title: Cavitands incorporating a Lewis acid dinickel chelate function as receptors for halide anions.
abstract: The halide binding properties of the cavitand [Ni2(L(Me2H4))](2+) (4) are reported. Cavitand 4 exhibits a chelating N3Ni(μ-S)2NiN3 moiety with two square-pyramidal Ni(II)N3S2 units situated in an anion binding pocket of ∼4 Å diameter formed by the organic backbone of the (L(Me2H4))(2-) macrocycle. The receptor reacts with fluoride, chloride (in MeCN/MeOH), and bromide (in MeCN) ions to afford an isostructural series of halogenido-bridged complexes [Ni2(L(Me2H4))(μ-Hal)](+) (Hal = F(-) (5), Cl(-) (6), and Br(-) (7)) featuring a N3Ni(μ-S)2(μ-Hal)NiN3 core structure. No reaction occurs with iodide or other polyatomic anions (ClO4(-), NO3(-), HCO3(-), H2PO4(-), HSO4(-), SO4(2-)). The binding events are accompanied by discrete UV-vis spectral changes, due to a switch of the coordination geometry from square-pyramidal (N3S2 donor set in 4) to octahedral in the halogenido-bridged complexes (N3S2Hal donor environment in 5-7). In MeCN/MeOH (1/1 v/v) the log K11 values for the 1:1 complexes are 7.77(9) (F(-)), 4.06(7) (Cl(-)), and 2.0(1) (Br(-)). X-ray crystallographic analyses for 4(ClO4)2, 4(I)2, 5(F), 6(ClO4), and 7(Br) and computational studies reveal a significant increase of the intramolecular distance between two propylene groups at the cavity entrance upon going from F(-) to I(-) (for the DFT computed structure). In case of the receptor 4 and fluorido-bridged complex 5, the corresponding distances are nearly identical. This indicates a high degree of preorganization of the [Ni2(L(Me2H4))](2+) receptor and a size fit mismatch of the receptor binding cavity for anions larger than F(-).
authors.affiliation: †Institut für Anorganische Chemie, Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Jeremies
authors.affiliation: †Institut für Anorganische Chemie, Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Lehmann
authors.affiliation: †Institut für Anorganische Chemie, Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany.
authors.forename: Sina
authors.initials: S
authors.lastname: Gruschinski
authors.affiliation: †Institut für Anorganische Chemie, Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany.
authors.forename: Frederik
authors.initials: F
authors.lastname: Schleife
authors.affiliation: ‡Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB), UMR CNRS 6302, 9, avenue Alain Savary, BP 47870, 21078 Dijon Cedex, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Meyer
authors.affiliation: §Research Institute for Physical Chemical Problems, Belarusian State University, Leningradskaya 14, 220030 Minsk, Belarus.
authors.forename: Vitaly
authors.initials: V
authors.lastname: Matulis
authors.affiliation: ∥Belarusian State University, 4 Nezavisimisti avenue, 220050 Minsk, Belarus.
authors.forename: Oleg A
authors.initials: OA
authors.lastname: Ivashkevich
authors.affiliation: †Institut für Anorganische Chemie, Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany.
authors.forename: Marcel
authors.initials: M
authors.lastname: Handke
authors.affiliation: †Institut für Anorganische Chemie, Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany.
authors.forename: Karolin
authors.initials: K
authors.lastname: Stein
authors.affiliation: †Institut für Anorganische Chemie, Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany.
authors.forename: Berthold
authors.initials: B
authors.lastname: Kersting