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

Highly efficient detection of Cu2+ and B4 O7 2- based on a recyclable asymmetric salamo-based probe in aqueous medium

An asymmetric salamo-based probe molecule (H₂ L) was synthesized and characterized structurally. When DMF/H₂ O (9:1) was used as the solvent, it was shown probe H₂ L has high sensitivity to Cu²⁺ . Using high-resolution mass spectrometry and theoretical calculation, it was found that probe H₂ L could form a more stable complex (1:1) with Cu²⁺ , the minimum limit of detection (LOD) of H₂ L for Cu²⁺ was calculated as 9.95 × 10^-8 M. In addition, probe H₂ L could also be used to identify B₄ O₇ ^2- under the same detection conditions and the minimum LOD of H₂ L for B₄ O₇ ^2- was calculated as 4.98 × 10^-7 M. At the same time, density functional theory theoretical calculation further proved the flexibility of probe H₂ L. Through the action of EDTA, probe H₂ L had a cyclic ability to recognize Cu²⁺ , and showed a better response in the physiological pH range; probe H₂ L had the characteristics of fast recognition speed and high efficiency. In addition, with probe H₂ L test paper for Cu²⁺ and B₄ O₇ ^2- , the effect was more obvious. Meanwhile, probe H₂ L can be used to quantitatively detect Cu²⁺ in water samples.

A highly sensitive and selective bis(salamo)-type fluorescent chemosensor for identification of Cu2+ and the continuous recognition of S2-, Arginine and Lysine

A novel bis(salamo)-type chemosensor H₃L was synthesized and characterized. It was found that the sensor molecule can selectively recognize Cu²⁺, and its L-Cu²⁺ is highly sensitive to the detection of S^2- anion, Arginine and Lysine when dissolved in ethanol solvent. The sensor H₃L can be used to identify a relay sensor for Cu²⁺, while the L-Cu²⁺ recognizes S^2- anion, Arginine and Lysine with high selectivity and sensitivity over an acceptable physiological pH range. The detection line of the sensor molecule H₃L is 1.02 × 10^-6 M, and its binding constant to Cu²⁺ is 1.54 × 10⁶ M^-1. The detection line of L-Cu²⁺ as a sensor is calculated as 5.57 × 10^-7 M, and its binding constants with S^2- anion, Arginine and Lysine are 2.80 × 10⁵ M^-1, 5.32 × 10⁶ M^-1 and 5.94 × 10⁶ M^-1, respectively. The crystal structure of the Cu(II) complex [Cu₄(L)₂(CH₃OH)₂]·2NO₃ with the sensor molecule H₃L has been determined by single crystal X-ray crystallography.

A Newly Synthesized Heterobimetallic NiII-GdIII Salamo-BDC-Based Coordination Polymer: Structural Characterization, DFT Calculation, Fluorescent and Antibacterial Properties

A unprecedented hetero-bimetallic 3d-4f BDC-salamo-based coordination polymer, [(L)Ni(BDC)Gd(NO3)(DMF)] was prepared and validated via elemental analyses, IR and UV–Visible absorption spectra, DFT calculation, and X-ray crystallography. The six-coordinated Ni1 ion lies at the N2O2 donor site of the L2− moiety, and one DMF O atom and carboxylate O atom occupy, collectively, the axial positions, and form a twisted octahedron. The nine-coordinated Gd1 ion consists of three oxygen atoms (O12, O13, and O14) of two carboxylate groups, two oxygen atoms (O8 and O9) derived from one bidentate nitrate group, and an O2O2 coordination site (O1, O2, O6, and O5) of the L2− unit, forming a twisted three-capped triangular prism coordination geometry. Compared to the ligand (H2L), the fluorescence intensity decreases due to the coordination of metal ions. Meanwhile, the antibacterial activities are researched.

Four rare structurally characterized hetero-pentanuclear [Zn4Ln] bis(salamo)-type complexes: syntheses, crystal structures and spectroscopic properties

Four new hetero-pentanuclear 3d–4f complexes [Zn₄(L)₂La(NO₃)₂(OEt)(H₂O)] (1), [Zn₄(L)₂Ce(NO₃)₂(OMe)(MeOH)] (2), [Zn₄(L)₂Pr(NO₃)₂(OEt)(EtOH)] (3) and [Zn₄(L)₂Nd(NO₃)₂(OMe)(MeOH)] (4) were synthesized by the reactions of a newly synthesized octadentate bis(salamo)-based tetraoxime ligand (H₄L) with Zn(OAc)₂·2H₂O and Ln(NO₃)₃·6H₂O (Ln = La, Ce, Pr and Nd), respectively, and characterized via elemental analyses, FT-IR, UV-Vis spectroscopy and single crystal X-ray crystallography. The X-ray crystallographic investigation revealed that all Zn^II ions were located in N₂O₃ coordination spheres, and possessed a trigonal bipyramid coordination environment. The Ln^III ion lay in an O₈ coordination sphere, and adopted a distorted square antiprismatic coordination environment. Furthermore, supramolecular interactions and fluorescence properties were investigated.

Four new hetero-pentanuclear 3d–4f complexes 1–4 were synthesized and characterized. Supramolecular interactions and fluorescence properties of complexes 1–4 were investigated.

A highly sensitive and selective fluorescent "off-on-off" relay chemosensor based on a new bis(salamo)-type tetraoxime for detecting Zn2+ and CN. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2019;222:117209. [PMID: 31200268 DOI: 10.1016/j.saa.2019.117209]

A new naphthalenediol-based bis(salamo)-type fluorescent probe H₄L for Zn²⁺ and CN^- was reported. Probe H₄L showed a highly selective fluorescence enhancement toward Zn²⁺ over other metal ions including Cd²⁺, and obtained the L-Zn²⁺complex can only detect CN^- in various anions. Their recognition mechanisms were explained by Job plots, fluorescent and UV-vis titrations, and theoretical calculations. The L-Zn²⁺complex has been synthesized and structurally characterized using Hirshfeld surface analysis, elemental analyses, IR, UV-Vis and fluorescent spectra. Additionally, the relay probe with the wide adaptability of pH range and excellent stability showed highly selectivity for CN^- recognition.

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.

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.

A Self-Assembled ZnII-NdIII Heterohexanuclear Dimer Based on a Hexadentate N2O4-Type Ligand and Terephthalic Acid: Synthesis, Structure, and Fluorescence Properties

A self-assembled Zn^II-Nd^III heterohexanuclear coordination compound [Zn₄Nd₂(L)₄(bdc)₂]·2NO₃ based on a hexadentate Salamo-like chelating ligand (H₂L = 1,2-bis(3-methoxysalicylideneaminooxy)ethane]) and H₂bdc (H₂bdc = terephthalic acid) has been synthesized and characterized by elemental analyses, IR and UV/Vis spectra, and X-ray crystallography. Two crystallographically equivalent [Zn₂Nd(L)₂] moieties lie in the inversion center linked by two (bdc)²⁻ ligands leading to a heterohexanuclear dimer in which the carboxylato group bridges the Zn^II and Nd^III atoms. The heteropolynuclear 3d-4f coordination compound includes four Zn^II atoms, two Nd^III atoms, four completely deprotonated (L)²⁻ units, two fully deprotonated (bdc)²⁻ units, and two crystalling nitrate ions. All of the Zn^II atoms in the Zn^II-Nd^III coordination compound possess trigonal bipyramidal geometries and the Nd^III atoms possess distorted bicapped square antiprism coordination arrangements. In addition, the fluorescence properties of the ligand and the Zn^II-Nd^III coordination compound were investigated.