The NO2S2-donor macrocycle (L1) was synthesised from the ring closure reaction between Boc-N-protected 2,2'-iminobis(ethanethiol) (3) and 2,2'-(ethylenedioxy)bis(benzyl chloride) (4) followed by deprotection of the Boc-group. alpha,alpha'-Dibromo-p-xylene was employed as a dialkylating agent to bridge two L1 to yield the corresponding N-linked product (L2). The X-ray structure of L2 (as its HBr salt) is described. A range of Cd(II) and Hg(II) complexes of L1 (6-9) and L2 (10-12) were prepared and characterised. Reaction of HgX2 (X = Br or I) with L1 afforded [Hg(L1)Br]2[Hg2Br6].2CH2Cl2 6 and [Hg(L1)I(2)] 7, respectively. For 6, the Hg(II) ion in the complex cation has a distorted tetrahedral coordination environment composed of S2N donor atoms from L1 and a bromo ligand. In 7 the coordination geometry is highly distorted tetrahedral, with the macrocycle coordinating in an exodentate manner via one S and one N atom. The remaining two coordination sites are occupied by iodide ions. [Hg(L1)(ClO4)]ClO4 8 was isolated from the reaction of Hg(ClO4)2 and L1. The X-ray structure reveals that all macrocyclic ring donors bind to the central mercury ion in this case, with the latter exhibiting a highly distorted octahedral coordination geometry. The O2S2-donors from the macrocyclic ring define the equatorial plane while the axial positions are occupied by the ring nitrogen as well as by an oxygen from a monodentate perchlorato ion. Reaction of Cd(NO3)(2).4H2O with L1 afforded [Cd(L1)(NO3)2](.)0.5CH2Cl2 9 in which L1 acts as a tridentate ligand, binding exo-fashion via its S2N donors. The remaining coordination positions are filled by two bidentate nitrate ions such that, overall, the cadmium is seven-coordinate. Reactions of HgX2(X = Br or I) with L2 yielded the isostructural 2 : 1 (metal : ligand) complexes, [Hg2(L2)Br4] 10 and [Hg2(L2)I(4)] 11. Each mercury ion has a distorted tetrahedral environment made up of S and N donors from an exodentate L2 and two coordinated halides. Contrasting with this, the reaction of L2 with Cd(NO3)(2).4H2O yielded a 1-D coordination network, {[Cd2(L2)(NO3)4].2CH2Cl2}n 12 in which each ring of L2 is exo-coordinated via two S atoms and one N atom to a cadmium ion which is also bound to one monodentate and one bidentate nitrate anion. The latter also has one of its oxygen atom attached to a neighboring cadmium via a nitroso (mu2-O) bridge such that the overall coordination geometry about each cadmium is seven-coordinate. The [Cd(L2)0.5(NO3)2] units are linked by an inversion to yield the polymeric arrangement.

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Recently, many efforts have been devoted to design and construction of fluorescent chemosensors that are capable of detecting metal ions. [1][2][3][4][5] In many cases, the fluorescent chemosensors have been made through the combination of a receptor molecule and a fluorophore. Owing to their selective complexation with metal species, macrocyclic ligands make them ideal candidates for the receptor molecules. However, the introduction of such cyclic receptors is often limited by high cost and the synthetic complexity. The alternate way to avoid such limitations is to develop the acyclic analogues for the cyclic receptors. Our interest has focused on the dipodal receptors containing quinoline moiety because this receptor has shown not only similar behaviors with cyclic receptors, 6,7 and the unique coordination ability for some transition metal ions 8,9 but also been synthesized easily in high yields. 10 Recently, we reported the unique pseudo-cyclic Cd(II) complexes, in which the dipodal receptor with quinoline end-groups wraps around the cadmium atom in a helical manner. 9 In connection with this reason, we have synthesized N-anthracenylmethyl dipodal receptor (L) with quinoline end-groups and have further carried out the exploration of its complexation and metal-induced fluorescence properties.In the synthesis of L (see Scheme 1), the starting material 2 was prepared as previously reported.11 The synthetic procedures for 3-6 are represented in the Supporting Information. L was prepared by the reaction of 6 and 9-chloromethylanthracene in CH 3 CN in the presence of K 2 CO 3 and KI under reflux condition. Purification by column chromatography afforded L as a yellow oil in 63% yield. This ligand was fully characterized by conventional methods.The photophysical properties of L were measured in CH 3 CN. In fluorescent spectrum of free L, upon excitation at 367 nm, typical emission bands from anthracene moiety were observed at 399, 419 and 442 nm. The quantum yield of fluorescence was determined as ca. 0.10 using 9-methylanthracene (0.284) as a reference compound. This fact would imply that quenching occurs in L, which might suggest that there was an effective quenching of the excited state of fluorophore by the receptor moiety, via photoinduced electron transfer (PET) before addition of metal ions (prior to metal ion recognition). Scheme 1. Synthesis of the dipodal fluorophore L.

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