A 20-membered O4S2 macrocycle (L(2)) was synthesized as a ditopic ligating system toward hard and soft metal ions simultaneously. Five complexes (3-7) of L(2) with different structures and coordination modes, including discrete to infinite forms, mono- to heteronuclear, and endo- to exo- and endo/exocoordination, were prepared and structurally characterized. First, the reaction of L(2) with Pb(ClO4)2·3H2O afforded a typical endocyclic mononuclear perchlorato complex [Pb(L(2))(ClO4)2] (3) in which one lead(II) is surrounded by the macrocycle adopting a "tight and bent" conformation. Meanwhile, the reaction with a softer metal salt AgNO3 resulted in the formation of the dinuclear bis(macrocycle) complex [Ag2(L(2))2(NO3)2] (4) in which two exocyclic silver(I) ions are doubly linked by two nitrate ions. The treatment of L(2) with CuI gave a mixture of the exocyclic monomer complex [Cu(L(2))I] (5) and the exocyclic dimer complex [(Cu2I2)(L(2))2] (6), which were separated manually because of their brick and rhomboid shapes of the crystals, respectively. Furthermore, the reaction of L(2) with a mixture of CuI and NaI afforded a photoluminescent heteronuclear complex [Na2(Cu6I8)(L(2))2(CH3CN)4]n (7) in the endo/exocyclic coordination mode. In this case, the endocyclic sodium(I) complex units are linked by the double-open cubanes-type cluster Cu6I8, yielding a two-dimensional network. The structural and binding properties of the complex of L(2) with silver(I) nitrate in solution were monitored by the NMR titration. Photophysical and thermal properties for complex 7 were also investigated and discussed.

We report how the metal cation and its counteranions cooperate in the complexation-based macrocyclic chemosensor to monitor the target metal ion via the specific coordination modes. The benzothiazolyl group bearing NO2S2-macrocycle L was synthesized, and its mercury(II) selectivity (for perchlorate salt) as a dual-probe channel (UV-vis and fluorescence) chemosensor exhibiting the largest blue shift and the fluorescence turn-off was observed. In the mercury(II) sensing with different anions, except ClO4(-) and NO3(-), no responses for mercury(II) were observed with other anions such as Cl(-), Br(-), I(-), SCN(-), OAc(-), and SO4(2-). A crystallographic approach for the mononuclear mercury(II) perchlorate complex [Hg(L)(ClO4)2]·0.67CH2Cl2 (1) and polymeric mercury(II) iodide complex [Hg(L)I2]n (2) revealed that the observed anion-controlled mercury(II) sensing in the fluorescence mainly stems from the endo- and exocoordination modes, depending on the anion coordinating ability, which induces either the Hg-Ntert bond formation or not. The detailed complexation process with mercury(II) perchlorate associated with the cation sensing was also monitored with the titration methods by UV-vis, fluorescence spectroscopy, and cold-spray ionization mass spectrometry.

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Some biological receptors change their shapes and rigidity by metalation to recognize substrates precisely via adaptive guest binding process. Herein we present a semi‐flexible tricyclic host molecule whose conformation is rigidified by dimetalation to uptake organic guests selectively. Considering two metal binding sites and an empty space between them, pillar[5]‐bis‐thiacrown (L) was synthesized. The tricyclic host L forms a disilver(I) complex [Ag2L(NO3)2], with an Ag⋅⋅⋅Ag separation of 9.976 Å. Binding studies based on 1H NMR including 2D NOESY and DOSY experiments towards α,ω‐dicyanoalkanes [CN(CH2)nCN, n=2–6, shortly C2–C6] demonstrated that the dimetalated L, Ag2L preferentially recognizes C2 over other guests than that of free L. Furthermore, the dimetalated the host only uptakes C2 in the presence of other guests. Crystal structures support the idea that the space between two silver(I) centers plays a decisive role on the selective guest binding forming an Ag‐C2‐Ag@L arrangement via the length‐selective recognition. This work demonstrates the chemical example of the adaptive guest binding and presents a new perspective on the metallosupramolecules of pillararenes.

a The macrocyclic pillar ligand, dipyridyldibenzotetraaza[14]annulene (H2L), in the absence and presence of the dicarboxylate coligands, biphenyl-4,4′-dicarboxylic acid (H2bpdc) or benzene-1,3-dicarboxylic acid (H2bdc), reacts with nickel(II), cobalt(II), and zinc(II) to yield [Ni(L)] (1), [Co(L)] (2), [Co(L)]n (3), {[Zn(H2L)(bdc)]•0.5DMF•1.5H2O}n (4), and {[Co4(L)2(bpdc)2]•2DMF•H2O}n (5) displaying both discrete and polymeric structures. Complexes 1 and 2 are isostructural, with the respective low-spin, square-planar metal ions occupying the macrocyclic cavity and bound to the N4-donor set of the macrocycle in its doubly deprotonated form. In 3, the cobalt(II) centre again occupies the macrocyclic cavity, but in this case one axial site is occupied by a pyridyl nitrogen from a second ligand complex, resulting in the formation of an infinite zigzag one-dimensional (1D) structure. Solvothermal reaction between Zn(NO3)2•4H2O, H2L and H2bdc afforded the 2D coordination polymer {[Zn(H2L)(bdc)]•0.5DMF•1.5H2O}n (4) in which H2L ligands crosslink 1D (bdc-Zn)n wavy backbones via Zn-Npyd bonds. In contrast, the solvothermal reaction of H2L with Co(NO3)2•6H2O in the presence of H2bpdc resulted in formation of the 2-fold interpenetrated 3D coordination polymer, {[Co4(L)2(bpdc)2]•2DMF•H2O}n (5), exhibiting a pillaredlayer structure. The 3D framework of 5 is based on dicobalt(II) cluster secondary building units (SBUs) to yield a rob net in which the bpdc/Co-based 2D nets are cross-linked by CoL macrocyclic pillar units; the framework of 5 is thermally stable until 350 °C.