Synthesis and organogelating behaviour of amino acid-functionalised triphenylenes

Article abstract of DOI:10.1039/c7sm00676d

Four novel amino acid-functionalised triphenylenes have been prepared with glycine, l-alanine, l-phenylalanine and l-tryptophan ethyl ester side-chains. The glycine derivative is a good gelator of chloroform, the alanine derivative gels ethanol and toluene, and the phenylalanine derivative gels benzene and toluene. The tryptophan derivative does not gel any of the solvents tested, most probably due to its more bulky structure, but forms microspheres by evaporation-induced self-assembly. The self-assembly properties of the π-gelators have been investigated using infrared, UV-absorption and fluorescence spectroscopy, concentration- and temperature-dependent NMR, and X-ray scattering experiments on dried xerogel as well as the wet organogel. The latter experiments suggest the glycine gel in chloroform includes columnar aggregates, with an overall disordered columnar oblique mesophase. These compounds are of interest because of the well-known hole-transporting properties of triphenylene liquid crystals: 1-D columnar assemblies of these compounds may find applications in organic electronic devices.

Full text of DOI:10.1039/c7sm00676d

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Meegan, X. Yang, R. Rungsirisakun, S. C. Cosgrove, R. J. Bushby, A. Sadeghpour, M. Rappolt and R.
Brydson, Soft Matter, 2017, DOI: 10.1039/C7SM00676D.
Volume 12 Number
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January 2016 Pages 1–314
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Rational design of molecularly imprinted polymers
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Page 1 of 21
Soft Matter
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DOI: 10.1039/C7SM00676D
Synthesis and organogelating behaviour of amino
acid-functionalised triphenylenes
a, ,d
a,e
a,f
a
Jonathan. E. Meegan
, Xiaofei Yang , Ratana Rungsirisakun , Sebastian C. Cosgrove ,
a
b,g b c
Richard J. Bushby , Amin Sadeghpour , Michael Rappolt , Rik Brydson and Richard J.
a
Ansell*
Four novel amino acidꢀfunctionalised triphenylenes have been prepared with glycine, Lꢀ
alanine, Lꢀphenylalanine and Lꢀtryptophan ethyl ester sideꢀchains. The glycine derivative is a
good gelator of chloroform, the alanine derivative gels ethanol and toluene, and the
phenylalanine derivative gels benzene and toluene. The tryptophan derivative does not gel
any of the solvents tested, most probably due to its more bulky structure, but forms
microspheres by evaporationꢀinduced selfꢀassembly.
The selfꢀassembly properties of the πꢀgelators have been investigated using infrared, UVꢀ
absorption and fluorescence spectroscopy, concentrationꢀ and temperatureꢀdependent NMR,
and Xꢀray scattering experiments on dried xerogel as well as the wet organogel. The latter
experiments suggest the glycine gel in chloroform includes columnar aggregates, with an
overall disordered columnar oblique mesophase. These compounds are of interest because of
the wellꢀknown holeꢀtransporting properties of triphenylene liquid crystals: 1ꢀD columnar
assemblies of these compounds may find applications in organic electronic devices.
Introduction
Triphenylene derivatives form a class of discotic mesogens capable of oneꢀdimensional faceꢀ
toꢀface assembly into columnar stacks. Since the report of their selfꢀassembly properties in
1
1
978 , they have been the focus of many investigations because of the possibility of oneꢀ
dimensional conductivity along the stack of overlapping πꢀelectron systems. Applications
2
3
have been proposed in electrophotography and organic electronics , organic LEDs ,
4
5
6
optoelectronics , surface modification , chemical sensing , as optical compensating films for
increasing the angle of view of liquid crystal displays , for controlling aggregation of
nanoparticles and the templating of inorganic mesostructures . Recently other applications
for triphenylene derivatives (not dependent on the selfꢀassembly properties) have been
suggested, as covalent scaffolds for organised macromolecular structures , molecular
7
8
9
10
11
12
receptors and drugꢀdelivery systems . All these applications rely on rational modification
of the molecular properties via the tailoring of the triphenylene sideꢀchains.
Although most of the work aiming at applications in devices has focussed on thermotropic
a
School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2
JT, UK Fax: +44 113 343 6565; Tel: +44 113 343 6415; Eꢀmail:
9
chmrja@leeds.ac.uk
b
School of Food Science and Nutrition, University of Leeds.
c
School of Chemical and Process Engineering, University of Leeds.
d
present address: Solvay Composite Materials, Wrexham, UK.
e
present address: School of Materials Science and Engineering, Jiangsu
University, Zhenjiang, China.
f
present address: Institute of Materials Sciences and Engineering
Research , King Mongkut’s University of Technology Thonburi, Bangkok,
Thailand.
g
present address: Empa ꢀ Swiss Federal Laboratories for Materials
Science and Technology, St. Gallen, Switzerland

Soft Matter
Page 2 of 21
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DOI: 10.1039/C7SM00676D
triphenylenes, which form liquid crystalline structures as homogeneous materials or blends
with other components, there has been an increasing number of triphenylenes reported with
lyotropic liquid crystal and/or solvent gelating properties. The first of these was
2
,3,6,7,10,11ꢀhexaꢀ(1,4,7ꢀtrioxaoctyl)ꢀtriphenylene (TP6EO2M), which forms hydrogels /
1
3, 14, 15
lyotropic phases in water
reported which are capable of gelating organic solvents
others have been shown to form physical gels in combination with an additional gelator .
This reflects an increasing interest in low molecular weight organogelators (LMOGs)
. Subsequently several triphenylene derivatives have been
6
, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26
, while
2
7
2
8
29
generally , and πꢀgelators in particular , due to their manifold potential technological
applications. In all the triphenylene organogels reported, the structure is proposed to include
columnar stacks of triphenylene derivatives, with the sideꢀchains playing an essential role via
hydrogen bonding or ionic interactions which reinforce the relatively weak πꢀ π interactions
and help to maintain the columnar organisation. However, while the columnar structures of
thermotropic liquid crystal triphenylenes have been demonstrated in many cases by smallꢀ
and wideꢀ angle Xꢀray scattering experiments (WAXS and SAXS), these experiments are
much more difficult on lyotropic/organogel systems, and the structure of the triphenylene
organogels has mostly been investigated by solution methods such as absorbance /
fluorescence spectroscopy, by Xꢀray studies of dried gels (xerogels), or by extrapolating from
the thermotropic behaviour of the pure compounds. Only one example of Xꢀray
measurements on an organogelating triphenylene in the lyotropic state has been reported, by
22
Mendes et al. , giving rather broad scattering peaks at about 25 and 14 Å which were
attributed to the distance between columns, but could not be assigned to any particular
packing arrangement.
3
0
Peptide gelators are well known and several reports have attempted to combine πꢀgelators
with amino acids or peptides, to create novel, functional, biomimetic structures, for example
3
1
32
using perylene bis(imide)s and other π ꢀgelator derivatives . Inspired by this vision of
functional biomaterials, we designed and synthesised novel compounds 2a-2d (Fig. 1),
incorporating glycine, Lꢀalanine, Lꢀphenylalanine and Lꢀtryptophan respectively, using a
modular approach which will be adaptable to the synthesis of a large range of new
triphenylenes. Use of amino acids provides an inexpensive approach to introduce chirality
into the sideꢀchains. Although Stoddart et al. reported sugarꢀappended triphenylenes capable
16
of forming lyotropic mesophases with organic solvents back in 2001 , and others have
1
7, 19, 20, 21, 24
reported organogelating triphenylenes containing amide groups
, the only previous
reports of triphenyleneꢀamino acid conjugates of which we are aware are three compounds
33
reported by Bechgaard et al. in 1997 but not investigated for lyotropic behaviour (the tertꢀ
butyl, rather than ethyl, derivatives of 2a and 2b, and the deprotected carboxylic acid variant
of 2b), and a recently reported triphenyleneꢀhomoserine conjugate whose selfꢀassembly
3
4
properties have not yet been reported . Only two examples have been reported of
1
6, 20
triphenylene organogelators with chiral sideꢀchains
. Thus, the aminoꢀacid functionalised
triphenylenes 2a-2d, studied in this work, comprise the first members of an interesting new
class of compounds.
Furthermore, we report also on the organogelating behaviour of these compounds, including
SAXS studies on 2a, 2b and 2c in the lyotropic state. The diffraction pattern for the gel of 2a
in chloroform is consistent with a disordered columnar oblique (Col ) structure, which is also
o

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evident in the powder diffraction pattern of the dried xerogel. This is, to our knowledge, the
first Xꢀray study of the structure of a triphenylene in the lyotropic state apart from a
1
3
preliminary result with TP6EO2M in D
.
2
O published in 1986 and the work of Mendes et al.
2
2
Further, ours is the first where a definitive structure can be assigned to the interꢀcolumnar
organization.
Figure 1. Synthesis of amino acidꢀfunctionalised triphenylenes 2a-2d.
Experimental
Instruments
1
H NMR investigations were conducted on a Bruker Avance 500 operating at 500 MHz.
For variable temperature experiments, samples were kept in the magnet at the set
temperature for 10 min prior to the collection of data. UV absorbance spectra were
recorded on an Agilent Carey 100 UVꢀVis spectrophotometer using 1 mm pathlength
quartz cuvettes. Fluorescence spectra were recorded on a Jobin Yvon Horiba Fluorolog 2
spectrofluorimeter, using 10 mm × 10 mm quartz fluorescence cuvettes in the frontꢀface
configuration (to minimise inner filter effects), excitation was at 320 nm and slit widths
were 0.5 nm. SEM secondary electron micrographs were obtained on a Carl Zeiss/LEO
1
530 field emission scanning electron microscope (FEGSEM) operated at low kV and
using an in lens detector. Powder Xꢀray diffraction analyses were performed with a
Bruker D8 Advance A25 diffractometer using CuꢀKα radiation (λ = 0.15418 nm). The

Soft Matter
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optical microscope was a Seben SBXꢀV Microscope 40×ꢀ2000×, equipped with a Seben
PC USB eyepiece. FTIR spectra were collected using a Thermo Scientific Nicolet iS5
spectrometer with an iD1 transmission cell. Samples were contained in a liquid cell
comprising NaCl windows separated by a 500 µm teflon spacer. Samples in gelling
solvents were heated until completely dissolved before filling the cell and allowing them
to cool.
Gelation studies
Gelation studies were carried out by dissolving triphenylene (1 mg) in solvent (50 – 800
ꢁ
l). The triphenylene was dissolved with heating in a sealed 2 ml glass vial (vials were
held in an ultrasonic bath at 50 C for c 2 min, then in an oil bath set to the solvent’s
boiling temperature for 30 s, for up to 5 cycles) and then left at room temperature for 1 h.
To test for gelation the vial was inverted. For SEM studies a small sample was removed
and smeared onto an SEM stub (aluminium, 10 mm diameter), dried at room temperature
under vacuum, and gold coated (20 mA current, 20 s coating time at 5 Torr) prior to
placement in an SEM.
SAXS
A SAXSpace system (Anton Paar, Graz, Austria) with an Xꢀray generator from GE
Inspection Technologies generating CuꢀKα radiation (wavelength λ=0.15418 nm) was
used. Disposable quartz capillaries (Capillary Tube Supplies Ltd, Cornwall, UK) were
filled with samples in liquid state and sealed with Seal Wax Red (Tesco, UK). The
capillaries were embedded into a homemade stainless holder which itself fits into the
sample stage in SAXSpace. The sample stage is equipped with a Peltier element (TCStage
1
50, Anton Paar, Graz, Austria) controlling the temperature with a precision of 0.1˚C.
While the Xꢀray exposure time for each measurement was 30 minutes, the overall
scattering pattern was obtained after integration and averaging of three consecutive
recorded scattering profiles.
The scattering patterns were corrected with respect to the position of the primary beam
using the SAXStreat software (Anton Paar, Graz, Austria). The relative intensity of
scattering data was further corrected using the transmittance of the Xꢀray beam at zero
angles and setting its attenuated scattering intensity to unity. Background subtraction was
carried out considering both the scattering from empty and solventꢀfilled capillaries. All
these corrections were made using the SAXSQuant software (Anton Paar, Graz, Austria).
Synthesis of materials
Veratrole, FeCl
phenylalanine ethyl ester hydrochloride, Lꢀtryptophan ethyl ester hydrochloride, Et
CO and AcOH were purchased from SigmaꢀAldrich (Gillingham, UK). Lꢀalanine ethyl
3
, bromoacetyl chloride, glycine ethyl ester hydrochloride, Lꢀ
3
N,
K
2
3
ester hydrochloride was from Alfa Aesar (Heysham, UK). Deionised water was used
throughout. Dimethylformamide (DMF) was purchased as anhydrous grade.

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Dichloromethane (DCM) was dried by continuous distillation over calcium hydride.
Other solvents were from varied suppliers and at least HPLC grade. Column
chromatography was carried out on silica (40ꢀ60 nm, SigmaꢀAldrich).
Hexahydroxy triphenylene (HATꢀ0): Hexahydroxy triphenylene was prepared from
3
veratrole (55.3 g, 0.4 mol) and FeCl (165 g, 1 mol) according to the method described by
3
3
Bechgaard et al. . Pure hexahydroxy triphenylene was recrystallised from a solution of
the crude product in acetic acid and water (800 mL, 1:1.5 v/v) as a dark grey crystalline
powder (21 g, mmol, 90%). (DMSOꢀd
δ
H
6
) 7.6 (s, 6H ArH), 9.33 (broad s, 6H ArOH).
Anal. Calcd. for C18 .C H O (acetate): C, 62.60; H, 4.20. Found: C, 62.90; H,
H
12
0
6
2 4 2
4
.20%.
2
ꢀ(2ꢀBromoꢀacetylamino)ꢀacetic acid ethyl ester (1a): The glycine intermediate was made
3
5
by a similar procedure to that of Lipowski et al. , syntheses have also been reported by
Kaverzneva et al. and Zhang et al. Bromoacetyl bromide (4.34 mL, 50 mmol) was
3
6
37
added dropwise to a magnetically stirred solution of glycine ethylester hydrochloride
(
3
6.14 g, 44 mmol) and Et N (12.2 mL, 88 mmol) in dry DCM (100 mL) and stirred under
Ar for 3h at 0 ºC. The solution was allowed to warm to room temperature overnight. The
reaction was quenched at room temperature by addition of water (100 mL) and separated.
The DCM extracts were washed with water (100 ml), HCl (1M, 100 mL), water (100
mL), NaHCO (100 mL), brine (100 mL), dried (MgSO ) and concentrated in vacuo to
3 4
yield the bromoamide as yellow/white solids which were used without further
purification. The crude product could be purified by flash column chromatography
(
6
EtOAc/CHCl
5%). (CDCl
NHCH C=O), 4.26 (q, 2H, CH
agreement with literature .
3
1:1 v/v) to give the bromoamide as a white solid (6.40 g, 28.6 mmol,
) 1.30 (t, 3H, CH CH O), 3.92 (s, 2H, BrCH C=O), 4.08 (m, 2H,
CH O), 6.95ꢀ7.06 (d, 1H, O=CNHCH ). Analytical data in
δ
2
H
3
3
2
2
3
2
2
3
5
Lꢀ2ꢀ(2ꢀBromoꢀacetylamino)ꢀpropionic acid ethyl ester (1b): The alanine intermediate was
3
6
previously prepared by Kaverzneva et al. , although those authors used sodium carbonate
as a base and published limited characterization data. Palsson et al. used this compound
3
8
as an intermediate , although they give no details of its synthesis or characterization.
Bromoacetyl bromide (5.22 mL, 60 mmol) was added dropwise to a magnetically stirred
3
solution of Lꢀalanine ethylester hydrochloride (6.14 g, 40 mmol) and Et N (11.2 mL, 80
mmol) in dry DCM (100 mL) and stirred under Ar for 15 h at room temperature. The
reaction was worked up in a similar manner to the glycine intermediate above to yield the
bromoamide as yellow/white solids which were used without further purification. The
crude product could be purified by flash column chromatography (EtOAc/CHCl
to give the bromoamide as a white solid which was shown by NMR to be an intractable
mixture of 95% bromoꢀ and 5% chloroꢀderivatives (6.38 g, 26.8 mmol, 67 %). [α]
24.3 (c 0.84, CHCl ).
(CDCl ) 1.30 (t, 3H, CH
.23 (q, 2H, CH CH O), 4.56 (m, 1H, NHCHC=O), 7.03ꢀ7.13 (d, 1H, O=CNHCH);
) 14.1, 18.3, 28.8, 48.5, 61.8, 165.1, 172.4; MS (ES): m/z 238.0071, expect
3
1:1 v/v)
D
=
+
3
δ
H
3
3 2 3 2
CH O), 1.45 (dꢀd, 3H, CH CHNH), 3.89 (s, 2H, BrCH C=O),
4
3
2
δ
C
(
2
CDCl
3
+
7 3
38.0079 for [MH ]. Anal. calcd. for C H12BrNO : C 35.3, H 5.08, N 5.88; Found C 35.2,
H 5.10, N 7.90%.

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Lꢀ2ꢀ(2ꢀBromoꢀacetylamino)ꢀ3ꢀphenylꢀpropionic acid ethyl ester (1c): The phenylalanine
3
9
intermediate was previously prepared by Gibb et al. , although those authors used
3
6
acetonitrile as solvent and sodium carbonate as a base. Kaverzneva et al. also reported a
synthesis using dichloromethane as solvent and sodium carbonate as base, but published
limited characterization data. The intermediate was synthesised similarly to the alanine
intermediate, except 3.48 mL (40 mmol) bromoacetyl bromide and 10.0 mL (72 mmol)
Et
used in place of Lꢀalanine ethylester hydrochloride to yield the bromoamide as a dark
grey oil. The crude product was purified on a flash silica column (1 : 4 v/v EtOAc/CHCl
3
N were used, and Lꢀphenylalanine ethylester hydrochloride (8.54 g, 36 mmol) was
3
)
to yield a light green solid which was shown by NMR to be an intractable mixture of 70%
bromoꢀ and 30% chloroꢀderivative (6.78 g, 21.6 mmol, 60%).
δ
4
7
H
(CDCl
.17 (q, 2H, CH
.65 (m, 5H, ArH). Analytical data in agreement with literature .
3
) 1.25 (t, 3H, CH
3
CH
2
O), 3.15 (d, 2H, CHCH
2
ArH
2
), 3.85 (s, 2H, BrCH
2
C=O),
3
CH O), 4.83 (q, 1H, NHCH(CH
2
2
)C=O), 6.88 (d, 1H, O=CNHCH
2
), 7.0 –
3
9
Lꢀ2ꢀ(2ꢀBromoꢀacetylamino)ꢀ3ꢀ(1Hꢀindolꢀ3ꢀyl)ꢀpropionic acid ethyl ester (1d): The
4
0
tryptophan intermediate was previously prepared by Pop et al. , although those authors
used sodium carbonate as a base and published no characterization data. The intermediate
was synthesised similarly to the alanine intermediate, except 4.0 mL (46 mmol)
3
bromoacetyl bromide and 8.4 mL (60 mmol) Et N were used, and Lꢀtryptophan ethylester
hydrochloride (8.08 g, 30 mmol) was used in place of Lꢀalanine ethylester hydrochloride
to yield the bromoamide as a dark grey oil. The crude product was purified on a flash
silica column (1:4 v/v EtOAc/CHCl
NMR to be an intractable mixture of 95% bromoꢀ and 5% chloroꢀderivatives (4.46 g, 12.6
mmol, 42%).[α] = +22.8 (c 1.0, CHCl
) 1.22 (t, 3H, CH CH O), 3.36 (m, 2H, CHCH
.15 (q, 2H, CH CH O), 4.88 (m, 1H, NHCH(CH )C=O), 6.94 (d, 1H, O=CNHCH
7.65 (m, 5H, ArH), 8.21 (s, 1H, NH). MS (ES): m/z 353.0481, expect 353.0501 for
3
) to yield a grey/yellow solid which was shown by
D
3
)
δ
4
–
H
(CDCl
3
3
2
2
ArH
2
), 3.82 (s, 2H, BrCH
2
C=O),
), 7.0
3
2
2
2
+
[
17 3 2
MH ]. Anal. Calcd. for C15H O N Br: C, 51.00; H, 4.85; N, 7.93. Found C, 51.20 ; H,
4
.95; N, 7.75%.
Hexakisꢀ(acetylaminoꢀacetic acidꢀethyl ester)ꢀoxy triphenylene (2a): 1a (3.36g, 15 mmol)
was dissolved in DMF (10 mL, anhydrous) to which hexahydroxytriphenylene (0.65g, 2.0
mmol) and powdered K CO (4.98 g, 36.0 mmol) were added. The suspension was stirred
2 3
under argon at room temperature for 5 days after which an excess of water was added and
the resulting precipitate was collected by filtration and dried. The dry precipitate was
purified by washing with water, and dissolving in CHCl
of petroleum ether. Pure 2a was recovered as a solid after evaporation of the remaining
solvent and drying (1.91g, 1.62 mmol, 81%). mp: 232ꢀ234°C. (DMSOꢀd ) 1.23 (t,
8H, CH CH O), 4.04 (d, 12H, NHCH C=O), 4.17 (q, 12H, CH CH O), 4.95 (s, 12H,
ArOCH ), 8.25 (s, 6H, ArH), 8.62 (t, 6H, O=CNHCH ). (DMSOꢀd ) 14.4, 39.8, 60.9,
8.7, 108.8, 124.0, 147.7, 168.8, 170.0. MS (ES): m/z 1205.4014, expect 1205.4026 for
3
and precipitation with an excess
δ
H
6
1
3
2
2
3
2
2
2
δ
C
6
6
+
[
MNa] Anal. Calcd. for C54
.55; N, 7.08%.
66 6
H N O24: C, 54.82; H, 5.62; N 7.10. Found: C, 54.73; H,
5

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Hexakisꢀ(2ꢀacetylaminoꢀacetic acid ethyl ester)ꢀoxy triphenylene (2b): 1b (2.84 g, 12
mmol) was dissolved in DMF (10 mL, anhydrous) to which hexahydroxytriphenylene
(
2 3
0.49 g, 1.5 mmol) and powdered K CO (4.15 g, 30 mmol) were added. The suspension
was stirred under argon at room temperature for 5 days after which an excess of water
was added and the resulting precipitate was collected by filtration and dried. The dry
precipitate was purified on a flash silica column (1:40 v/v EtOAc/CHCl
3
) to give 2b as a
light yellow solid (1.25 g, 0.99 mmol, 66%). [α]
D
= +9.5 (c 0.81, CHCl ); mp: 222ꢀ
3
2
δ
CH
7
1
23 °C.
(CHCl
CH O), 4.72 (m, 6H, NHCHCH
.98 (s, 6H, ArH). (CHCl ) 14.1, 18.1, 48.0, 61.7, 69.0, 108.5, 124.4, 147.4, 167.8,
72.8. MS (ES): m/z 1289.4803, expect 1289.4965 for [MNa] . Anal. Calcd. for
24: C 56.86, H 6.20, N 6.63; Found: C 56.1, H 6.40, N 6.50%.
H
3
) 1.27 (t, 18H, CH
3
CH
2
O), 1.52 (d, 18H, CH
3
CHC=O), 4.20 (q, 12H,
3
2
), 4.86 (s, 12H, ArOCH ), 7.54 (d, 6H, O=CNHCH),
3 2
δ
C
3
+
60 78 6
C H N O
LꢀHexakisꢀ(2ꢀacetylaminoꢀ3ꢀphenylꢀpropionic acid ethyl ester)ꢀoxy triphenylene (2c): 2c
was prepared using the same protocol as for 2a with the exception that 1c (3.77 g, 12
mmol) was used instead of 1a, and the amounts of HATꢀ0 and K
2
CO
3
were reduced to
0
.49g(1.5 mmol) and 4.15 g (30 mmol) respectively. The dry precipitate was purified on a
3
flash silica column (1:4 v/v EtOAc/CHCl ) to give 2c as a yellow solid (1.86 g, 1.08
mmol, 72%). mp: 155 °C. [α]
D
= +78 (c 0.95, CHCl
= 1.21 (t, 18H, CH CH O), 3.16 (t, 12H, CHCH
.69 (q, 12H, OCH C=O), 4.96 (q, 6H, NHCHC=O), 7.04 (m, 30H, PhH), 7.41 (d, 6H, NH),
.84 (s, 6H, ArH). (CHCl ) 14.1, 37.9, 53.0, 61.7, 69.7, 109.5, 124.8, 127.0, 128.5, 129.2,
35.8, 147.9, 168.1, 171.4. MS (ES): m/z=1745.6859, expect 1745.6843 for [MNa] . Anal.
24: C 66.88, H 5.96, N 4.88; Found: C 66.6, H 5.90, N 4.80%.
3
)
δ
4
7
1
H
(CHCl
3
)
δ
3
2
2 3 2
Ph), 4.17 (q, 12H, CH CH O),
2
δ
C
3
+
102 6
Calcd. C96H N O
LꢀHexakisꢀ(2ꢀacetylaminoꢀ3ꢀ(1Hꢀindolꢀ3ꢀyl)ꢀpropionic acid ethyl ester)ꢀoxy triphenylene
2d): 2d was prepared using the same protocol as for 2a with the exception that 1c (2.12
g, 6 mmol) was used instead of 1a, and the amounts of HATꢀ0 and K CO were reduced
to 0.26 g (0.75 mmol) and 2.77 g (20 mmol) respectively. The dry precipitate was
purified by using flash chromatography (1:4 EtOAc/CHCl v/v) to give 2c as a
yellow/grey solid (0.98g, 0.50 mmol, 67%) mp: 120 °C. [α] = +90.6 (c 0.98, CHCl
(500 MHz, CDCl ) 1.24 (t, 18H, CH CH O), 3.36 (m, 12H, CHCH Ar), 4.15 (q, 12H,
CH CH O), 4.55 (s, 12H, ArOCH C=O), 4.88 (m, 6H, NHCH(CH )C=O), 7.1 (d, 6H,
O=CNHCH ), 7.0 – 7.65 (m, 6H, ArH). (CDCl ) 14.1, 26.9, 51.8, 62.1, 68.6, 107.9,
08.6, 111.5, 118.0, 119.3, 122.1, 122.9, 124.1, 127.1, 136.3, 146.7, 168.5, 172.4. MS
(
2
3
3
D
3
)
δ
H
3
3
2
2
3
2
2
2
2
δ
C
3
1
+
(
ES): m/z=1979.7530, expect 1979.7497 for [M+Na] . Anal. Calcd. for
O: C, 64.46; H, 5.71; N, 8.36. Found: C 64.6; H 5.6; N 8.2%.
C
108 108 24 2
H O N12.3H
Results and Discussion
The synthesis of the tꢀbutyl derivative of 2a has previously been reported by Bechgaard et
3
3
al. , in four steps starting from HATꢀ0. When we attempted to use a similar procedure to
generate the ethyl derivative 2a, we experienced difficulties in isolating a pure product

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from the second step. Hence the reaction scheme in Fig. 1 was designed, where the preꢀ
synthesised sideꢀchain bromoacetyl amino acid ethyl ester is coupled to HATꢀ0 in a
single step. In our hands, this route gave pure products (after crystallisation or flash
chromatography) in acceptable yields, both for 2a and for the other amino acid variants.
Bromoacetyl amino acid ethyl esters have been prepared by different routes: the method
3
5
of Lipowska et al. using dichloromethane as solvent and triethylamine as base was
found to be most successful, although the intermediates were usually obtained as
intractable mixtures of bromoꢀ and chloroꢀderivatives. These however reacted completely
with hexahydroxy triphenylene and the general route in Fig. 1 was successfully used to
synthesise novel compounds 2a-2d.
The solubility and gelation results for 2a-2d are summarised in Table 1. 2a was found to
be capable of gelating chloroform and dichloromethane at relatively low concentrations.
ꢀ
1
ꢀ1
Samples containing as little as 2ꢀ10 mg mL in chloroform or 0.5ꢀ2 mg mL in DCM
exhibited clots of gelled solvent although they were not completely gelled throughout
(
Table 2). These compare favorably with the lowest reported critical gel concentrations
1
7, 18, 20, 22
for other triphenylene derivative organogelators
mg/ml in chloroform, 2 mg mL in DCM)) led to the formation of self supporting opaque
gels (Fig. 2), SEM examination of these gels showed them to be composed of thick (>
. High concentrations of 2a (10
ꢀ
1
2
00 nm wide) tendrilꢀlike organogel fibres (Fig. 3a).
Table 1. Solubility study results.
2
a
2b
2c
I
2d
I
H
2
O
I
I
H
C
C
MeOH
EtOH
I
I
I
200 , P
800
1000
400
50
600
800
400
50
H
200 , G
H
C
THF
100 , P
H
C
C
DCM
200 , G
50
50
50
50
H
CHCl3
DMSO
DMF
200 , G
50
400
50
300
400
50
50
50
C
H
C
C
C
C
MeCN
Benzene
Toluene
200, P
100 , P
200, P
H
200
200
H
C
C
I
I
200 , P
200 , G
H
H
H
C
200 , G
200 , G
200 , P
Numbers indicate volume of solvent (ꢁL) needed to solubilise 10 mg sample at room temperature after heating
on an oil bath to 120 ºC or to the solvent’s boiling temperature (whichever is lowest) and cooling to room
temperature for 1 h. I: insoluble (doesn’t dissolve even in 10 mL); P: precipitate; G: gel; H: on heating; C:
H
cooling down. For example: 200 means 10 mg sample are completely dissolved in 200 ꢁL solvent on heating,
C
however it precipitates out when cooling down to room temperature (P ) or forms a gel when cooling down to
C
room temperature(G ).
Table 2. Gel concentration results.

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Min. concn. for loose/partial
Min. concn. for full gel
ꢀ
1
ꢀ1
gel / mg mL
(selfꢀsupporting) / mg mL
2
a in CHCl
a in CH Cl
b in toluene
3
2
< 0.5
0.5
2
10
2
2
2
2
2
40
25
15
30
2
b in EtOH
2
c in toluene
1
2
c in benzene
2
Samples at different concentrations were heated to the solvent’s boiling temperature then cooled to RT.
Interestingly whilst 2b and 2c did not gel chloroform or DCM, they were both capable of
gelling toluene (Fig. 2, 3b and 3c), whilst 2a could not even be dissolved in toluene on
heating. These gels when examined under the SEM comprised narrower fibres, of 50ꢀ100
nm diameter (Fig. 3bꢀc). 2b also gelled ethanol, at relatively high concentrations, and this
gel comprised even narrower fibres of 20ꢀ50 nm diameter (Fig. 3d). 2c was also able to
gel benzene. Other aromatic solvents were investigated but the derivatives all exhibited
limited solubility.
Figure 2. Photographs of the heated sols (top), and the gels formed at room temperature
ꢀ
1
ꢀ1
(
bottom), from 10 mg mL 2a in chloroform (left) and 20 mg mL 2b in toluene (right).
2
d was found to be soluble in all of the solvents studied with the exception of water and
incapable of gelating any of them. Optical microscopy studies of 2d solutions (MeOH,
ꢀ
1
EtOH, THF, DCM, 1 mg mL 2d) dispersed on glass slides showed however that 2d was
completely dissolved in the solution, up until sufficient solvent had been removed by
evaporation into the atmosphere to cause the formation of 2d microspheres of ~ 1 ꢀm.
These can be seen by optical microscopy (Fig. 4) along with slightly larger aggregates.
Although organogelators have been observed forming spherical micelles or spherulites on
the nanoscale, there are only a few published examples of the formation of such regular
microspheres by evaporationꢀinduced selfꢀassembly of low molecular weight organic
4
1
molecules , and the process is not well understood. The regular arrangement of the

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triphenylene microspheres is suggestive of photonic crystals, for example. The properties
of the 2d microspheres and their selfꢀassembly are the subject of ongoing research.
ꢀ
1
Figure 3. SEM images of xerogels formed by drying organogels of a) 2a (10 mg mL ) in
ꢀ
1
ꢀ1
chloroform, b) 2b (20 mg mL ) in toluene, c) 2c (20 mg mL ) in toluene, d) 2b (25 mg
ꢀ
1
mL ) in EtOH. Original magnification in each case ×50,000. Scale bar (bottom left) is 1
m.
ꢀ

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Figure 4. Optical micrograph of 2d microspheres, Scale bar = 10ꢁm.
The ability of LMOGs to gel different solvents is a complicated balance between the
strength of gelatorꢀgelator (soluteꢀsolute) interactions and soluteꢀsolvent interactions.
Although some progress has been made in correlating the gelating ability of particular
4
2
LMOGs with solvent parameters , there is no rule set which can be universally applied.
In the case of 2a ꢀ 2d, it is clear that 2a has lower solubility, in general, than the other
triphenylene derivatives, indicating that 2aꢀ2a interactions are, relatively, stronger than
2
bꢀ2b for example. Interestingly, all of the combinations that give rise to gels occur when
ꢀ
1
the maximum solubility of the triphenylene derivative in hot solvent is about 50 mg mL
(
~ 50 mM). This may indicate the optimum balance of solventꢀsolute vs. soluteꢀsolute
ꢀ
1
interactions. Thus 2b dissolves in hot EtOH at 50 mg mL and cools to give a gel: the
other triphenylene derivatives are less soluble in EtOH and do not form gels, perhaps
indicating the soluteꢀsolute interactions in these cases are too strong. 2a dissolves in hot
ꢀ
1
CHCl
3
or DCM at 50 mg mL , and cools to form a gel, while 2b-2d are too soluble in
where the
these solvents (soluteꢀsolvent interactions are too strong) – except 2d in CHCl
3
ꢀ
1
solubility is too low. 2b and 2c dissolve in hot toluene at 50 mg mL and cool to give
gels: 2a is too insoluble, and 2d precipitates rather than forming a gel, perhaps because
the indole side chains sterically hinder 1D aggregation. There are other exceptions for
example 2a, 2c and 2d dissolve in hot MeCN at about 50 mg mL yet none form gels:
perhaps because the polar aprotic solvents solvate the amide group particularly
effectively.
ꢀ
1
1
The selfꢀassembly behaviours of the triphenylenes were further investigated by Hꢀ
NMR and some chemical shift/concentration plots are shown in Figure 5a. For 2a in
CDCl
an increase in shielding as the concentration of 2a increases; however the protons
associated with the amino acid sideꢀchain (H , H and H ) appear to exhibit a slight
3 A B
the protons on and directly adjacent to the triphenylene core (H and H ) undergo
D
E
F
decrease in shielding. It is suggested that these changes are attributable to individual 2a
monomers forming one dimensional aggregates in solution: as the triphenylene cores
stack the ring protons (H
triphenylene ring systems directly above and below them; the deshielding of the sideꢀ
chain protons (H , H and H ) may be caused by the sideꢀchains being forced out into the
plane of the triphenylene aromatic system and away from the shielding region generated
A B
and H ) are shielded by the π electron clouds of the
D
E
F

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4
3
by the aromatic ring current , or simply by the influence of hydrogen bonds forming
between sideꢀchains.
1
Figure 5. a) Concentration dependant H NMR study of 2a and 2d in CDCl
3
. b)
ꢀtoluene. c)
at different temperatures. d) Corresponding
1
Temperature dependent H NMR study of 2a in CDCl
Corresponding spectra for 2a in CDCl
3 8
and 2c in d
3

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8
spectra for 2c in d ꢀtoluene at different temperatures. Black symbols correspond to 2a,
blue to 2c and red to 2d throughout.
In the case of 2b, 2c and 2d in CDCl
3
the chemical shifts of all the studied protons remain
more or less constant, implying that the protons remain in a similar chemical environment
over the concentration range studied (data for 2d are shown in Fig 5a).
1
Since the gels are thermoreversible, variableꢀtemperature HꢀNMR was also conducted
(
3 A B
Fig. 5b). For 2a in CDCl , H and H become progressively more deshielded as the
temperature increases, corresponding to aggregates dissociating and the triphenylenes
reverting to the monomeric state, in agreement with the concentrationꢀdependent results
(
Fig. 5c). For 2c in d
suggesting the aromatic protons are again more shielded in the aggregated state.
However, the change in chemical shift for H with increasing temperature is minimal,
whilst the amide proton H is progressively more shielded with increasing temperature
for 2a, H barely changes with temperature). Other nuclei including H
phenyl protons also demonstrated changes in shift with temperature for 2c in d
and there were quite dramatic changes in lineshape: e.g. H of 2c in d
8 A
ꢀtoluene, H becomes more deshielded with increasing temperature,
B
C
(
C
D
, H
G
and the
ꢀtoluene
8
B
8
ꢀtoluene is a singlet
at low temperature as might be expected, but splits into two strongly coupled doublets at
high temperature (Fig. 5d). These observations suggest the mode of aggregation of 2c in
d
8
ꢀtoluene may be significantly different from that of 2a in CDCl
implicated in aggregation perhaps via hydrogenꢀbonding and the phenyl group involved
via πꢀπ interactions. At high temperature (in the nonꢀaggregated state) the two H protons
3
, with the amide group
B
become nonꢀequivalent, indicating that there is some preferred conformation of the sideꢀ
chains in which the symmetry of these protons is lost: on aggregation, the sideꢀchains
may be forced into a different conformation where the H
again.
B
protons become equivalent
The absorbance and emission properties of 2a-d were studied in different solvents. Figure
shows the spectra of 2a in MeCN (a nonꢀgelling solvent) and in CHCl (a gelling
6
3
solvent), and of 2b in MeCN (a nonꢀgelling solvent) and toluene (a gelling solvent). The
absorption spectra (Fig. 6a) appear similar in each case, with a maximum about 277 nm
(
although this is harder to discern in toluene due to the background absorption), and are
4
4
quite similar to those of HATꢀ5 in heptane described by Markovitski et al. and of the
1
4
poly(ethoxylated) triphenylene TP6EO2M in dichloromethane . By analogy with
Markovitsi the main peak can be assigned to the S ꢀS transition. When 2a is measured in
the gelling solvent CHCl , its absorbance is very slightly higher than in nonꢀgelling
MeCN, but there is little change in λmax. Similarly, when spectra are recorded for 2a at
increasing concentration in CHCl there is little change in the shape of the spectrum (see
0
4
3
3
supplementary information Figure S9). By contrast, the spectrum of 2b in toluene (a
gelling solvent) is different from that in MeCN, in particular the shoulder at 320 nm (due
to the S
other organogelating triphenylene derivatives have been inconclusive: Shinkai et al.
compared their triphenylene derivatives in CHCl (a nonꢀgelling solvent) and in
cyclohexane (a gelling solvent) and observed a significant blue shift , but Kimura et al.
0 3
ꢀS transition) shows lower absorbance. Absorbance spectroscopy studies of
3
4
5

Soft Matter
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compared their derivatives in methoxyethanol (a gelling solvent) above and below the gel
2
6
temperature and saw little change .
In MeCN (nonꢀgelling) the emission spectra (Fig. 6b) of all compounds are similar, with
λ
max at 379 nm and shoulders at 367 and 397 nm. 2b shows higher fluorescence than 2a.
Moving from nonꢀgelling MeCN to gelling CHCl , the emission from 2a shows little
change in intensity but is slightly redꢀshifted (λmax = 381 nm). Similarly, when spectra are
3
ꢀ
1
ꢀ1
recorded for 2a in CHCl
3
at increasing concentrations (1.0 µg mL to 1.0 mg mL ), λmax
shifts from 379 to 384 nm (see supplementary information Figure S9). These results are
2
1
consistent with observations on organogelating triphenylenes by Bai et al. , Kimura et
2
6
25
45
al. and Munoz Resta et al. , but again contrast with those of Shinkai et al. who
observed emission spectra similar to Fig. 6b for their triphenylene derivative in
chloroform (no gel) but a large new emission peak above 500 nm, attributed to excimer
emission, for their triphenylene in cyclohexane (gel). Moving from MeCN (nonꢀgelling)
to toluene (gelling), the emission of 2b is also red shifted (λmax = 383 nm), broadens and
falls, though the latter may be due to the reduced absorbance observed for 2b in toluene at
the excitation wavelength of 320 nm.
Shinkai et al. explained the dramatic changes in fluorescence observed for their
organogelating triphenylene by proposing the compound was able to adopt an eclipsed
1
7
configuration in the aggregated state, which stabilised the excimer . Most triphenylenes
aggregate in staggered conformations and exhibit smaller changes in their fluorescence
behaviour, as observed here for 2aꢀ2c. Our resuts are consistent with the case of
TP6EO2M in D
over three decades of concentration , and with other works cited above. The columnar
organisation of TP6EO2M in D O is supported by Xꢀray and other evidence and is not
disputed. Moreover, the concentrations studied here are below the gel concentrations
reported in Table 2. Thus, the small changes in fluorescence wavelength for 2a in CHCl
2
O, where the emission peak does not change shape and shifts by just 7nm
1
4
2
3
,
and for 2b and 2c in toluene, are consistent with πꢀπ interactions and columnar
aggregation in the corresponding organogels.

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Figure 6. a) UV absorbance, and b) fluorescence emission (λex = 320 nm) spectra of 0.5
mM 2a in MeCN (black, solid line) and in chloroform (black dashed line), and of 0.5 mM
2
b in MeCN (green solid line) and in toluene (green dashed line).
Infrared spectroscopy provides a further tool for studying the assembly of organogelators.
Previous published studies have compared FTIR spectra of gelators in different solvents,
1
9, 25, 46
corresponding to the gel and solution state
. Spectra for 2c in DCM (solution) and
toluene (gel) are compared in figure 7. The carbonyl stretching bands move noticeably:
ꢀ
1
ꢀ1
the ester band from 1733 to 1738 cm and the amide I band from 1683 to 1669 cm . A
1
9
similar shift for the amide I band was observed by Tao et al. when they compared their
triphenylene amine gelator in DMF solution and pꢀxylene gel state, and such a change is
4
6
characteristic of increased hydrogen bonding . Furthermore the ꢀNH stretch changes
ꢀ
1
ꢀ1
dramatically: the signal at 3410 cm in DCM, moves to 3301 cm in toluene, again
similarly to the change observed by Tao et al. when comparing the solution and gel state.
ꢀ
1
Figure 7. FTIR spectra for 20 mg mL 2c in toluene (gel, top) and in DCM (solution,
bottom). Regions of the spectra subject to noise due to the high absorbance of the solvent
have been deleted.

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To provide further information on the molecular organisation of the triphenylenes, dried
xerogel formed from 2a organogel in CHCl was subjected to powder Xꢀray diffraction
Fig. 8). The scattering pattern shows broad peaks in the wide angle range corresponding
3
(
to spacings of about 0.35 nm and 0.42 nm, closely analogous to equivalent patterns for
xerogels derived from other triphenylene organogels, in which these peaks have been
1
7, 20, 24, 25, 26
attributed to the faceꢀtoꢀface distance between discs
disordered sideꢀchains
and to scattering from
1
7, 24, 25
, as well as one corresponding to d = 0.71 nm, which is hard
to assign but would correspond to alternate stacked πꢀsystems. Other studies on xerogels
from dried triphenylene derivative organogels have observed one or two sharper peaks in
the small angle regime, corresponding to spacings from 1.7 to 5.1 nm, which have been
1
7, 20, 24, 25
attributed to the spacing between columns
. Where more than one peak is visible,
1
7, 25
columnar hexagonal, rectangular or oblique structures have tentatively been assigned
.
In Figure 8 three small angle peaks are observed corresponding to spacings of 2.93, 1.90
and 1.57 nm. These do not fit the pattern expected for a columnar hexagonal structure, but
do fit a columnar rectangular, or columnar oblique structure such has been observed also
4
7
for example in some pure thermotropic triphenylene derivatives .
3
Figure 8. Xꢀray scattering pattern for powdered xerogel from dried gel of 2a in CHCl .
The structure of a dried xerogel does not necessarily correspond to the original organogel,
but measurements on wet gels are challenging and rarely reported: there is only one
example of WAXS on an organogelating triphenylene in the wet gel state, in which broad,
noisy diffractions corresponding to spacings of about 0.45, 1.4 and 2.5 nm were observed
2
2
and no particular interꢀcolumnar organization was assigned . We undertook SAXS
studies of the wet gels of 2a in CHCl , 2b and 2c in toluene (Fig. 9). The highest packing
order was found for 2a in CHCl (panel a). The three peaks assigned 10, 01 and 11
3
3
correspond to dꢀspacings of 2.94, 1.94 and 1.57 nm, in good agreement with the pattern
for the dried xerogel. They can be fitted to a monoclinic lattice with a = 2.94 nm, b = 1.94
o
nm and γ = 94°, corresponding to a columnar oblique (Col ) structure overall. At high
ꢀ
1
temperature (65 °C), an additional diffraction peak can be seen around q = 1.2 nm that
vanishes when the sample is cooled down to 25 °C. The origin of this diffraction peak
remains unclear, but it might arise from a temporarily coexisting superlattice as observed
4
7
by Mu et al. in liquid crystalline triphenylene polymers.
It is important to note that the thickness of the fibres observed by SEM (20ꢀ200 nm) is
much greater than the separation between columns of molecules (order 2 nm) revealed by
the SAX studies and so each fibre must be composed of a ‘bundle’ of molecular columns.

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The fact that the dispersity in thickness of the fibres varies little within any given sample
Fig. 3) further suggests that there is some factor which controls and limits the sideways
growth of these fibres.
(
2
c in toluene (Fig. 9b) by contrast shows a less ordered structure. We note, that clearly
the first two diffraction orders are seen. A straightforward interpretation could be that
each column is only coupled to two nearest neighbours, leading to stable layers of
columns with a thickness of 2.1 nm. However, adjacent layers are not in registry
otherwise additional diffraction peaks indicating a 2Dꢀlattice would be observed. In the
third sample of 2b in toluene an even weaker coupling between the columns is evident.
Only a very broad first order diffraction peak evidences a highly disordered layering of
the columns with a dꢀspacing of about 1.9 nm. The closer spacing observed with 2b
compared to 2c is consistent with the less bulky nature of the sideꢀchains.
3
Figure 9. SAXS pattern of a) 2a in CHCl , b) 2c in toluene and c) 2b in toluene, and their structural
interpretation (right hand side). Pattern recorded at initially 25 °C (blue), at 65 °C (red) and after
cooling back to 25 °C (blue dashed) are shown. For 2a, the twoꢀdimensional index assignments of the
main peaks are shown. * indicates a peak that could not be assigned, and was visible at high
temperature only.

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Conclusion
The four amino acidꢀfunctionalised triphenylenes 2a-2d have been successfully prepared and
characterized. The synthetic approach developed should allow for the preparation of other
functionalised triphenylenes in a modular fashion. The glycine derivative 2a is a good gelator
of chloroform, the alanine derivative 2b gels ethanol and toluene, the phenylalanine
derivative 2c gels benzene and toluene, but the tryptophan derivative 2d does not gel any of
1
the solvents tested. For 2a in CHCl , concentrationꢀ and temperatureꢀdependent H NMR
3
suggests aggregation is driven by πꢀπ interactions rather than hydrogen bonds, since the
aromatic protons (and protons close to the aromatic core) undergo significantly greater
changes in chemical shift upon aggregation than the amide protons. The changes in
absorbance and emission spectra on aggregation are small, but supportive of πꢀπ interactions
in the gelling solvents (by analogy with the case of TP6EO2M in water). Further, Xꢀray
studies on the dried xerogel, and SAXS on the wet gel in its lyotropic state, argue
persuasively for a disordered columnar oblique mesophase. This phase is relatively unusual
in lyotropic liquid crystal systems, hexagonal mesophases being more commonly observed.
2a may therefore be of interest, for the templating of novel porous structures for example.
For 2b in toluene, NMR evidence suggests the aromatic core of the molecule is again
involved in aggregation, but the sideꢀchains (and the amide proton in particular) are more
intimately involved than for 2a in CHCl , implying a different type of structure. The fibres
3
formed by 2b and 2c in toluene are narrower, and selfꢀsupporting gels form at higher
concentrations. FTIR indicates the amide groups in both compounds are involved in stronger
hydrogenꢀbonding in the gelling solvents than in nonꢀgelling ones. SAXS suggests less
ordered structures however, for 2b and 2c, than for 2a. These could be columnar aggregates
with loose linear coupling between columns, since only a 1D lattice was observed. The 2D
columnar organisation may be disrupted by more bulky sideꢀchains. Consequently, work is
underway to investigate mixtures of 2b or 2c with the less bulky derivative 2a. We are also
investigating the influence of the chirality of the sideꢀchains for 2b, 2c and 2d (in the current
work, only the Lꢀamino acid derivatives have been used, but we anticipate that the racemic
compounds, and mixtures of Lꢀ and Dꢀ derivatives, may assemble differently. Further work
aims to elucidate more fully the structures of the organogels, as well as the microspheres
formed during evaporation of solutions of 2d, to extend the range of compounds, and to
investigate their optoelectronic and templating applications.
Acknowledgements
This work was supported by the EPSRC (Doctoral Training Grant to JM), HEFCE (Overseas
Research Scholar award to XY), the Royal Thai government (Scholarship to RR) and the
University of Leeds. The authors are grateful to Dr. Andrew Brown and Dr. John Harrington
(both School of Chemical and Process Engineering, University of Leeds) for assistance with
SEM, Simon Barrett (School of Chemistry, University of Leeds) for assistance with NMR,
and to Dr. Leon Lever (School of Electronic and Electrical Engineering, University of Leeds)
for helpful discussions.

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Soft Matter
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DOI: 10.1039/C7SM00676D
Novel triphenylene derivatives form fibrous gels: SAXS on a wet gel shows these
comprise 1-D stacks in a Col arrangement.
O