The Heck reaction as a tool to expand polyoxovanadates towards thiol-sensitive organic-inorganic hybrid fluorescent switches

Article abstract of DOI:10.1039/c8dt02340a

Among the Lindqvist-type hexavanadates synthesised herein by the palladium-catalysed Heck reactions a C-C cross-coupled organic-inorganic hybrid with the largest conjugated, stilbene-derivatised π ligands is reduced in the presence of thiols producing a r

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The Heck reaction as a tool to expand
polyoxovanadates towards thiol-sensitive
Cite this: DOI: 10.1039/c8dt02340a
organic–inorganic hybrid fluorescent switches†
Received 7th June 2018,
Accepted 17th August 2018
Oliver Linnenberg, Lisa Mayerl and Kirill Yu. Monakhov
*
DOI: 10.1039/c8dt02340a
rsc.li/dalton
Among the Lindqvist-type hexavanadates synthesised herein by activity, their stability towards hydrolysis in a wide acidic and
the palladium-catalysed Heck reactions
C–C cross-coupled basic pH window and their intense and characteristic 51V NMR
a
organic–inorganic hybrid with the largest conjugated, stilbene- signal. The latter method enables a simple and fast detection
derivatised π ligands is reduced in the presence of thiols producing of the fully-oxidised POV with striking opportunities in cross-
a remarkable increase in fluorescence intensity with respect to the disciplinary research at the frontiers of chemistry, biology,
fully-oxidised variant. This enhanced emission (ON-state) of the medicine and information technology.14
reduced species can be switched OFF if the solution is subjected
This gave us the impulse to boost the further development
in the field of the organic post-functionalisation of Lindqvist-
type ({V6}) polyoxo(alkoxo)vanadates, with specific focus on
their ability to implement cross-coupling reactions. Herein we
target for the first time an exhaustive experimental study of
palladium-catalysed Heck reactions15 of the aryl iodide-
terminated {V6} polyoxo(alkoxo)anion with commonly available
and simple reactants under mild conditions. We showcase the
cross-coupling directed formation of the stimuli-responsive
POV-based organic–inorganic hybrids granting access to the
redox-driven optical switching initiated by thiols16 as model
reductants. The developed molecules can also be used for
the destruction of hazardous waste.17 The synthesised com-
pounds were characterised by 1H, 13C, and 51V nuclear mag-
netic resonance (NMR), infrared (IR), ultraviolet–visible
(UV/Vis) absorption and fluorescence spectroscopy, electro-
spray ionisation mass spectrometry (ESI-MS), thermo-
gravimetric analysis (TGA) and single-crystal X-ray diffraction.
Density functional theory (DFT) calculations were used to gain
insights into the electronic structure of the target compounds,
supporting experimental studies of the absorption and emis-
sion properties.
to e.g. air where the species is re-oxidised.
The rapidly growing field of polyoxometalate (POM)-based
organic–inorganic hybrid compounds1 with their potential
application in e.g. (bio-)organic or polymer materials science2
strives for new functionalisation and particularly C–C linkage
approaches. Contrary to direct functionalisation, the post-
functionalisation3 of organically pre-modified POMs enables
their convenient binding onto substrates4 or materials5 with
intrinsic physicochemical properties via well-established reac-
tion pathways or mechanisms.
In contrast to the Lindqvist-, Keggin-, Anderson–Evans- and
Wells–Dawson-type iso- and hetero-POMs containing Mo or W
ions for which the different post-functionalisation through e.g.
esterification, amidation, cross-coupling, azide–alkyne cyclo-
addition or Diels–Alder click reactions has been extensively
developed,1,3,6 the controlled organic derivatisation of
vanadium-oxo clusters or so-called polyoxovanadates7 (POVs)
is not well studied yet. Beside the widely explored esterifica-
tion8 only amidation reactions9 and the recently described
Cu(I)-catalysed Huisgen 1,3-dipolar cycloaddition10 have been
reported up to now. Compared to polyoxomolybdates and poly-
oxotungstates or hetero-POVs,11 Lindqvist-type POVs12 benefit
in the functionalisation procedures13 from their smart redox
To explore the Lindqvist hexavanadate in the
Pd-catalysed Heck cross-coupling reactions, compound
(nBu4N)2[V6O13{(OCH2)3CCH2OCH2-4-C6H4I}2] ((TBA)21, TBA =
nBu4N+) was synthesised and fully characterised (see
Scheme S1, Fig. S1 and Table S4 in the ESI†). The obtained
fully-oxidised hexavanadate core is capped by two (tris)alkoxo
ligands with the structurally exposed aryl iodide functionalities
in a transoid (anti-) fashion as depicted in Fig. 1a.
Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1,
52074 Aachen, Germany. E-mail: kirill.monakhov@ac.rwth-aachen.de
†Electronic supplementary information (ESI) available: Crystal data and struc-
ture refinement details of compounds, their thermal, spectroscopic and cyclic
voltammetry data, and details of DFT calculations. CCDC 1581481–1581483. For
ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/
c8dt02340a
The cross-coupling of polyoxo(alkoxo)anion 1 was first
probed with n-butyl acrylate using the different types of
common Heck catalysts, in order to largely optimise the reac-
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pheral substituents (= R) with the less electron-withdrawing at
1
the aliphatic CvC double bonds, as evidenced by the H NMR
spectroscopy. All compounds with the cinnamate-derivatised
groups ((TBA)22a–(TBA)22e) additionally display the intense car-
bonyl (CvO) and olefin (CvC) bands in the IR spectra at ca.
1716–1697 cm−1 (2e (NCvO): 1648 cm−1) and 1633–1635 cm−1
(2e: 1610 cm−1), respectively. For compounds (TBA)22f–(TBA)22i
only a weak CvC stretching band at 1623–1632 cm−1 is
observed. All isolated products (TBA)22a–(TBA)22i are character-
ised by a unique [M + TBA]+ fragment in the ESI-MS and an
intense 51V NMR signal at ca. −495 ppm, which demonstrate the
structural integrity of the fully-oxidised hexavanadate cage.
Next, compounds (TBA)21 as a reference and (TBA)22f–
(TBA)22i with the extended π systems were analysed as to their
optical properties (Table 2). The compounds exhibit the typical
ligand-to-metal charge transfer (LMCT, Ocage → V) bands for
(tris)alkoxo-{V6}-hybrids in the region of ca. 200–360 nm
(ref. 18) (measured for c = 1 × 10−5 M and 1 × 10−6 M, see
Fig. 1 Ball and stick representation of the crystal structures of the
polyoxo(alkoxo)anions in compound (TBA)21 (a) and in compound
(TBA)22e (b). TBA countercations are omitted for clarity. ORTEP of the
structures are reported in the ESI.† Colour code: I = violet, V = orange
polyhedra, O = red, N = blue, C = grey, H = white.
tion parameters (see Tables S1–S3 in the ESI†), not being Fig. S16–S20 in the ESI†). The absorption spectra of (TBA)22f–
reported previously for POVs. The major challenges, caused by (TBA)22i are also characterised by strong absorption bands
an almost impossible work-up of the product mixtures contain- between 295 and 335 nm (ε = 5.58–11.1 × 104 L (cm mol)−1),
ing mono- and bi-functionalised products and their diastereo- corresponding to the πligand–π*ligand transitions of the peri-
mers, were here to achieve a full conversion, high selectivity and pheral stilbene-derivatised moieties. Compound (TBA)22h
the facile removal of the catalyst. On the other hand, the shows a more complex spectrum including several additional
number of potential reactants and solvents was limited by the bands with moderate absorbance below 310 nm.
oxidative behaviour and the solubility features of compound
The emission spectra of (TBA)22f–(TBA)22i (see Fig. S21–S24
(TBA)21. As a result, we successfully implemented the moderate in the ESI†) were recorded analogously to the absorption
reaction conditions (temperature and time) and the relatively spectra for c = 1 × 10−6 M in dry degassed MeCN, for the
cheap and common substrates (catalyst, solvent, base).
absorption band with the most intensive relative fluorescence
These optimised reaction parameters were further used to intensity (absorbance for all bands of all compounds < 0.1).
perform the Pd-catalysed Heck cross-coupling reactions of (TBA)22i exhibits the largest conjugated ligand π system with
(TBA)21 with a large variety of olefins such as acrylates, metha- the highest absorption (327 nm) and emission bands (λex
=
max
crylates, acrylamides, vinyl ether, allyl alcohol, styrene deriva- 330 nm, λ
= 377 nm), followed by (TBA)22h (λex = 321 nm,
em
max
max
em
tives, 4-vinyl pyridine and 2-vinyl naphthalene. As can be seen
λ
= 380 nm), (TBA)22g (λex = 319 nm, λ
= 357 nm) and
em
max
in Table 1 the fully-oxidised and bi-functionalised polyoxo (TBA)22f (λex = 310 nm, λ
= 377 nm). The quantum yields
em
(alkoxo)anions [V6O13{(OCH2)3CCH2OCH2-4-C6H4CHvCHR}2]2− (QYs) obtained for fully-oxidised (TBA)22f–(TBA)22i at room
(2a–2i) were isolated with the charge-balancing TBA cations in temperature lie between 0.1% ((TBA)22i) and 1.7% ((TBA)22h).
moderate to high yields (59–98%). Unexpectedly, the reaction of The fluorescence properties of weak-emitting (TBA)22i as well
(TBA)21 with methyl methacrylate, 4-vinyl pyridine, n-butyl vinyl as its absorption characteristics (with the highest and a clearly
ether or allyl alcohol resulted only in inseparable mixtures of defined absorption) prompted us to study (TBA)22i in more
the starting material (TBA)21 and the mono- and/or bi-functio- detail, with respect to the reduction of the {V6} building block
nalised species with low conversions (<5–60%).
Single-crystals suitable for X-ray diffraction analysis and DFT calculations.
were obtained only for compound (TBA)22e (Table 1)
The redox properties of (TBA)22i were analysed by CV
with the formula
by using cyclic voltammetry (CV), fluorescence spectroscopy
(TBA)2[V6O13{(OCH2)3CCH2OCH2-4- measurements (0.1 M TBAClO4 in dry degassed MeCN) at
C6H4CHCHCONMe2}2] (including disordered, uncoordinated different scan rates (dE/dt = 25, 50 and 100 mV s−1; see
CH2Cl2 as indicated in Fig. S2 and Table S4 in the ESI†). Fig. S36 in the ESI†). The oxidation region of the voltammo-
Fig. 1b depicts the molecular structure of the Lindqvist-type gram shows several differently shaped, overlaid waves (Eox
polyoxo(alkoxo)anion 2e, illustrating the favoured linear aryla- −0.61 to 0.70 V) that cannot be directly assigned to the oxi-
tion of the olefin.
dation of the {V6} skeleton and to the irreversible oxidation of
=
Compounds (TBA)22a–(TBA)22e and 2g(TBA)2 exhibit the peripheral organic substituents. The well-defined, single
characteristic 1H NMR signals at δ = ca. 7.50, 6.50 and wave at Ered = −0.70 V (referenced vs. E1/2(Fc/Fc+)) in the
4.45 ppm with a J-coupling constant of 15.0–16.0 Hz, revealing reduction region reflects the typical one-electron transfer ({VV6 }/
the formation of the linear trans products (Table 1). {VI1VV5V}) and is in agreement with the calculated lowest unoc-
Compounds (TBA)22f, (TBA)22h and (TBA)22i show the cis-iso- cupied molecular orbital (LUMO) located on the hexavanadate
meric forms resulting from the spatial arrangement of the peri- skeleton (EDFT = ca. −3.6 eV and Eexp = ca. −4.1 eV).
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Table 1 Reaction of compound (TBA)21 (100 mg) with different olefins (10 eq.) using Pd(OAc)2 (0.05 eq.) as catalyst and Cs2CO3 (2 eq.) in DMF
(5 mL) at 80 °C for the indicated reaction time (t)
Olefin
t/h
Conversiona
>99%
Yieldb
96%
Compound
Isomerc
6
(TBA)22a
trans
20
45%c
—
6
6
6
6
>99%
>99%
>99%
>99%
85%
86%
79%
93%
(TBA)22b
(TBA)22c
(TBA)22d
(TBA)22e
trans
trans
trans
trans
20
20
6
60%c
17%c
>99%
—
—
98%
(TBA)22f
cis
20
20
6
<5%c
>99%
>99%
>99%
—
59%
80%
69%
(TBA)22g
(TBA)22h
(TBA)22i
trans
cis
20
cis
a Based on functional group (aryl iodide) of compound (TBA)21. b After purification. c Determined via 1H NMR.
Table 2 Absorption and emission bands of compounds (TBA)21 and (TBA)22f–(TBA)22i, c = 1 × 10−6 M in dry degassed MeCN
Compound
λmax (ε/L (cm mol)−1)/nm
λem (λex)a/nm
(TBA)21
231 (57 700), 266 (19 900), 357 (7000)
—
(TBA)22f
(TBA)22g
(TBA)22h
223 (44 100), 239 (31 300), 286 (54 900), 299 (62 600), 310 (61 200), 324 (42 200)
230 (50 500), 296 (59 600), 306 (63 700), 320 (63 600), 335 (45 500), 370 (6400)
203 (54 700), 228 (50 700), 240 (38 400), 252 (32 200), 273 (45 000), 283 (47 500),
306 (45 000), 321 (55 800), 333 (43 200), 355 (12 400)
363, 3
341, 3
361, 3
̲7̲7̲
̲5̲7̲
̲8̲0̲
(TBA)22i
228 (59 500), 327 (110 500), 342 (77 800), 381 (6800)
3̲7̲7̲, 395, 417 (330)
a Underlined values correspond to the most intense emission bands; values in brackets show the excitation wavelength.
As the model reductants for {V6} we have chosen thiophenol compared to primary thiols like PrSH.13a,19 It is noteworthy
(PhSH) and cyclopentanethiol (C5H9SH) revealing a stronger that Lindqvist-type hexavanadates were demonstrated to
reducing affinity for an instantaneous complete reduction undergo reduction without structural changes in the presence
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of thiols.13a The reduction of the hexavanadate cage in (TBA)22i
under inert atmosphere (N2) was confirmed via 1H and 51V
NMR spectra showing the absence of the –CH2OCH2– and V
signals, respectively (see Fig. S32, S33 and S35 in the ESI†).
This reduction is accompanied by a significant colour change
from orange to green to green-blue13a,18 (see Fig. S34†), which
is a typical observation in polyoxovanadate redox chemistry.
Interestingly, the use of stronger reductants such as NaBH4 or
diisobutylaluminiumhydrid than thiols or H2/Pd/C led to a
partial destruction of the hexavanadate skeleton which is evi-
denced by ESI-MS. The UV/Vis spectra of (TBA)22i with PhSH
(c(PhSH) = 1 × 10−4 M) show only a slightly increased absor-
bance around 330 nm and a strongly increased one below
290 nm due to the additional d(V), p(Ocage) → π* transition
and the added PhSH as well as the partly in situ formed Ph2S2.
Remarkably, the fluorescence spectra of reduced (TBA)22i
Table 3 Selected energy values of fully-oxidised 2i and six-fold proto-
nated, fully-reduced H62i, obtained at the COSMO/ZORA-B3LYP/TZ2P
level of theory. For computational details see the ESI
Model
EHOMOs/eV
ELUMOs/eV
ΔE/eV
[2i]2−
−5.71, −5.75
−3.64
ca. 2.09
HOMO, HOMO−1
p(C), πligand
LUMO
π
ligand → d(V)
ca. 3.95
ligand → π*ligand
Mainly d(V)
−1.81, −1.76
LUMO+18/+19
p(C), π*ligand
−1.80, −1.76
LUMO/+1/+2/+3 d(V), p(O) → π*ligand
p(C), π*ligand ca. 3.95
ligand → π*ligand
π
[H62i]2− −5.46
ca. 3.68
HOMO
d(V), p(O)
−5.72, −5.74
HOMO−1/−2/−3/−4
p(C), πligand
π
recorded under inert atmosphere exhibit a ca. 4 to 6 times states which gives rise to the low or rather quenched fluo-
increased integrated fluorescence intensity and quantum yield rescence intensity20 at λem = 380/381 nm of the π*ligand
→
after addition of PhSH (QY = 0.7%, λem = 365, 380, 398 nm) or
C5H9SH (QY = 0.6%, c((TBA)22i) = 1 × 10−6 M, λex = 330 nm,
π
ligand transition (Fig. 2).
(ii) Upon reduction the {V6} gains d1 electrons and the
λem = 365, 381, 399 nm) to fully-oxidised (TBA)22i (Fig. 2 and POV’s charge density increases.
Fig. S27 in the ESI†). The integrated emission bands as well as
(iii) Contrary to the frontier orbital situation of the oxidised
the quantum yield reach a maximum for c(PhSH) = 1 × 10−4 species, the highest occupied molecular orbital (HOMO) of the
(see Fig. S31 in the ESI†). It has to be mentioned that the very charge-identical (2−) reduced species (E = −5.46 eV) described
weak blue absorption band at around ca. 800 nm is expected by the d(V) and p(Ocage) contributions is lifted slightly above
to reduce the fluorescence intensity, but due to the weakness the π orbitals of the peripheral 4-phenyl stilbene moieties (E =
of this band its influence on the total emission is – as we ca. −5.70 eV).
anticipate – marginal.
(iv) Additionally to the still present πligand → π*ligand tran-
The increase of the fluorescence intensity of 2i can also be sition (ΔE = ca. 3.95 eV), another energetically nearly equal
explained via DFT calculations (Table 3 and Tables S6–S8 in charge transfer (d(V), p(Ocage) → π*ligand, ΔE = ca. 3.68 eV) that
the ESI†), that provide first important insights into intriguing occurs between the d(V) and p(Ocage) orbitals of the fully-
optical properties of the developed hybrid systems, as follows:
reduced (VI6V), six-fold protonated (at bridging μ-O2− ‡) dianio-
(i) The oxidised {V6} exhibits a detectable πligand → π*ligand nic and hence donating {H6VI6V} unit and the ligands π system
(ΔE = ca. 3.95 eV) charge transfer and an experimentally not is possible. Compared with the experimentally determined
observed or very weak πligand → d(V) transfer (ΔE = ca. 2.09 eV). data, both HOMO to LUMO charge transfers are in line with
Furthermore, we partly expect a charge transfer between the the recorded absorption wavelengths at 327 nm and 326 nm.
excited singlet π* states of the ligands and the d(V) triplet These values correspond to the experimentally determined
HOMO–LUMO gap energy Eexp = ca. 3.80 eV that is in good
agreement with the DFT data (see Table 3).
(v) Furthermore, these switching effects between fully-oxi-
dised 2i and fully-reduced 2i (Fig. 3), which are due to the energy
lifting of the HOMO with the contributions from vanadium in
the latter species (Table 3), are additionally benefited by the
spatial (sterical) arrangement of the 4-styryl-phenyl ligand substi-
tuents in the cis-isomeric form with respect to the {V6} unit. This
thus enables the easier electron exchange between the hexavana-
date cage (d(V), p(Ocage)) and the ligands π system (π*ligand).
We note that time-dependent DFT calculations would likely
give better accuracy for the provided DFT data, however for
these hybrid π-conjugated systems the computational costs
would be prohibitive for a minimal gain.
Overall, the above-described cooperative and electronical
Fig. 2 Left: Emission spectra of (TBA)22i (c = 1 × 10−6 M) without
(orange coloured curve) and with (cyan coloured curve) PhSH (c = 1 ×
10−4 M) in dry degassed MeCN at room temperature. Right: Charge
effects can be responsible for the substantially increased fluo-
rescence emission of reduced18 2i (Fig. 3), even though the
–CH2OCH2– spacer between the POV unit and the conjugated
π organic part most likely acts as an insulator.
transfers (CTs) proposed for fully-oxidised 2i (orange) and its corres-
ponding fully-reduced species (cyan), X = CH2OCH2.
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In summary, the so far not described palladium-catalysed
Heck reactions between different olefins and the Lindqvist-
type hexavanadate were explored and they resulted in the C–C
coupling products in good yield. Although the performed
cross-coupling reactions occur remote from the central {V6}
core and the latter does not chemically influence the peri-
pheral reaction sites, the hexavanadate(V) skeleton as electron
acceptor unit provides an essential fixture for photophysical
processes,21 operating with thermodynamically stable,
vanadium-centered redox states. Our case study with the
organic–inorganic hybrid compound containing the largest
conjugated, stilbene-derivatised π ligands shows the best poss-
ible proof-of-concept for the development of highly susceptible
POV-based fluorescent redox switches for detecting environ-
mentally unfriendly reductants comprising e.g. thiol groups.
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
This work was supported by the Emmy Noether programme of
the Deutsche Forschungsgemeinschaft (DFG).
Fig. 3 (a) HOMOs (blue/red coloured orbitals) and LUMOs (orange/
cyan coloured orbitals) plotted over the structures of fully-oxidised 2i (a)
highlighting the πligand → d(V) transition and of six-fold protonated, fully-
reduced H62i (b) highlighting the d(V), p(Ocage) → π*ligand transition.
Isosurface value is 0.02. Computed at COSMO/ZORA-B3LYP/TZ2P.
Colour code: V = orange, O = red, N = blue, C = grey, H = white.
Notes and references
‡It should be mentioned that Zubieta and co-workers have verified the protona-
tion of the Lindqvist-type anti-hexavanadates, showing that it occurs at the six
bridging μ-O2− atoms, rather than at the terminal oxygens.18
If the concentration of PhSH (c = 1 × 10−3 M and 1 × 10−2
M) is increased, a lower fluorescence intensity caused by a
stronger absorption is observed (see Fig. S26 in the ESI†).
Importantly, an intermolecular charge transfer between the
d(V), p(Ocage) of the hexavanadate and the π* orbitals of PhSH
or Ph2S2 can be excluded due to the high-lying LUMOs of
these reductants (π*(PhSH): −0.56 eV, π*(Ph2S2): −1.14 eV; see
Table S8 in the ESI†).
Moreover, if the reduction of (TBA)22i is not performed
under inert conditions, no significant changes in the fluo-
rescence intensities are observed, which is due to the immedi-
ate re-oxidation of the hexavanadate molecules at low concen-
trations (c = 1 × 10−6 M). Also the relative fluorescence inten-
sity decreases if the solution containing reduced 2i is sub-
jected to air. Alternatively, re-oxidised 2i in highly concentrated
solutions (MeCN or MeOH) can be obtained after several
seconds via the addition of a small amount of aqueous H2O2
or tert-butyl hydroperoxide (TBHP), as verified via 1H NMR
spectroscopy (see Fig. S32 and S33 in the ESI†). However, if the
oxidising agent (H2O2 or TBHP) was not removed via precipi-
tation (Et2O) after a few minutes, 2i undergoes a slight
decomposition (e.g. oxidation of the double bonds) as identi-
fied in the ESI mass spectra.
1 A. Dolbecq, E. Dumas, C. R. Mayer and P. Mialane, Chem.
Rev., 2010, 110, 6009–6048.
2 (a) L. Fu, H. Gao, M. Yan, S. Li, X. Li, Z. Dai and S. Liu,
Small, 2015, 11, 2938–2945; (b) W. Qi and L. Wu, Polym.
Int.,
2009,
58,
1217–1225;
(c)
V.
Kalyani,
V. S. V. Satyanarayana, V. Singh, C. P. Pradeep, S. Ghosh,
S. K. Sharma and K. E. Gonsalves, Chem. – Eur. J., 2015, 21,
2250–2258; (d) M.-P. Santoni, G. S. Hanan and
B. Hasenknopf, Coord. Chem. Rev., 2014, 281, 64–85.
3 See, e.g.: (a) Y. Hou and C. L. Hill, J. Am. Chem. Soc., 1993,
115, 11823–11830; (b) A. Proust, B. Matt, R. Villanneau,
G. Guillemot, P. Gouzerh and G. Izzet, Chem. Soc. Rev.,
2012, 41, 7605–7622; (c) B. Riflade, D. Lachkar, J. Oble,
J. Li, S. Thorimbert, B. Hasenknopf and E. Lacôte, Org.
Lett., 2014, 16, 3860–3863; (d) G. Izzet, F. Volatron and
A. Proust, Chem. Rec., 2017, 17, 250–266.
4 A. Lombana, C. Rinfray, F. Volatron, G. Izzet, N. Battaglini,
S. Alves, P. Decorse, P. Lang and A. Proust, J. Phys. Chem. C,
2016, 120, 2837–2845.
5 Y. Ji, J. Hu, L. Huang, W. Chen, C. Streb and Y.-F. Song,
Chem. – Eur. J., 2015, 21, 6469–6474.
6 (a) K. Micoine, B. Hasenknopf, S. Thorimbert, E. Lacôte
and M. Malacria, Org. Lett., 2007, 9, 3981–3984; (b) Y. Zhu,
This journal is © The Royal Society of Chemistry 2018
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Dalton Transactions
L. Wang, J. Hao, P. Yin, J. Zhang, Q. Li, L. Zhu and Y. Wei,
ed. C. Pena, Nova Science Publishers, Hauppauge, 2017,
Chem. – Eur. J., 2009, 15, 3076–3080; (c) M.-B. Hu, N. Xia,
pp. 39–66.
W. Yu, C. Ma, J. Tang, Z.-Y. Hou, P. Zheng and W. Wang, 13 (a) J. W. Han and C. L. Hill, J. Am. Chem. Soc., 2007, 129,
Polym. Chem., 2012, 3, 617–620; (d) H.-K. Yang, M.-M. Su,
L.-J. Ren, J. Tang, Y.-K. Yan, W.-K. Miao, P. Zheng and
W. Wang, Eur. J. Inorg. Chem., 2013, 1381–1389;
(e) S. Vanhaecht, J. Jacobs, L. Van Meervelt and T. N. Parac-
15094–15095; (b) C. Allain, S. Favette, L. Chamoreau,
J. Vaissermann, L. Ruhlmann and B. Hasenknopf,
Eur. J. Inorg. Chem., 2008, 3433–3441; (c) M. Santoni,
A. K. Pal, G. S. Hanan, M. Tang, K. Venne, A. Furtos,
P. Ménard-Tremblay, C. Malveau and B. Hasenknopf,
Chem. Commun., 2012, 48, 200–202; (d) Z. Huo, D. Zang,
S. Yang, R. Farha, M. Goldmann, B. Hasenknopf,
H. Xu and L. Ruhlmann, Electrochim. Acta, 2015, 179, 326–
335.
Vogt,
Dalton
Trans.,
2015,
44,
19059–19062;
(f) A. Macdonell, N. A. B. Johnson, A. J. Surman and
L. Cronin, J. Am. Chem. Soc., 2015, 137, 5662–5665;
(g) S. Vanhaecht, T. Quanten and T. N. Parac-Vogt, Dalton
Trans., 2017, 46, 10215–10219.
7 (a) D. Gatteschi, L. Pardi, A. L. Barra and A. Müller, Mol. 14 (a) D. Rehder, in Vanadium in Biological Systems, ed.
Eng., 1993, 3, 157–169; (b) J. Livage, Coord. Chem. Rev.,
1998, 178–180, 999–1018; (c) Y. Hayashi, Coord. Chem. Rev.,
2011, 255, 2270–2280; (d) C. Streb, in Struct. Bond.,
Springer, Berlin, Heidelberg, 2017, pp. 1–7.
8 (a) P. Wu, Z. Xiao, J. Zhang, J. Hao, J. Chen, P. Yin and
Y. Wei, Chem. Commun., 2011, 47, 5557–5559; (b) P. Yin,
N. D. Chasteen, Springer, Netherlands, 1990, pp. 173–197;
(b) M. Aureliano, World J. Biol. Chem., 2011, 2, 215–225;
(c) K. Y. Monakhov, M. Moors and P. Kögerler, in Adv.
Inorg. Chem., Polyoxometalate Chemistry, ed. R. van Eldik
and L. Cronin, Academic Press, Elsevier, Amsterdam, 2017,
vol. 69, pp. 251–286.
P. Wu, Z. Xiao, D. Li, E. Bitterlich, J. Zhang, P. Cheng, 15 (a) R. F. Heck and J. P. Nolley, J. Org. Chem., 1972, 37,
D. V. Vezenov, T. Liu and Y. Wei, Angew. Chem., Int. Ed., 2011,
50, 2521–2525; (c) Z. Xiao, K. Chen, B. Wu, W. Li, P. Wu and
2320–2322; (b) H. A. Dieck and R. F. Heck, J. Am. Chem.
Soc., 1974, 96, 1133–1136.
Y. Wei, Eur. J. Inorg. Chem., 2016, 808–811; (d) B. Huang, 16 R. Munday, Free Radicals Biol. Med., 1989, 7, 659–
Z. Xiao, B. Wu, X. Hu, X. Hu, P. Wu and Y. Wei, Inorg. Chem. 673.
Front., 2017, 4, 165–170; (e) A. Bayaguud, J. Li, S. She and 17 K. P. Sullivan, W. A. Neiwert, H. Zeng, A. K. Mehta, Q. Yin,
Y. Wei, Dalton Trans., 2017, 46, 4602–4608.
D. A. Hillesheim, S. Vivek, P. Yin, D. L. Collins-Wildman,
E. R. Weeks, T. Liu and C. L. Hill, Chem. Commun., 2017,
53, 11480–11483.
9 D. Li, J. Song, P. Yin, S. Simotwo, A. J. Bassler, Y. Aung,
J. E. Roberts, K. I. Hardcastle, C. L. Hill and T. Liu, J. Am.
Chem. Soc., 2011, 133, 14010–14016.
18 Q. Chen, D. P. Goshorn, C. P. Scholes, X. L. Tan and
J. Zubieta, J. Am. Chem. Soc., 1992, 114, 4667–4681.
10 (a) O. Linnenberg, A. Kondinski, C. Stöcker and
K. Y. Monakhov, Dalton Trans., 2017, 46, 15636–15640; 19 A. Bayaguud, K. Chen and Y. Wei, Nano Res., 2016, 9, 3858–
(b) H. Jia, Q. Li, A. Bayaguud, Y. Huang, S. She, K. Chen
and Y. Wei, Dalton Trans., 2018, 47, 577–584.
11 K. Y. Monakhov, W. Bensch and P. Kögerler, Chem. Soc.
Rev., 2015, 44, 8443–8483.
3867.
20 F. Odobel, M. Séverac, Y. Pellegrin, E. Blart, C. Fosse,
C. Cannizzo, C. R. Mayer, K. J. Elliott and A. Harriman,
Chem. – Eur. J., 2009, 15, 3130–3138.
12 O. Linnenberg, A. Kondinski and K. Y. Monakhov, in 21 J. M. Cameron, D. J. Wales and G. N. Newton, Dalton
Supramolecular Systems: Chemistry, Types and Applications, Trans., 2018, 47, 5120–5136.
Dalton Trans.
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