Jeremies Alexander, Lehmann Ulrike, Gruschinski Sina, Schleife Frederik, Meyer Michel, Matulis Vitaly, Ivashkevich Oleg A, Handke Marcel, Stein Karolin, Kersting Berthold
†Institut für Anorganische Chemie, Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany.
‡Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB), UMR CNRS 6302, 9, avenue Alain Savary, BP 47870, 21078 Dijon Cedex, France.
Inorg Chem. 2015 Apr 20;54(8):3937-50. doi: 10.1021/acs.inorgchem.5b00123. Epub 2015 Apr 6.
The halide binding properties of the cavitand Ni2(L(Me2H4)) (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)) receptor and a size fit mismatch of the receptor binding cavity for anions larger than F(-).
