Mixed-Metal Coordination Polymers and Molecular Squares Based on a Ferrocene-Containing Multidentate Ligand 1,2-Di(4-pyridylthio)ferrocene

Various metalloligands and inorganic–organic hybrid bridging ligands have been incorporated in polynuclear complexes and bimetallic coordination polymers. Ferrocene, exhibiting redox activity and facile chemical modification, is a versatile metalloligand component. However, most metal complexes with ferrocene-containing ligands form discrete low-dimensional chelate complexes or coordination polymers. Thus, we designed and synthesized ferrocene-based multidentate ligands, 1,2-di­(4-pyridylthio)­ferrocene (<b>L1</b>) and 1,2-di­(2-pyridylthio)­ferrocene (<b>L2</b>). Here we report the synthesis and structures of molecular square complexes and coordination polymers containing <b>L1</b>, which reacted with M­(hfac)₂ (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate) and AgCF₃SO₃ to yield molecular square complexes [M­(hfac)₂­(<b>L1</b>)]₂­·2C₆H₅CH₃ [M = Ni (<b>1</b>) and Co (<b>2</b>)] and [Ag­(CF₃SO₃)­(<b>L1</b>)­(H₂O)_0.5]₂­·2CH₂Cl₂·H₂O (<b>3</b>). The molecular square units comprise two metal ions bridged by two ligands. Isomorphic complexes <b>1</b> and <b>2</b> accommodate two toluene molecules above and below the molecular square. <b>L1</b> reacted with Cu­(hfac)₂ and CuI to yield zigzag, {[Cu­(hfac)₂(<b>L1</b>)]}_<i>n</i>­·0.25<i>n</i>(CH₂Cl₂) (<b>4</b>), and ribbon-shaped, {[Cu₄I₄(<b>L1</b>)₂]}_<i>n</i> (<b>5</b>), coordination polymers. In <b>4</b>, <b>L1</b> behaves as a bidentate <i>N</i>,<i>N</i>-ligand bridging the Cu^II ions, while in <b>5</b> it acts as a tridentate <i>S</i>,<i>N</i>,<i>N</i>-ligand linking the stepped-cubane Cu₄I₄ units. <b>L1</b> reacted with AgX to form two-dimensional coordination polymers {[Ag­(ClO₄)­(<b>L1</b>)]}_<i>n</i> (<b>6</b>) and {[Ag­(<b>L1</b>)]­PF₆}_<i>n</i> (<b>7</b>), in which it acted as a tetradentate <i>S</i>,<i>S</i>,<i>N</i>,<i>N</i>-ligand. These complexes have topologies based on multidentate coordination of 1,2-substituted <b>L1</b>

Flupyrimin: A Novel Insecticide Acting at the Nicotinic Acetylcholine Receptors

A novel chemotype insecticide flupyrimin (FLP) [<i>N</i>-[(<i>E</i>)-1-(6-chloro-3-pyridinylmethyl)­pyridin-2­(1<i>H</i>)-ylidene]-2,2,2-trifluoroacetamide], discovered by Meiji Seika Pharma, has unique biological properties, including outstanding potency to imidacloprid (IMI)-resistant rice pests together with superior safety toward pollinators. Intriguingly, FLP acts as a nicotinic antagonist in American cockroach neurons, and [³H]­FLP binds to the multiple high-affinity binding components in house fly nicotinic acetylcholine (ACh) receptor (nAChR) preparation. One of the [³H]­FLP receptors is identical to the IMI receptor, and the alternative is IMI-insensitive subtype. Furthermore, FLP is favorably safe to rats as predicted by the very low affinity to the rat α4β2 nAChR. Structure–activity relationships of FLP analogues in terms of receptor potency, featuring the pyridinylidene and trifluoroacetyl pharmacophores, were examined, thereby establishing the FLP molecular recognition at the <i>Aplysia californica</i> ACh-binding protein, a suitable structural surrogate of the insect nAChR. These FLP pharmacophores account for the excellent receptor affinity, accordingly revealing differences in its binding mechanism from IMI