UNIVERSITY COLLEGE DUBLIN � DUBLIN CITY UNIVERSITY � TYNDALL NATIONAL INSTITUTE

This work is supported by Science Foundation Ireland under grant 07/CE/I1147

CuN

N

N

N

C

C

C

C

N N

NN

C

C C

CN

N

N

NCuCu

Transparent PVC membrane

Cu2+/Co2+

Co2+Cu2+

Multifunctional Ionic Liquids and their use in the formation of co-ordinated structures

Andrew Kavanagh, Robert Byrne, Dermot Diamond, Aleksandar RaduCLARITY, The Centre for Sensor Web Technologies,National Centre for Sensor Research,

School of Chemical Sciences,Dublin City University,Ireland.

ACKNOWLEDGEMENT:

This work was supported by DCU Research Career Start Fellowship 2008, Enterprise Ireland (grant 07/RFP/MASF812) and Science Foundation Ireland (grant 07/CE/I1147).

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Raman Shift:(cm -1)

CoDCA CuDCA DCA aq.

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wavenumber:(cm-1)

Co-DCA DCA Cu-DCA M2+ aq.

Fig 4: Vibrational spectra obtained for the complexation of Co2+and Cu2+ to [DCA]-. The primary binding mode of the ligand appears to be end to end bridging through both terminal cyanideNitrogen atoms.

Highlighted above are the cyanide stretches observed in both i) Raman and ii) Infrared Spectroscopy. Upon complexation a new stretch is formed in this region, this new stretch is a function of the electronegativity of the metal2.

Fig 2: A) One of the many possible co-ordinated structures of dicyanamide (DCA)B) As opposed to a colourless IL based membrane, a complex metal ion-[DCA]

membrane is highly coloured, enabling optical detection, eliminating the need for aresponsive chromophore.

C) Multianalyte recognition based on two distinct absorption maxima;By keeping the concentration of Co2+ constant, and incrementally increasing the amount ofCu2+ (left hand side), we have noted an inverse relationship in the absorption maxima. We also noted the same inverse relationship when doing the mirror experiment (right hand side).

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abs

orba

nce:

(a.u

.)wavelength:(nm)

Cu 1 : 1 Co Cu 1 : 10 Co Cu 1 : 25 Co Cu 1 : 50 Co

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abso

rban

ce:(

a.u.

)

w ave length:(nm )

C o 1 : 50 Cu C o 1 : 16 Cu C o 1 : 10 Cu C o 1 : 6 .25 C u C o 1 : 5 Cu C o 1 : 2 .5 C u

Fig 1 :The Ionic Liquids used in this study; i) trihexyltetradecylphosphonium, ii) methyltriisobutyl phosphonium, iii) toluene sulfonate, iv) dodecylbenzene sulfonate, v) dicyanamide and vi) methane sulfonate.

INTRODUCTION:

We have studied the IL [P6,6,6,14][DCA] as a self-indicating, simultaneous,multianalyte recognition system for heavy metal ions such as Cu2+ and Co2+. Whenincorporated into a polymer membrane, this system maintains all these attractivefeatures with the added bonus of the IL now being self-plasticizing.

Other anions mentioned are considered to be “soft” or non-coordinating1. We haveused heat to change the chemistry of these anions, resulting in ion coordination topreviously solvating molecules. These solvating anions have in common a sulfonatemoiety that can co-ordinate to a given heavy metal.2 The formation of these structures has been characterized via UV/Vis and Infrared Spectroscopy.

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wavenumber:(cm-1)

P6,6,6,14

DBSA Co-DBSA Co2+ aq.

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P 6,6,6,14

MeSO3

Cu-MeSO3

Ni-MeSO3

Fig 3:A) The various colours seen upon thermal activation of IL’s containg [DBSA]- and [TOS]-

B) IR spectra obtained for the thermal complexation of i) Co2+ to the [DBSA]- anionand ii) Ni2+ to the [TOS]- anion.The most striking difference appeared at 1200cm-1, which we attributed to one of the contributions of the SO3 group.C) UV/Vis absorption spectra obtained before and after thermal activation of anionsD) IR spectrum obtained for phosphonium IL containing methane sulfonate,which co-ordinates to heavy metals through its sulfonate group. We observed similarIR features at 1200cm-1. REFERENCES:

1. MacFarlane et al; ChemComm, 1905-1917; 20062. Nakamoto, K; Infrared and Raman Spectra of Inorganic and Coordination Compounds, 5th Edition ed.; Wiley: New York, 1997

CONCLUSION:Due to their inherent natural composition, these Ionic liquids have proven to be a good media in which to study co-ordination chemistry.We have demonstrated firstly the multifunctional co-ordination chemistry of theanion [DCA]- used in modern day Ionic Liquids. Adding to this multifunctionality is the plasticizing feature of this system, attributed to the largephosphonium cation.We have also demonstrated the interesting effects of heat on the chemistry of other widely used Ionic Liquids, with possibly some new structures formed.

PC6H13 C6H13

C6H13C14H29

P

H3C C4H9

C4H9C4H9

i) [P6,6,6,14]+ ii) [P1,4,4,4]+

NC

NC

N

v) [ DCA]-

H3C SO3

vi) [MeSO3]-

B.

C.

A. B.

C.

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Δ

[P1,4,4,4][TOS][P6,6,6,14][DBSA]

Ni2+Co2+ Δ Co2+ Ni2+

A.

D.

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rban

ce:(

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.)

wavelength:(nm)

P6,6,6,14

DBSA P

6,6,6,14 TOS

Co-TOS Co-DBSA Co2+ aq.

CH3 S

O

iv) [TOS]-

C12H25 S

O

v) [ DBSA]-

O

O

O

O