Cyclic and open-chain aza–oxa ferrocene-functionalised derivatives as receptors for the selective electrochemical sensing of toxic heavy metal ions in aqueous environments

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José M. Lloris, Ramón Martínez-Máñez, Miguel E. Padilla-Tosta, Teresa Pardo, Juan Soto, Paul D. Beer, James Cadman and David K. Smith


Abstract

A new family of aza–oxa open-chain and macrocyclic molecules functionalised with ferrocenyl groups have been synthesized and characterised. The crystal structures of the [HL1][PF6], [H2L3][PF6]2, [H2L4][PF6]2 and [H2L5][PF6]2 salts have been determined by single crystal X-ray procedures {L1 = 10-ferrocenylmethyl-1,4,7-trioxa-10-azacyclododecane, L3 = 7,13-bis(ferrocenyl)-1,4,10-trioxa-7,13-diazacyclopentadecane, L4 = 1,8-bis[bis(ferrocenylmethylamino)]-3,6-dioxaoctane, L5 = 1,8-bis(ferrocenylmethylamino)-3,6-dioxaoctane}. They consist of cationic protonated amines linked via ionic interactions with hexafluorophosphate anions. Additionally hydrogen-bonding interactions have also been found. The receptors have been designed to promote discrimination, using electrochemical techniques, between toxic heavy metal ions such as Hg2+ over other commonly water present cations in aqueous environments. The presence in the receptors of oxygen and nitrogen donor atoms has been used to control the selectivity of large metal ions over small ones. Potentiometric and electrochemical studies have been mainly carried out to find pH ranges of selective electrochemical recognition. Potentiometric titrations were carried out in water (25 °C, 0.1 mol dm–3 potassium perchlorate) for L1 and L2 [1,1′-(5,8-dioxa-2,11-diazadodecane-1,12-diyl)ferrocene] and in 1,4-dioxane–water (25 °C, 0.1 mol dm–3 potassium nitrate) for L3 and L5 with Ni2+, Cu2+, Zn2+, Cd2+, Pb2+ and Hg2+. All receptors show larger stability constants with Hg2+ than with the remaining metal ions studied. This is especially so for L1 and L2. The receptors L1, L2 and L5 are able electrochemically and selectively to sense the presence of Hg2+, whereas maximum electrochemical shifts are produced in L3 upon addition of Pb2+. Of importance is the large and selective electrochemical shift monitored in water for L2 and Hg2+ with an anodic displacement of the oxidation potential of ca. 130 mV which is one of the largest shifts ever reported in electrochemical cation sensing in water using related receptors. A good agreement has been found between potentiometric and electrochemical results. Selective electrochemical response against Hg2+ appears to be associated with (i) pH ranges of selective complexation or (ii) the existence of strong predominant receptor–metal complexes in a wide pH range. Additionally the electrochemical behaviour of receptors L1 and L2 in the presence of metal ions can be roughly predicted from potentiometric data. The stability constants of the complexes between L1 and Cu2+, Cd2+, Pb2+ and Hg2+ were also determined in the presence of Cl. Whereas there is no important change in the stability constants of the L–H+–M2+ systems when M2+ = Cu2+, Cd2+ or Pb2+, there is a decrease of the co-ordination ability of L1 towards Hg2+. This is also reflected in electrochemical studies which demonstrate that [Hg(L1)]2+ electrochemically sense Cl at pH 7. To the best of our knowledge this is the first time it has been shown that metal complexes functionalised with ferrocenyl groups can electrochemically sense anions.


References

  1. P. D. Beer, Chem. Soc. Rev., 1989, 18, 409 RSC; Adv. Inorg. Chem., 1992, 39, 79 Search PubMed; Acc. Chem. Res., 1998, 31, 71 Search PubMed.
  2. A. W. Czarnik, Acc. Chem. Res., 1994, 27, 302 CrossRef CAS; V. Balzani and F. Scandola, Supramolecular Photochemistry, Ellis Horwood, Chichester, 1991 Search PubMed.
  3. J. C. Medina, T. T. Goodnow, M. T. Rojas, J. L. Atwood, B. C. Lynn, A. E. Kaifer and G. W. Gokel, J. Am. Chem. Soc., 1992, 114, 10583 CrossRef CAS.
  4. P. D. Beer, Z. Chen, M. G. B. Drew, J. Kingston, M. Ogden and P. Spencer, J. Chem. Soc., Chem. Commun., 1993, 1046 RSC.
  5. A. Benito, J. Cano, R. Martínez-Máñez, J. Soto, J. Payá, F. Lloret, M. Julve, J. Faus and M. D. Marcos, Inorg. Chem., 1993, 32, 1197 CrossRef CAS.
  6. G. De Santis, L. Fabbizzi, M. Licchelli and P. Pallavicini, Inorg. Chim. Acta, 1994, 225, 239 CrossRef CAS.
  7. M. J. L. Tendero, A. Benito, J. Cano, J. M. Lloris, R. Martínez-Máñez, J. Soto, A. J. Edwards, P. R. Raithby and M. A. Rennie, J. Chem. Soc., Chem. Commun., 1995, 1643 RSC.
  8. A. Ori and S. Shinkai, J. Chem. Soc., Chem. Commun., 1995, 1771 RSC.
  9. C. Dusemund, K. R. A. S. Sandanayake and S. Shinkai, J. Chem. Soc., Chem. Commun., 1995, 333 RSC.
  10. M. J. L. Tendero, A. Benito, R. Martínez-Máñez, J. Soto, J. Payá, A. J. Edwards and P. R. Raithby, J. Chem. Soc., Dalton Trans., 1996, 343 RSC.
  11. M. J. L. Tendero, A. Benito, R. Matínez-Máñez, J. Soto, E. García-España, J. A. Ramírez, M. I. Burguete and S. V. Luis, J. Chem. Soc., Dalton Trans., 1996, 2923 RSC.
  12. M. J. L. Tendero, A. Benito, R. Martínez-Máñez and J. Soto, J. Chem. Soc., Dalton Trans., 1996, 4121 RSC.
  13. P. D. Beer, Z. Chen, M. G. B. Drew, A. O. M. Johnson, D. K. Smith and P. Spencer, Inorg. Chim. Acta, 1996, 246, 143 CrossRef CAS.
  14. H. Yamamoto, A. Ori, K. Ueda, C. Dusemund and S. Shinkai, Chem. Commun., 1996, 407 RSC.
  15. R. C. Mucic, M. K. Herrlein, C. A. Mirkin and R. L. Letsinger, Chem. Commun., 1996, 555 RSC.
  16. A. Benito, R. Martínez-Máñez, J. Soto and M. J. L. Tendero, J. Chem. Soc., Faraday Trans., 1997, 2175 RSC.
  17. M. E. Padilla-Tosta, R. Martínez-Máñez, T. Pardo, J. Soto and M. J. L. Tendero, Chem. Commun., 1997, 887 RSC.
  18. P. D. Beer, M. G. B. Drew and D. K. Smith, J. Organomet. Chem., 1997, 543, 259 CrossRef CAS.
  19. H. Plenio, D. Burth and R. Vogler, Chem. Ber., 1997, 130, 1405 CrossRef CAS.
  20. A. Benito, J. M. Lloris, R. Martínez-Máñez and J. Soto, Polyhedron, 1998, 17, 491 CrossRef CAS.
  21. J. M. Lloris, R. Martínez-Máñez, T. Pardo, J. Soto and M. E. Padilla-Tosta, Chem. Commun., 1998, 837 RSC.
  22. J. M. Lloris, R. Martínez-Máñez, T. Pardo, J. Soto and M. E. Padilla-Tosta, J. Chem. Soc., Dalton Trans., 1998, 2635 RSC.
  23. J. M. Lloris, R. Martínez-Máñez, M. E. Padilla-Tosta, T. Pardo, J. Soto and M. J. L. Tendero, J. Chem. Soc., Dalton Trans., 1998, 3657 RSC.
  24. J. M. Lloris, A. Benito, R. Martínez-Máñez, M. E. Padilla-Tosta, T. Pardo, J. Soto and M. J. L. Tendero, Helv. Chim. Acta, 1998, 81, 2024 CrossRef CAS.
  25. P. D. Beer, J. Cadman, J. M. Lloris, R. Martínez-Máñez, M. E. Padilla-Tosta, T. Pardo, D. K. Smith and J. Soto, J. Chem. Soc., Dalton Trans., 1999, 127 RSC.
  26. G. Gran, Analyst (London), 1952, 77, 661 RSC; F. J. Rossotti and H. J. Rossotti, J. Chem. Educ., 1965, 42, 375 CrossRef CAS.
  27. P. Gans, A. Sabatini and A. Vacca, J. Chem. Soc., Dalton, Trans., 1985, 1195 RSC.
  28. P. D. Beer and D. K. Smith, J. Chem. Soc., Dalton Trans., 1998, 417 RSC.
  29. SHELXTL, Version 5.03, Siemens Analytical X-Ray Instruments, Madison, WI, 1994.
  30. J. Cano, A. Benito, R. Martínez-Máñez, J. Soto, J. Payá, F. Lloret, M. Julve, M. D. Marcos and E. Sinn, Inorg. Chim. Acta, 1995, 231, 45 CrossRef CAS.
  31. E. Luboch, A. Cygan and J. F. Biernat, Inorg. Chim. Acta, 1983, 68, 201 CrossRef CAS.
  32. K. A. Byriel, K. R. Dunster, L. R. Gahan, C. H. L. Kennard, J. L. Latten and I. L. Swann, Inorg. Chim. Acta, 1993, 205, 191 CrossRef CAS.
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