Competitive Transmetalation of First-Row Transition-Metal Ions between Trinuclear Triple-Stranded Side-by-Side Helicates.

A hybrid tris-bidentate neutral ligand (L) composed of a central 2,2'-bipyridine and two terminal triazolyl-pyridine chelating units connected by methylene spacers is employed to synthesize trinuclear triple-stranded side-by-side helicates of first-row transition-metal(II) ions. Three such new homometallic helicates LM(OTf) [ M = Cu (4); Ni (5); Co (6)], along with our recently reported helicates LFe(OTf) (1), LZn(OTf) (2), and LFeZn(OTf) (3) are taken into consideration for competitive formation and transmetalation studies. Single-crystal X-ray structures of LCu(OTf) (4) and LNi(OTf) (5) show the formation of trinuclear triple-stranded side-by-side helicates with alternating Λ and Δ chiralities at the metal ions as earlier observed in cases of LFe(OTf) (1), LZn(OTf) (2), and LFeZn(OTf) (3).

Polyamide-Polyamine Cryptand as Dicarboxylate Receptor: Dianion Binding Studies in the Solid State, in Solution, and in the Gas Phase.

Polyamide-polyamine hybrid macrobicycle L is explored with respect to its ability to bind α,ω-dicarboxylate anions. Potentiometric studies of protonated L with the series of dianions from succinate (suc) through glutarate (glu), α-ketoglutarate (kglu), adipate (adi), pimelate (pim), suberate (sub), to azelate (aze) have shown adipate preference with association constant value of K = 4900 M in a HO/DMSO (50:50 v/v) binary solvent mixture. The binding constant increases from glu to adi and then continuously decreases with the length of the anion chain.

Threading of various 'U' shaped bidentate axles into a heteroditopic macrocyclic wheel via Ni/Cu templation.

The threading of 'U' shaped bent axles having diverse functionalities (Axle1-Axle10) is investigated by using a heteroditopic amido-amine macrocyclic (MC) wheel via Ni or Cu metal ion templation. These bent shaped axles are the derivatives of 4,4'-substituted 2,2'-bipyridine, which are composed of various terminal groups like alkene, alkyne, bromide, hydroxyl and azide. Such metallo [2]pseudorotaxanes are well characterised by ESI-MS, EPR and FT-IR spectroscopic studies, UV-Vis absorption studies, elemental analysis and single-crystal X-ray diffraction studies wherever possible.

Selective recognition and extraction of KBr via cooperative interactions with a urea functionalized crown ether dual-host.

Selective solid-liquid extraction of KBr is demonstrated for the first time with a crown ether based pentafluorophenyl urea functionalized dual-host receptor. (1)H-NMR and ITC studies have been carried out to illustrate the effect of cooperativity towards the recognition of alkali metal salts.

Formation and Transmetalation Mechanisms of Homo- and Heterometallic (Fe/Zn) Trinuclear Triple-Stranded Side-by-Side Helicates.

A novel linear hybrid tris-bidentate neutral ligand having 2,2'-bipyridine and two terminal triazolylpyridine coordination sites (L) was efficiently synthesized and explored in the synthesis of trinuclear triple-stranded homometallic side-by-side helicates L3Fe3(OTf)6 (1) and L3Zn3(OTf)6 (2), in which the three metal centers display alternating Λ and Δ configurations. Selective formation of the analogous heterometallic side-by-side helicate L3Fe2Zn(OTf)6 (3) was achieved from a mixture of L, Fe(CH3CN)2(OTf)2, and Zn(OTf)2 (1:1:1) in acetonitrile at room temperature. Various analytical techniques, i.

Encapsulation of [(SO₄)₄(H₂O)1₁₂]⁸⁻ clusters in a metal organic framework of pyridyl functionalized cyanuric acid based tris-urea.

Encapsulation of hydrated sulfate in a bowl-shaped metal organic coordination polymer formed by Zn(2+) assisted self-assembly of a 3-pyridyl terminated cyanuric acid platform based urea receptor is reported in aqueous medium. Trapping of an unusual [(SO4)4(H2O)12](8-) cluster in a [Zn(H2O)6](2+) capped self-assembled structure is characterized by single crystal X-ray crystallography. Furthermore, selective binding of SO4(2-) is established from the (1)H-NMR titration study.

[2]Rotaxane with multiple functional groups.

High-yield syntheses of Cu(II)- and Ni(II)-templated [2]pseudorotaxane precursors (CuPRT and NiPRT, respectively) were achieved by threading bis(azide)bis(amide)-2,2'-bipyridine axle into a bis(amide)tris(amine) macrocycle. Single-crystal X-ray structural analysis of CuPRT revealed complete threading of the axle fragment into the wheel cavity, where strong aromatic π-π stacking interactions between two parallel arene moieties of the wheel and the pyridyl unit of axle are operative in addition to metal ion templation. Attachment of a newly developed bulky stopper molecule with a terminal alkyne to CuPRT via a Cu(I)-catalyzed azide-alkyne cycloaddition reaction failed as a result of dethreading of the azide-terminated axle under the reaction conditions.

Synthesis of a preorganized hybrid macrobicycle with distinct amide and amine clefts: tetrahedral versus spherical anions binding studies.

A new C3v symmetric amido-amine hybrid macrobicycle, L is synthesized toward anion recognition in its protonated states. L contains tri-amide and tetra-amine clefts separated by p-phenylene spacers. The solid-state structure of methanol-encapsulated L exhibits an overall cavity length of ~12.

Selective recognition of sulphate in a Cu(II) assisted 1D polymer of a simple pentafluorophenyl substituted pyridyl-urea via second sphere coordination.

A pentafluorophenyl (–C6F5) substituted 3-pyridyl urea, L(1), is explored extensively to demonstrate SO4(2-) binding exclusively via second sphere coordination in the cavity of a 1D polymeric self-assembly of L(1), selectively assisted by Cu2+. A single crystal X-ray diffraction study depicts SO4(2-) encapsulation in the C2 symmetric cleft via nine hydrogen bonding interactions contributed by eight urea protons of four L(1) moieties in [CuL(1)4(DMF)2]SO4 (1). To revalidate the importance of Cu2+ selective anion coordination via exclusive second sphere coordination, a complex of L(1) and Cu(NO3)2, i.

A series of amino acid functionalized tripodal hexaamide anion receptors: ion-pair-assisted capped-cleft formation by a pentafluorophenyl-functionalized amide.

A new series of tris(2-aminoethyl)amine (tren)-based L-alanine amino acid backboned tripodal hexaamide receptors (L1-L5) with various attached moieties based on electron-withdrawing fluoro groups and lipophilicity have been synthesized and characterized. Detailed binding studies of L1-L5 with different anions, such as halides (F(-), Cl(-), Br(-), and I(-)) and oxyanions (AcO(-), BzO(-) (Bz=benzoyl), NO(3)(-), H(2)PO(4)(-), and HSO(4)(-)), have been carried out by isothermal titration calorimetric (ITC) experiments in acetonitrile/dimethylsulfoxide (99.5:0.