Controlling Photoisomerization Reactivity Through Single Functional Group Substitutions in Ruthenium Phosphine Sulfoxide Complexes

Article abstract of DOI:10.1021/jacs.8b05957

We report the crystallography, emission spectra, femtosecond pump-probe spectroscopy, and density functional theory computations for a series of ruthenium complexes that comprise a new class of chelating triphenylphosphine based ligands with an appended sulfoxide moiety. These ligands differ only in the presence of the para-substitutent (e.g., H, OCH₃, CF₃). The results show a dramatic range in photoisomerization reactivity that is ascribed to differences in the electron density of the phosphine ligand donated to the ruthenium and the nature of the excited state.

Full text of DOI:10.1021/jacs.8b05957

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Communication
Controlling Photoisomerization Reactivity Through Single Functional
Group Substitutions in Ruthenium Phosphine Sul-foxide Complexes
Gilbert K. Kosgei, Douglas Breen, Robert W. Lamb, Maksim Y. Livshits, Laura
A. Crandall, Christopher J. Ziegler, Charles Edwin Webster, and Jeffrey J. Rack
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.8b05957 • Publication Date (Web): 26 Jul 2018
Downloaded from http://pubs.acs.org on July 26, 2018
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Controlling Photoisomerization Reactivity Through Single
Functional Group Substitutions in Ruthenium Phosphine Sul-
foxide Complexes
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Gilbert K. Kosgei,a Douglas Breen,a Robert W. Lamb,b Maksim Y. Livshits,a Laura A. Crandall,c Chris-
topher J. Ziegler,c* Charles Edwin Webster,b* and Jeffrey J. Racka*
a. Department of Chemistry and Chemical Biology, 1 University of New Mexico, Albuquerque, NM 87131
b. Department of Chemistry, Box 9573, Mississippi State University, Mississippi State, MS 39762-9573
c. Department of Chemistry, The University of Akron, Akron, OH 44325
Supporting Information Placeholder
ruthenium and osmium polypyridine based complexes
whose photochromic action is based on an ES sulfoxide
isomerization reaction.1-4 In this case, the GS isomer is
S-bonded and the metastable isomer is O-bonded. This
reaction can be efficient, with quantum yields nearing
unity, and rapid, with electronic absorption changes oc-
curring on the picosecond timescale. We report here a
ligand design that permits simple group changes on the
periphery of the molecule that leads to remarkable con-
trol of the ES isomerization reaction. In the series of
three complexes reported here, we have found that the
ABSTRACT: We report the crystallography, emission
spectra, femtosecond pump-probe spectroscopy, and
DFT computations for a series of ruthenium complexes
that comprise
a
new class of chelating tri-
phenylphosphine based ligands with an appended sul-
foxide moiety. These ligands differ only in the presence
of the para-substitutent (e.g., H, OCH3, CF3). The re-
sults show a dramatic range in photoisomerization reac-
tivity that is ascribed to differences in the electron densi-
ty of the phosphine ligand donated to the ruthenium and
the nature of the excited state.
quantum yield of isomerization (ΦS O) may vary from
→
0.8 to 0.0.
Phosphine ligands are well known to modulate the elec-
tron density of the metal through a combination of σ-
and π-bonding. Indeed, depending upon the R groups in
PR3 ligands, the ligand may be classified as a σ-only
donor (e.g., PMe3) or as a strong π-acid or acceptor (e.g.,
PPh3 or PF3). While commonly employed in organome-
tallic chemistry, this ligand class is not widely utilized in
the design of photoactive chromophores.5-17 We ques-
tioned whether a family of chelating phosphine sulfox-
ide ligands would impart tunable properties in the pho-
tochromic behavior of these compounds. The salient
connection is that different groups on the phosphine lig-
and alter the energy of the Ligand Field (LF) or Metal-
Centered (MC) states relative to the charge transfer (CT)
states during ES evolution, thus modifying reactivity.
An important goal in photoscience is the ability to intro-
duce single atom or simple group changes within a mol-
ecule in order to alter the fate of an excited state (ES)
reaction. In principle, such advances lead to improve-
ments in photocatalysis schemes, molecular photovoltaic
devices, and artificial photosynthetic materials. In prac-
tice, most such chemical synthetic changes offer only
modest or subtle modification of ES processes, because
the relaxation processes do not involve vibrations or
other atomic motions responsive to these particular syn-
thetic alterations. Moreover, for transition metal com-
plexes, the situation is further confounded by the rela-
tively large number of available electronic states (rela-
tive to organic systems), which can further mitigate a
substituent effect.
Photochromic compounds feature large changes in both
electronic and molecular structure following visible light
exposure. Thus, these compounds exhibit dramatic
changes in the electronic absorption spectra upon irradi-
ation of the ground state (GS) isomer to form a new
metastable structure on the GS potential energy surface.
We have created and studied a family of photochromic
Scheme 1. Molecular structures determined from the X-ray
analysis of the S-bonded isomers of RuL1OH (left),
RuL2OOCH3 (center), and RuL3OCF3 (right). Hydrogen atoms
are omitted for clarity.
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Shown in Scheme 1 are the complexes described in this
typically an ES absorption (reduced bpy, π→π* ligand
centered transition) near 380 nm, its detection is ob-
scured by the coincidence of the MLCT bleach. Evi-
dence of this ES absorption can be seen at λ < 350 nm.
Wavenumber (cm-1)
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report. Each molecular structure (determined by single
crystal X-ray diffraction) features the identical
[Ru(bpy)2]2+ core and a different chelating phosphine
sulfoxide ligand that differs only in the substituent in the
4-position on the terminal phenyl rings of the tri-
phenylphosphine moiety. For RuL1OH, this substituent
is H, for RuL2OOCH3 this substituent is OCH3, and for
RuL3OCF3 this substituent is CF3. This simple substitu-
ent modification results in rather modest GS structural
differences, but generates rather dramatic and remarka-
ble distinctions in ES reactivity.
30000 27500
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0
0.004
The electronic absorption spectra of these three com-
plexes are quite similar revealing absorption maxima of
351, 353, and 348 nm, respectively for S-
[(bpy)2Ru(L1OH)]2+, S-[(bpy)2Ru(L2OOCH3)]2+, and S-
[(bpy)2Ru(L3OCF3)]2+, respectively (Figure 1A). These
data demonstrate the effect of the structurally distant
substituent group (H vs. OCH3 vs CF3) on the Ru dπ to
bpy π* charge transfer (CT) transition, which is con-
firmed by TD-DFT (vide infra) computations. Irradia-
tion of RuL3OCF3 at 355 nm results in striking changes
in the electronic absorption spectrum (Figure 1B), with
the emergence of a new absorption maximum at 422 nm,
and isosbestic points at 332 and 376 nm. Based on litera-
ture precedence, we ascribe the newly formed spectrum
to the O-bonded isomer of the ruthenium phosphine sul-
foxide complex. For example, Wolf has reported the
absorption maximum of [(bpy)2Ru(PO)]2+ is 412 nm,
where PO is 2-diphenylphosphino-(anisole). This com-
plex features a P and O donor on [Ru(bpy)2]2+.18-19 The
bold red trace displayed in Figure 1B represents pure O-
0.000
C
D
-0.004
0.004
0.000
350
400
450
500
550
600
Wavelength (nm)
Figure 1. (A) Absorption spectra for S-[(bpy)2Ru(L1OH)]2+
(black), (red), and S-
S-[(bpy)2Ru(L2OOCH3)]2+
[(bpy)2Ru(L3OCF3)]2+ (blue) (B) Spectra obtained from
bulk photolysis (λexc 355 nm) of [(bpy)2Ru(L3OCF3)]2+ in
dichloroethane solution. Spectra obtained at 80 second in-
tervals. Black dashed trace is difference spectrum (O iso-
mer – S isomer) extracted from bulk photolysis data. (C)
Time resolved spectra of [(bpy)2Ru(L3OCF3)]2+ obtained at
different pump-probe delays of 2.0 ps (red), 20.1 ps (or-
ange), 202 ps (olive green), 2000 ps (green), and 4990 ps
(violet). The new absorption maximum centered at 422 is
evidence of a photoproduct, consistent with the bulk pho-
[(bpy)2Ru(L3OCF3)]2+ formed from irradiation (Φ
=
O
tolysis
data.
(D)
Time
resolved
spectra
of
→
S
[(bpy)2Ru(L2OOCH3)]2+ obtained at different pump-probe
delays of 0.41 ps (red), 2.51 ps (orange), 199 ps (green),
1000 ps (blue), and 4660 ps (violet). These traces provide
no evidence for the formation of a photoproduct (isomeri-
zation), consistent with the bulk photolysis data.
0.8±0.2) at 355 nm or 405 nm. Excitation of RuL1OH at
either 355 or 405 nm produces a similar change in the
absorption spectrum (Φ O = 0.2±0.1). In extraordinary
→
S
contrast, irradiation of RuL2OOCH3 at any wavelength
that overlaps with the GS absorption spectrum does not
result in any spectral changes, thus providing no indica-
tion of isomerization. These observations are supported
by computational results and confirmed by time resolved
spectroscopy (vide infra). It is remarkable that such a
small structural replacement of either H or CF3 with
OCH3 alters the photochemical reactivity so dramatical-
ly.
Representative pump probe data for RuL3OCF3 docu-
ment the absorption changes observed during bulk pho-
tolysis (Figure 1C). The early time spectral features are
emblematic of an MLCT state, as described above. In
contrast to RuL2OOCH3, the spectra indicate the for-
mation of a GS photoproduct (isomerization), by the
emergence of a new absorption maximum at 422 nm,
coincident with loss of absorption in the red portion of
the spectrum. The loss of absorption at long wavelengths
Ultrafast visible pump probe spectroscopy was em-
ployed to monitor the spectral changes in these com-
plexes. For [(bpy)2Ru(L2OOCH3)]2+, the early time spec-
tra are reminiscent of those obtained for many ruthenium
polypyridine complexes (Figure 1D). That is, visible
light excitation produces an MLCT with expected fea-
tures that relax to re-form the GS with a lifetime of 790
± 60 ps. The ES absorption in the red portion of the
spectrum is attributed primarily to unreduced bpy →
RuIII LMCT transitions, whereas the GS bleach is ob-
served in the blue portion of the spectrum. While there is
3
indicates a transition from the MLCT surface to the GS
surface. The absorption maximum observed in the bulk
photolysis data is nicely reproduced in the pump-probe
data, demonstrating formation of the same complex.
This is readily observed through visual comparison of
the transient spectrum obtained at long pump-probe de-
lays (~5000 ps, vilet trace Figure 1C) with the difference
in GS spectra (O-bonded – S-bonded, black dashed
trace, Figure 1B) obtained from bulk photolysis. Global
fitting analysis and single wavelength kinetics reveal a
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time constant for formation of the O-bonded isomer of
630±77 ps. Multiplying by Φ (0.80) yields a time
RuL2O. First, the NTOs identify differences in Ru and
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sulfoxide character in the hole orbital; second, while
calculations do not provide information on the isomeri-
zation pathway, at least they indicate that the O-bonded
RuL2O state is thermodynamically uphill.
→
S
O
constant for isomerization (τ O) of 790 ps. The ab-
→
S
sorption changes in RuL1OH and RuL3OCF3 associated
with the picosecond isomerization are completely re-
versible. Reversion rate constants of (300 s)–1 and (770
s)–1 are found for RuL1OH and RuL3OCF3, respectively
(Figure S7). Future studies will reveal the bonding de-
tails that are responsible for this unusual reactivity.
Structural data obtained from single crystal X-ray dif-
fractometry reveal only subtle differences between the
three complexes. The Ru–S bond distances vary only
over a small range: 2.2185(6) Å in RuL1OH, 2.218(1) Å
in RuL2OOCH3, and 2.233(2) and 2.235(2) Å in
RuL3OCF3 (there are two unique molecules in this unit
cell). The S–O bond distances display a smaller varia-
9
We performed DFT and TDDFT computations to deter-
mine if there were differences in electronic structure that
might explain the observed differences in photochemis-
try for this family of complexes. Shown in Figure 2 are
the NTOs (natural transition orbitals; see the SI for full
computational details) of the hole (left) and particle
(electron, right) that describe the CT excited states for
RuL2OOCH3 (top) and RuL3OCF3 (bottom). While these
images show similar bipyridine contributions to the par-
ticle orbital, the Ru and sulfoxide contribution to the
hole orbital for RuL3OCF3 is considerable in comparison
to the hole orbital for RuL2OOCH3, which exhibits a large
contribution from the methoxyphenyl moiety of the
phosphine ligand.
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tion: 1.479(9) Å in RuL1OH, 1.475(4) Å in RuL2OOCH3
,
and 1.479(6) and 1.463(5) Å in RuL3OCF3. Interestingly,
the Ru–S and S–O bond distances are equivalent in
RuL1OH and RuL2OOCH3, two complexes that display
dramatically different photochemical reactivity. The
metrical parameters do not reveal any significant differ-
ences in the Ru–P distances or in any pertinent angles,
thus suggesting that any differences in the photophysical
behavior or photochemical reactivity in these complexes
is due to an ES phenomenon and not to GS geometric
differences.
Emission spectra provide compelling evidence for isom-
erization at 77K. Shown in Figure 3 is the 77 K steady
state emission spectrum for S-RuL3OCF3 in a 4:1 mix-
ture of tetrahydrofuran and propylene carbonate. The
emission spectrum reveals two maxima at 525 and 650
nm (340 nm excitation). The lifetimes at these two
wavelengths are 33 and 50 µs, respectively indicative of
a CT ES. Indeed, these lifetimes are much longer than
those observed in [Ru(bpy)3]2+ (τ = ~5 µs at 77K; we
obtain 7.7 µs on our instrument).20 The two different
lifetimes indicate two non-interacting emissive popula-
tions. Excitation scans at 525 nm and 650 nm reveal
peaks at 340 nm and 440 nm, respectively corresponding
to the absorption maxima of S- and O-RuL3OCF3 iso-
mers. The 650 and 525 nm emission bands are assigned
to the O- and S-bonded isomers, respectively. We note
that the differences in absorption (0.62 V) and emission
maxima (0.57 V) are in accord with the difference in
reduction potentials (0.66 V) for the S- and O-bonded
isomers. While we cannot be certain that there is no O-
bonded isomer in the original solution, we interpret the-
se results as formation of an O-bonded emissive CT
state at 77 K, produced from excitation of an S-bonded
GS, which relaxes to both S- and O-bonded GS isomers.
The computational data are consistent with these obser-
vations. There are weak transitions in these regions for
both isomers.
Figure 2. Natural Transition Orbitals (NTOs) for the hole
(left) and particle (right) for S-[(bpy)2Ru(L2OOCH3)]2+
(Top) and S-[(bpy)2Ru(L3OCF3)]2+ (Bottom). The NTOs for
S-[(bpy)2Ru(L1OH)]2+ are qualitatively similar to S-
[(bpy)2Ru(L3OCF3)]2+.
The relative energies from triplet single-point computa-
tions on time-dependent DFT singlet optimized geome-
tries (3TD/BS2//1TD/BS1) demonstrate that the O-bound
isomer in the ES (relative to S-bound in the ES) is disfa-
vored for RuL2OOCH3 (ΔGrxn = 2.2 kcal mol–1), competi-
tive for RuL1OH (ΔGrxn = 0.2 kcal mol–1), and favored
for RuL3OCF3 (ΔGrxn = –3.5 kcal mol–1). This trend cor-
roborates the experimental observations of isomerization
with RuL1OH and RuL3OCF3 and no isomerization with
RuL2OOCH3. Furthermore, these data show that the
isomerization behavior for this class of complexes can
be predictably controlled based on the logic of electron
density within the aromatic system of the ligands and, by
extension, the degree of electron donation to the metal
center. Thus, the computational results provide two in-
sights into the change in reactivity between RuL3O and
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Wavenumbers (cm-1)
Funding Sources
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2
24000 21000
18000
15000
12000
The authors declare no competing financial interest.
1.0
0.8
0.6
0.4
0.2
0.0
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ACKNOWLEDGMENT
JJR acknowledges the National Science Foundation (Grant
CHE 1602240) and the University of New Mexico for fi-
nancial support. This work was supported by the Mississip-
pi State University Office of Research and Economic De-
velopment and the National Science Foundation (OIA-
1539035). Computations were performed at the Mississippi
State University High Performance Computing Collabora-
tory (HPC2) and the Mississippi Center for Supercomputing
Research.
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REFERENCES
400
450
500
550
600
650
700
750
800
850
Wavelength (nm)
1.
Rack, J. J., Coordination Chemistry Reviews 2009, 253 (1-
2), 78-85.
2.
Figure 3. Corrected steady state emission spectrum of
[(bpy)2Ru(L3OCF3)]2+ at 77 K.
King, A. W.; Wang, L.; Rack, J. J., Accounts Chem. Res.
2015, 48 (4), 1115-1122.
3.
Garg, K.; King, A. W.; Rack, J. J., J. Am. Chem. Soc. 2014,
The 77 K emission data suggest that isomerization oc-
curs adiabatically along the CT surface, whereas the
room temperature pump-probe data do not provide evi-
dence for the formation of an O-bonded excited state.
We propose that isomerization occurs through non-
adiabatic coupling between adiabatic surfaces, which
also serve as the basis of the above calculations. Taken
together, the temperature dependent data hint at an intri-
cate balance of couplings between surfaces, both excited
state and ground state, as well as S-bonded and O-
bonded.
136 (5), 1856-1863.
4.
Garg, K.; Engle, J. T.; Ziegler, C. J.; Rack, J. J., Chem.-
Eur. J. 2013, 19 (35), 11686-11695.
5.
Angell, S. E.; Rogers, C. W.; Zhang, Y.; Wolf, M. O.;
Jones, W. E., Coordination Chemistry Reviews 2006, 250 (13-14),
1829-1841.
6.
Dixon, I. M.; Lebon, E.; Sutra, P.; Igau, A., Chem. Soc.
Rev. 2009, 38 (6), 1621-1634.
7.
Gutmann, R.; Czermak, G.; Dumfort, A.; van der Veer, W.
E.; Hong, B.; Kopacka, H.; Ongania, K. H.; Bechtold, T.; Bruggeller,
P., Inorg. Chem. Commun. 2005, 8 (3), 319-322.
8.
Lebon, E.; Bastin, S.; Sutra, P.; Vendier, L.; Piau, R. E.;
Dixon, I. M.; Boggio-Pasqua, M.; Alary, F.; Heully, J. L.; Igau, A.;
Juris, A., Chem. Commun. 2012, 48 (5), 741-743.
In summary, these results indicate that isomerization
occurs efficiently in certain of these ruthenium phos-
phine sulfoxide complexes, and that the phosphine moie-
ty provides remarkable control of the photoisomeriza-
tion. Moreover, we report the first data that shows evi-
dence of isomerization at 77 K from an unequivocal CT
state. Future studies will focus on understanding the un-
usual reactivity exhibited by these complexes.
9.
Lebon, E.; Sylvain, R.; Piau, R. E.; Lanthony, C.; Pilme, J.;
Sutra, P.; Boggio-Pasqua, M.; Heully, J. L.; Alary, F.; Juris, A.; Igau,
A., Inorganic Chemistry 2014, 53 (4), 1946-1948.
10.
Litke, S. V.; Ershov, A. Y.; Meyer, T. J., J. Phys. Chem. A
2011, 115 (50), 14235-14242.
11.
Rogers, C. W.; Patrick, B. O.; Rettig, S. J.; Wolf, M. O., J.
Chem. Soc.-Dalton Trans. 2001, (8), 1278-1283.
12.
Sutra, P.; Igau, A., Coordination Chemistry Reviews 2016,
308, 97-116.
13.
Dixon, I. M.; Lebon, E.; Loustau, G.; Sutra, P.; Vendier, L.;
Igau, A.; Juris, A., Dalton Trans. 2008, (41), 5627-5635.
ASSOCIATED CONTENT
14.
H. D.; Kato, M., Inorganic Chemistry 2003, 42 (3), 785-795.
15. Carlson, B.; Phelan, G. D.; Kaminsky, W.; Dalton, L.;
Suzuki, T.; Kuchiyama, T.; Kishi, S.; Kaizaki, S.; Takagi,
Supporting Information. Detailed synthetic and experi-
mental procedures, and computational details for
[(bpy)2Ru(L1OH)]2+,
[(bpy)2Ru(L2OOCH3)]2+,
and
Jiang, X. Z.; Liu, S.; Jen, A. K. Y., J. Am. Chem. Soc. 2002, 124 (47),
14162-14172.
[(bpy)2Ru(L3OCF3)]2+. CCDC 1843478-1843480 contain
the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cam-
16.
Klassen, D. M.; DelPup, R. V., Inorganic Chemistry 2002,
41 (12), 3155-3160.
17.
La Pensee, A. A.; Bickley, J.; Higgins, S. J.; Marcaccio,
bridge
Crystallographic
Data
Centre
via
M.; Paolucci, F.; Roffia, S.; Charnock, J. M., J. Chem. Soc.-Dalton
Trans. 2002, (22), 4095-4104.
www.ccdc.cam.ac.uk/structures/. The Supporting Infor-
mation is available free of charge on the ACS Publications
website.
18.
Jones, W. E., Inorganic Chemistry 2005, 44 (21), 7377-7384.
19. Rogers, C. W.; Wolf, M. O., Chem. Commun. 1999, (22),
2297-2298.
Angell, S. E.; Zhang, Y.; Rogers, C. W.; Wolf, M. O.;
AUTHOR INFORMATION
Corresponding Author
20.
Juris, A.; Balzani, V.; Barigelletti, F.; Campagna, S.;
Belser, P.; Vonzelewsky, A., Coordination Chemistry Reviews 1988,
84, 85-277.
* J.J.R. E-mail: jrack@unm.edu
* C.E.W. E-mail: ewebster@chemistry.msstate.edu
* C.J.Z. E-mail: ziegler@uakron.edu
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O
hν
(bpy)2(R3P)RuII
(bpy)2(R3P)RuII
S
S
O
Me
R
Me
R
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9
Φ(S → O) = 0.8
Φ(S → O) = 0.2
Φ(S → O) = 0.0
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