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Tetrathiaoxa Macrocycles with Dibenzo-subunits: A Search for New Tl(I)- and Ag(I)-Selective Ionophores

Novel S4O n mixed donor macrocycles (1, n=1; 2, n=2) were synthesized by the coupling reactions of corresponding dichlorides with dithiols under high dilution conditions. Synthesis and crystal structures of Tl+ and Ag+ complexes, [Tl(2)+ and Ag(2)+], with macrocycle 2 are described. The electrode based on macrocycle 2 showed excellent potentiometric sensing ability for Tl+ and Ag+ ions. This remarkable sensing of the proposed electrode can be understood in terms of the synergy effect of a soft–soft acid–base interaction and π-coordination, especially for the Tl+ ion, which was observed from the crystal structure of the corresponding complex.

Donor-set-induced coordination sphere and oxidation-state switching in the copper complexes of O2S2X (X = S, O and NH) macrocycles.

Reaction of the O(2)S(2)X-macrocycles (L(1), X = S; L(2), X = NH; and L(3), X = O) with Cu(ClO(4))(2) x 6 H(2)O affords 1:1 (M/L) square-pyramidal Cu(II) complexes when X = S and NH but yields a rare 1:2 sandwich-type tetrahedral Cu(I) complex when X = O; the X-ray structures of all three complexes are reported. Substitution of O for S or NH in the ligand structure thus results in a donor-set-induced II/I oxidation state change of the copper, and this is accompanied by a square-pyramidal to tetrahedral topological change in the solid state. Spectrophotometric titration data (including Job plots) indicate that similar behavior occurs in acetonitrile. In further experiments aimed at investigating the generality of the above redox behavior, it was shown that the 16- and 18-membered analogs of the 17-membered L(3) also induce a similar II/I redox change in acetonitrile. It was demonstrated for L(3) that the above-induced Cu(II/I) change is also maintained when the reaction solvent is changed from acetonitrile to methanol or ethanol.

Copper(II) interaction with mono-, bis- and tris-ring N3O2 macrocycles: synthetic, X-ray, competitive membrane transport, and hypochromic shift studies.

New N-phenyl (L(1)), azo-coupled (L(2)), and tri-linked (L(3)) substituted derivatives of a parent dibenzo-N(3)O(2) macrocycle, 1,12,15-triaza-3,4:9,10-dibenzo-5,8-dioxacycloheptadecane (L(4)), have been synthesized. Competitive seven-metal transport studies across a bulk chloroform membrane employing an aqueous source phase containing equal molar concentrations of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Ag(I), and Pb(II) as their nitrate salts have been performed using both L(1) and L(3) as the ionophore, with the results discussed in terms of those obtained previously for related mono-ring (L(5)) and di-linked (L(6)) macrocyclic systems. Sole transport selectivity for Cu(II) was observed in each case. On a per macrocyclic cavity basis the tri-linked analogue L(3) gave less efficient Cu(II) transport than its monomeric or di-linked analogues. At least in part, this may reflect the tendency of tri-linked derivative L(3) to form a 2:1 complex (metal/ligand) with Cu(II) under the conditions employed; such a stoichiometry was demonstrated to occur in acetonitrile using both spectrophotometric titration and Job plot procedures. The azo-coupled derivative (L(2)) yields a red solution (lambda(max) = 495 nm, epsilon(max) = 23000 M(-1) cm(-1)) and undergoes significant hypochromic metal-induced shifts (Delta lambda(max) = 54-174 nm) on metal addition. Cu(II) induces the largest shift (Delta lambda(max) = 174 nm), corresponding to a color change from red to pale-yellow. The X-ray structures of red L(2) x HNO(3) together with its Cu(II) complexes, [Cu(L(2))NO(3)]NO(3) x CH(2)Cl(2) (6) (pale-yellow) and [{Cu(L(2))}(2)(mu-OH)(2)](ClO(4))(2) x 2 CH(2)Cl(2) x 2 H(2)O (7) (dark-red), are reported. The structural determinations have allowed insight into the structure-function relationships governing the observed color variation between these species.

Donor effect on supramolecular structures of silver(I) perchlorate complexes of macrocycles with O2S2X (XS, O and NH) donor sets

By virtue of simple one donor variations of O(2)S(2)X-donor macrocycles (L(1): X=S, L(2): X=O and L(3): X=NH) towards silver(I) perchlorates, four supramolecular complexes (1-3) with different topologies have been isolated; L(1) afforded solvent- and anion-free sandwich complex (1), otherwise L(2) and L(3) gave the dimeric (2a), 1-D polymeric (2b), and tetrameric bowl-type (3) complexes with solvent or anion coordination.

Crystal structure of a looped-chain CoII coordination polymer: catena-poly[[bis­(nitrato-κO)cobalt(II)]bis­[μ-bis­(pyridin-3-ylmeth­yl)sulfane-κ2N:N′]]

The reaction of cobalt(II) nitrate with bis(pyridin-3-ylmethyl)sulfane ligand, afforded a one-dimensional looped polymeric chain. The CoII cation displays a distorted octahedral geometry coordinated by four pyridine N atoms from four individual ligands and two O atoms from two monodentate nitrate anions. Two symmetry-related ligands are connected by two symmetry-related CoII cations, forming a 20-membered cyclic dimer. These cyclic dimers are connected to each other by sharing CoII atoms, forming a looped chain. In the crystal, adjacent looped chains are connected by intermolecular π–π stacking interactions and C—H⋯π and C—H⋯O hydrogen bonds, resulting in the formation of a three-dimensional supramolecular architecture.

Crystal structure of a zigzag CoII coordination polymer: catena-poly[[di­chlorido­bis­(methanol-κO)cobalt(II)]-μ-bis­(pyridin-3-ylmeth­yl)sulfane-κ2N:N′]

In the title compound, each CoII ion is coordinated by two pyridine N atoms from two individual dipyridyl ligands, two methanol O atoms and two chloride anions in an elongated octahedral geometry. Each dipyridyl ligand links two CoII ions, forming infinite zigzag chains.