Supporting Information for ‘Electronic Structure of
Hemin in Solution Studied by Resonant X-ray
Emission Spectroscopy and Electronic Structure
Calculations’
Kaan Ataka,b, Ronny Golnaka,c, Jie Xiaoa, Edlira Suljotia, Mika Pflügera, Tim Brandenburga,
Bernd Wintera, Emad F. Aziz*,a,b
a
Joint Laboratory for Ultrafast Dynamics in Solutions and at Interfaces (JULiq) Helmholtz-
Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
b
Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, D-14195 Berlin, Germany
c
Freie Universität Berlin, Fachbereich Chemie, Takustr. 3, D-14195 Berlin, Germany
*
Corresponding Author
Email: [email protected]
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Computational details
During the optimization of the molecular geometries and the subsequent application of
DFT/ROCIS for obtaining the XA spectra, we used the spin-unrestricted Kohn-Sham (UKS)
method available in the ORCA software due to the open-shell nature of the TM complex under
investigation. This leads to a good agreement with the experiment. Yet our interpretation suffers
from the unrestricted nature of the method; the orbitals are split into two sets with α and β spin
wavefunctions, with no restriction on the spatial part of the orbitals. This does not present a
theoretical problem as individual MOs are not observables, but the spectra are. On the other
hand, to be able to interpret the orbitals in the sense of bonding structure or energy levels, the use
of one orbital set is more convenient, and can be provided by applying a restricted open-shell
Kohn-Sham (ROKS) method. ORCA itself creates a similar set of orbitals called the quasirestricted orbital set for the DFT/ROCIS part, but ROKS can provide human readable orbital
visualizations and population analyses in a straightforward fashion. However, ROKS
calculations are more difficult to perform, during which self-consistent-field (SCF) convergence
becomes problematic. Therefore, we calculated the spectra for different spin states and
conformations using UKS method, and selected the best matching spectrum to the experimental
result. We then repeated the XAS calculation for that particular case with ROKS method, and
verified the spectrum to be essentially the same. The orbital energies presented by ROKS and the
quasi restricted orbital method by DFT/ROCIS are found to be very similar. Unfortunately both
of the methods suffer from the same well-known drawback: the violation of the Aufbau principle
in determining the energies of the SOMOs.1–3 Therefore, when presenting the MO energies in
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Table 1, it should be kept in mind that, the relative energies between these orbitals should be
considered more physical than the absolute values.
FePPIXCl S=2.5
FePPIXCl S=1.5
FePPIXCl S=0.5
Fe-Cl bond distance (Å)
2.239
2.292
2.236
Fe-N bond distance (Å)
2.101, 2.107, 2.094, 2.103
2.025, 2.032, 2.016, 2.025
2.005, 2.016, 2.010, 2.012
Cl-Fe-N bond angle (⁰)
106.0, 105.5, 103.0, 103.1
100.2, 100.3, 97.8, 97.9
97.5, 100.8, 94.6, 96.9
N-Fe-N bond angle (⁰)
86.4, 86.7, 86.1, 86.6
88.5, 88.8, 88.3, 88.8
89.0, 89.4, 88.3, 89.6
4.14
4.85
3.92
-96826.98
-96826.90
-96826.38
Total dipole moment
(Debye)
Total single point energy
(eV)
Table SI-1. The coordination of iron in FePPIX chloride varying with different spin
configurations according to the B3LYP/def2-TZVP(-f)/def2-TZV/J unrestricted open shell DFT
optimization calculations.
FePPIX S=2.5
FePPIX S=1.5
FePPIX S=0.5
Fe-N bond distance (Å)
2.062, 2.056, 2.059, 2.055
1.977, 1.973, 1.974, 1.970
1.994, 1.999, 1.990, 1.993
N-Fe-N bond angle (⁰)
90.0, 90.2, 89.5, 90.3
90.1, 90.2, 89.6, 90.3
89.9, 90.3, 89.7, 90.2
7.39
6.98
7.05
-84298.21
-84298.59
-84297.96
Total dipole moment
(Debye)
Total single point energy
(eV)
Table SI-2. The coordination of iron in FePPIX varying with different spin configurations
according to the B3LYP/def2-TZVP(-f)/def2-TZV/J unrestricted open shell DFT optimization
calculations.
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Figure SI-1. Experimental iron L-edge PFY spectrum of 50mM FePPIX chloride solution in
DMSO and DFT/ROCIS XA calculations for spin multiplicity 6 with the presence and absence
of spin-orbit coupling effect. (a), (b), and (c) refer to pre-maximal, maximal and post-maximal
features respectively.
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Figure SI-2. Inner valence molecular orbitals of FePPIX chloride (in high spin configuration,
S=2.5) with prominent iron contribution (refer to Table 1) according to the B3LYP/def2-TZVP(f)/def2-TZV/J restricted open shell single point DFT calculation.
References
(1) Plakhutin, B. N.; Davidson, E. R. Koopmans’ Theorem in the Restricted Open-Shell
Hartree−Fock Method. 1. A Variational Approach†. J. Phys. Chem. A 2009, 113, 12386–
12395.
(2) Plakhutin, B. N.; Davidson, E. R. Canonical Form of the Hartree-Fock Orbitals in OpenShell Systems. J. Chem. Phys. 2014, 140, 014102.
(3) Jensen, F. Introduction to Computational Chemistry; John Wiley & Sons: Chichester,
England; Hoboken, NJ, 2007.
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