Detalle de: Multi-Ferrocene-Containing Silanols as Redox-Active Anion Receptors

The ability of diferrocenylsilanediol, Fc 2 Si(OH) 2 ( 5 ), and 1,1,3,3-tetraferrocenyldisiloxane-1,3-diol, Fc 2 (HO)Si–O–Si(OH)Fc 2 ( 6 ), to act as new electroactive anion receptors for either acetate or chloride anions has been investigated in solution, in the solid state, and in the gas phase. 1 H NMR spectroscopic titrations with anions reveal that the binding interaction causes chemical-shift perturbations not only in the Si–OH hydrogen-bonding donor motif but also in the ferrocenyl protons of receptors 5 and 6 . Square-wave voltammetric studies evidence that multiferrocenyl silanols 5 and 6 exhibit higher ability for electrochemical sensing of acetate than chloride, since the corresponding half-wave potentials ( E 1/2 ) for the successive ferrocene oxidations display a higher cathodic shift in the presence of such an anion. Furthermore, single-crystal X-ray diffraction analyses of the tetrabutylammonium salts of complexes [Fc 2 Si(OH) 2 ·CH 3 COO] − ( 8 ), [Fc 2 Si(OH) 2 ·Cl] − ( 9 ), [Fc 2 (HO)Si–O–Si(OH)Fc 2 ·CH 3 COO] − ( 10 ), [{Fc 2 (HO)Si–O–Si(OH)Fc 2 } 2 ·CH 3 COO] − ( 11 ), and [Fc 2 (HO)Si–O–Si(OH)Fc 2 ·Cl] − ( 12 ) confirm that redox-active silanol receptors 5 and 6 can bind the acetate and chloride anions in the solid state. Electronic structure calculations were carried out for 5 to explore the intrinsic ability of the silanediol group to bind these anions in a vacuum.