Diastereoselective Control of Tetraphenylethene Reactivity by Metal Template Self-Assembly

Article abstract of DOI:10.1002/chem.201806259

The reaction of 4,4′,4′′,4′′′-(ethene-1,1,2,2-tetrayl)tetraaniline with 2-pyridinecarboxaldehyde and iron(II) chloride resulted, after aqueous workup, in the diastereoselective formation of an [Fe₂L₃]⁴⁺ triple-stranded hel

Full text of DOI:10.1002/chem.201806259

A Journal of
Accepted Article
Title: Diastereoselective control of tetraphenylethene reactivity by
metal template self-assembly
Authors: Aaron D. W. Kennedy, Nicholas de Haas, Hasti Iranmanesh,
Ena T Luis, Chao Shen, Pi Wang, Jason R Price, William A.
Donald, Feihe Huang, and Jonathon Edward Beves
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To be cited as: Chem. Eur. J. 10.1002/chem.201806259
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10.1002/chem.201806259
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Diastereoselective control of tetraphenylethene reactivity by
metal template self-assembly
Aaron D. W. Kennedy,[a] Nicholas de Haas,[a] Hasti Iranmanesh,[a] Ena T. Luis,[a] Chao Shen,[a] Pi
Wang,[a],[b] Jason R. Price,[c] William A. Donald,[a] Joakim Andréasson,[d] Feihe Huang,[b] and Jonathon
E. Beves*[a]
Abstract:
The
reaction
of
4,4',4'',4'''-(ethene-1,1,2,2-
bonded networks,[5] halogen bonded networks,[6] stimuli
tetrayl)tetraaniline with 2-pyridinecarboxaldehyde and iron(II)
chloride resulted, after aqueous workup, in the diastereoselective
formation of a [Fe2L3]4+ triple-stranded helicate structure, irrespective
of the stoichiometry employed. The helicate structure was
characterized in solution by multinuclear NMR, and in the solid state
by single crystal X-ray crystallography. The reaction of iron(II)
tetrafluoroborate or iron(II) bistriflimide with the tetraaniline and 2-
pyridinecarboxaldehyde allowed the formation of a [Fe8L6]16+ cube
when appropriate stoichiometry is used, but these structures are
unstable with respect to hydrolysis. The pendant amine groups on
the helicate can be functionalized by reaction with acid chlorides or
acid anhydrides and the resulting functionalized tetraphenylethene
(TPE) units were isolated by reaction of the helicate with tris(2-
aminoethyl)amine. The emission properties of the TPE units were
studied in THF/water mixtures, and found by dynamic light scattering
to self-assemble into large (250 nm) ordered structures.
responsive polymers,[7] supramolecular polymers,[8] and organic
10]
capsules.[9] The host-guest chemistry[8,
and self-
organization[11] properties have allowed small molecule
sensors,[12] including for water,[13] to be developed. The
fluorescence properties of TPE have been applied in biological
imaging,[14] including for cancer cells[15] and as DNA probes.[16]
Hydrophobic stacking interactions can drive the formation of
vesicles,[17] and recent examples of mechanochromism[18] have
also opened new exciting opportunities for functional materials.
The well-defined geometry of the unit is also appealing for self-
assembly into metallosupramolecular structures, and a handful
of examples having been reported using palladium(II),[19]
platinum(II),[20] ruthenium(II),[21] silver(I)[22] or lanthanide[23] ions.
Cube-like
structures
formed
with
iron(II)
trifluoromethanesulfonate have been characterized in the solid
state,[24] although solution state behavior remains unclear, and a
very recent report of an analogous structure was reported using
zinc(II) ions.[25] In light of the interesting properties of TPE and
the promising results outlined above, we aimed to use the TPE
unit to form imine chelate groups suitable for binding first row
transition metal ions. Metal template self-assembled triple-
stranded helicate[26] structures of the type [M2L3]n+ are well
established in the literature, including through the use of one-pot
Introduction
Tetraphenylethene (TPE) has been known since the 19th century
to be
a fascinating organic compound. The features of
aggregation-induced emission (AIE)[1] and other luminescent
and redox properties[2] have been combined with many other
functional properties, such as self-assembly and sensing. For
example, the TPE unit has been incorporated into metal-organic
frameworks (MOFs),[3] covalent networks,[4] organic hydrogen-
syntheses
of
diimine
chelate
units
from
2-
pyridinecarboxaldehyde and suitable diamine units.[26c] Nitschke
and coworkers have used a similar self-assembly approach to
prepare an impressive
4+
N
[a]
[b]
A. D. W. Kennedy, N. de Haas, H. Iranmanesh, E. T. Luis, C. Shen,
Dr P. Wang, Dr W. A. Donald, Dr J. E. Beves
School of Chemistry
UNSW Sydney
Sydney NSW 2052, Australia
Fe
H2N
N
5
H2N
NH2
Fe Cl2
D2
C
D1
B
O
E-mail: j.beves@unsw.edu.au
Prof. F. Huang, Dr P. Wang
3
4
4
3
N
2
6
State Key Laboratory of Chemical Engineering
Center for Chemistry of High-Performance & Novel Materials
Department of Chemistry
Zhejiang University
Hangzhou 310027, China
2
1
1
H2N
N
H2N
NH2
Fe
N
7
1
A
3
6
4
5
[c]
[d]
Dr J. Price
ANSTO - Australian Synchrotron
800 Blackburn Road, Clayton, Victoria 3168, Australia
Prof. J. Andréasson
Department of Chemical and Biological Engineering,
Chalmers University of Technology
412 96 Göteborg, Sweden
4+
2
[Fe2( )3]
Scheme 1 Synthesis of triple-stranded helicate [Fe2(2)3]4+ from tetraaniline 1,
2-pyridinecarboxaldehyde and iron(II) chloride and the numbering scheme
adopted.
Supporting information for this article is given via a link at the end of
the document.
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collection of more elaborate functional assemblies,[27] including
helicate. Where iron(II) bistriflimide is used with tetraimine 3 in
acetonitrile (SI-S16.2–S16.3), the 1H NMR spectrum features
significantly broader signals, consistent with the formation of
larger species. ESI-MS of this sample was consistent with the
formation of a [Fe8(3)6]16+ cube (SI-S17), analogous to previous
reports.[24] However, when this sample is subjected to aqueous
work-up conditions, the major product is the [Fe2(2)3]4+ helicate
(Figure S59), indicating the cube structure is susceptible to
hydrolysis. Reactivity towards other metal ions is presented in
the Supplementary Information (SI-8–10) which show self-
assembled structures are also formed with silver(I) and zinc(II)
ions.
cubic [M8L8]16+ molecular cages from
tetraaniline-functionalized porphyrin unit,[27b,
a
C4-symmetric
and related
28]
structures.[29] Inspired by these reports, here we investigate the
C2-symmetric 4,4',4'',4'''-(ethene-1,1,2,2-tetrayl)tetraaniline (1)
as a component for metal-template self-assembly with iron(II)
salts.
Results and Discussion
Tetraaniline 1 was prepared in 76% yield following literature
procedures[30] from 1,1,2,2-tetrakis(4-nitrophenyl)ethene[31] using
Pd/C and hydrazine (see Section SI-S2). The reaction of
tetraaniline 1 with iron(II) chloride and 2-pyridinecarboxaldehyde
in ethanol or dimethylformamide (DMF), followed by anion
exchange with aqueous potassium hexafluorophosphate gave a
N
N
N
N
N
N
1
single species as identified by H NMR spectroscopy in CD3CN
(Figure 3c). Electrospray ionization mass spectrometry (ESI-MS,
Figure 1, Figure S12) identified the major species as the
[Fe2(2)3]4+ triple-stranded helicate shown in Scheme 1. The
same product was obtained in up to 83% isolated yield, with
large variations of stoichiometry of the reagents used (Section
SI-S4.7), and the structure is stable in acetonitrile solution, as
determined by 1H NMR spectroscopy (SI-S4.8).
N
N
3
Figure 2 Structure of tetraimine functionalized tetraphenylethene 3.
Characterization of [Fe2(2)3]4+ by NMR
The 1H NMR spectrum (Figure 3c) of the self-assembled product
showed the tetraaniline core was non-symmetrical, with signals
for the phenyl rings being split into two groups. The typical shifts
of the pyridine ring on coordination are observed, with a
significant upfield shift of the HA6 proton (∆δ = -1.6 ppm, see
Scheme 1 for labelling) due to deshielding by an adjacent
pyridine ring.[32] The phenyl ring closest to the metal center
(labelled ‘B’, Scheme 1) was found to exhibit slow rotation on the
1
NMR timescale, to give four separate H NMR signals similar to
that observed for literature examples of related self-assembled
systems.[27b] The ring furthest from the metal center (labelled ‘C’)
1
showed unrestricted rotation to give two H NMR signals only.
The aromatic 1H NMR signals of HB2/B6 are shifted upfield by
over 1 ppm unit (from 6.36 ppm to 5.30 and 5.15 ppm),
Figure 1 ESI-MS of [Fe2(2)3]4+ in acetonitrile with an inset of the measured 4+
peak (blue) and theoretical values (red).
1
consistent with shielding by adjacent phenyl rings. The H NMR
signals corresponding to the non-coordinated ring (HC2, HC3) are
essentially unchanged between the free amine and the helicate,
indicating this environment located on the periphery of the
helicate is not significantly influenced by the helical core.
Variable temperature 1H NMR spectra of [Fe2(2)3](PF6)4 in
CD3CN (Figure S14) showed a sharpening of the signals of the
C ring upon heating, a result of the increased rate of exchange
of the amine protons at higher temperature. However, the 1H
NMR signals of the ‘B’ ring broadened on heating, consistent
with the proposed restricted rotation.
The use of pre-formed tetraimine 3 (Figure 2, SI-S3) with iron(II)
chloride in DMF or ethanol gave, after workup, the same result
as the self-assembly directly from tetraaniline 1: exclusive
isolation of the triple-stranded helicate product. This indicates
that the formation of the helicate is not due to simple differences
in stoichiometry, or due to the slow formation of the tetraimine.
To further explore the factors controlling these assemblies, we
considered the use of different metal ion salts and solvents.
The use of Fe(BF4)2·6H2O as the iron(II) source in DMF (SI-15.1,
S15.2) or acetonitrile (SI-15.3) resulted in the formation of new
products controlled by reaction stoichiometry, with different
ratios of tetraaniline 1, 2-pyridinecarboxaldehyde and the iron
salt giving mixtures of species which are difficult to assign by 1H
NMR spectroscopy. However, after aqueous workup the major
species in all instances remained the [Fe2(2)3]4+ triple-stranded
Two-dimensional
NMR
spectroscopy
was
used
to
unambiguously establish the structure of the [Fe2(2)3]4+ helicate
in solution (Figures S6-10). A 1H-1H NOESY spectrum was used
to identify interactions between rings (key NOE interactions
shown in Figure 4a) which allowed assignment of the 1H signals
of the B and C rings (Figure S10). Multinuclear 1H-13C HSQC
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Figure 3 1H NMR (500 MHz, CD3CN, 298 K) spectra of a) tetraaniline 1, b) 2-pyridinecarboxaldehyde, c) [Fe2(2)3]4+, d) [Fe2(4)3]4+, e) [Fe2(5)3]4+ and f) [Fe2(6)3]4+
.
See Scheme 1 for numbering scheme adopted.
on rings B and C (i.e., HB3–CD1; HB5–CD1; HC3–CD2). This allows
the assignment of the orientation of the ethylene bond and
shows exclusive formation of the 1,1-isomer of the helicate in
solution with no evidence for formation of the 1,2-isomer (Figure
5).
The observed formation and stability of exclusively the 1,1–
isomer of the helicate indicates the 1,2-isomer—a conformation
that must be present in the [Fe8(3)6]16+ cube or any helicate
formed with a mixture of 1,1- and 1,2-isomers—must be
significantly less thermodynamically stable. An unfavorable
distortion within the TPE unit as it coordinates to the iron(II)
center to produce the 1,2-isomer is the likely origin of the
instability of these structures. Such unfavorable distortion does
not appear to be required for the formation of the 1,1-isomer,
allowing the observed stereoselective formation of the 1,1-
helicate structure.
N
H2N
H2N
N
Fe
5
6
D1
C
B
3
3
N
Fe
N
2
2
7
6
A
5
3
4
Figure 4 a) 1H-1H NOESY (400 MHz, CD3CN) interactions observed for 1,1-
isomer of [Fe2(2)3]4+ showing the interaction between HB3 and HC3, and HC2
and the amine protons. b) Observed 1H-13C HMBC (600 MHz, CD3CN)
isomer
1,2-aniline
Figure 5 The structure of (non-observed) 1,2-isomer of [Fe2(2)3]4+
.
couplings of [Fe2(2)3]4+
.
X-Ray crystallography
Figure S7) and HMBC (Figures 4b, S8, S9) spectra allowed
identification of all quaternary carbons, and importantly
confirmed the presence of two different quaternary alkene
environments, with appropriate HMBC coupling to the protons
Single crystals of 2[Fe2(2)3](PF6)8·H2O were grown by slow
evaporation of a DMF solution of the complex. The asymmetric
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4+
4+
unit has two crystallographically independent but structurally
similar[33] complexes and one is shown in Figure 6. The complex
is the same 1,1-isomer as identified in solution by NMR
spectroscopy. The two iron(II) centers are 11.4 Å apart and have
the same stereochemistry with coordination geometries around
the metal ions that are unremarkable. The Nimine···Nimine
distances within one ligand range from 9.56(1) to 9.75(1) Å,
which is consistent with expected values (e.g. separations of
O
O
N
N
i)
R
O
R
R'/R
O
Fe
Fe
NH
N
5
H2N
N
5
or
O
ii)
D2
D1
4
B
D2
D1
4
R' Cl
4
3 3
4
3 3
6
CH3CN
6
C
B
C
O
2
1
2
1
2
1
2
1
NH
N
H2N
N
Fe
N
Fe
N
R'/R
7
7
amine
groups
in
the
structure
of
tetrakis(4-
A
dimethylaminophenyl)ethene are 9.578(9) and 9.636(8) Å,
CSDCODE: GORFUO[2b]). This is consistent with the ligand
undergoing minimal strain to accommodate the metal centers.
The central alkene bond lengths range from 1.34(2) to 1.38(1) Å,
as expected for the formal double bond of unsubstituted TPE[34]
(C=C 1.35 Å, CSDCODE: TPHETY[35]). There are no significant
differences between the Calkene–CAr bond lengths on the imine
side of the TPE compared with the amine side (i.e. CD1–CB4 vs
CD2–CC4, labelling in Scheme 1) with bond lengths ranging from
1.44(2) to 1.56(1) Å and from 1.45(2) to 1.52(2) Å respectively.
These bond lengths are in the range expected for typical neutral
TPE derivatives (e.g. the equivalent bond lengths for TPE = 1.49
Å, CSDCODE: TPHETY[35]), indicating the introduction of
positively charged metal centers adjacent to the TPE unit have
minimal structural effects on the TPE unit.
A
3
6
3
6
4
5
4
5
4+
=
=
2
4
)
]
3
5
R
Me
Ph
[Fe2( )3]
[Fe2
(
4+ (90%)
[Fe2( )3]4+ (67%)
4+
R
=
R' Ph
5
85
(
%)
[Fe2( )3]
4+
=
R' C7H
6
)
%)
15 [Fe2
(
]
(90
3
Scheme
2 Functionalization of helicate [Fe2(2)3)](PF6)4 by reaction with
anhydrides or acyl chlorides.
cage degradation was observed. Although previous reports
suggest similar self-assembled systems are not stable to
chloride anions,[27f] acylation can also be performed using acid
chloride reagents under much milder conditions. Reaction of
[Fe2(2)3](PF6)4 with benzoyl chloride or octanoyl chloride in
acetonitrile at room temperature for 2 h gave the acylated cages
[Fe2(5)3](PF6)4 and [Fe2(6)3](PF6)4 in 85% and 90 % yields
respectively.
The 1H NMR spectra of the derivatized cages are shown in
Figure 3d–f, with additional spectra in the SI (SI-S5–S7). In all
cases the 1H NMR signal corresponding to the amine proton
(4.15 ppm) is replaced by a new downfield signal ([Fe2(4)3]4+ and
[Fe2(6)3]4+: 8.24 ppm; [Fe2(5)3]4+: 8.69 ppm) consistent with the
formation of an amide bond. The 1H NMR signals corresponding
to the non-coordinated ring (HC2, HC3) are both shifted downfield
(∆δ HC3 ≈ 0.3 ppm; ∆δ HC2 ≈ 1.0 ppm) and are sharper as the
amide nitrogen undergoes slow proton exchange compared with
the exchange rate of the free amine. The protons on the rings A
and B do not shift significantly upon forming the amide,
indicating the helical structure is retained upon functionalization.
Two-dimensional NMR techniques (see Figures 7, S5.1–5.5,
S6.1–6.4; S7.1–7.2) allowed unambiguous assignment of the
derivatized helicates, analogous to that described for the parent
helicate. The 1H NMR signal of the amide proton is identified
from the 1H–13C HSQC spectrum, where no coupling is observed
to a 13C NMR signal.
Figure 6 Single crystal X-ray structure of 2[Fe2(2)3](PF6)8·H2O. Anions and
solvent have been removed for clarity. a) Stick representation of one of the
two cations in the structure, with the three independent ligands shown in red,
blue, and green. b) CPK representation of the same cation, viewed
approximately down the crystallographic c axis.
Reactivity of [Fe2(2)3]4+
Without the metal ion to template[36] the formation of the helicate,
discrimination of reactivity between the different possible amine
sites of ligand 1 would be difficult. We looked to perform post-
synthetic modification[27f, 27k, 37] upon the helicate to selectively
functionalize the TPE core. Previous studies have shown that
pendant amines of self-assembled structures can be modified
using acylation and azidation.[27f] The reaction of [Fe2(2)3](PF6)4
with acetic anhydride or benzoic anhydride in acetonitrile at
70 °C for 18 h gave the acylated helicates [Fe2(4)3](PF6)4 and
[Fe2(5)3](PF6)4 in good yield (90 and 67% respectively), see
Scheme 2. The success of these reactions also reflects the
stability of the triple-stranded helicate product. Despite extended
heating in acetonitrile and the presence of multiple equivalents
of acid (formed as a by-product of the amide formation), minimal
In the 1H–13C HMBC spectrum of [Fe2(4)3]4+ (Figure S19) the 13
C
NMR signal at 168.6 ppm for the carbonyl carbon is coupled to
the 1H signals of the NH proton (8.24 ppm) and the methyl group
(1.98 ppm), confirming the connectivity of the amide functionality
to the helicate. We see no evidence of lower symmetry
structures (i.e. those with free amine groups), although this may
be because such structures would have significantly reduced
intensity in the 1H NMR spectrum due to loss of symmetry.
High resolution ESI-MS of helicates [Fe2(4)3]4+ (Figures S23–24),
[Fe2(5)3]4+ (Figures S32–33), and [Fe2(6)3]4+ (Figures S37–38)
showed a series of peaks with the formula Mn+ = [(Fe2(L)3) +
-
n+
(PF6 )4-n
]
where n = 1–4, which match the predicted isotope
patterns and confirm the helicate structure is retained.
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Unexpectedly, when samples of [Fe2(4)3]4+ and [Fe2(5)3]4+ were
analyzed under identical conditions to [Fe2(2)3]4+ a number of
additional ESI-MS peaks were observed consistent with
cube assembly, which has a diffusion coefficient corresponding
to a hydrodynamic radius of 15.6 Å, in good agreement with the
previous reported X-ray structure (half the longest axis = 13.2
Å).[24]
[Fe4(L)6]8+ and [Fe2(L)4]4+ stoichiometries, potentially
a
tetrahedron and an intermediate between this and the helicate
(Figures S24, S33).
Electronic properties of iron(II) helicates
The UV-Vis spectra of helicates [Fe2(2)3](PF6)4, [Fe2(4)3](PF6)4,
[Fe2(5)3](PF6)4 and [Fe2(6)3](PF6)4 were each recorded in
acetonitrile (Figure 8), and compared with the parent ligand 1.
Tetraaniline 1 has two strong absorptions centered at 276 and
348 nm, corresponding to π–π* and n–π* transitions respectively.
The π-π* transition is at approximately the same energy in
[Fe2(2)3](PF6)4 as in the free ligand 1, although two overlapping
bands are observed, and the increase in absorptivity is
proportional to the number of TPE units in the helicate. The
lower energy n–π* transition is red-shifted from
1
to
[Fe2(2)3](PF6)4 and is significantly broadened, overlapping with
the metal centered and associated charge transfer transition(s).
The lowest energy metal-to-ligand charge transfer absorption of
the helicate is centered at 575 nm and is essentially identical to
that of the mononuclear model complex [Fe(7)3](PF6)2 (7 = 1-
(pyridin-2-yl)-N-(p-tolyl)methanimine, see SI-S11), suggesting
that the responsible chromophore is largely localized on the
pyridyl-imine unit with little involvement of the TPE unit. This is
also consistent with the solid-state X-ray data where no
significant difference in the TPE bond lengths is observed upon
coordination of the pendant chelate groups to the iron(II) centers.
Figure 7 Partial 1H-13C HMBC (500 MHz, CD3CN) couplings of [Fe2(5)3]4+
.
Key interactions are HC3-CD2 and HB3-CD1 and HB5-CD1
stereochemistry has been retained on functionalization.
,
indicating
Diffusion NMR
Diffusion NMR[38] is commonly used to probe the hydrodynamic
radii of self-assembled systems to provide information about
relative sizes of species in solution.[39] Table 1 shows the
diffusion coefficients and the calculated hydrodynamic radii for
each of the self-assembled structures analyzed here. Although
the helicates possess significant shape anisotropy, the longest
radius in the solid-state structure of [Fe2(2)3]4+ (half the distance
between the pendant nitrogen atoms = 9.8 Å) is in good
agreement with the measured hydrodynamic radius (10.3 Å).
The derivatized helicates all have larger hydrodynamic radii than
the parent [Fe2(2)3]4+ helicate with the benzoyl functionalized
helicate diffusing the slowest. No evidence for larger species
Figure 8 UV-Visible absorption spectra (acetonitrile) of tetraaniline 1, and the
helicates [Fe2(L)3]4+ (L = 2, 4-6).
Table 1. Diffusion coefficients for selected compounds as calculated by NMR[a]
Complex
Diffusion coefficient
/ 10-10 m2.s-1[b]
6.2±0.2
Hydrodynamic radius
/ Å
The emission spectrum of dilute [Fe2(2)3](PF6)4 in acetonitrile
was collected (0.8 µM, λex = 280 nm), and the complex was
found to be non-emissive. This is consistent with both quenching
of the TPE emission by the iron(II) center and that the TPE units
are non-planar with considerable degrees of freedom under
these conditions. Aggregation-induced-emission (AIE) is
[Fe2(2)3](PF6)4
[Fe2(4)3](PF6)4
[Fe2(5)3](PF6)4
[Fe2(6)3](PF6)4
[Fe8(3)6)(NTf)16
10.3±0.3
11.5±0.5
13.4±0.3
11.9±0.5
5.6±0.2
4.8±0.1
5.4±0.2
4.1±0.1
15.6±0.4
[a] CD3CN, 298 K, 500 MHz, all collected with δ = 2 ms and ∆ = 100 ms.
Average diffusion values were determined by multiple 1H NMR signals for each
structure. Hydrodynamic radii were calculated using the Stokes-Einstein
equation. [b]Errors are estimated as 3% for the diffusion coefficient as data
fitting for any data set gives errors below 1%, which are not reasonable.
typically responsible for significant enhancement in TPE
1b]
emission by preventing vibrational relaxation,[1a,
a
phenomenon not likely for
a dilute solution of helicate
[Fe2(2)3](PF6)4.
was detected in the diffusion experiments. This indicates that if
these species are present, as suggested by ESI-MS, then their
abundance is insufficient to identify by 1H NMR spectroscopy.
Diffusion measurements were also performed on the [Fe8(3)6]16+
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Isolation of selectively functionalized TPE
molecules
water, followed by a decrease in intensity at higher water
contents, similar to other TPE derivatives.
We initially attempted to isolate the free organic components
using ethylenediaminetetraacetic acid (EDTA) to sequester the
iron(II) ions, and hydrolysis of the imine bonds to generate the
free amine. This approach invariably gave complex mixtures of
products which were difficult to isolate. However, imine
(PF6)4
N
R
Fe
NH
N
5
O
exchange as Nitschke has used to great effect to manipulate
D2
D1
4
4+
4+
4+
=
=
=
R
R
R
Me
4
[Fe2( )3]
27c-e]
metal-template assemblies,[27a,
was extremely effective.
4
3 3
Ph
5
[Fe2( )3]
6
C
B
C7H15
6
Reaction of helicates [Fe2(4)3](PF6)4, [Fe2(5)3](PF6)4 or
[Fe2(6)3](PF6)4 with an excess of the competitive tridentate
amine tris(2-aminoethyl)amine (tren) resulted in the quantitative
formation of monomeric complex [Fe(trenpy3)]2+, as found for
related systems,[40] and the release of the organic compound 8,
9 or 10 respectively (Scheme 3). Isolation of the organic units
was achieved by extraction of the reaction mixture with diethyl
ether, followed by column chromatography giving organic units 8,
9 and 10 in 50, 53 and 86% yields respectively. The resulting
units were characterized by NMR (Figure 10) and ESI-MS (SI-
19). Upon release from the helicate the signals corresponding to
protons HB2 and HB6 move significantly downfield (∆δ ≈ 1.1 ppm)
and coalesce as the phenyl ring is no longer undergoing slow
rotation. The signals corresponding to protons HB3 and HB5 move
slightly upfield (∆δ –0.4 and –0.1 ppm respectively) and
coalesce. The protons on rings C (and E in the case of 9) are
mostly unaffected, consistent with their distance from the helical
structure.
The entire synthesis of the functionalized ligands can also be
completed in one pot, without isolation of the helicate species
(SI-S20). Combination of 1, 2-pyridinecarboxaldehyde and
Fe(NTf2)2·4H2O in acetonitrile led to in situ formation of the
[Fe2(2)3]4+ helicate which was reacted directly with octanoyl
chloride. After complete conversion to the [Fe2(6)3]4+ species,
tren was added to facilitate the imine exchange and the organic
component 10 was isolated in a non-optimized yield of 21%. The
spectral data for this compound was identical to that reported
above, proving the versatility of this method for generating
unsymmetrical functional TPE units.
[Fe2( )3]
O
R
2
1
2
1
NH
N
Fe
N
A
7
3
6
4
5
NH2
NH2
r.t., 20 h
CH3CN,
N
H2N
R
NH
NH2
O
N
N
N
N
N
Fe
x
3
D2
C
D1
x
2
+
5
6
4
(PF6)2
4
3 3
N
B
N
O
R
2
1
2
1
NH
NH2
[Fe(trenpy3)]2+
=
=
=
R
R
R
Me
Ph
C7H15
8
9
10
Scheme 3 Isolation of functionalized TPE units by imine exchange.
Electronic properties of organic components
1, 8, 9 and 10
The UV-visible absorption spectra of tetraaniline 1 and the
functionalized units 8–10 were recorded in THF (SI-21). The
absorption spectra of 1 and 8–10 in THF are essentially identical,
indicating the peripheral functionalization does not significantly
change the electronic properties of the central chromophore.
The absorption and emission behavior were studied using
solutions of 1, 8–10 in THF with increasing water content (SI-22).
All compounds showed an increase in the emission intensity on
water addition, consistent with an emission in the aggregated
state. The parent tetraaniline 1 displays complex behavior
consistent with multiple emissive species, presumably different
protonation states. Compound 8 is emissive in pure THF with
the emission intensity increasing with water content up to 30%
Figure 9 Emission data for a) 9 and b) 10 in THF/water mixtures.
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10.1002/chem.201806259
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Figure 10 1H NMR spectra (CD3CN, 500 MHz, 298 K) showing isolation of functionalized TPE units by imine exchange. a) [Fe(trenpy3)]2+, b) [Fe2(5)3]4+, c)
combination of tren and [Fe2(5)3]4+ and d) isolated 9.
Compounds 9 and 10 show similar emission profiles at low
water content, but significant differences were found at higher
water content (Figure 9). An enhancement of emission intensity
was found for 9 and 10 up to 85% and 30% water content
respectively (Figure 9, SI-S83, SI-S84), with the emission of 9
being red-shifted and approximately four times higher than that
of 10. The red-shift of the emission maxima is as expected as
emission intensity. However, at higher water content (e.g. 90%)
larger structures are assembled with an average diameter of 250
nm and low polydispersity (PdI = 0.10). These large species are
significantly less emissive than the smaller aggregates,
indicating that the assembly disrupts the efficient packing of the
TPE cores to result in a decrease in the emission intensity.
Intermolecular hydrophobic interactions between the octyl
the solvent polarity increases.[41] At higher water content (≈ 90%), chains presumably drive the self-assembly of these large
the emission intensity of 10 is reduced, likely due to the
structures.
formation of larger non-emissive aggregates.
Dynamic Light Scattering (DLS) was used to estimate the size
distribution of the aggregates formed in solution (SI-23).
Compound 8 showed different sized aggregates at varying water
content. At 30% water content, which corresponded to the
conditions of the most intense emission, only small aggregates
are formed (d ≈ 5 nm). At 80–90% water content much larger
aggregates (d ≈ 80-200 nm) are formed, which correspond to the
sample with a red-shifted and weaker emission. Intermolecular
hydrogen-bonding by compound 8 may limit the π- π stacking
interactions that result in increased emission.
Conclusions
The amine functionalized TPE derivative 1 is suitable for forming
imines for metal ion complexation and subsequent self-assembly
into larger structures. Reaction with iron(II) ions and 2-
pyridinecarboxaldehyde, followed by an aqueous workup
procedure, gives a disastereoselective [M2L3]4+ helicate with
pendant amines suitable for functionalization. This metal
template synthesis demonstrates the ability to control
functionalization of organic components by selective metal ion
coordination controlled by the geometry and separation of the
binding sites and may allow their selective inclusion into larger
molecules and assemblies. Finally, the ‘supramolecular
protecting group’ strategy allowed the synthesis of functionalized
TPE derivatives with amphiphilic character that can be self-
assembled into large emissive assemblies in solution.
Compound 9 displays typical TPE emission: as water content is
increased the absorption undergoes minimal changes, while the
emission intensity increases to reach a maximum at 85% water
content, with a maximum emission at 490 nm. DLS data did not
indicate the formation of larger structures, with small aggregates
(d ≈ 5 nm) at low water content, and higher water content
leading to polydisperse aggregates too large to be measured
using DLS. The pendant benzoyl groups may drive self-
assembly behavior towards 2D sheets, allowing favorable π- π
interactions between adjacent units without requiring the
flattening of the TPE units. This is consistent with the behavior of
the tetrakis(4-benzoyloxyphenyl)ethene derivative, which is
suggested to form 2D hydrogen-bonded networks.[2c]
Experimental Section
Instrumentation and methods
NMR spectra were recorded at 298 K on Bruker Avance III 400, 500 or
600 MHz spectrometers. The chemical shifts for the 1H and 13C{1H} NMR
spectra conducted are referenced to residual solvent resonances.
Coupling constants (J) are reported in hertz (Hz). High-resolution mass
spectrometry experiments were performed on a hybrid linear quadrupole
ion trap mass spectrometer (Thermo LTQ Orbitrap XL) equipped with
electrospray ionization (ESI) source using ‘soft’ ion source conditions
Compound 10 showed more interesting self-assembly behavior.
Below 30% water content small aggregates (d ≈ 4 nm) dominate,
and these are the conditions which correspond to maximum
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10.1002/chem.201806259
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FULL PAPER
42]
detailed elsewhere.[39f,
UV-Visible absorption spectra were recorded
(24), 327 (26), 527 sh (5), 575 (6). ESI-MS m/z 322.08 [Fe(3)3]2+ requires
322.12, 788.67 [(Fe(3)3) + PF6]+ requires 789.20.
on a Varian Cary 60 or Cary 50 spectrophotometer. Fluorescence
measurements were performed using
a
Varian Cary Eclipse
spectrophotometer. Dynamic light scattering measurements were
performed on a Malvern Zetasizer Particle Sizer. Commercially available
reagents were used as received. Fe(NTf2)2·4H2O was prepared
according to the literature.[27h]
Synthesis of [Fe2(2)3](PF6)4 helicate
1,1,2,2-Tetrakis(4-aminophenyl)ethene (200 mg, 0.51 mmol) was added
to a solution of 2-pyridinecarboxaldehyde (97 μL, 110 mg, 1.0 mmol) in
ethanol (100 mL) and the solution was stirred at room temperature for
five minutes. FeCl2·4H2O (68 mg, 0.34 mmol) was then added, resulting
in the formation of a dark red solution which was stirred for 24 hours.
Excess saturated aqueous KPF6 was added (150 mL) and the resulting
purple-red precipitate was collected on Celite, washed with water (3 x 50
mL), DCM (2 x 50 mL) and diethyl ether (2 x 50 mL). The solid was
dissolved in acetonitrile and solvent was removed under reduced
pressure to afford the title compound as a dark purple-red solid (341 mg,
0.14 mmol, 83 %). 1H NMR (500 MHz, CD3CN) δ 8.69 (s, 2H, HA7), 8.42
(d, J = 7.4 Hz, 6H, HA3), 8.31 (dd, J = 7.8, 1.1 Hz, 6H, HA4), 7.66 (td, J =
6.7, 1.3 Hz, 6H, HA5), 7.20 (d, J = 5.4 Hz, 6H, HA6), 7.01 (dd, J = 8.3, 1.7
Hz, 6H, HB3), 6.79 (dd, J = 8.2, 1.7 Hz, 6H, HB5), 6.61 (d, J = 8.7 Hz, 12H,
HC3), 6.30 (d, J = 5.3 Hz, 12H, HC2), 5.30 (dd, J = 8.3, 2.3 Hz, 6H, HB2),
5.15 (dd, J = 8.2, 2.3 Hz, 6H, HB6), 4.15 (s, 12H, HNH). 13C{1H} NMR (101
MHz, CD3CN) δ 175.9 (CA7), 159.1 (CA2), 156.7 (CA6), 149.5 (CB1), 148.3
(CC1), 146.6 (CD2), 146.0 (CB4), 140.5 (CA4), 134.3 (CB3), 133.5 (CD1),
133.5 (CC3), 133.1 (CC4), 133.0 (CB5), 132.2 (CA3), 130.6 (CA5), 121.4
(CB2), 120.9 (CB6), 114.5 (CC2). UV-vis: 8.3 x 10-6 mol dm-3, MeCN, λmax
/nm (ε / 103 dm3 mol-1 cm-1) 282 (113), 574 (14). ESI-MS m/z 455.9079
[Fe2(2)3]4+ requires 455.9097; 571.2610 [2 + H]+ requires 571.2610;
656.1994 [(Fe2(2)3) + PF6]3+ requires 656.2010; 1056.7800 [(Fe2(2)3) +
(PF6)2]3+ requires 1056.7835.
Synthesis of 1,1,2,2-tetrakis(4-nitrophenyl)ethene
Synthesized following
a
modified literature procedure.[31] 1,1,2,2-
Tetraphenylethene (2.00 g, 6.02 mmol) was added in portions to 70%
HNO3 (50 mL) and stirred at 50 °C for 24 hours. An orange solid was
precipitated with excess water and recrystallized from
a
1,4-
dioxane/water mixture (4:1) to afford 1,1,2,2-tetrakis(4-nitrophenyl)ethene
as yellow crystals (2.18 g, 4.25 mmol, 71 %). 1H NMR (400 MHz, CDCl3)
δ 8.07 (dt, J = 8.8 Hz, 2.1 Hz, 8H, H2), 7.19 (dt, J = 8.8, 2.1 Hz, 8H, H3).
13C NMR (101 MHz, CD3CN) δ 148.7 (C1), 148.2 (C5), 142.4 (C4), 133.0
(C3), 124.5 (C2). The 1H NMR data matches that reported.[30]
Synthesis of 4,4',4'',4'''-(ethene-1,1,2,2-tetrayl)tetraaniline (1)
Synthesized following a literature procedure.[30] Hydrazine monohydrate
(6.4 mL, 132 mmol, 90 eq.) was added to a stirring solution of 1,1,2,2-
tetrakis(4-nitrophenyl)ethene (745 mg, 1.45 mmol) and 10% Pd/C (75 mg,
cat.) in ethanol (150 mL). The reaction was heated at reflux for 24 hours
and filtered through Celite. Evaporation of the filtrate afforded 4,4',4'',4'''-
(ethene-1,1,2,2-tetrayl)tetraaniline as an orange solid (432 mg, 1.10
mmol, 76 %) 1H NMR (400 MHz, CD3CN) δ 6.69 (dt, J = 8.7, 2.1 Hz, 8H,
H2), 6.36 (dt, J = 8.7, 2.1 Hz, 8H, H3), 4.00 (s, 8H, HNH). 13C NMR (101
MHz, CD3CN) δ 146.7 (C1), 138.8 (C5), 135.4 (C4), 133.0 (C3), 114.5 (C2).
ESI-MS m/z 393.42 [M+H]+ requires 393.21; 785.92 [2M+H]+ requires
785.41
Synthesis of [Fe2(4)3](PF6)4 helicate
Acetic anhydride (21 µL, 22 mg, 220 µmol) was added to a solution of
[Fe2(2)3](PF6)4 (79 mg, 33 µmol) in dry CH3CN (4 mL). The mixture was
heated at 70 °C for 18 h, then cooled and poured into excess aqueous
KPF6 solution (20 mL) leading to the formation of a dark burgundy
precipitate. The precipitate was collected on Celite and washed with H2O
(2 × 10 mL) and DCM (2 × 10 mL), then dissolved in CH3CN (20 mL) and
the solvent removed under reduced pressure to give the title compound
as a purple solid (80 mg, 92%) 1H NMR (500 MHz, CD3CN) δ 8.75 (s, 6H,
HA7), 8.46 (d, J = 7.7 Hz, 6H, HA3), 8.33 (t, J = 7.7 Hz, 6H, HA4), 8.27 (s,
6H, -NH), 7.68 (s, 6H, HA5), 7.31 (d, J = 8.2 Hz, 12H, HC2), 7.21 (d, J =
5.4 Hz, 6H, HA6), 7.06 (d, J = 8.1 Hz, 6H, HB3), 6.85 (m, 18H, HC3+B5),
5.36 (d, J = 7.5 Hz, 6H, HB2), 5.20 (d, J = 7.5 Hz, 6H, HB6), 2.01 (s, 18H,
HC6). 13C{1H} NMR (151 MHz, CD3CN) δ 176.2 (CA7), 169.6 (CC=O), 159.0
(CA2), 156.7 (CA6), 150.2 (CB1), 144.8 (CB4), 144.6 (CD2) 140.6 (CA4),
139.4 (CC1), 139.3 (CC4), 137.0 (CD1), 134.4 (CB3), 133.1 (CB5), 132.7
(CC2), 132.5 (CA3), 130.7 (CA5), 121.7 (CB2), 121.0 (CB6), 119.3 (CC3), 24.4
(CMe). UV-vis: 7.8 x 10-6 mol dm-3, MeCN, λmax /nm (ε / 103 dm3 mol-1 cm-
1) 279 (163), 361 (60), 574 (18). ESI-MS m/z 518.9232 [Fe2(4)3]4+
requires 518.9255; 655.2811 [4 + H]+ requires 655.2821; 682.4916
Synthesis of tetraimine 3
2-Pyridinecarboxaldehyde (19.6 µL, 22 mg, 0.21 mmol) was added to a
solution of 1,1,2,2-tetrakis(4-aminophenyl)ethene (20 mg, 51 μmol) in
methanol (20 mL) and heated at reflux for 2 hours. The resulting
precipitate was collected via filtration and washed with methanol (2 × 15
mL) to give a yellow solid (36 mg, 48 μmol, 94%). 1H NMR (500 MHz,
CDCl3) δ 8.69 (dt, J = 4.6, 1.4 Hz, 4H, HA6), 8.60 (s, 4H, HNH), 8.18 (dt, J
= 8.0, 1.1 Hz, 4H, HA3), 7.80 (td, J = 7.8, 1.8 Hz, 4H, HA4), 7.35 (ddd, J =
7.5, 4.8, 1.3 Hz, 4H, HA5), 7.19 – 7.08 (m, 16H, HB2+B3). 13C NMR (101
MHz, CDCl3) δ 160.3 (CA7), 154.8 (HA2), 149.8 (HA6), 149.3 (CB1), 142.5
(CB4), 140.5 (CC=C), 136.8 (CA4), 132.6 (CB3), 125.2 (CA5), 121.96 (CA3),
120.99(CB2).
Synthesis of [Fe(7)3](PF6)2
[Fe2(4)4]4+ requires 682.4941; 740.2191 [(Fe2(4)3)
+
PF6]3+ requires
p-Toludine (50 mg, 0.47 mmol) and Fe(BF4)2·6H2O (57 mg, 0.17 mmol)
was added to a solution of 2-pyridinecarboxaldehyde (45 µL, 51 mg, 0.47
mmol) in methanol (30 mL) and stirred at room temperature for 2 hours.
Excess saturated aqueous KPF6 was added and the resulting purple
solid was collected on Celite, washed with water (3 × 30 mL), DCM (2 ×
30 mL) and diethyl ether (1 × 30 mL). The solid was dissolved in
acetonitrile and solvent was removed to afford the title compound as a
purple solid (110 mg, 0.12 mmol, 70%) 1H NMR (500 MHz, CD3CN) δ
9.26 (s, 1H), 9.06 (s, 1H), 8.76 (d, J = 3.4 Hz, 2H), 8.54 – 8.47 (m, 2H),
8.42 (dt, J = 7.6, 1.1 Hz, 1H), 8.37 – 8.29 (m, 2H), 8.24 (td, J = 7.8, 1.3
Hz, 1H), 8.00 (td, J = 7.7, 1.3 Hz, 1H), 7.97 – 7.91 (m, 1H), 7.93 – 7.83
(m, 2H), 7.74 – 7.64 (m, 2H), 7.61 (d, J = 5.5 Hz, 1H), 7.53 (dd, J = 7.7,
5.6 Hz, 2H), 7.35 (d, J = 5.5 Hz, 1H), 7.15 (d, J = 8.0 Hz, 2H), 7.01 (d, J =
8.0 Hz, 1H), 6.96 (d, J = 7.9 Hz, 2H), 6.78 (d, J = 8.0 Hz, 2H), 6.62 (d, J =
8.3 Hz, 2H), 6.53 (d, J = 8.2 Hz, 2H), 6.05 (d, J = 8.3 Hz, 2H), 5.31 (d, J =
8.3 Hz, 1H), 2.32 (s, 2H), 2.28 (s, 3H), 2.24 (s, 3H), 2.14 (s, 4H). UV-vis:
1.6 x 10-5 mol dm-3, MeCN, λmax /nm (ε / 103 dm3 mol-1 cm-1) 238 (33), 284
740.2221; 917.2562 [(Fe4(4)6)+3PF6]5+ requires 917.2594; 958.3106
[(Fe2(4)4)+PF6]3+ requires 958.3136; 1182.8118 [(Fe2(4)3) + 2(PF6)]2+ and
[(Fe4(4)6) + 4PF6]4+ require 1182.8153; 1625.4045 [(Fe4(4)6) + 5PF6]3+
requires 1625.4084.
Synthesis of [Fe2(5)3](PF6)4 helicate
Benzoic anhydride (50 mg, 220 µmol) was added to a solution of
[Fe2(2)3](PF6)4 (80 mg, 33 µmol) in dry CH3CN (5 mL) . The solution was
heated at 70 °C for 18 h, then cooled and poured into excess aqueous
KPF6 solution (15 mL) leading to the formation of a dark burgundy
precipitate. The precipitate was collected on Celite and washed with H2O
(2 × 10 mL), DCM (2 × 5 mL), then dissolved in CH3CN and the solvent
removed under reduced pressure to give the title compound as a purple
solid (67 mg, 67%). 1H NMR (500 MHz, CD3CN) δ 8.79 (s, 6H, HA7), 8.71
(s, 6H, -NH), 8.47 (d, J = 7.3 Hz, 6H, HA3), 8.28 (t, J = 7.6 Hz, 6H, HA4),
This article is protected by copyright. All rights reserved.

10.1002/chem.201806259
Chemistry - A European Journal
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-
7.84 (d, J = 7.4 Hz, 12H, HE2), 7.66-7.56 (m, 18H, HD4+A5), 7.56-7.47 (m,
24H, HD3+C2), 7.18 (d, J = 5.4 Hz, 6H, HA6), 7.15 (d, J = 8.2 Hz, 6H, HB3),
6.95 (d, J = 8.3 Hz, 12H, HC3), 6.89 (d, J = 8.4 Hz, 6H, HB5), 5.42 (d, J =
8.3 Hz, 6H, HB2), 5.28 (d, J = 6.6 Hz, 6H, HB6). 13C{1H} NMR (151 MHz,
CD3CN) δ 176.2 (CA7), 166.8 (CC=O), 158.8 (CA2), 156.7 (CA6), 150.3 (CB1),
144.8 (CB4), 144.5 (CD2), 140.6 (CA4), 139.9 (CC1), 139.2 (CC4), 137.4
(CD1), 135.8 (CE1), 134.5 (CB3), 133.3 (CB5), 132.8 (CE4), 132.5 (CA3),
130.7 (CA5), 129.5 (CE3), 128.4 (CE2), 121.8 (CB2), 121.1 (CB6), 120.4
(CC3). UV-vis: 5.3 x 10-6 mol dm-3, MeCN, λmax /nm (ε / 103 dm3 mol-1 cm-1)
291 (272), 574 (10). ESI-MS m/z 611.9465 [Fe2(5)3]4+ requires 611.9490;
779.3125 [5 + H]+ requires 779.3134; 806.7737 [Fe2(5)4]4+ requires
806.7754; 864.2507 [Fe2(5)3 + PF6]3+ requires 864.2534; 1066.2945
[(Fe4(5)6) + 3(PF6)]5+ requires 1066.2969; 1124.0203 [(Fe2(5)4 + PF6]3+
requires 1124.0220; 1369.1093 [Fe2(5)3 + 2(PF6)]2+ and [(Fe4(5)6) +
4(PF6)]4+ requires 1368.8622.
similar bond lengths (using SADI). There are 3 partial occupancy PF6
anions in the unit cell, with a combined occupancy of 2. Two of these
were modelled isotropically due to poor data quality.
2[Fe2(C38H30N6)3](PF6)8·H2O, M= 4825.24, brown plate, triclinic, space
group P-1, a= 19.445(4), b= 20.664(4), c= 33.774(7) Å, α=75.14(3),
β=87.00(3), γ=64.24(3), U=11786(5) Å3, Z= 2, Dc= 1.360 g/cm3, μ(MoK
α)= 0.393 mm-1, T= 100 K, 84580 reflections collected. Refinement of
2930 parameters using 23222 independent reflections against F2
converged at final R1= 0.1266 (R1 all data= 0.1593), wR2= 0.3579 (wR2
all data= 0.3913), GOF= 1.512. CCDC: 1589666
Acknowledgements
This work was supported by the Australian Research Council
[DP160100870] and UNSW Sydney. A.D.W.K and E.T.L. thank
the Australian government for an Australian Postgraduate Award
scholarship. Access to the Australian Synchrotron was possible
by a Collaborative Access Program (MXCAP9824/10598). This
research was undertaken in part using the MX2 beamline at the
Australian Synchrotron, part of ANSTO, and made use of the
ACRF detector. Dr Derrick Roberts and Dr Tanya Ronson are
thanked for their helpful discussions. Sandy Wong is thanked for
her assistance with DLS measurements.
Synthesis of [Fe2(6)3](PF6)4 helicate
Octanoyl chloride (14 µL, 13 mg, 80 µmol) was added to a solution of
[Fe2(2)3](PF6)4 (30 mg, 12.5 µmol) in dry CH3CN (6 mL) . The solution
was stirred at room temperature for 2 h, then poured into excess
aqueous KPF6 solution (30 mL) leading to the formation of a dark
burgundy precipitate. The precipitate was collected on Celite and washed
with H2O (3 × 10 mL) then dissolved in CH3CN (15 mL) and the solvent
removed under reduced pressure to give the title compound as a purple
solid (35 mg, 90%). 1H NMR (500 MHz, CD3CN) δ 8.73 (s, 1H, HA7), 8.45
(d, J = 7.8 Hz, 1H, HA3), 8.32 (t, J = 7.8 Hz, 1H, HA4), 8.25 (s, 1H, -NH),
7.66 (t, J = 7.8 Hz, 1H, HA5), 7.31 (d, J = 8.3 Hz, 2H, HC2), 7.19 (d, J = 5.6
Hz, 1H, HA6), 7.06 (d, J = 8.0 Hz, 1H, HB3), 6.89 – 6.76 (m, 3H, HC3+B5),
5.36 (dd, J = 8.4, 2.4 Hz, 1H, HB2), 5.20 (dd, J = 8.4, 2.4 Hz, 1H, HB6),
1.64 – 1.51 (m, 2H, HE3), 1.38 – 1.22 (m, 8H, HE4), 0.96 – 0.82 (m, 3H, -
CH3). Note that HE1 could not be properly assigned due to overlap with
the HDO peak. 13C{1H} NMR (101 MHz, CD3CN) δ 172.8 (CC=O), 159.0
(CA2), 156.7 (CA6), 150.2 (CB1), 144.8 (CB2), 144.7 (CD2), 140.6 (CA4),
139.4 (CC1), 139.3 (CC4),136.9 (CD1) 134.5 (CB3), 133.2 (CB5) 132.7 (CC1),
132.61 (CA3), 130.7 (CA5), 121.7 (CB2), 121.0 (CB6), 119.4 (CC3), 37.7
(CE2), 32.4 (CE4-7), 29.9 (CE4-7), 29.7 (CE4-7), 26.2 (CE3), 14.4 (CMe). UV-
Vis: 1.0 x 10-6 mol dm-3, MeCN, λmax /nm (ε / 103 dm3 mol-1 cm-1) 279
(144), 360 (57), 574 (11). ESI-MS 645.0653 [Fe2(6)3]4+ requires
Keywords: Self-assembly • metal template • tetraphenylethene •
emission • post-synthetic modification
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+
F]3+ requires 866.4213; 908.4090
[3]
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requires 1119.2847; 1435.5980 [(Fe2(6)3) + 2PF6]2+ and [(Fe4(6)6) +
4PF6]4+ requires 1435.0970 and 1435.3470 m/z respectively.
X-Ray crystallography
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Brown plate like crystals of 2[Fe2(2)3](PF6)8·H2O were grown by slow
evaporation of a DMF/methanol solution of the complex. The crystal with
dimensions of 0.03 × 0.02 × 0.01 mm was coated in immersion oil type
NVH and transferred to the goniometer, where it was cooled with a
nitrogen cold stream (100 K) provided by an Oxford Instruments Cryojet
5. Diffraction measurements were carried out using Si<111>
monochromated synchrotron X-ray radiation (λ = 0.71023 Å) (MX2
Beamline at Australian Synchrotron). Data collection was carried out
using Blu-Ice suite of software and unit cell refinement, data reduction
and processing was carried out with XDS.[43] Absorption correction was
carried out with SADABS.[44] The structure was solved using dual space
methods with SHELXT.[45] The full-matrix least-square refinements were
carried out using SHELXL-2015[45] through Olex2[46] suite of software.
The crystal only diffracted to low resolution. One molecule of solvent
water could be identified from the difference map and was included in the
least-squares refinement. The structure has large solvent accessible
voids in the crystal lattice. To address this, solvent mask was used in
Olex2 (similar to the SQUEEZE procedure in PLATON). As a result of
this solvent mask the R1 was improved 4.67% (from 17.33% to 12.66%
and represented two major voids (140 electrons each, possibly two
disordered DMF solvent molecules). The PF6- anions in the unit cell were
disordered and were restrained to have similar ADPs (using RIGU) and
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Entry for the Table of Contents (Please choose one layout)
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Fluorescent tetraphenylethenes prepared by
supramolecular control of reactivity
Aaron D. W. Kennedy, Nicholas de
Haas, Hasti Iranmanesh, Ena T.
Luis, Chao Shen, Pi Wang, Jason R.
Price, William A. Donald, Joakim
Andréasson, Feihe Huang, and
Jonathon E. Beves*
Page No. – Page No.
Diastereoselective control of
tetraphenylethene reactivity by
metal template self-assembly
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