C38H38Zn2N2O14

C38H38Zn2N2O14, monoclinic, P21/n (no. 14), a = 9.6906(6) Å, b = 7.9055(5) Å, c = 24.0501(18) Å, β = 99.878(7)°, Z = 2, V = 1815.1(2) Å3, Rgt(F) = 0.0474, wRref(F2) = 0.1143, T = 293 K.

A supramolecular tetranuclear zinc(II) complex constructed from an asymmetrical Salamo-type ligand: synthesis, structure and fluorescence properties

The tetranuclear Zn(II) complex, [{ZnL(μ-OAc)Zn(CH3CH2CH2OH)}2], derived from an asymmetrical Salamo-type chelate ligand H3L (5-methoxy-6′-hydroxy-2,2′-[ethanedioxybis(nitrilomethylidyne)]diphenol) has been synthesized and structurally characterized by elemental analysis, IR spectrum, X-ray crystallography, UV/Vis and fluorescence spectra. The structure is made up of four Zn(II) atoms, μ 2-coordinated acetate ions and two coordinated n-propanol molecules, and forms an infinite one-dimensional supramolecular structure via intermolecular C–H···π interactions. The four Zn(II) atoms are penta-coordinated and show slightly distorted trigonal bipyramidal and tetragonal pyramidal symmetries.

Crystal structure of bis(pyridine)-bis(2-formyl-4,6-dichlorophenolato)cobalt(II), C24H16Cl4CoN2O4

C24H16Cl4CoN2O4, triclinic, P1̄, (no. 2) a = 8.6148(13) Å, b = 12.2201(16) Å, c = 13.4807(16) Å, α = 115.198(12)°, β = 101.596(11)°, γ = 96.518(12)°, V = 1225.8(3) Å3, Z = 2, R gt(F) = 0.0524, wR ref(F 2) = 0.1109, T = 173(1) K.