Multichannel recognition of hydrogen sulphate anion by a Zn(II)–triazole–pyridine complex bearing a ferrocenyl pendant

Abstract

Receptors ferrocene–triazole–pyridine triads assembled with Zn(II) or Cd(II) metal cations behave as chemosensor molecules for HSO₄ ⁻  anions through electrochemical and optical channels: the redox peak of the ferrocene/ferrocenium redox couple is shifted cathodically by 72–53 mV, and a new absorption band appeared in the UV–vis spectrum upon complexation with the HSO₄ ⁻  anion. Association constants, detection limits and stoichiometries of the recognition processes have been determined, whereas ¹H NMR experiments and density functional theory calculations are used to suggest the plausible binding mode taking place in the new supramolecular assembly formed.

Keywords:

• ferrocene
• triazole
• pyridine
• chemosensor
• hydrogensulphate

Acknowledgements

We gratefully acknowledge the financial support MICINN-Spain (Project CTQ 2011/27175) and Fundación Séneca (Agencia de Ciencia y Tecnología de la Región de Murcia) project 04509/GERM/06 (Programa de Ayudas a Grupos de Excelencia de la Región de Murcia, Plan Regional de Ciencia y Tecnología 2007/2010).

Notes

^1. OSWV technique has been employed to obtain well-resolved potential information, while the individual redox process is poorly resolved in the CV experiments in which individual E _1/2 potential cannot be easily or accurately extracted from the data.

^2. Specfit/32 Global Analysis System, 1999–2004, Spectrum Software Associates ([email protected]). The Specfit program was acquired from Bio-logic, S.A. (Claix (Grenoble), France) (www.bio-logic.info) in January 2005.

^3. In the inner part of the intermetallic axis, the hydrogenosulphate O–Zn bond (d _O–Zn = 2.114 Å; WBI = 0.199; LBO = 0.580; ) is stronger than the triflate O–Zn bond (d _O–Zn = 2.196 Å; WBI = 0.172; LBO = 0.488; ).

^4. ORCA – an ab initio, DFT and semiempirical SCF-MO package. Written by Neese, F., Max Planck Institute for Bioinorganic Chemistry, D-45470 Mülheim/Ruhr, 2012. Version 2.9.0. Web page: http://www.mpibac.mpg.de/bac/logins/neese/description.php.

^5. Loose convergence criteria for optimisations in ORCA: energy change 3.0 × 10^− 5 hartree; maximum gradient 2.0 × 10^− 3 hartree/a ₀; RMS gradient 5.0 × 10^− 4 hartree/a ₀; maximum displacement 1.0 × 10^− 2 a ₀; RMS displacement 7.0 × 10^− 3 a ₀.