420
P. P. Roma´ nczyk and S. S. Kurek
to the terminal S-ligand increases the oxidation potential by ∼130 mV. However, the
main alkylene chain orientation change, accompanied by the Fe–S–C–C dihedral
angle variation, induced by the H-bond formation, cannot be excluded, which also
may affect the reduction potential.
We note that such geometrical effects can considerably alter the reduction potential, examples of which are salen-type Cu(II) complexes (an effect of 160 mV) [44]
and a chelate [W(NO)(Tp
Me2 )O(CH 2 ) 4 O] complex which undergoes reduction at a
potential 180 mV more anodic than its diethoxy analogue [45]. The redox potential
shift in the latter example is excellently reproduced by DFT calculations (at the level
of theory pointed out in Fig. 2) [37].
2.5 Further Relevant Reports
Recent literature provides a wealth of new successful applications of quantum chemical calculations that reveal how DFT/ISM approaches can be employed to design
new complexes with specific redox potentials, interesting examples of which we
shall refer to only briefly. Bím et al. [46] provided an example of how computational electrochemistry can be used to resolve the interpretation of electrochemical
data obtained for experimentally elusive ferryl species, like [(N4Py)Fe
IV O] (N4Py
N,N-bis(2-pyridylmethyl)-bis(2-pyridyl)methylamine), by using a protocol based
on B3LYP-D3 energetics and COSMO-RS solvation, first created and calibrated for
accurate evaluation of one-electron reduction potentials of a set of diverse mononuclear non-haem iron redox couples. Rudshteyn et al. [47] explained using a combined electrochemical and DFT study (SMD/B3LYP/LANL2DZ/6-311G*), how
redox potentials may be affected by thermodynamic and structural factors in the
case of tungsten–alkylidyne W(CR)L 4 X complexes (L is a neutral ligand, and X is
an anionic ligand), which are of interest owing to their application as photoreductants
and in the H 2 activation. In a review of the recent progress in the quantum chemical
modelling of homogeneous water oxidation catalysis, Liao and Siegbahn [48] also
discussed the DFT/ISM approach, including the B3LYP-D3, B3LYP*-D3 and M06
series of functionals that are commonly applied in this field, to calculate redox potentials. Knowing them enables constructing catalytic cycles and hence revealing the
reaction mechanisms. Some DFT functionals like MN12-L with Wertz’s correction
and TPSS-D3 with the IEF-PCM/scaled-UAKS implicit solvation model may attain
the accuracy (RMSD 154 mV with respect to experiment) of CCSD(T) methods
for specific classes of complexes, as demonstrated by Šebesta et al. [49] in the evaluation of reduction potentials for the Pt(IV) complexes: tetraplatin, satraplatin and
its derivatives, well known for their anticancer activity.
P. P. Roma´ nczyk and S. S. Kurek
to the terminal S-ligand increases the oxidation potential by ∼130 mV. However, the
main alkylene chain orientation change, accompanied by the Fe–S–C–C dihedral
angle variation, induced by the H-bond formation, cannot be excluded, which also
may affect the reduction potential.
We note that such geometrical effects can considerably alter the reduction potential, examples of which are salen-type Cu(II) complexes (an effect of 160 mV) [44]
and a chelate [W(NO)(Tp
Me2 )O(CH 2 ) 4 O] complex which undergoes reduction at a
potential 180 mV more anodic than its diethoxy analogue [45]. The redox potential
shift in the latter example is excellently reproduced by DFT calculations (at the level
of theory pointed out in Fig. 2) [37].
2.5 Further Relevant Reports
Recent literature provides a wealth of new successful applications of quantum chemical calculations that reveal how DFT/ISM approaches can be employed to design
new complexes with specific redox potentials, interesting examples of which we
shall refer to only briefly. Bím et al. [46] provided an example of how computational electrochemistry can be used to resolve the interpretation of electrochemical
data obtained for experimentally elusive ferryl species, like [(N4Py)Fe
IV O] (N4Py
N,N-bis(2-pyridylmethyl)-bis(2-pyridyl)methylamine), by using a protocol based
on B3LYP-D3 energetics and COSMO-RS solvation, first created and calibrated for
accurate evaluation of one-electron reduction potentials of a set of diverse mononuclear non-haem iron redox couples. Rudshteyn et al. [47] explained using a combined electrochemical and DFT study (SMD/B3LYP/LANL2DZ/6-311G*), how
redox potentials may be affected by thermodynamic and structural factors in the
case of tungsten–alkylidyne W(CR)L 4 X complexes (L is a neutral ligand, and X is
an anionic ligand), which are of interest owing to their application as photoreductants
and in the H 2 activation. In a review of the recent progress in the quantum chemical
modelling of homogeneous water oxidation catalysis, Liao and Siegbahn [48] also
discussed the DFT/ISM approach, including the B3LYP-D3, B3LYP*-D3 and M06
series of functionals that are commonly applied in this field, to calculate redox potentials. Knowing them enables constructing catalytic cycles and hence revealing the
reaction mechanisms. Some DFT functionals like MN12-L with Wertz’s correction
and TPSS-D3 with the IEF-PCM/scaled-UAKS implicit solvation model may attain
the accuracy (RMSD 154 mV with respect to experiment) of CCSD(T) methods
for specific classes of complexes, as demonstrated by Šebesta et al. [49] in the evaluation of reduction potentials for the Pt(IV) complexes: tetraplatin, satraplatin and
its derivatives, well known for their anticancer activity.