Counteranion-driven self-assembly of di- and tetra-nuclear Zn(II) single‐armed salamo‐type complexes

Spectroscopic and theoretical studies on a novel bis(salamo)-like probe for highly effective fluorimetric-colorimetric identification of Fe3+ and Cu2+ in aquo-organic medium

A novel bis(salamo)-type sensor FT for fluorescence-colorimetric recognition of Fe3+/Cu2+ has been created, which revealed significant fluorescent performance and colorimetric sensing ability for Cu2+ and Fe3+ ions, superior to other related competitive metal ions. Interestingly, the binding of the FT probe with Cu2+ ions manifested an instant color change from colorless to red in sunlight, which is detectable by the naked-eye, and a fluorescence turn-off response under UV light for Fe3+ and Cu2+. The results demonstrated that the probe exhibits better sensitivity, greater affinity and lower limit of detection leading to quick response time in an aquo-organic medium. The excited state property of the FT probe and in the presence of Cu2+/Fe3+ was evaluated on the basis of DFT & TD-DFT results. Furthermore, test strips have been provided for convenient monitoring of Cu2+ and Fe3+ ions by naked eye and fluorescence method.

Coordination-Driven Salamo-Salen-Salamo-Type Multinuclear Transition Metal(II) Complexes: Synthesis, Structure, Luminescence, Transformation of Configuration, and Nuclearity Induced by the Acetylacetone Anion

A flexible polydentate Salamo-Salen-Salamo hybrid ligand H₄L was designed and synthesized, which has rich pockets (salamo and salen pockets) so that it may have fascinating coordination patterns with transition metal(II) ions. Four multinuclear transition metal(II) complexes, novel butterfly-shaped homotetranuclear [Ni₄(L)(μ₁-OAc)₂(μ_1,3-OAc)₂(H₂O)_0.5(CH₃CH₂OH)_3.5]·4CH₃CH₂OH (1), helical homotrinuclear [Zn₃(L)(μ₁-OAc)₂]·2CH₃CH₂OH (2), double-helical homotrinuclear [Cu₂(H₂L)₂]·2CH₃CN (3), and mononuclear [Ni(H₂L)]·1.5CH₃COCH₃ (4), have been synthesized and characterized by single-crystal X-ray diffraction. The effects of different anions [OAc^- and (O₂C₅H₇)^2-] on the complexation behavior of H₄L with transition metal(II) ions were studied by UV-vis spectrophotometry. The fluorescent properties of the four complexes were studied with zebrafish, which are expected to be a potential light-emitting material. Ultimately, interaction region indicator (IRI) valuations, Hirshfeld surface analyses, density functional theory (DFT & TD-DFT), electrostatic potential analyses (ESP), and simulations were carried out to further demonstrate the weak interactions and electronic properties of the free ligand and its four complexes.

Orthogonal, modular anion-cation and cation-anion self-assembly using pre-programmed anion binding sites

Subcomponent self-assembly relies on cation coordination whereas the roles of anions often only emerge during the assembly process. When sites for anions are instead pre-programmed, they have the potential to be used as orthogonal elements to build up structure in a predictable and modular way. We explore this idea by combining cation (M⁺) and anion (X^-) binding sites together and show the orthogonal and modular build up of structure in a multi-ion assembly. Cation binding is based on a ligand (L) made by subcomponent metal-imine chemistry (M⁺ = Cu⁺, Au⁺) while the site for anion binding (X^- = BF₄ ^-, ClO₄ ^-) derives from the inner cavity of cyanostar (CS) macrocycles. The two sites are connected by imine condensation between a pyridyl-aldehyde and an aniline-modified cyanostar. The target assembly [LM-CS-X-CS-ML],⁺ generates two terminal metal complexation sites (LM and ML) with one central anion-bridging site (X) defined by cyanostar dimerization. We showcase modular assembly by isolating intermediates when the primary structure-directing ions are paired with weakly coordinating counter ions. Cation-directed (Cu⁺) or anion-bridged (BF₄ ^-) intermediates can be isolated along either cation-anion or anion-cation pathways. Different products can also be prepared in a modular way using Au⁺ and ClO₄ ^-. This is also the first use of gold(i) in subcomponent self-assembly. Pre-programmed cation and anion binding sites combine with judicious selection of spectator ions to provide modular noncovalent syntheses of multi-component architectures.