Paper SS-ThP17
Analyte Binding to CoPc: A Comparison of Analyte Binding Strength and Basicity

Thursday, October 18, 2007, 5:30 pm, Room 4C

A recent study has shown a strong correlation between analyte electron donor ability and chemiresistive Cobalt phthalocyanine (CoPc) sensor response.¹ The -H_BF3 scale method was used as a measure of the electron pair donor ability of the 10 analytes investigated.² It is speculated that sensor response is dictated by the degree of charge transfer in CoPc-analyte complexes as opposed to analyte binding strength. To investigate this hypothesis, the binding strength of these electron donating analytes (acetonitrile being the weakest and triethylamine the strongest electron donor) to the Co metal of CoPc was calculated using density functional theory. Subsequently, the atomic charges of the CoPc and CoPc-analyte complex will be analyzed to measure the degree of charge transfer between the analyte and Co metal. The interaction of a neurotoxin analogue, dimethyl methylphosponate (DMMP) with CoPc is also being investigated to determine the potential for use of CoPc sensors to detect organophosphate neurotoxins. Preliminary DFT simulations show that although O₂ binding to the Co metal is weak (less than -0.1 eV exothermic), a large effect on the CoPc electronic structure and charge transfer is observed. Weak analyte-MPc binding with a large change in electronic structure are the key properties of a good sensor because a reversible absorption will result in a large change the conductivity of the MPc film.

¹ F. Bohrer, A. Sharoni, C. N. Colesniuc, J. Park, I. K. Schuller, A. Kummel, and W. C. Trogler, Journal of the American Chemical Society submitted (2007).
² P. C. Maria and J. F. Gal, Journal of Physical Chemistry 89 (7), 1296 (1985).