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

J M  Lloris; R  Martinez-Manez; M E  Padilla-Tosta; T  Pardo; J  Soto; P D  Beer; J  Cadman; D K  Smith

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

J M Lloris, R Martinez-Manez, M E Padilla-Tosta, T Pardo, J Soto, P D Beer, J Cadman, D K Smith

Chemistry

Research output: Contribution to journal › Article › peer-review

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 {L-1 = 10-ferrocenylmethyl-1,4,7-trioxa-10-azacyclododecane, L-3 = 7,13-bis(ferrocenyl)-1,4,10-trioxa-7,13-diazacyclopentadecane, L-4 = 1,8-bis[bis(ferrocenylmethylamino)]- 3,6-dioxaoctane, L-5 = 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 degrees C, 0.1 mol dm(-3) potassium perchlorate) for L-1 and L-2 [1,1'-(5,8-dioxa-2,11-diazadodecane-1,12-diyl)ferrocene] and in 1,4-dioxane-water (25 degrees C, 0.1 mol dm(-3) potassium nitrate) for L-3 and L-5 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 L-1 and L-2. The receptors L-1, L-2 and L-5 are able electrochemically and selectively to sense the presence of Hg2+, whereas maximum electrochemical shifts are produced in L-3 upon addition of Pb2+. Of importance is the large and selective electrochemical shift monitored in water for L-2 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 L-1 and L-2 in the presence of metal ions can be roughly predicted from potentiometric data. The stability constants of the complexes between L-1 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 L-1 towards Hg2+. This is also reflected in electrochemical studies which demonstrate that [Hg(L-1)](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.

Original language	English
Pages (from-to)	2359-2369
Number of pages	11
Journal	JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS
Issue number	14
Publication status	Published - 1999

Keywords

TRANSITION-METAL
MACROCYCLIC LIGANDS
CHELATING LIGANDS
ANIONIC GUESTS
REDOX
RECOGNITION
WATER
MOLECULES
POLYAZA
CATIONS

Cite this

@article{74f4fdaca4c4421485adeeb699cd74ad,

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

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 {L-1 = 10-ferrocenylmethyl-1,4,7-trioxa-10-azacyclododecane, L-3 = 7,13-bis(ferrocenyl)-1,4,10-trioxa-7,13-diazacyclopentadecane, L-4 = 1,8-bis[bis(ferrocenylmethylamino)]- 3,6-dioxaoctane, L-5 = 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 degrees C, 0.1 mol dm(-3) potassium perchlorate) for L-1 and L-2 [1,1'-(5,8-dioxa-2,11-diazadodecane-1,12-diyl)ferrocene] and in 1,4-dioxane-water (25 degrees C, 0.1 mol dm(-3) potassium nitrate) for L-3 and L-5 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 L-1 and L-2. The receptors L-1, L-2 and L-5 are able electrochemically and selectively to sense the presence of Hg2+, whereas maximum electrochemical shifts are produced in L-3 upon addition of Pb2+. Of importance is the large and selective electrochemical shift monitored in water for L-2 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 L-1 and L-2 in the presence of metal ions can be roughly predicted from potentiometric data. The stability constants of the complexes between L-1 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 L-1 towards Hg2+. This is also reflected in electrochemical studies which demonstrate that [Hg(L-1)](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.",

keywords = "TRANSITION-METAL, MACROCYCLIC LIGANDS, CHELATING LIGANDS, ANIONIC GUESTS, REDOX, RECOGNITION, WATER, MOLECULES, POLYAZA, CATIONS",

author = "Lloris, {J M} and R Martinez-Manez and Padilla-Tosta, {M E} and T Pardo and J Soto and Beer, {P D} and J Cadman and Smith, {D K}",

year = "1999",

language = "English",

pages = "2359--2369",

journal = "JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS",

issn = "1472-7773",

publisher = "The Royal Society of Chemistry",

number = "14",

}

Cyclic and open-chain aza-oxa ferrocene-functionalised derivatives as receptors for the selective electrochemical sensing of toxic heavy metal ions in aqueous environments. / Lloris, J M ; Martinez-Manez, R ; Padilla-Tosta, M E et al.
In: JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS, No. 14, 1999, p. 2359-2369.

Research output: Contribution to journal › Article › peer-review

TY - JOUR

T1 - Cyclic and open-chain aza-oxa ferrocene-functionalised derivatives as receptors for the selective electrochemical sensing of toxic heavy metal ions in aqueous environments

AU - Lloris, J M

AU - Martinez-Manez, R

AU - Padilla-Tosta, M E

AU - Pardo, T

AU - Soto, J

AU - Beer, P D

AU - Cadman, J

AU - Smith, D K

PY - 1999

Y1 - 1999

N2 - 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 {L-1 = 10-ferrocenylmethyl-1,4,7-trioxa-10-azacyclododecane, L-3 = 7,13-bis(ferrocenyl)-1,4,10-trioxa-7,13-diazacyclopentadecane, L-4 = 1,8-bis[bis(ferrocenylmethylamino)]- 3,6-dioxaoctane, L-5 = 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 degrees C, 0.1 mol dm(-3) potassium perchlorate) for L-1 and L-2 [1,1'-(5,8-dioxa-2,11-diazadodecane-1,12-diyl)ferrocene] and in 1,4-dioxane-water (25 degrees C, 0.1 mol dm(-3) potassium nitrate) for L-3 and L-5 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 L-1 and L-2. The receptors L-1, L-2 and L-5 are able electrochemically and selectively to sense the presence of Hg2+, whereas maximum electrochemical shifts are produced in L-3 upon addition of Pb2+. Of importance is the large and selective electrochemical shift monitored in water for L-2 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 L-1 and L-2 in the presence of metal ions can be roughly predicted from potentiometric data. The stability constants of the complexes between L-1 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 L-1 towards Hg2+. This is also reflected in electrochemical studies which demonstrate that [Hg(L-1)](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.

AB - 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 {L-1 = 10-ferrocenylmethyl-1,4,7-trioxa-10-azacyclododecane, L-3 = 7,13-bis(ferrocenyl)-1,4,10-trioxa-7,13-diazacyclopentadecane, L-4 = 1,8-bis[bis(ferrocenylmethylamino)]- 3,6-dioxaoctane, L-5 = 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 degrees C, 0.1 mol dm(-3) potassium perchlorate) for L-1 and L-2 [1,1'-(5,8-dioxa-2,11-diazadodecane-1,12-diyl)ferrocene] and in 1,4-dioxane-water (25 degrees C, 0.1 mol dm(-3) potassium nitrate) for L-3 and L-5 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 L-1 and L-2. The receptors L-1, L-2 and L-5 are able electrochemically and selectively to sense the presence of Hg2+, whereas maximum electrochemical shifts are produced in L-3 upon addition of Pb2+. Of importance is the large and selective electrochemical shift monitored in water for L-2 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 L-1 and L-2 in the presence of metal ions can be roughly predicted from potentiometric data. The stability constants of the complexes between L-1 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 L-1 towards Hg2+. This is also reflected in electrochemical studies which demonstrate that [Hg(L-1)](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.

KW - TRANSITION-METAL

KW - MACROCYCLIC LIGANDS

KW - CHELATING LIGANDS

KW - ANIONIC GUESTS

KW - REDOX

KW - RECOGNITION

KW - WATER

KW - MOLECULES

KW - POLYAZA

KW - CATIONS

M3 - Article

SN - 1472-7773

SP - 2359

EP - 2369

JO - JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS

JF - JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS

IS - 14

ER -