Kinetic investigation of the dissociation of dinuclear hierarchically assembled titanium(iv) helicates

Article abstract of DOI:10.1039/c9dt01065c

Hierarchically assembled helicates consisting of lithium-bridged triscatecholate titanium(iv) complexes represent a powerful self-assembled supramolecular system with applications as e.g. molecular balances for the evaluation of weak interactions, stereos

Full text of DOI:10.1039/c9dt01065c

View Article Online
View Journal
Dalton
Transactions
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: D. Van Craen, M.
Schlottmann, W. Stahl, C. Räuber and M. Albrecht, Dalton Trans., 2019, DOI: 10.1039/C9DT01065C.
This is an Accepted Manuscript, which has been through the
Volume 45 Number
1 7 January 2016 Pages 1–398
Royal Society of Chemistry peer review process and has been
accepted for publication.
Dalton
Transactions
Accepted Manuscripts are published online shortly after
An international journal of inorganic chemistry
www.rsc.org/dalton
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1477-9226
PAPER
Joseph T. Hupp, Omar K. Farha et al.
Efficient extraction of sulfate from water using
framework
a Zr-metal–organic
rsc.li/dalton

Please do not adjust margins
Page 1 of 8
Dalton Transactions
View Article Online
DOI: 10.1039/C9DT01065C
Journal Name
ARTICLE
Kinetic investigation of the dissociation of dinuclear hierarchically
assembled titanium(IV) helicates
David Van Craen,a Marcel Schlottmann,a Wolfgang Stahl,b Christoph Räuber,a Markus Albrecht*a
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Hierarchically assembled helicates consisting of lithium-bridged triscatecholate titanium(IV) complexes represent a
powerful self-assembled supramolecular system with applications as e.g. molecular balances for the evaluation of weak
interactions, stereoselectivity switches in asymmetric synthesis or molecular switch. The respective applications or
properties are based on the monomer-dimer equilibrium which easily can be observed in solution. The dimer is the only
species in the crystal. After dissolution, the dimer slowly dissociates into the monomer until the equilibrium is reached.
This can be followed by NMR spectroscopy to observe the kinetics of the dissociation process. A strong steric effect can be
found studying differently substituted ligands. Activation energies of the dissociation process can be correlated with the
www.rsc.org/
size of the ester substituents and the system may be described as
a
molecular buckle.
well as the influence of the electron density at the carbonyl
group30 were pointed out earlier. Solvents which can
coordinate lithium cations well in solution (e.g. DMSO)
destabilize the dimer, while solvents which show a lower
affinity (e.g. methanol) result in a higher dimer stability. In a
recent study the effect of weak interactions, e.g. solvent as
well as dispersive forces between the ester side chains has
been addressed. In the earlier study it was realized that the
thermodynamic equilibrium in some cases needs some time to
be reached.31 This observation of a “slow” equilibration
behaviour in DMSO opens up the way for kinetic investigations
of the monomer-dimer equilibrium by NMR spectroscopy and
finally allows the determination of activation barriers.
Introduction
In 1987 Jean-Marie Lehn defined the term “helicate” for
coordination compounds in which two or more ligand strands
twist around two or more metal centers.1 In the following
years the chemistry of helicates gained more and more
interest as simple models for the understanding of
supramolecular key principles like self-assembly.2,3 Besides the
classical “helicate” possessing covalently bridged ligand
strands, hierarchically assembled helicate-type systems4–15
came into focus more than a decade later. A first example of
those remarkable supramolecular structures16 had already
been known 25 years before Lehn’s pioneering work on
helicates. Hierarchical assembly is based on two (or more)
consecutive recognition events: the formation of a Werner-
Furthermore, understanding the kinetics of the system cannot
be underestimated in order to use the dimerization process at
its equilibrated state for the development of molecular
devices, like switches.32
type complex is followed by dimerization 17, 18–21
.
Our group utilizes catechol ligands with aldehyde, ketone or
ester substituents in the 3-position for the formation of
hierarchically assembled lithium-bridged titanium(IV)17,22–27
gallium(III)17, boron(III)28 and molybdenum(VI)dioxo29 helicate-
type complexes. It was shown in the past that the dimer is
usually found in the solid state while in solution both
monomer and dimer can be easily observed via 1H NMR
spectroscopy.17,25,26 The dimer stability depends on the
strength of the coordination of lithium cations to the salicylate
units of two monomers. The crucial role of the solvent17,23 as
,
Results and discussion
Catecholester ligands are obtained via esterification of the
corresponding
alcohol
with
2,3-dioxosulfinylbenzoyl
chloride33–36 which in situ is readily prepared from 2,3-
dihydroxybenzoic acid and thionyl chloride. Formation of
titanium(IV) complexes takes place in methanol with the
ligands (3 eq.), titanoyl acetylacetonate (1 eq.) and lithium
carbonate (1 eq.).
Dissolution of the solid dimeric complexes Li[Li3{(L)3Ti}2] at
room temperature in DMSO-d6 at a concentration of 2.0·10-3
mol L-1 initially leads to a solution of dimer which slowly
dissociates and finally ends up in the thermodynamic ratio
between monomer and dimer (scheme 1). In order to obtain
energetic parameters for the reaction the disappearance of
the dimer and the appearance of the monomer are followed.
a. Institut für Organische Chemie, RWTH Aachen University, Landoltweg 1, 52074
Aachen; Germany; markus.albrecht@oc.rwth-aachen.de.
b. Institut für Physikalische Chemie, RWTH Aachen University, Landoltweg 2, 52074
Aachen; Germany.
† Electronic Supplementary Information (ESI) available: [NMR spectra, solution of
the kinetic equation and kinetic plots]. See DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 2 of 8
ARTICLE
Journal Name
To observe a significant change of both dimer and monomer After 22 minutes the concentration of the monomer already
View Article Online
DOI: 10.1039/C9DT01065C
NMR signals, complexes with low dimerization tendency in exceeds the one of the dimer (twice the amount equivalent
DMSO-d6 provide the best results, causing a fast initial increase protons is present in the dimeric structure compared to the
of the monomer signals which is essential to reduce errors monomeric one). The equilibrium is reached after 106.5
based on the signal to noise ratio.
minutes with a final dimer concentration of 9.13·10-4 mol L-1
and a monomer concentration of 2.17·10-3 mol L-1.
Visualizing the dimer Li[Li3{(Me)3Ti}2] concentration (figure 2,
top) in dependency to time results in an expected exponential
decay of the dimer (red) while the amount of monomer
Li2[(Me)3Ti] (blue) increases.
The other investigated complexes show slower equilibration
behaviour in contrast to the methyl substituted complex
(figure 2, bottom). The necessary period for reaching the
equilibrium is multiple times higher for the cyclobutyl
substituted complex Li[Li3{(cyBu)3Ti}2] and drastically increases
for the 3-pentyl complex Li[Li3{(3-Pent)3Ti}2], which is followed
for eleven hours (not all data points are shown in figure 2, see
SI for the full measurement). At this point the equilibrium state
was not even close. The dimerization constant Kdim., which is
necessary for the determination of the rate constants, was
measured for Li[Li3{(3-Pent)3Ti}2] after three days.
O
O
O
O
O
O
O
O
O
O
Ti
O
Li2
Ti
O
R
R
R
O
O
+
R
R
R
O
O
O
O
O
R
R
k1
O
O
O
O
O
R
R
O
O
O
O
O
dissociation
O
O
Li
Li
Li
Li
O
association
k2
O
O
O
R
O
O
O
O
R
Ti
O
O
O
Ti
O
Li2
O
O
O
O
O
"dimer"
L
Li[Li3{( )3Ti}2]
"monomers"
Li2[( )3Ti]
L
Me cyBu
3-Pent
3,5-F -Bz
3,5-Cl -Bz
2
3,5-Br2-Bz
R =
,
,
,
,
,
2
Br
F
Cl
Br
F
Cl
Scheme 1: Studied equilibria between hierarchical helicates as
dimers and the corresponding triscatecholate complexes as
monomers.
1
The H NMR spectrum of Li[Li3{(Me)3Ti}2] (figure 1) shows two
sets of aromatic signals (doublet of doublets, triplet and
doublet of doublets) as well as singlets for each, the dimer
(red) and the monomer (blue). The initial spectrum (measured
4 minutes after dissolving the dimer) shows small signals of the
monomer.
Figure 2: Concentration of monomer and dimer of the methyl
substituted complex in DMSO-d6 depending on the time after
dissolution (top). Comparison of the time dependent increase
of monomer concentration of all investigated complexes
(bottom).
The complexes with methyl and benzyl esters show a
significant faster dissociation behaviour than the cyclobutyl
and the 3-pentyl substituted coordination compounds. The
halogenated benzyl esters (scheme 1) are investigated to
understand the impact of the distance between the sterical
demanding residue and the helical cleft. The choice of
1
Figure 1: H NMR observation (c0 = 2 mM) of the equilibration
process. (Regions without signals were removed for clarity
reasons - see supporting information for the full spectra)
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 8
Dalton Transactions
Please do not adjust margins
Journal Name
ARTICLE
halogenated benzyl esters depends also on their low dimer The rate constants for all complexes are “mVirierworAirnticgle”Ontlhinee
stability which is comparable to the stability of the alkyl ester behaviour observed in figure 2 bottom. Complexes bearing
DOI: 10.1039/C9DT01065C
complexes. The low dimer stability is crucial in order to fluoride, chloride and bromide substituents in the meta
observe sufficient concentration changes of the monomer and position of the benzyl ester show very similar rate constants
dimer species via NMR spectroscopy and to minimize errors. (table 1, entry 4-6). The methyl complex (table 1, entry 1)
The difference in between the halogenated benzyl series is not shows a dissociation rate which is twice as high than the ones
significant and shows that the kinetics depend mainly on steric of the halogenated benzyl complexes while a lower rate is
effects in close proximity of the helical structure or even in the observed for the cyclobutyl substituted complex (table 1, entry
helical cleft. The obtained rate constants provide a more 2). On the other hand the association rate of the methyl
detailed comparison and allow the calculation of the activation substituted monomers is slightly increased in comparison to
energies. The approach to solve the kinetics (see supporting the halogenated ones while the association of the cyclobutyl
information for mathematic solution) of the reaction leads to a bearing monomer units is significantly reduced. The 3-pentyl
linear equation including the rate constant k2 as slope.
complex (table 1, entry 3), which bears the most sterically
hindered residue of this series, shows drastically reduced
dissociation and association rates which are around one order
of magnitude lower. The values reveal the strong dependency
of the dissociation and association rates on steric effects close
to the helical cleft. The benzyl systems including a methylene
spacer between the carboxyl function and the bulky aromatic
residues are right beyond the methyl complex according to
their equilibration behaviour while cyclic and branched
systems without a methylene unit show significantly lower
rate constants.
풅풂
= ― 풌ퟏ풂 + 풌ퟐ풃ퟐ
풅풕
풚 = ― 풌ퟐ풕 + 풄
풌ퟏ = 푲 ∙ 풌ퟐ
ퟏ
푲 =
푲푫풊풎.
Table 1: Rate constants determined by following the kinetic
approach for the dissociation and association of dimeric
hierarchically assembled helicates in DMSO-d6 at 25 °C.
dissociation
rate k2
association
rate k1
KDim.
entry substituent
[L mol-1]
[L mol-1 s-1]
6.39·10-2
[s-1]
3.29·10-4
 0.46·10-4
9.99·10-5
 0.49·10-5
1.80·10-5
 0.04·10-5
3.20·10-4
 0.13·10-4
3.04·10-4
 0.58·10-4
2.10·10-4
 0.45·10-4
1
2
3
4
5
6
Me
194  20
174  18
57  6
 0.90·10-2
1.74·10-2
cyBu
 0.09·10-2
1.03·10-3
3-Pent
 0.03·10-3
2.24·10-2
Figure 3: Calculation of rate constants by following the kinetic
approach (top) and based on the initial slope (bottom).
3,5-F2-Bz
3,5-Cl2-Bz
3,5-Br2-Bz
70  7
 0.09·10-2
2.70·10-2
89  9
 0.51·10-2
2.64·10-2
The kinetics are solved for the dimer dissociation. K represents the
dissociation constant. The rate k1 can be calculated via k2 and K. The
final data points close to the equilibrium show a stepwise shape
and are excluded in the linear regression to maintain accuracy. The
rate constants for the association and dissociation of the methyl
complex Li[Li3{(Me)3Ti}2] in DMSO-d6 are k2 = 6.39·10-2 L mol-1 s-1
and k1 = 3.29·10-4 s-1. The rate constant k1 can also be obtained via
the initial slope of ln(cd/cd,t=0) as a function of time.37 At this point k1
can be estimated according to a first order reaction. The rate
constant k1 = 3.76·10-4 s-1 obtained by this route results in a similar
value with a difference of 14 % according to the previous calculated
rate constant following the kinetic approach.
126  13
 0.57·10-2
Dispersive forces may occur between the ester residues of two
dimer halfs31. Dispersion is negligible for the methyl and
cyclobutyl complex due to the long CH-CH distances between
the ester residues as shown already in earlier studies.31
Thus, steric demand is the main reason for the different kinetic
behaviour and the system can be described as a molecular
symmetric buckle. The size of the “teeth” of the buckle halves
reflects the steric demand of the ester residue.
The activation energies for the association and dissociation of
the methyl and cyclobutyl substituted complexes are shown as
exemplary systems to illustrate this model. The equilibration
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 4 of 8
ARTICLE
Journal Name
behaviour therefore was monitored at five different
temperatures (figure 4). Starting from 25 °C the temperature
was increased in steps of 10 °C up to 65 °C.
activation energy of the dimerization going from the methyl to
View Article Online
the cyclobutyl derivative. More energy DisOnI:e10e.d10e3d9/iCn9DoTr0d1e0r65tCo
lock the bigger groups in the dimer or to disrupt the dimer to
form the monomers.
Thus, the system mimics a symmetric molecular buckle.
Closing the lock with bigger “teeth” (increased steric demand)
takes more strength to push the halves together as well as to
open the lock.
Conclusions
Herein we investigated the kinetics of the formation of
hierarchically assembled lithium-bridged titanium(IV) helicates
(dimer) as well as their dissociation to the corresponding
“Werner” type triscatecholate complexes (monomer). The
kinetic behaviour shows that the underlying processes in this
system behave like a molecular buckle. With bigger side
groups the necessary energy for closing and opening the lock
increases, resulting in lower reaction rates.
Understanding the kinetics of this system changes our
perspective for so far more challenging systems bearing
extreme bulky ester substituents. Thus, investigating the limit
of the steric demand of the substituents is required for the
design of future functional materials.
Figure 4: Calculation of activation energies of the dimer
association for the methyl (top) and cyclobutyl substituted
complex (bottom). The red values obtained at 65 °C are
excluded in the linear regression analysis.
Figure 5: Visualization of the symmetric molecular snap lock with the methyl (left) and the cyclobutyl complex (right).
The rate constant at 65°C represents an aberration due to the
rapid equilibration coming along with too less values for an
accurate calculation of the rate constants by linear regression.
Experimental
It is excluded in both cases.
Materials and methods:
Energies of activation are obtained with the assumption of a
nearly temperature independent Arrhenius factor. The values
(figure 5) reflect the behaviour of the rate constants for the
methyl Li[Li3{(Me)3Ti}2] and the cyclobutyl complex
Li[Li3{(cyBu)3Ti}2]. An increase of 6 kJ mol-1 is observed for the
2,3-Dihydroxybenzoic acid was purchased from FluoroChem, thionyl
chloride from Acros and the corresponding alcohols from Alfa
Aesar, abcr GmbH and TCI. All chemicals were used without further
purification. The used DMSO-d6 (99.9 %, with 0.05 % TMS as
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 5 of 8
Dalton Transactions
Please do not adjust margins
Journal Name
ARTICLE
internal standard) was procured from Cambridge Isotope Harom.), 5.65 (s, 1H, OH), 5.32 (s, 2H, OCH2) ppm. 13C NVMieRw A(1rt5ic1le MOnHlinze,
DOI: 10.1039/C9DT01065C
Laboratories. NMR spectroscopy was carried out on a Mercury 300 CDCl3, 25 °C): δ = 169.9 (CO2CH2), 149.2 (Carom.), 145.2 (Carom.), 138.6
as well as a Varian NMR 400 and 600 device. Mass spectrometry (Carom.), 135.5 (Carom.), 128.9 (Carom.), 126.6 (Carom.), 120.7 (Carom.),
was measured using a LTQ Orbitrap XL device. IR spectra were 120.4 (Carom.), 119.6 (Carom.), 112.1 (Carom.), 65.5 (CO2CH2) ppm. MS
obtained with
a
Perkin-Elmer Spektrum 100 spectrometer. (negative ESI-FMTS, MeOH): m/z (%) = 310.9881 (50, [M-H+],
-
Elemental composition was detected with a Heraeus CHN-O-Rapid C14H9Cl2O4 , calc.: 310.9883). IR (in KBr): ṽ (cm-1): 3443 (m), 3239
device.
(m), 3086 (w), 1677 (s), 1598 (m), 1571 (m), 1467 (s), 1375 (s), 1306
(vs), 1237 (s), 1144 (s), 1067 (m), 1015 (m), 920 (m), 843 (s), 799 (s),
736 (s). Elemental analysis C14H10Cl2O4: calc. C = 53.70 %, H =
3.22 %; found C = 53.68 %, H = 3.21 %.
General method for ligand synthesis:
2,3-Dihydroxybenzoic acid (1 eq.) was heated under reflux
conditions in thionyl chloride (30 eq.) for three hours. Full
conversion was observed (transition from a suspension to clear
3,5-Dibromobenzyl-2,3-dihydroxybenzoate ((3,5-Br2-Bz)-H2):
solution). After this time remaining thionyl chloride was removed Yield: 69 % (418.0 mg, 1.04 mmol, colourless solid). M.p. = 114 °C.
under reduced pressure. The obtained 2,3-dioxosulfinylbenzoyl 1H NMR (300 MHz, CDCl3, 25 °C): δ = 10.70 (s, 1H, OH), 7.67 (t, J =
chloride was not further purified and diluted with chloroform. A 1.7 Hz, 1H, Harom.), 7.52 (d, J = 1.7 Hz, 2H, Harom.), 7.41 (dd, J = 8.0,
solution of the corresponding alcohol (5 eq.) and triethylamine (5 1.5 Hz, 1H, Harom.), 7.17-7.09 (m, 1H, Harom.), 6.83 (t, J = 8.0 Hz, 1H,
eq.) in chloroform was added to the solution of the 2,3- Harom.), 5.64 (s, 1H, OH), 5.31 (s, 2H, OCH2) ppm. 13C NMR (151 MHz,
dioxosulfinylbenzoyl chloride in chloroform, resulting in a 0.2 molar CDCl3, 25 °C): δ = 169.9 (CO2CH2), 149.2 (Carom.), 145.2 (Carom.), 139.1
solution. The mixture was heated under reflux conditions for 24 (Carom.), 134.4 (Carom.), 130.0 (Carom.), 123.4 (Carom.), 120.7 (Carom.),
hours. Afterwards the reaction mixture was washed with saturated 120.4 (Carom.), 119.6 (Carom.), 112.1 (Carom.), 65.4 (CO2CH2) ppm. MS
NaHCO3 solution and dried over MgSO4. The desired product was (negative ESI-FTMS, MeOH, acidified): m/z (%) = 400.8859 (100,
-
isolated and purified by column chromatography with silica gel 60 [M-H+], C14H9Br2O4 , calc.: 400.8853). IR (in KBr): ṽ (cm-1) = 3510 (m),
(35 – 70 µm).
3404 (m), 3070 (w), 1668 (s), 1557 (m), 1467 (s), 1381 (m), 1303
(vs), 1139 (vs), 1070 (m), 991 (m), 846 (s), 744 (vs). Elemental
analysis C14H10Br2O4: calc. C = 41.83 %, H = 2.51 %; found C = 41.81
%, H = 2.67 %.
General method for helicate synthesis:
Catechol ligand (3 eq.), TiO(acac)2 (1 eq.) and Li2CO3 (1 eq.) were
dissolved in MeOH (0.02 M) and stirred for 24 hours. Afterwards,
the solvent was removed under reduced pressure and the desired
complex was received as a red solid without further purification.
Li[Li3{(3,5-F2-Bz)3Ti}2]:
1
Yield: quantitative (140 mg, 78 µmol, red solid). H NMR (400 MHz,
DMSO-d6, 25 °C): Monomer (major component): δ = 6.83 (dd, J =
7.8, 1.5 Hz, 1H, Harom.), 6.29 (t, J = 7.8 Hz, 1H, Harom.), 6.17 (dd, J =
7.8, 1.5 Hz, 1H, Harom.), 5.19 (s, 2H, OCH2) ppm. Dimer (minor
component): δ = 7.03 (dd, J = 7.9, 1.4 Hz, 1H, Harom.), 6.96-6.88 (m,
2H, Harom.), 6.54 (dd, J = 7.9, 1.4 Hz, 1H, Harom.), 6.38 (t, J = 7.9 Hz,
1H, Harom.), 4.63 (d, J = 13.7 Hz, 1H, OCH2), 3.98 (d, J = 13.7 Hz, 1H,
OCH2) ppm. The other benzyl ester signals are overlapping and are
not assigned. MS (negative ESI-FTMS, MeOH): m/z (%) = 1785.1838
31
Literature known compounds: Catechol ligands Me-H217, cyBu-H2
31
and 3-Pent-H2 as well as their corresponding titanium complexes
Li[Li3{(Me)3Ti}2]17, Li[Li3{(cyBu)3Ti}2]31 and Li[Li3{(3-Pent)3Ti}2]31 are
well described in the literature.
3,5-Difluorobenzyl-2,3-dihydroxybenzoate ((3,5-F2-Bz)-H2):
Yield = 45 % (810 mg, 2.89 mmol, colourless solid). M.p. = 98 °C. 1H
NMR (400 MHz, CDCl3, 25 °C): δ = 10.71 (s, 1H, OH), 7.42 (dd, J =
8.1, 1.5 Hz, 1H, Harom.), 7.16-7.12 (m, 1H, Harom.), 7.00-6.93 (m, 2H,
Harom.), 6.86-6.77 (m, 2H, Harom.), 5.64 (s, 1H, OH), 5.35 (s, 2H, OCH2)
ppm. 13C NMR (101 MHz, CDCl3, 25 °C): δ = 169.8 (CO2CH2), 163.1
(Carom.), 149.0 (Carom.), 145.1 (Carom.), 138.9 (Carom.), 120.5 (Carom.),
-
(100, [M-Li+], C84H48F12O24Li3Ti2 , calc.: 1785.1788). IR (in KBr):
ṽ (cm-1) = 3372 (w), 1677 (s), 1597 (s), 1443 (s), 1384 (m), 1209 (s),
1065 (m), 946 (s), 844 (s), 744 (s). Elemental analysis
C84H48F12O24Li4Ti2 × 3 H2O: calc. C = 54.63 %, H = 2.95 %; found C =
54.42 %, H = 3.02 %.
120.2 (Carom.), 119.4 (Carom.), 111.9 (Carom.), 110.6 (Carom.), 103.9 Li[Li3{(3,5-Cl2-Bz)3Ti}2]:
(Carom.), 65.5 (CO2CH2) ppm. 19F NMR (376 MHz, CDCl3, 25 °C): δ =
1
Yield: quantitative (136 mg, 68 µmol, red solid). H NMR (400 MHz,
DMSO-d6, 25 °C): Monomer (major component): δ = 7.44 (d, J = 1.5
Hz, 2H, Harom.), 6.81 (dd, J = 7.8, 1.5 Hz, 1H, Harom.), 6.29 (t, J = 7.8 Hz,
1H, Harom.), 6.16 (dd, J = 7.8, 1.5 Hz, 1H, Harom.), 5.18 (s, 2H, OCH2)
ppm. Dimer (minor component): δ = 7.25 (d, J = 1.8 Hz, 2H, Harom.),
7.02 (dd, J = 7.8, 1.4 Hz, 1H, Harom.), 6.54 (dd, J = 7.8, 1.5 Hz, 1H,
Harom.), 6.39 (t, J = 7.8 Hz, 1H, Harom.), 4.59 (d, J = 13.5 Hz, 1H, OCH2),
3.99 (d, J = 13.5 Hz, 1H, OCH2) ppm. The not assigned benzyl ester
signal is overlapping. MS (negative ESI-FMTS, MeOH): m/z (%) =
-108.9 (t, J = 7.6 Hz) ppm. MS (negative ESI-FTMS, MeOH): m/z (%) =
-
279.0495 (95, [M-H+], C14H9F2O4 , calc.: 279.0474). IR (in KBr): ṽ
(cm-1) = 3434 (w), 3214 (w), 2939 (w), 1682 (vs), 1629 (m), 1596 (s),
1469 (s), 1389 (m), 1298 (s), 1255 (s), 1150 (s), 1116 (s), 1072 (m),
1033 (w), 989 (m), 961 (s), 844 (s), 748 (s), 694 (s). Elemental
analysis C14H10F2O4: calc. C = 60.01 %, H = 3.60 %; found C = 59.92
%, H = 3.67 %.
3,5-Dichlorobenzyl-2,3-dihydroxybenzoate ((3,5-Cl2-Bz)-H2):
-
1982.8169 (100, [M-Li+], C84H48Cl12O24Li3Ti2 , calc.: 1982.8154). IR (in
Yield = 35 % (716.8 mg, 2.29 mmol, colourless solid). M.p. = 103 °C.
1H NMR (400 MHz, CDCl3, 25 °C): δ = 10.70 (s, 1H, OH), 7.41 (dd, J =
8.1, 1.5 Hz, 1H, Harom.), 7.36 (t, J = 1.8 Hz, 1H, Harom.), 7.32 (d, J = 1.8
Hz, 2H, Harom.), 7.17-7.09 (m, 1H, Harom.), 6.83 (t, J = 8.0 Hz, 1H,
KBr): ṽ (cm-1) = 3366 (w), 1678 (s), 1569 (s), 1440 (s), 1374 (m), 1251
(s), 1151 (s), 1011 (s), 921 (m), 849 (s), 797 (s), 681 (s). Elemental
analysis C84H48Cl12O24Li4Ti2 × 5 H2O: calc. C = 48.50 %, H = 2.81 %;
found C = 48.54 %, H = 2.71 %.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 6 of 8
ARTICLE
Journal Name
11 M. Albrecht, K. Witt, P. Weis, E. Wegelius and R. Fröhlich,
Li[Li3{(3,5-Br2-Bz)3Ti}2]:
View Article Online
Inorganica Chim. Acta, 2002, 341, 25–32.
DOI: 10.1039/C9DT01065C
1
Yield: quantitative (128 mg, 51 µmol, red solid). H NMR (400 MHz,
DMSO-d6, 25 °C): Monomer (major component): δ = 7.61 (d, J = 1.1
Hz, 2H, Harom.) 6.81 (dd, J = 7.8, 1.2 Hz, 1H, Harom.), 6.29 (t, J = 7.8 Hz,
1H, Harom.), 6.16 (dd, J = 7.8, 1.2 Hz, 1H, Harom.), 5.17 (s, 2H, OCH2)
12 J. Heinicke, N. Peulecke, K. Karaghiosoff and P. Mayer, Inorg.
Chem., 2005, 44, 2137–2139.
13 S. Hiraoka, Y. Sakata and M. Shionoya, J. Am. Chem. Soc., 2008,
130, 10058–10059.
14 Y. Sakata, S. Hiraoka and M. Shionoya, Chem. - Eur. J., 2010, 16,
3318–3325.
15 G. Bauer, Z. Benkő, J. Nuss, M. Nieger and D. Gudat, Chem. -
Eur. J., 2010, 16, 12091–12095.
16 D. H. Busch and D. C. Jicha, Inorg. Chem., 1962, 1, 884–887.
17 M. Albrecht, S. Mirtschin, M. de Groot, I. Janser, J. Runsink, G.
Raabe, M. Kogej, C. A. Schalley and R. Fröhlich, J. Am. Chem. Soc.,
2005, 127, 10371–10387.
18 K. Yoneda, K. Adachi, K. Nishio, M. Yamasaki, A. Fuyuhiro, M.
Katada, S. Kaizaki and S. Kawata, Angew. Chem. Int. Ed., 2006, 45,
5459–5461.
ppm. Dimer (minor component): δ = 7.42 (d, J = 1.1 Hz, 2H, Harom.
)
7.05-6.99 (m, 1H, Harom.), 6.57-6.51 (m, 1H, Harom.), 6.40 (t, J = 7.8 Hz,
1H, Harom.), 4.57 (d, J = 13.7 Hz, 1H, OCH2), 3.98 (d, J = 13.7 Hz, 1H,
OCH2) ppm. The other signal from the benzyl ester residue is
overlapping and cannot be assigned. MS (negative ESI-FMTS,
-
MeOH): m/z (%) = 2516.1992 (100, [M-Li+], C84H48Br12O24Li3Ti2 ,
calc.: 2516.2054). IR (in KBr): ṽ (cm-1) = 3365 (w), 2070 (w), 1678 (s),
1556 (m), 1441 (s), 1209 (s), 1009 (s), 907 (w), 848 (m), 742 (s), 681
(s). Elemental analysis C84H48Br12O24Li4Ti2 × 4 H2O: calc. C = 38.87 %,
H = 2.17 %; found C = 38.88 %, H = 2.29 %.
19 A.-X. Zhu, J.-P. Zhang, Y.-Y. Lin and X.-M. Chen, Inorg. Chem.,
2008, 47, 7389–7395.
20 G. N. Newton, T. Onuki, T. Shiga, M. Noguchi, T. Matsumoto, J.
S. Mathieson, M. Nihei, M. Nakano, L. Cronin and H. Oshio,
Angew. Chem. Int. Ed., 2011, 50, 4844–4848.
Conflicts of interest
“There are no conflicts to declare”
21 M. Okamura, M. Kondo, R. Kuga, Y. Kurashige, T. Yanai, S.
Hayami, V. K. K. Praneeth, M. Yoshida, K. Yoneda, S. Kawata and S.
Masaoka, Nature, 2016, 530, 465–468.
Acknowledgements
22 M. Albrecht, M. Baumert, H. D. F. Winkler, C. A. Schalley and R.
Fröhlich, Dalton Trans., 2010, 39, 7220–2.
23 M. Baumert, M. Albrecht, H. D. F. Winkler and C. A. Schalley,
Synthesis, 2010, 2010, 953–958.
We gratefully thank the international research training group
SeleCa (Selectivity in Chemo- and Biocatalysis) of the DFG for
support.
24 M. Albrecht, E. Isaak, M. Baumert, V. Gossen, G. Raabe and R.
Fröhlich, Angew. Chem. Int. Ed., 2011, 50, 2850–2853.
25 M. Albrecht, E. Isaak, V. Moha, G. Raabe and R. Fröhlich, Chem.
- Eur. J., 2014, 20, 6650–8.
26 M. Albrecht, E. Isaak, H. Shigemitsu, V. Moha, G. Raabe and R.
Fröhlich, Dalton Trans., 2014, 43, 14636–14643.
27 D. Van Craen, M. Albrecht, G. Raabe, F. Pan and K. Rissanen,
Chem. - Eur. J., 2016, 22, 3255–3258.
28 M. Albrecht, M. Fiege, M. Baumert, M. De Groot, R. Fröhlich, L.
Russo and K. Rissanen, Eur. J. Inorg. Chem., 2007, 609–616.
29 M. Albrecht, M. Baumert, J. Klankermayer, M. Kogej, C. A.
Schalley and R. Fröhlich, Dalton Trans., 2006, 4395–400.
30 D. Van Craen, M. de Groot, M. Albrecht, F. Pan and K. Rissanen,
Z. Anorg. Allg. Chem., 2015, 641, 2222–2227.
31 D. Van Craen, W. H. Rath, M. Huth, L. Kemp, C. Räuber, J. M.
Wollschläger, C. A. Schalley, A. Valkonen, K. Rissanen and M.
Albrecht, J. Am. Chem. Soc., 2017, 139, 16959–16966.
32 (a) X. Chen, T. M. Gerger, C. Räuber, G. Raabe, C. Göb, I. M.
Oppel and M. Albrecht, Angew. Chem. Int. Ed., 2018, 57, 11817–
11820. See for comparison: (b) M. Albrecht, X. Chen, D. VanCraen,
Chem. Eur. J. 2019, 25, 4265-4273; (c) X. Chen, M. Baumert, R.
Fröhlich, M. Albrecht, J. Incl. Phen. Macrocycl. Chem. 2019, DOI:
10.1007/s10847-019-00888-9; (d) Y. Suzuki, T. Nakamura, H. Iida,
N. Ousaka, and E. Yashima, J. Am. Chem. Soc. 2016, 138, 4852–
4859; (e) N. Ousaka, K. Shimizu, Y. Suzuki, T. Iwata, M. Itakura, D.
Taura, H. Iida, Y. Furusho, T. Mori, and E. Yashima, J. Am. Chem.
Soc. 2018, 140, 17027-17039;
References
1 J. M. Lehn, A. Rigault, J. Siegel, J. Harrowfield, B. Chevrier and D.
Moras, Proc. Natl. Acad. Sci. U. S. A., 1987, 84, 2565–9.
2 Reviews: (a) C. Piguet, G. Bernardinelli and G. Hopfgartner, Chem.
Rev., 1997, 97, 2005–2062; (b) M. Albrecht, Chem. Rev., 2001,
101, 3457–3498; (c) E Yashima, N Ousaka, D Taura, K Shimomura,
T. Ikai, and K. Maeda, Chem. Rev. 2016, 116, 13752-13990.
3 Recent highlights in helicate chemistry: (a) B. Song , C. D. B.
Vandevyver , A.-S. Chauvin, and J.-C. G. Bünzli Org. Biomol. Chem.,
2008, 6, 4125; (b) A. D. Faulkner, R. A. Kaner, Q. M. A. Abdallah, G.
Clarkson, D. J. Fox, P. Gurnani, S. E. Howson, R. M. Phillips, D. I.
Roper, D. H. Simpson, and P. Scott, Nature Chem. 2014, 6, 797; (c)
E. Chinnaraja, R. Arunachalam, E. Suresh, S. K. Sen, R. Natarajan,
and P. S. Subramanian, Inorg. Chem. 2019, 58, 4465-4479; (d) Y.
Zhang, B. Ali, J. Wu, M. Guo, Y. Yu, Z. Liu, and J. Tang, Inorg. Chem.
2019, 58, 3167-3174; (e) J.-F. Ayme, J. E. Beves, C. J. Campbell,
and D. A. Leigh, J. Am. Chem. Soc. 2019, 141, 3605-3612.
4 T. Konno, K. Tokuda, T. Suzuki and K. Okamoto, Bull. Chem. Soc.
Jpn., 1998, 71, 1049–1054.
5 A. K. Das, A. Rueda, L. R. Falvello, S.-M. Peng and S. Bhattacharya,
Inorg. Chem., 1999, 38, 4365–4368.
6 X. Sun, D. W. Johnson, D. L. Caulder, R. E. Powers, K. N. Raymond
and E. H. Wong, Angew. Chem. Int. Ed., 1999, 38, 1303–1307.
7 M. Albrecht, K. Witt, H. Röttele and R. Fröhlich, Chem. Commun.,
2001, 1330–1331.
8 X. Sun, D. W. Johnson, K. N. Raymond and E. H. Wong, Inorg.
Chem., 2001, 40, 4504–4506.
9 X. Sun, D. W. Johnson, D. L. Caulder, K. N. Raymond and E. H.
Wong, J. Am. Chem. Soc., 2001, 123, 2752–2763.
33 E. J. Corey and S. Bhattacharyya, Tetrahedron Lett., 1977, 18,
3919–3922.
34 E. J. Corey and S. D. Hurt, Tetrahedron Lett., 1977, 18, 3923–
3924.
35 F. L. Weitl and K. N. Raymond, J. Am. Chem. Soc., 1979, 101,
2728–2731.
10 J. Hamblin, L. J. Childs, N. W. Alcock and M. J. Hannon, J. Chem.
Soc. Dalton Trans., 2002, 46, 164–169.
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 7 of 8
Dalton Transactions
Please do not adjust margins
Journal Name
ARTICLE
36 C. J. Gramer and K. N. Raymond, Org. Lett., 2001, 3, 2827–2830.
37 K. J. Hall, T. I. Quickenden and D. W. Watts, J. Chem. Educ.,
1976, 53, 493–493.
View Article Online
DOI: 10.1039/C9DT01065C
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins

Dalton Transactions
Page 8 of 8
View Article Online
DOI: 10.1039/C9DT01065C