Title

Understanding Ion Sensing in Zn(II) Porphyrins: Spectroscopic and Computational Studies of Nitrite/Nitrate Binding

Document Type

Article

Publication Date

2012

Digital Object Identifier (DOI)

https://doi.org/10.1021/ic300039v

Abstract

The development of effective sensor elements relies on the ability of a chromophore to bind an analyte selectively and then study the binding through changes in spectroscopic signals. In this report the ability of Zn(II) Tetraphenyl Porphyrin (ZnTPP) to selectively bind nitrite over nitrate ions is examined. The results of Benesi–Hildebrand analysis reveals that ZnTPP binds NO2– and NO3– ions with association constants of 739 ± 70 M–1 and 134 ± 15 M–1, respectively. Interestingly, addition of a pyridine ligand to the fifth coordination site of the Zn(II) center enhances ion binding with the association constants increasing to 71,300 ± 8,000 M–1 and 18,900 ± 3,000 M–1 for nitrite and nitrate, respectively. Density functional theory calculations suggest a binding mechanism through which Zn(II)–porphyrin interactions are disrupted by ligand and base coordination to Zn(II), with Zn(II) having more favorable overlap with nitrite orbitals, which are less delocalized than nitrate orbitals. Overall, these provide new insights into the ability to tune the affinity and selectivity of porphyrin based sensors utilizing electronic factors associated with the central Zn(II) ion.

Was this content written or created while at USF?

Yes

Citation / Publisher Attribution

Inorganic Chemistry, v. 51, issue 8, p. 4756-4762

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