Heterobimetallic 3d–4f Zn(II)–Ln(III) (Ln = Sm, Eu, Tb and Dy) complexes with a N 2 O 4 bisoxime chelate ligand and a simple auxiliary ligand Py: Syntheses, structures and luminescence properties

Magnetic properties of a europium(III) complex - possible multiplet crossover

A dinuclear complex [(H2O)Zn(LH)Eu(NO3)3] containing a hexadentate Schiff-base {N2O4}-donor ligand LH2- was prepared and characterized by X-ray structural analysis and IR, electronic and fluorescence spectroscopy. DC magnetic data show that upon heating the diamagnetic complex with the ground state Eu(III)-7F0 and Zn(II)-1S switches to paramagnetic species due to the population of 7FJ (J = 1 to 6) magnetic multiplets. The magnetic susceptibility increases from zero, passes through a maximum, and then decreases upon heating. This behaviour can be explained using a spin-orbit Hamiltonian with an axial distortion term. There is an alternative interpretation of the susceptibility data based on a two-level model similar to that used in the spin crossover theory.

One-dimensional lanthanide coordination polymers supported by pentadentate Schiff-base and diphenyl phosphate ligands: single molecule magnet behavior and photoluminescence

Four one-dimensional lanthanide coordination polymers constructed from Ln₂ dimers showing single molecule magnet behavior and photoluminescence are reported.

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.

Structurally characterized homo-trinuclear ZnII and hetero-pentanuclear [ZnII4LnIII] complexes constructed from an octadentate bis(Salamo)-based ligand: Hirshfeld surfaces, fluorescence and catalytic properties

One 3d and five 3d-4f complexes were synthesized. Complexes 1–6 were characterized via elemental analyses, FT-IR, UV-Vis spectroscopy and X-ray crystallography, and their fluorescence properties, catalytic activities and Hirshfeld surface analyses were studied.

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.

Heterometallic ZnII⁻LnIII⁻ZnII Schiff Base Complexes with Linear or Bent Conformation-Synthesis, Crystal Structures, Luminescent and Magnetic Characterization

A series of racemic, heteronuclear complexes [Zn₂Nd(ac)₂(HL)₂]NO₃·3H₂O (1), [Zn₂Sm(ac)₂(HL)₂]NO₃·3CH₃OH·0.3H₂O (2), [Zn₂Ln(ac)₂(HL)₂]NO₃·5.33H₂O (3–5) (where HL is the dideprotonated form of N,N′-bis(5-bromo-3-methoxysalicylidene)-1,3-diamino-2-propanol, ac = acetate ion, and Ln = Eu (3), Tb (4), Dy (5), respectively) with an achiral multisite coordination Schiff base ligand (H₃L) were synthesized and characterized. The X-ray crystallography revealed that the chirality in complexes is centered at lanthanide(III) ions due to two vicinally located μ-acetato-bridging ligands. The presented crystals have isoskeletal coordination units but they crystallize in monoclinic (1, 2) or trigonal crystal systems (3–5) with slightly different conformation. In 1 and 2 the Zn^II–Ln^III–Zn^II coordination core is linear, whereas in isostructural crystals 3–5 the chiral coordination cores are bent and lie on a two-fold axis. The complexes 1, 3–5 show a blue emission attributed to the emission of the ligand. For Zn^II₂Sm^III complex (2) the characteristic emission bands of f-f* transitions were observed. The magnetic properties for compounds 1, 4 and 5 are characteristic for the paramagnetism of the corresponding lanthanide(III) ions.

A heterotrimetallic Ni(II)–Dy(III) bis(salamo)-based complex: synthesis, structure and fluorescent property

A discrete heterotrinuclear complex [{Ni2LDy(OAc)3(CH3OH)}2] · 2CH3OH · 3CH2Cl2, with a naphthalenediol-based acyclic bis(salamo) ligand H4L, has been synthesized and structurally characterized using elemental analyses, IR, UV/Vis and fluorescence spectra and single crystal X-ray diffraction. The crystal structure shows two crystallographically independent but chemically identical molecules (moleculesIandII). All the Ni(II) atoms are hexa-coordinated with slightly distorted octahedral geometries. The central Dy atoms are nona-coordinated with slightly distorted tricapped trigonal prism geometries. An infinite 3D supramolecular structure is formed via intermolecular hydrogen bonding and C–H…π interactions.

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.

Structural and Luminescent Properties of Heterobimetallic Zinc(II)-Europium(III) Dimer Constructed from N2O2-Type Bisoxime and Terephthalic Acid

A new heterohexanuclear ZnII–EuIII dimer [{(ZnL)2Eu}2(bdc)2]·2Cl constructed from a N2O2-type chelating ligand H2L (6,6′-Dimethoxy-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol), Zn(OAc)2·2H2O, EuCl3·6H2O and H2bdc (terephthalic acid) was synthesized, and characterized using elemental analyses, IR (Infrared), UV-Vis (Ultraviolet–visible) spectra and X-ray single crystal diffraction method. There are two crystallographically equivalent [(ZnL)2Eu] moieties in the ZnII–EuIII complex, the two [(ZnL)2Eu] moieties are linked by two bdc2– ligand leading to a heterohexanuclear dimer, in which the carboxylato groups bridge the ZnII and EuIII atoms. Furthermore, the luminescence properties of H2L and its ZnII–EuIII complex have been studied.

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.

Synthesis, crystal structure, luminescence and electrochemical properties of a Salamo-type trinuclear cobalt(II) complex

A trinuclear Co(II) complex, [{CoL(C4H9OH)}2-(OAc)2Co]·C3H7NO, was synthesized by the reaction of a Salamo-type chelating ligand (H2L=4,42′-dinitro-2,2′-[1,2-ethylenedioxybis(nitrilomethylidyne)]diphenol) with cobalt(II) acetate tetrahydrate in n-butanol, and characterized by elemental analyses, X-ray crystallography, FT-IR and UV/Vis spectra. In the Co(II) complex, there are two ligand L2− units, two μ 2-acetate ions, two coordinated n-butanol molecules and one non-coordinated N,N-dimethylformamide molecule. The Co(II) atoms in the structure of the Co(II) complex adopt slightly distorted octahedra geometries. Furthermore, through intermolecular C–H···O, O–H···O and C–H···π interactions, infinite layer-like, plane-like and 3D supramolecular structures are constructed. The fluorescence and electrochemical properties of the Co(II) complex have also been investigated.

Synthesis and Fluorescence Properties of Asymmetrical Salamo-Type Tetranuclear Zinc(II) Complex

A new tetranuclear zinc(II) complex with an asymmetrical Salamo-type chelating ligand, H3L (5-methoxy-6′-hydroxy-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol), was synthesized and characterized using FT-IR, elemental analyses, X-ray single crystal diffraction method, UV-Vis, and fluorescence spectra. The zinc(II) complex possesses the cell parameters a = 8.1960(7) Å, b = 9.8127(8) Å, c = 16.5428(15) Å, Z = 1, V = 1172.5(2) Å3, R1 = 0.0722, and wR2 = 0.1558, and crystallizes in the triclinic system, with space group P-1. X-ray crystal structure analysis reveals that Zn1 and Zn2 atoms are all pentacoordinated and adopt slightly twisted tetragonal pyramidal and trigonal bipyramidal geometries. The zinc(II) complex forms a 1D supramolecular chain via intermolecular hydrogen bonds along the b axis. Besides, the fluorescence properties have been discussed.

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.

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.

Tri- and Mono-Nuclear Zinc(II) Complexes Based on Half- and Mono-Salamo Chelating Ligands

Two newly designed complexes, [Zn(L1)(EtOH)] (1) and [{Zn(L2)(OAc)2}2Zn]·CHCl3 (2) derived from salamo and half-salamo chelating ligands (H2L1 and HL2) have been synthesized and characterized by elemental analyses, IR and UV-VIS spectra, fluorescence spectra, and X-ray crystallography. Complex 1 shows a slightly distorted tetragonal pyramid and forms an infinite 3D supramolecular structure. All of the Zn(II) ions in complex 2 are hexa-coordinated with slightly distorted octahedral geometries. Complex 2 possesses an infinite 2D space structure. The fluorescence titration experiments were used to characterize fluorescence properties of complexes 1 and 2. And the normalized fluorescent spectra exhibit that complexes 1 and 2 have favourable fluorescent emissions in different solvents.

Two Supramolecular Cobalt(II) Complexes: Syntheses, Crystal Structures, Spectroscopic Behaviors, and Counter Anion Effects

Two new Co(II) complexes, [{Co(L)}2{Co(Pic)2(CH3OH)2}] (1) and [{CoL(μ-OAc)}2Co] (2), where H2L = 2,2′-[Ethylenedioxybis(nitrilomethylidyne)]dinaphthol, were designed, synthesized and characterized by elemental analysis, FT-IR spectra, UV-Vis spectra, and X-ray crystallography. Complex 1 consists of two [CoL] and one [Co(Pic)2(CH3OH)2] (Pic = picrate) units and in the [CoL] unit, the Co(II) atom is tetra-coordinated with a slightly distorted square-planar geometry. In the [Co(Pic)2(CH3OH)2] unit, the Co(II) atom is hexa-coordinated with a slightly distorted octahedral geometry. Meanwhile in complex 2, two acetate ions coordinate to three Co(II) atoms through Co-O-C-O-Co bridges and four μ-naphthoxo oxygen atoms from two [CoL] units also coordinated to the central Co(II) atom. Thus, complex 2 has two distorted square pyramidal coordination geometries around the terminal Co(II) atom and an octahedral geometry around the central Co(II) atom. The supramolecular structures of complex 1 is a 3D-network supramolecular structure linked by C-H···O hydrogen bonds and π···π stacking interaction, but complex 2 possesses a self-assembled 2D-layer supramolecular structure linked by C-H···π and π···π stacking interactions. The structure determinations show that the coordination anions are important factors influencing the crystalline array.

Syntheses, Crystal Structures and Thermal Behaviors of Two Supramolecular Salamo-Type Cobalt(II) and Zinc(II) Complexes

This paper reports the syntheses of two new complexes, [Co(L1)(H2O)2] (1) and [{Zn(L2)(μ-OAc)Zn(n-PrOH)}2] (2), from asymmetric halogen-substituted Salamo-type ligands H2L1 and H3L2, respectively. Investigation of the crystal structure of complex 1 reveals that the complex includes one Co(II) ion, one (L1)2− unit and two coordinated water molecules. Complex 1 shows slightly distorted octahedral coordination geometry, forming an infinite 2D supramolecular structure by intermolecular hydrogen bond and π–π stacking interactions. Complex 2 contains four Zn(II)ions, two completely deprotonated (L2)3− moieties, two coordinated μ-OAc− ions and n-propanol molecules. The Zn(II) ions in complex 2 display slightly distorted trigonal bipyramidal or square pyramidal geometries.

Syntheses, crystal structures and catalytic activities of two solvent-induced homotrinuclear Co(ii) complexes with a naphthalenediol-based bis(Salamo)-type tetraoxime ligand

Two homotrinuclear cobalt(ii) complexes with different solvent molecules that coordinate to the central Co(ii) ion, show different supramolecular interactions and exhibit catalytic activities in relation to catechol oxidase.