TY - JOUR
T1 - Probing surface-porphyrazine reduction potentials by molecular design
AU - Sun, Peng
AU - Zong, Hong
AU - Salaita, Khalid
AU - Ketter, Jacob B.
AU - Barrett, Anthony G.M.
AU - Hoffman, Brian M.
AU - Mirkin, Chad A.
N1 - Copyright:
Copyright 2015 Elsevier B.V., All rights reserved.
PY - 2006/9/21
Y1 - 2006/9/21
N2 - This manuscript reports electrochemical and angle-resolved X-ray photoelectron spectroscopy measurements of surface-bound porphyrazine monolayers in which the molecule-surface distance and molecular orientation of the porphyrazine are controlled through the design of the adsorbates. This system has allowed us to probe the importance of molecule-surface interaction in determining the shift in reduction potential upon binding to a gold surface. This quantity currently is in theoretical dispute, with one computation indicating that a porphyrazine/porphyrin exhibits an extremely large covalent binding energy (∼10 eV) to a gold surface, whereas a more recent one finds the binding energy to be only a fraction of an electronvolt. Our study indicates that the shift in reduction potential upon surface binding is not a discontinuous function of the molecule-surface distance, as would be the case if covalent interaction of the porphyrazine core with the gold surface were controlling, but rather varies smoothly. This, therefore, rules out the possibility that the large potential shift seen for a porphyrazine whose macrocyclic core lies ∼3.9 Å above the gold surface, relative to one that lies ∼8.9 Å above the surface, ΔΔE = 340 mV, is caused by direct covalent binding of the π-system to the metal surface.
AB - This manuscript reports electrochemical and angle-resolved X-ray photoelectron spectroscopy measurements of surface-bound porphyrazine monolayers in which the molecule-surface distance and molecular orientation of the porphyrazine are controlled through the design of the adsorbates. This system has allowed us to probe the importance of molecule-surface interaction in determining the shift in reduction potential upon binding to a gold surface. This quantity currently is in theoretical dispute, with one computation indicating that a porphyrazine/porphyrin exhibits an extremely large covalent binding energy (∼10 eV) to a gold surface, whereas a more recent one finds the binding energy to be only a fraction of an electronvolt. Our study indicates that the shift in reduction potential upon surface binding is not a discontinuous function of the molecule-surface distance, as would be the case if covalent interaction of the porphyrazine core with the gold surface were controlling, but rather varies smoothly. This, therefore, rules out the possibility that the large potential shift seen for a porphyrazine whose macrocyclic core lies ∼3.9 Å above the gold surface, relative to one that lies ∼8.9 Å above the surface, ΔΔE = 340 mV, is caused by direct covalent binding of the π-system to the metal surface.
UR - http://www.scopus.com/inward/record.url?scp=33749595385&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33749595385&partnerID=8YFLogxK
U2 - 10.1021/jp065089v
DO - 10.1021/jp065089v
M3 - Article
C2 - 16970430
AN - SCOPUS:33749595385
VL - 110
SP - 18151
EP - 18153
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
SN - 1520-6106
IS - 37
ER -