A lanthanide luminescent sensor for the detection of 4-nitrophenol in aqueous media

The development of facile luminescent sensors for detecting nitrophenols in aqueous media is of great necessity for the safety of the environment and human health, as they are a class of widespread toxic organic pollutants that cause serious adverse effects upon consumption. Based on a new multidentate asymmetric ligand (H2L) in which salicylamide and 4-nitryl-salicylaldimine are spaced by 1,2-bis(2-ethoxy)ethyl, a new hydrostable lanthanide intercycle, [Tb2L2(NO3)2]·CH3CN (Tb-[2]c), was prepared to act as a new luminescent sensor for 4-NP in water media. Structural analysis indicated that two fully deprotonated L2- ligands in cis-configuration and μ2-L-κ2O1:κO2:κO4:κN2:κO5 coordination mode were interlocked by two TbIII ions to render the emitted TbIII encapsulated by L2- for lessening non-radiative transitions. The excellent sensitizing capability of the ligand L2- to TbIII was ascertained by both experimental methods and theoretical calculations. The sensing exploration indicated that Tb-[2]c exhibited highly sensitive and selective recognition of 4-NP against other nitroaromatics in aqueous media. The recognition mechanism could be attributed to the internal filtration effect (IFE) mechanism when DFT calculations and accumulating experimental evidence were combined.

Insight into Rare Structurally Characterized Homotrinuclear CuII Non-Symmetric Salamo-Based Complex

A rare homotrinuclear CuII salamo-based complex [Cu3(L)2(μ-OAc)2(H2O)2]·2CHCl3·5H2O was prepared through the reaction of a non-symmetric salamo-based ligand H2L and Cu(OAc)2·H2O, and validated by elemental analyses, UV-Visible absorption, fluorescence and infrared spectra, molecular simulation and single-crystal X-ray analysis techniques. It is shown that three CuII atoms and two wholly deprotonated ligand (L)2− moieties form together a trinuclear 3:2 (M:L) complex with two coordination water molecules and two bi-dentate briging μ-acetate groups (μ-OAc−). Besides, the Hirshfeld surface analysis of the CuII complex was investigated. Compared with other ligands, the fluorescent strength of the CuII complex was evidently lowered, showing that the CuII ions possess fluorescent quenching effect.

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.

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.

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.

Unprecedented Hexanuclear Cobalt(II) Nonsymmetrical Salamo-Based Coordination Compound: Synthesis, Crystal Structure, and Photophysical Properties

A novel hexanuclear Co(II) coordination compound with a nonsymmetrical Salamo-type bisoxime ligandH4L, namely [{Co3(HL)(MeO)(MeOH)2(OAc)2}2]·2MeOH, was prepared and characterized by elemental analyses, UV–vis, IR and fluorescence spectra, and X-ray single-crystal diffraction analysis. Each Co(II) is hexacoordinated, and possesses a distorted CoO6 or CoO4N2 octahedrons. The Co(II) coordination compound possesses a self-assembled infinite 2D supramolecular structure with the help of the intermolecular C–H···O interactions. Meanwhile, the photophysical properties of the Co(II) coordination compound were studied.

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.