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57 Fe Mössbauer and DFT study of the electronic and spatial structure of the iron(II) (pseudo)clathrochelates: the effect of a ligand field strength

Authors:
Denis Balatskiy at Institute of Chemistry of Far Eastern Branch of Russian Academy of Sciences
Denis Balatskiy
  • Institute of Chemistry of Far Eastern Branch of Russian Academy of Sciences
Alexander S. Chuprin at Russian Academy of Sciences
Alexander S. Chuprin
Semyon V. Dudkin at A.N. Nesmeyanov Institute of Organoelement Compounds RAS
Semyon V. Dudkin
  • A.N. Nesmeyanov Institute of Organoelement Compounds RAS
Luis Felipe Desdín García
Luis Felipe Desdín García
Luis Felipe Desdín García
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Abstract

Combined experimental 57Fe Mössbauer and theoretical DFT study of a series of iron(II)-centered (pseudo)macrobicyclic analogs and homologs was performed. The field strength of the corresponding (pseudo)encapsulating ligand was found to affect both the spin state of a caged iron(II) ion and the electron density at its nucleus. In a row of the iron(II) tris-dioximates, passing from the non-macrocyclic complex to its monocapped pseudomacrobicyclic analog caused an increase both in the ligand field strength and in the electron density at the Fe2+ ion, and, therefore, a decrease in the isomer shift (IS) value (so-called "semiclathrochelate effect"). Its macrobicyclization, giving the quasiaromatic cage complex, caused a further increase in the two former parameters and a decrease in IS (so-called "macrobicyclic effect"). The trend of their IS values was successfully predicted using the performed quantum-chemical calculations and the corresponding linear correlation with the electron density at their 57Fe nuclei was plotted. A variety of different functionals can be successfully used for such excellent prediction. The slope of this correlation was found to be unaffected by the used functional. In contrast, the predictions of both the sign and the values of quadrupole splitting (QS) for them, based on the theoretical calculations of EFG tensors, were found to be a real great challenge, which could not be solved at the moment even in the case of these C3-pseudosymmetric iron(II) complexes with known XRD structures. The latter experimental data allowed us to deduce a sign of the QSs for them. The straightforwarded molecular design of a (pseudo)encapsulating ligand is proposed to control both the spin state and the redox characteristics of an encapsulated metal ion.
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Mossbauer1_si_24.04.2023.docx / 19 June 2023 1
Mossbauer1_si_24.04.2023.docx / 19 June 2023 1
Supporting Information
for
57Fe Mössbauer and DFT study of the electronic and spatial structure of the
iron(II) (pseudo)clathrochelates: the effect of a ligand field strength
Denis V. Balatskiy,a Alexander S. Chuprin,b,c Semyon V. Dudkin,b,c Luis Felipe
Desdín-García,d Angel Luis Corcho-Valdés,d Manuel Antuch,d
Vyacheslav M. Buznik,c Svetlana Yu. Bratskaya,a Yan Z. Voloshin b,c
a Institute of Chemistry, Far Eastern Branch of the Russian Academy of
Sciences, 159 100-letiya Vladivostoka pr., 690022 Vladivostok, Russia
b Nesmeyanov Institute of Organoelement Compounds of the Russian Academy
of Sciences, 28-1 Vavilova st., 119334 Moscow, Russia
c Kurnakov Institute of General and Inorganic Chemistry of the Russian
Academy of Sciences, 31 Leninsky pr., 119991 Moscow, Russia
d Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear, No. 502, Calle 30
y 5ta Ave. Miramar, CP 11300 La Habana, Cuba
Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics.
This journal is © the Owner Societies 2023
Mossbauer1_si_24.04.2023.docx / 19 June 2023 2
Mossbauer1_si_24.04.2023.docx / 19 June 2023 2
N
N
Fe2+
N
N N
O
O
OB
NHNHNH
N
Cl
Chemical drawing
Experimental 57Fe Mössbauer data:
(Isomer shift, IS, relative to -Fe) = 0.99 mm/s
Eq (Quadrupole splitting, QS) = 3.55 mm/s
Fe2+@L1
Figure S1. General view of the molecule Fe(PzOx)3(BC6H5)Cl
High-spin iron(II) complex
X-Ray
Mossbauer1_si_24.04.2023.docx / 19 June 2023 3
Mossbauer1_si_24.04.2023.docx / 19 June 2023 3
N
N
Fe2+
N
NN
O
O
O
B
N
H3C
H3CCH3
(ClO4–)
+
Chemical drawing
Figure S2. General view of the molecule [Fe(AcPyOx)3(BC6H5)](ClO4)
Low-spin iron(II) complex
X-Ray
Mossbauer1_si_24.04.2023.docx / 19 June 2023 4
Mossbauer1_si_24.04.2023.docx / 19 June 2023 4
N
N
Fe2+
N
N N
O
O
O
B
OHOHO
N
O
Chemical drawing
Figure S3. General view of the molecule FeNx(HNx)2(B4-C6H4CHO)
Low-spin iron(II) complex
X-Ray
Mossbauer1_si_24.04.2023.docx / 19 June 2023 5
Mossbauer1_si_24.04.2023.docx / 19 June 2023 5
N
N
Fe2+
N
N N
O
O
O
B
OO
B
O
N
Cl
Cl
Cl
Cl
O
O
Cl
Cl
Chemical drawing
Figure S4. General view of the molecule Fe(Cl2Gm)3(B3-C6H4CHO)2
Low-spin iron(II) complex
X-Ray
Mossbauer1_si_24.04.2023.docx / 19 June 2023 6
Mossbauer1_si_24.04.2023.docx / 19 June 2023 6
Fe2+
N
N N
O
O
OB
OO
BO
N
S
S
O
O
N
N
S
SS
S
Chemical drawing
Figure S5. General view of the molecule Fe(S2-C6H4Gm)3(B3-C6H4CHO)2
Low-spin iron(II) complex
X-Ray
Mossbauer1_si_24.04.2023.docx / 19 June 2023 7
Mossbauer1_si_24.04.2023.docx / 19 June 2023 7
N
N
Fe2+
N
N N
O
O
OB
OOO
N
B
O
O
Chemical drawing
Figure S6. General view of the molecule FeNx3(B4-C6H4CHO)2
Low-spin iron(II) complex
X-Ray
Mossbauer1_si_24.04.2023.docx / 19 June 2023 8
Mossbauer1_si_24.04.2023.docx / 19 June 2023 8
DFT calculation of QS values
Regarding the quadrupolar splitting, it should be said that the potential caused
by a point charge at a certain distance r from a nucleus is given by V(r) = q/r. The
electric field is the gradient of the potential, taken with a negative sign, i.e.
, and the gradient of the electric field is known as the electric field gradient
𝐸 = ‒ ∇𝑉
(EFG), which may be expressed as . The EFG may be written in matrix
𝐸𝐹𝐺 = ‒ ∇2𝑉
form, according to Eq. S1.
(S1),
𝐸𝐹𝐺 = ‒ ∇2𝑉=
[
𝑉𝑥𝑥 𝑉𝑥𝑦 𝑉𝑥𝑧
𝑉𝑦𝑥 𝑉𝑦𝑦 𝑉𝑦𝑧
𝑉𝑧𝑥 𝑉𝑧𝑦 𝑉𝑧𝑧
]
where , where and stand for combinations of the Cartesian
𝑉𝑖𝑗 =∂2𝑉 ∂𝑟𝑖∂𝑟𝑗𝑖 𝑗
coorinates , or .
𝑥 𝑦 𝑧
The hyperfine quadrupole splitting is originated from the coupling of a nuclear
electric quadrupole moment ( ) for nuclei with nuclear spin and a non-zero
𝑄 𝐼 > 1/2
EFG. In the case of the 57Fe nucleus, the nuclear transition occurs at
𝐼 = 1/2↔𝐼 = 3/2
14.41 eV. The spectral difference between the Kramers doublet
𝐼 = 3/2 𝑀𝐼 = ± 3/2
and may be expressed according to Eq. S2.
𝑀𝐼 = ± 1/2
(S2)
∆𝐸𝑄=
𝑒𝑄𝑉𝑧𝑧
2
(
1 + 𝜂2
3
)
where is an asymmetry parameter reflecting the asymmetry in
𝜂=
(
𝑉𝑥𝑥 ‒ 𝑉𝑦𝑦
)
/
(
𝑉𝑧𝑧
)
the distribution of the electrons around the nucleus; each component is taken as
. For the calculation of it is worth to consider that
|
𝑉𝑧𝑧
|
≥
|
𝑉𝑦𝑦
|
≥
|
𝑉𝑥𝑥
|
∆𝐸𝑄
, for 57Fe (where 1 ) and is calculated
𝑒= 1.602 ∙10 ‒19𝐶 𝑄 = 150 ‒ 160 𝑚𝑏 𝑚𝑏 = 10 ‒31 𝑚2𝑉𝑧𝑧
in atomic units ( ) via DFT (where ). The product
𝑎.𝑢. 1 𝑎.𝑢. = 9.717365 ∙10 21𝑉/𝑚2𝑒𝑄𝑉𝑧𝑧
has conventional units of while and
[𝐶][𝑚2][𝑉/𝑚2] = [𝐽] 1 𝐽 = 6.242 ∙10 18𝑒𝑉
.
1 𝑚𝑚/𝑠 = 4.805 ∙10 ‒8𝑒𝑉
Mossbauer1_si_24.04.2023.docx / 19 June 2023 9
Mossbauer1_si_24.04.2023.docx / 19 June 2023 9
Table S1. Calculation of an electron density at the 57Fe nucleus in the complex
(Fe2+)@L4 using the different convergence criteria; B3LYP functional; NRAD =
300
Electron density
Convergence
11578.995020
1.00E-05
11578.995008
1.00E-06
11578.995009
1.00E-07
Mossbauer1_si_24.04.2023.docx / 19 June 2023 10
Mossbauer1_si_24.04.2023.docx / 19 June 2023 10
Table S2. Calculation of an electron density at the 57Fe nucleus in the complex
(Fe2+)@L4 using the different NRAD values; B3LYP functional;
convergence = 1d-06
Electron density
Convergence
11578.995075
100
11578.995010
200
11578.995008
300
11578.995008
400
11578.995010
500
Mossbauer1_si_24.04.2023.docx / 19 June 2023 11
Mossbauer1_si_24.04.2023.docx / 19 June 2023 11
Table S3. Calculation of an electron density at the 57Fe nucleus in the complex
(Fe2+)@L4 using the experimental XRD and DFT-optimized geometries
Method
Electrond density
XRD
11578.995010
DFT
11578.995015
Mossbauer1_si_24.04.2023.docx / 19 June 2023 12
Mossbauer1_si_24.04.2023.docx / 19 June 2023 12
Table S4. The calculated QS values (mm/s) which were obtained using various
DFT functionals
Functional
Compound
Vzz (a.u.)
Vyy (a.u.)
Vxx (a.u.)
η
QScalcd
QSexp
(Fe2+)@L1
1.08
–0.82
–0.26
0.525
1.761
3.55
(Fe2+)@L2
0.06
–0.05
–0.01
0.632
0.096
0.00
(Fe2+)@L3
0.31
–0.27
–0.04
0.762
0.531
0.56
(Fe2+)@L4
–0.55
0.31
0.24
0.115
–0.867
0.71
(Fe2+)@L5
–0.16
0.13
0.03
0.592
–0.265
0.70
B3LYP
(Fe2+)@L6
–0.35
0.31
0.04
0.766
–0.604
0.65
(Fe2+)@L1
–0.88
0.82
0.06
0.854
–1.541
3.55
(Fe2+)@L2
0.28
–0.15
–0.13
0.089
0.434
0.00
(Fe2+)@L3
0.18
–0.16
–0.024
0.740
0.313
0.56
(Fe2+)@L4
–0.22
0.14
0.08
0.292
–0.342
0.71
(Fe2+)@L5
–0.10
0.08
0.02
0.589
–0.166
0.70
BP86
(Fe2+)@L6
0.11
–0.10
–0.005
0.898
0.189
0.65
(Fe2+)@L1
–0.81
0.63
0.18
0.553
–1.328
3.55
(Fe2+)@L2
0.28
–0.15
–0.13
0.082
0.439
0.00
(Fe2+)@L3
0.18
–0.16
–0.03
0.716
0.309
0.56
(Fe2+)@L4
–0.10
0.08
0.02
0.617
–0.162
0.71
(Fe2+)@L5
–0.85
0.79
0.06
0.855
–1.487
0.70
OLYP
(Fe2+)@L6
0.11
–0.10
–0.007
0.865
0.189
0.65
(Fe2+)@L1
–0.85
0.79
0.06
0.855
–1.487
3.55
(Fe2+)@L2
0.28
–0.15
–0.13
0.086
0.446
0.00
(Fe2+)@L3
0.18
–0.15
–0.025
0.720
0.302
0.56
(Fe2+)@L4
–0.20
0.13
0.07
0.298
–0.322
0.71
(Fe2+)@L5
–0.10
0.077476
0.02
0.609
–0.160
0.70
RPBE
(Fe2+)@L6
0.01
–0.092
–0.008
0.833
0.174
0.65
(Fe2+)@L1
0.89
–0.73
–0.15
0.654
1.487
3.55
(Fe2+)@L2
0.22
–0.12
–0.10
0.125
0.343
0.00
(Fe2+)@L3
0.19
–0.17
–0.023
0.764
0.333
0.56
(Fe2+)@L4
–0.26
0.15
0.10
0.202
–0.407
0.71
(Fe2+)@L5
–0.11
0.083918
0.02
0.590
–0.175
0.70
TPSS
(Fe2+)@L6
0.14
–0.13
–0.007
0.900
0.245
0.65
Mossbauer1_si_24.04.2023.docx / 19 June 2023 13
Mossbauer1_si_24.04.2023.docx / 19 June 2023 13
Table S5. The calculated QS values (mm/s) for the complex (Fe2+)@L4 which
were obtained using various basis sets
Basis set
Vzz (a.u.)
Vyy (a.u.)
Vxx (a.u.)
η
QScalcd
QSexp
STO-6G
–0.29
0.17
0.12
0.19
–0.454
631-G
–0.38
0.22
0.16
0.15
–0.595
CCT
–0.44
0.25
0.19
0.13
–0.685
TZV
–0.55
0.31
0.24
0.11
–0.867
SPKrTZV
–0.45
0.26
0.20
0.13
–0.713
0.71
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Article
  • Mar 2022
Hybrid metallo(IV)phthalocyaninate-capped tris-dioximate iron(II) complexes (termed as "phthalocyaninatoclathrochelates") with non-equivalent apical fragments and functionalized with one terminal reactive vinyl group were prepared for the first time using three different synthetic approaches: (i) transmetallation (capping group exchange) of the appropriate labile boron,antimony-capped cage precursors, (ii) capping of the initially isolated reactive semiclathrochelate intermediate, and (iii) direct one-pot template condensation of their ligand synthons on the iron(II) ion as a matrix. The obtained polytopic cage complexes were characterized using elemental analysis, 1H NMR, MALDI-TOF MS and UV-vis spectra, and the single-crystal X-ray diffraction experiments. One of the obtained vinyl-terminated iron(II) phthalocyaninatoclathrochelates and its semiclathrochelate precursor were tested as monomers in a copolymerization reaction with styrene as the main component. These vinyl-terminated (semi)clathrochelate iron(II) complexes were found to be successfully copolymerized with this industrially important monomer, affording the intensely colored copolymer products. Because of a low solubility of the tested zirconium(IV) phthalocyaninate-capped tris-nioximate monomer in styrene as a solvent, a molar ratio of 1 : 500 was used. The obtained copolymer products and the kinetics of their formation were studied using GPC, FTIR, UV-vis, TGA and DSC methods. Even at such a low concentration of the Fe,Zr-binuclear metallocomplex component, an increase in the rate of the UV-light degradation of the organo-inorganic products, as well as in their thermal stability, was observed.
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