Journal article
Surface directed reversible imidazole ligation to nickel(ii) octaethylporphyrin at the solution/solid interface: a single molecule level study
Physical chemistry chemical physics : PCCP, Vol.18(30), pp.20819-20829
07/27/2016
Handle:
https://hdl.handle.net/2376/110117
PMID: 27416994
Abstract
Scanning tunneling microscopy (STM) is used to study for the first time the reversible binding of imidazole (Im) and nickel(ii) octaethylporphyrin (NiOEP) supported on highly oriented pyrolytic graphite (HOPG) at the phenyloctane/NiOEP/HOPG interface at 25 °C. The ligation of Im to the NiOEP receptor while not observed in fluid solution is readily realized at the solution/HOPG interface. The coordination process scales with increasing Im concentration and can be effectively modeled by the Langmuir isotherm. At room temperature it is determined that the standard free energy of adsorption is ΔGc = -15.8 kJ mol(-1) and the standard enthalpy of adsorption is estimated to be ΔHc ≈ -80 kJ mol(-1). The reactivity of imidazole toward NiOEP adsorbed on HOPG is attributed to charge donation from the graphite stabilizing the Im-Ni bond. This charge transfer pathway is supported by molecular and periodic modeling calculations which indicate that the Im ligand behaves as a π-acceptor. DFT calculations also show that the nickel ion in the Im-NiOEP/HOPG complex is in a singlet ground state. This is surprising since both our calculations and previous experimental studies find a triplet ground state for the five and six coordinated Im-nickel(ii) porphyrins in the gas-phase or in solution. Both the experimental and the theoretical findings provide information that is useful for better understanding of chemical sensing/recognition and catalytic processes that utilize metal-organic complexes adsorbed on surfaces where the reactivity of the metal is moderated by the substrate.
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Details
- Title
- Surface directed reversible imidazole ligation to nickel(ii) octaethylporphyrin at the solution/solid interface: a single molecule level study
- Creators
- Goutam Nandi - Department of Chemistry and Materials Science and Engineering Program, Washington State University, Pullman, Washington 99164-4630, USA. umazur@wsu.edu hipps@wsu.eduBhaskar Chilukuri - Department of Chemistry and Materials Science and Engineering Program, Washington State University, Pullman, Washington 99164-4630, USA. umazur@wsu.edu hipps@wsu.eduK W Hipps - Department of Chemistry and Materials Science and Engineering Program, Washington State University, Pullman, Washington 99164-4630, USA. umazur@wsu.edu hipps@wsu.eduUrsula Mazur - Department of Chemistry and Materials Science and Engineering Program, Washington State University, Pullman, Washington 99164-4630, USA. umazur@wsu.edu hipps@wsu.edu
- Publication Details
- Physical chemistry chemical physics : PCCP, Vol.18(30), pp.20819-20829
- Academic Unit
- Chemistry, Department of
- Publisher
- England
- Identifiers
- 99900547299401842
- Language
- English
- Resource Type
- Journal article