5.8.2 Diffuse Reflectance Spectra
The diffuse reflectance spectra, taken in the near-infrared region, are in agreement
with the absorption calculated from the ESR spectra.
The calculated energy (from the g values) of the d xz,yz ! d
2
z increases with the
axial coordination in connection with the decrease of g xx,yy in agreement with the
resonance spectrum in Fig. 5.9.
5.9 Chemical Message
At a variance with the CoAcacen, CoPc displays a ground state well suitable to
transfer the unpaired electron to the oxygen molecules, provided the coordination
site is not occupied by other previously coordinated base molecules (e.g., in the bis
adduct [CoPc(4Mepy) 2 ]). This confirms in CoPc the same mechanism of the
oxygen chemisorption as in CoAcacen. The mechanism could be suggested also for
the natural porphyrin complexes, responsible for the modification of the chemisorbed oxygen, which accepts and reversibly returns the unpaired electron.
5.10 The Case of Oxygen Reduction by CoPc Supported
on Inorganic Oxide
The progresses in heterogeneous catalysis with porphyrin-like complexes have
prompted a direct spectroscopic investigation on the catalyst surface [11]. CoPc
supported on ϒ Al 2 O 3 has been investigated in order to understand the role of these
Fig. 5.9 Diffuse reflectance
spectra of __bCoPc …aCoPc
- - -CoPc 4Mepy (a and b are
polymorphous forms where
the a one contains intermolecular axial interaction between
the two Pc rings) [9, 10]
96
5 The Symmetry Properties Describe the Electronic Structure …
The diffuse reflectance spectra, taken in the near-infrared region, are in agreement
with the absorption calculated from the ESR spectra.
The calculated energy (from the g values) of the d xz,yz ! d
2
z increases with the
axial coordination in connection with the decrease of g xx,yy in agreement with the
resonance spectrum in Fig. 5.9.
5.9 Chemical Message
At a variance with the CoAcacen, CoPc displays a ground state well suitable to
transfer the unpaired electron to the oxygen molecules, provided the coordination
site is not occupied by other previously coordinated base molecules (e.g., in the bis
adduct [CoPc(4Mepy) 2 ]). This confirms in CoPc the same mechanism of the
oxygen chemisorption as in CoAcacen. The mechanism could be suggested also for
the natural porphyrin complexes, responsible for the modification of the chemisorbed oxygen, which accepts and reversibly returns the unpaired electron.
5.10 The Case of Oxygen Reduction by CoPc Supported
on Inorganic Oxide
The progresses in heterogeneous catalysis with porphyrin-like complexes have
prompted a direct spectroscopic investigation on the catalyst surface [11]. CoPc
supported on ϒ Al 2 O 3 has been investigated in order to understand the role of these
Fig. 5.9 Diffuse reflectance
spectra of __bCoPc …aCoPc
- - -CoPc 4Mepy (a and b are
polymorphous forms where
the a one contains intermolecular axial interaction between
the two Pc rings) [9, 10]
96
5 The Symmetry Properties Describe the Electronic Structure …