White-light-emitting lanthanide and lanthanide-iridium doped supramolecular gels: modular luminescence and stimuli-responsive behaviour

Article abstract of DOI:10.1039/C8TC03487G

Light-emitting materials are of significant interest owing to their potential applications in electroluminescent devices/displays and sensors. Herein, light-emitting metallogel systems are developed using self-assembled Ln(iii)-complexes (Ln(iii) = Eu(iii

Full text of DOI:10.1039/C8TC03487G

View Article Online
View Journal
Journal of
Materials Chemistry C
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: T. Singha
Mahapatra, H. Singh, A. Maity, A. Dey, S. K. Pramanik, E. Suresh and A. Das, J. Mater. Chem. C, 2018, DOI:
10.1039/C8TC03487G.
This is an Accepted Manuscript, which has been through the
Volume
4 Number 1 7 January 2016 Pages 1–224
Royal Society of Chemistry peer review process and has been
accepted for publication.
Journal of
Materials Chemistry C
Accepted Manuscripts are published online shortly after
Materials for optical, magnetic and electronic devices
www.rsc.org/MaterialsC
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 2050-7526
PAPER
~
Nguyên T. K. Thanh, Xiaodi Su et al.
Fine-tuning of gold nanorod dimensions and plasmonic properties using
the Hofmeister effects
rsc.li/materials-c

Page 1 of 12
JPolueransael odfoMnaotetraiadljsuCsht emmairsgtriynsC
View Article Online
DOI: 10.1039/C8TC03487G
Journal Name
ARTICLE
White-Light-Emitting Lanthanide and Lanthanide-Iridium Doped
Supramolecular Gels: Modular Luminescence and Stimuli-
Responsive Behaviour
Received 00th January 20xx,
Accepted 00th January 20xx
Tufan Singha Mahapatra,*a Harwinder Singh,a Arunava Maity,a Ananta Dey,a Sumit Kumar
Pramanik,a Eringathodi Suresha and Amitava Das*a
DOI: 10.1039/x0xx00000x
www.rsc.org/
Light-emitting materials are of significant interest owing to their potential applications in electroluminescent devices/
displays and sensors. Herein, light-emitting metallogel systems are developed using self-assembled Ln(III)-complexes (Ln(III)
= Eu(III) and Tb(III)) of 4′-p-fluorophenyl-2,2′:6′,2′′-terpyridine (L-F) and 4′-p-chlorophenyl-2,2′:6′,2′′-terpyridine (L-Cl)
ligands. The luminescence of these metallogels could be tuned over a wide spectrum. A near-white light emission (CIE
coordinates: (0.31, 0.36) and (0.34, 0.36)) was achieved by controlling the [L-X] (X= F, Cl)/[Eu(III)]/[Tb(III)] stoichiometry.
Adopting an alternate strategy, near white light emission was also achieved using metallogel derived from EuL-F-Ir (CIE
coordinates: 0.28, 0.35) and EuL-Cl-Ir (CIE coordinates: 0.31, 0.35). For this, a blue emissive [IrIII(F2ppy)2(biimid)]PF6 complex
was used along with Eu(III)-terpyridine gel systems (red emissive component). EuL-F, TbL-F and EuL-F-Ir (1 wt%) could
also be incorporated into poly(methyl methacrylate) (PMMA) polymer matrix for developing transparent red, green and
white luminescent PMMA films with excellent UV-shielding properties. Being colourless to the naked eye and luminescent
on exposure to a UV-irradiation, such metallogels have the potential to be used as an invisible security ink. Moreover,
dynamic nature of Ln−N(terpyridine) coordination bonds was utilized for demonstrating the chemo/ vapor-responsive
behaviour of the lanthanide-based gel systems, which could offer a suitable pathway for future engineering of stimuli-
responsive gel materials.
properties into the LMWGs that are typical for the metal-ligand
complex system. Lately, luminescent supramolecular
metallogels have been explored by various researchers where
Introduction
Supramolecular gels derived from small molecules are
commonly known as low molecular weight gelators (LMWGs).
Such LMWGs have captivated great interest across various
research disciplines owing to their potential applications as
biomaterials, smart or adaptive materials, color tuneable
displays, chemical sensors, electronic materials, and in many
such associated fields.1-12 In an appropriate solvent system,
individual gelator molecules could self-assemble to form an
entangled network by participating in multiple non-covalent
interactions, such as hydrogen bonding, van der Waals
interactions, π∙∙∙π stacking interactions, CH∙∙∙π interaction,
hydrophobic-hydrophobic interactions etc., and a combination
metallogels are derived from Eu(III) and Tb(III) ions for achieving
an interesting light emitting properties. Key features of the
emission property of such gels include sharp and well-defined
emission bands, long luminescent lifetimes (in the millisecond
range), relatively high emission quantum yields and less
sensitivity towards emission quenching through the vibrational
energy transfer of the surrounding ligand systems.2,8,18-28
Recent reports on lanthanide (LnIII)-based luminescent gels by
Gunnlaugsson,18-20 Holten-Andersen,2,48 Liu,8 Maitra,21,22
Maji,23,24,27,28 Jung,25 and their co-workers have discussed
LMWGs that show various material properties, including
tuneable luminescence and white light emission. White-light-
emitting materials usually are comprised of single or multiple
components that can emit either the three primaries (red,
green, and blue) or two complementary (orange and turquoise)
colors.11 Using lanthanide-based complexes, white light
emitting systems are contrived by mixing red emissive Eu(III)
and green emissive Tb(III) in an appropriate ratio in
combination with a blue emissive ligand.2,23,24,28-30 De Cola,31
Ward et al.32,33 and their collaborators have elegantly
demonstrated that using appropriate IrIII-EuIII based dyads, a
delicate balance between Ir(III)-based blue emission and the
sensitized Eu(III)-based red emission could be achieved for
of such interactions eventually induce
a sol to gel
transformation.13-17 Appropriate choice of the metal ions,
coordinating ligand(s) and metal-ligand coordination offer an
option for introducing optical or/and physicochemical
a.
Analytical and Environmental Science Division and Centralized Instrument Facility,
CSIR-Central Salt & Marine Chemicals Research Institute, Bhavnagar 364002,
Gujarat, India. *E-mail: tufansmp@gmail.com, a.das@csmcri.res.in
Electronic Supplementary Information (ESI) available: [details of any supplementary
information available should be included here]. See DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 2 of 12
ARTICLE
Journal Name
generating the white light. Despite such advances, reports on Terpyridine derivatives, 4′-p-fluorophenyl-2,2′:6′,2′′-terpyridine
View Article Online
LnIII-IrIII doped white emissive metallogels are scanty in (L-F) and 4′-p-chlorophenyl-2,2′:6′,2′′-terpyridine (L-Cl) were
DOI: 10.1039/C8TC03487G
literature. There are examples of white light generation using synthesized following previously reported procedures.50,51
organic molecules as LMWG. However, relative instability of the Condensation of 2-acetylpyridine with the appropriate p-
photo-excited state and subsequent photo-bleaching on halobenzaldehydes (Scheme S1) yielded the desired
irradiation have restricted the use of such material for device compounds. Following necessary purification procedures, each
application.34-37
desired compound was isolated in pure form. The purity of
The supramolecular gel that alters its phase, photophysical each, the compound was ensured based on the results of the
properties and/or morphology in responses to some external various spectroscopic (1H NMR, HR-MS spectroscopy) and single
stimuli such as light, temperature, pH, molecular/ionic input, crystal structural studies.
etc. has significance in contemporary research for developing
stimuli-responsive smart gels. Among the various stimuli-
responsive materials, lanthanide-based gels with dynamic
metal-ligand coordination have significance primarily due to the
ease of synthesis of Ln(III)-terpyridyl complexes, their tuneable
luminescence behaviour, and stable photo-excited states. Such
tunable and stimuli-responsive gels are important for diverse
applications, including energy efficient luminescent displays,
imaging probes, molecular receptors, and metal-controlled
photo-modulation properties.2,38-42 Although there are
literature reports on stimuli-responsive (thermo-, mechano-,
photo-, and chemo-responsive) organogels or hydrogels,43-47
reports on lanthanide-based gels are rather limited.2,24,48
Herein, we have discussed unique gelation properties of two
different derivatives of 4′-p-halophenyl-2,2′:6′,2′′-terpyridine
(L-X, X= F, Cl) (Fig. 1). The choice of the terpyridine moiety is
based on its demonstrated ability to act as a light-harvesting
antenna for sensitization of the Ln(III) ion.49 The gelation
propensity of the terpyridine ligands (L-X) in the presence of
Eu(III) and Tb(III) are explored to obtain bright red and green
emissive gels, respectively. The optical properties of these gel
systems could be tuned by modulating the stoichiometric ratio
of [Eu(III)]:[Tb(III)] to obtain yellow and near white emissions.
White light emission is also achieved by doping either red
Fig. 1 (a) Molecular structure of L-X (X = F and Cl); (b) L-F gel under day light; (c)
photographs displaying thermal reversibility of L-Cl gel (CGC is 1.6 wt% in MeCN);
(d) ORTEP depiction of L-F showing 30% probability ellipsoids. Colour code: N,
blue; C, grey; F, yellow and H, white; and (e) molecular structure of
[IrIII(F2ppy)2(biimid)]PF6.
Synthesized terpyridine derivatives (L-F and L-Cl) formed
thermoreversible (Tgel = 50 °C) white colour opaque gels in
MeCN, MeCN/DMF (1:1, v/v) and DMF (Fig. 1a-d). Gel formation
in each instance was subsisted with the inversion test and no
mass flow was observed upon upending the glass vials (Fig. 1b).
The critical gelation concentration (CGC) value was found to be
1.6 wt% in MeCN and MeCN/DMF (1:1, v/v) solvents, whereas
in DMF solvent CGC was evaluated as 2.2 wt%. It was presumed
that the self-assembly process of the terpyridyl derivatives L-
F/L-Cl was induced typically by various hydrogen bonding (H-
bonding) and intermolecular π∙∙∙π stacking interactions among
the respective terpyridyl moieties (L-X). This was further
confirmed by single crystal X-ray structure and the analyses of
the powder X-ray diffraction (PXRD) pattern. Interestingly, the
fibers of L-F gel in MeCN/DMF (1:1, v/v) was transformed into
X-ray quality crystalline rods when the gel was kept at room
temperature for 14-18 days (Fig. 1d). The ligand was found to
be crystallized in monoclinic P21/c space group and selected
metric parameters are summarized in Table S1. X-ray structure
divulged that adjacent L-F molecules were connected through
C−H∙∙∙F (2.529 and 2.568 Å) and C−H∙∙∙N (2.716 Å) H-bonding
interactions and two layers were associated through face-to-
face π∙∙∙π stacking interactions between the aromatic moieties
(intercentroid distance: 3.836 Å) (Fig. 2). The powder X-ray
diffraction (PXRD) pattern of L-F xerogel was consistent with its
simulated data, obtained from the single crystal X-ray
diffraction data (.cif files) using the CCDC Mercury software (Fig.
S1, ESI†). To realize the role of the halogen atom in terpyridine
moiety, gelation test was performed using the model terpyridyl
derivatives, 4′-p-methylphenyl-2,2′:6′,2′′-terpyridine (L-Me)
emissive EuL-Cl or EuL-F gel system with an appropriate blue
emissive complex, [IrIII(F2ppy)2(biimid)]PF6. All the metallogels
are comprised of entangled fibrous networks as evident from
FESEM micrographs. Furthermore, we have explored the
reversible chemo/ vapor-responsive properties of the
lanthanide-based gels by utilizing the dynamic coordination
behaviour of the terpyridyl moiety of L-X towards Eu(III)/Tb(III)
ions. Being colourless to the naked eye and luminescent on
exposure to a UV-irradiation, such metallogels have the
potential to be used as an invisible security ink. In addition, we
have successfully prepared luminescent films by simple drop
casting of Ln
agarose gel support or by incorporating Ln

L-F (Ln is EuIII or TbIII) solutions on transparent
L-F or Eu L-F-Ir into


the poly(methyl methacrylate) (PMMA) polymer matrix without
amending the optical properties of the metallogels. The results
from UV-transmittance spectra indicate that the Ln
L-F-PMMA
and Eu L-F-Ir-PMMA films could be used as a novel UV absorber

for developing transparent UV-shielding film.
Results and discussion
Synthesis and gelation property of L-X ligands (X = F and Cl)
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 12
Journal of Materials Chemistry C
Please do not adjust margins
Journal Name
ARTICLE
View Article Online
DOI: 10.1039/C8TC03487G
Fig. 2 Crystal structure of L-F showing the self-assembly through H-bonding and π∙∙∙π stacking interactions, Colour code: N, blue; C, grey; F, yellow and H, white & pink
(those involved in H-bonding interactions)
Fig. 3. Spectral changes in (a) the Tb(III) and (b) Eu(III) centred luminescence spectra upon titrating L-F or L-Cl (1.0 × 10−5 M) with Tb(III)/Eu(III) (0
MeCN. Insets: Representations for describing a mechanism for sensitized lanthanide (EuIII or TbIII) luminescence.
 1 mole equiv.) in
and 4′-p-hydroxyphenyl-2,2′:6′,2′′-terpyridine (L-OH) and no gel a red shift was observed for the 276 nm band. A new sharp band
formation was observed (Scheme S2, ESI†). This further appeared at around 289 nm for both Tb(III) and Eu(III),
confirmed the significance of the C−H∙∙∙X (X = F, Cl) H-bonding indicating the formation of the respective TbIII

L-F, TbIII
L-Cl,
interactions that were otherwise operational for L-X derivatives. EuIII L-F and EuIII
 L-Cl complexes (Fig. S2, ESI†, vide infra). The
Interaction of L-F/Cl with Tb/Eu(NO3)3·6H2O in solution
steady state luminescence spectrum (λexL-F or λexL-Cl : 285 nm) of
L-F and L-Cl in MeCN solution (1.0 × 10−5 M) exhibited strong
emission band maxima at 352 and 355 nm, respectively, which
were associated with terpyridine-based π→π* transitions. With
the incremental addition (0 - 1 mole equivalents) of Tb(III) to the
L-F solution, a decrease in luminescence intensity of the ligand
centred emission band at 352 nm with the concomitant
emergence of sharp bands at 491 nm, 544 nm, 585 nm, and 623
nm, respectively, were observed. These emission bands were
The interaction of either of the two terpyridyl derivatives (L-F or
L-Cl) with lanthanide ions (Tb(III) or Eu(III)) was investigated in
MeCN solution at low concentration by monitoring the changes
in the absorption and luminescence spectra of L-F/ L-Cl and
Tb(III)/ Eu(III) centred emissions. The electronic spectrum of L-
F/L-Cl in MeCN solution (1.0 × 10−5 M) consisted of two main
bands centred at 252/253 nm (εL-F = 31600 & εL-Cl = 32400 L mol-
1
cm-1) and 276 nm (εL-F = 29200 & εL-Cl = 33760 L mol-1 cm-1).
assigned to 5D4
→ → → →
7F6, 5D4 7F5, 5D4 7F4, and 5D4 7F3 based
Both bands were predominantly due to terpyridine-based
π→π* transitions (Fig. S2, ESI†). Electronic spectra were also
recorded for the acetonitrile solution of L-F/L-Cl in presence of
varying concentration (0 - 1 mole equiv.) of Tb(III) or Eu(III).
Spectral changes were almost identical for both L-F and L-Cl and
transitions, respectively, for Tb(III) (Fig. 3a). The similar trend
was observed upon addition of Eu(III) (0 - 1 mole equivalents) to
the L-Cl (1.0 × 10−5 M in MeCN) with the occurrence of five
characteristics Eu(III)-based emission bands having maxima at
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 4 of 12
ARTICLE
Journal Name
581 nm (5D0
651 nm (5D0
→
7F0), 596 nm (5D0
→
7F1), 617 nm (5D0
→
7F2),
View Article Online
DOI: 10.1039/C8TC03487G
→
7F3), and 687 nm (5D0
→
7F4) (Fig.3b). This
sensitized emission was a direct consequence of the binding of
Tb(III) or Eu(III) to the respective terpyridine based ligands (L-F/
L-Cl) (Fig. 3 and Fig. S3, ESI†). Upon irradiation with a suitable
wavelength, the short-lived singlet electronically excited state
(So→S1) of the terpyridine moiety was populated and this
subsequently underwent intersystem crossing (ISC) for
generating the longer-lived lower lying triplet excited state (T1).
5
Next, sensitization happens by populating the excited state D0
5
of Eu(III) and D4 of Tb(III) through energy transfer from the T1
7
state of the terpyridine with subsequent deactivation to the FJ
ground states, which accounted for the characteristic emission
bands (Scheme S3, ESI†).49 Respective binding constants was
evaluated using Benesi-Hildebrand (B−H) plots for the
Scheme 1. Schematic showing the probable self-assembled supramolecular
formation of complexes between L-X (X
= F, Cl) and
structure in EuL-X and TbL-X gels (X= F, and Cl). Colour Code: N, blue; C, green;
Tb(III)/Eu(III): KL-F/Tb(III) = 7.56 0.22 × 104 and KL-Cl/Eu(III) = 2.43

Eu/Tb, pink.
0.14 × 104 (Fig. S4, ESI†). A good linear fit of the B-H plot also
supports the 1:1 (M:L) binding stoichiometry.52,53
Formation of metal-based gels from L-F/L-Cl and their
photophysical properties
The individual gels showed bright red (EuL-X) and green (TbL-
X) fluorescence upon exposure to UV light irradiation at 365 nm
(Fig. 4). The colour perceptions of each individual gel were
further analyzed using the CIE (Commission International de
L’Eclairage) chromaticity diagram.
The gelation propensity of L-X (X = F, Cl) in presence of
respective Eu(III) and Tb(III) ions was explored in DMF solvent.
The lanthanide-based gels were obtained by mixing solutions
containing a 1:1 molar ratio of L-X and Eu(NO3)3·6H2O or
Tb(NO3)3·6H2O. Formation of coordinated Eu(III) and Tb(III) in
corresponding Eu
the results of the FT-IR and luminescence spectral studies. The
presence of the coordinated nitrato group in Eu L-F and Tb L-F
xerogels was confirmed by the characteristic asymmetric
stretching (
ONO) frequency at 1382 cm−1 in the FT-IR spectra
(Fig. S5a, ESI†). Eu/Tb-terpyridyl coordination presumably
prevails in the formation of Eu L-X/Tb L-X involving L-X
L-X and TbL-X xerogels was confirmed from





ligand.2,23,24 Coordination of six O-atoms from the three
bidentate nitrate ions is also proposed (Scheme S4, ESI†).54-57
To gain insight into the molecular packing of these lanthanide
gels PXRD patterns of the air-dried gels were recorded. PXRD
patterns of EuL-F and TbL-F gels were exhibited peaks at
higher 2θ values 16.46, 16.98, 17.73, 19.64 and 25.74 with
respective d-spacing values of 5.38 Å, 5.22 Å, 4.99 Å, 4.52 Å, and
3.50 Å (Fig. S5b, ESI†). Peaks at 2θ = 25.74 with d-spacing values
3.50 Å suggested the presence of intermolecular π∙∙∙π stacking
interactions in metallogels,6 which confirmed the formation of
higher order self-assembled supramolecular structure in those
metallogels (Scheme 1).
Fig. 4 Photographs of metallogels (a) in day light and (b & c) their respective
luminescence under UV light irradiation (λex = 365 nm). Corresponding CIE
coordinates are mentioned below. I: Eu
L-F, II: Tb
L-F, III: EuL-F-TbL-F, IV: EuL-
F-2(TbL-F), V: Ir-L-F, VI: EuL-F-Ir, and VII: EuL-Cl-Ir.
The emission spectrum (λex = 285 nm) of the EuL-F gel (CIE
coordinates: 0.52, 0.32) exhibited characteristics sharp
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 5 of 12
Journal of Materials Chemistry C
Please do not adjust margins
Journal Name
ARTICLE
View Article Online
DOI: 10.1039/C8TC03487G
Fig. 5. Luminescence spectra of (a) Eu

L-F and (b) Tb

L-F gels obtained from DMF; (c) CIE chromaticity diagram of EuL-F (1) and TbL-F (2)
Fig. 6 Luminescence spectra of respective gel: (a) Eu
of corresponding gels under UV light. (c and f) CIE chromaticity diagram of Eu
Break from 645-675 to cut-off the peak at twice the excitation wavelength (λex = 330 nm) due to 2nd-order transmission.

L-F-Tb

L-F, (b) Eu

L-F-2(Tb

L-F), (λex = 285 nm), (d) Eu

L-F-Ir and (e) Eu•L-Cl-Ir (λex = 330 nm). Insets: Photographs

L-F-Tb

L-F (6), Eu L-F-2(Tb L-F) (7), Eu



L-F-Ir (8) and Eu L-Cl-Ir (9). Note: (d and e) Axis-

emission bands for Eu(III) at 582, 594, 617, 652, and 693 nm, observation for Eu
which were associated with 5D0 7FJ (J = 0−4) based transitions These coordinates were close to that of pure white light (0.33,
and a ligand centred band with maximum at 374 nm (Fig. 5a,c). 0.33). (Fig. S6c and S7, ESI†). The emission spectra (λex = 285 nm)
Likewise, Tb L-F gel (CIE coordinates: 0.28, 0.47) displayed of these mixed Eu L-X-Tb L-X gels cover the entire visible
sharp bands for Tb(III) at 491, 545, 584 and 622 nm and were spectrum with characteristic bands from ligand, Tb(III) at 491,
assigned to 5D4 7FJ (J = 6−3) based transitions (Fig. 5b,c). The 545 and 584 nm (green) and Eu(III) at 594, 617, 652 and 693 nm
same overall trend was observed in the emission spectra of (red) (Fig. 6a,c), which presumably accounted for the observed
Eu L-Cl (CIE coordinates: 0.44, 0.30) and Tb L-Cl (CIE white light emission. Whereas, the Eu L-F-2(Tb L-F) gel
coordinates: 0.27, 0.42) gels (Fig. S6a,b, and S7, ESI†). (Eu(III):Tb(III) = 1:2) obtained from DMF solvent exhibited
L-Cl-TbL-Cl, (CIE coordinates: 0.34, 0.36).
→



→




The entire visible spectrum (400–750 nm) can be covered using yellow emission (CIE coordinate: 0.36, 0.45) upon exposure to
the red, green, and blue (RGB) mixing approach. To accomplish UV light (λex = 285 nm, Table 1, Fig. 6b,c and 4). Similarly, yellow
this, the emission properties of mixed metallogels were emission was observed from EuL-Cl-2(TbL-Cl) (CIE
investigated further by mixing both Eu(III) and Tb(III) to L-X in coordinates: 0.30, 0.41) (Fig. S6d and S7, ESI†). In all of these
different stoichiometry in DMF solvent. However, in all such metallogels, L-X acted as a sensitizer for both Eu(III) and Tb(III)
mixed metallogels, [L-X]:[Ln] ([Ln] = [Eu] + [Tb]) ratio was fixed centres. A combination of emissions that originated from L-X,
at 1:1. Interestingly, mixed EuL-F-TbL-F gel obtained by mixing Eu(III) and Tb(III) in appropriate ratio accounted for the eventual
the equimolar amount of Eu(III) and Tb(III) into L-F in DMF white emission. A modification of the ratio of the three emissive
solvent, exhibited almost white light emission (CIE coordinates: components helped in achieving tuneable luminescent
0.31, 0.36) (Table 1 and Fig. 6a,c and 4). Similar was the metallogels. However, a possibility of partial energy transfer
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 6 of 12
ARTICLE
Journal Name
from Tb(III) to the Eu(III) centre cannot be completely ruled an intention to fabricate optical materials having moderate
View Article Online
out.22,28,29
luminescence and option for easy colour tunability, we have
DOI: 10.1039/C8TC03487G
White light can also be created by combining a blue emitting prepared luminescent films on transparent agarose gel support
Ir(III) component to the sensitized red emission of the Eu(III) by simple drop casting of the lanthanide sols on freshly
component. With this rationale, we synthesized a mononuclear prepared agarose gel. The snapshots of the Eu
[IrIII(F2ppy)2(biimid)]PF6 complex (Fig. 1e) using 2,2´-biimidazole Eu
L-F-Tb L-F and Eu L-F-2(Tb L-F) coated-agarose gel showed
(biimid) (2.4 eq) and Ir(III)-dimer complex, [(F2ppy)2Ir(µ-Cl)]2 (1 red, green, white and yellow light emission (λex = 365 nm),
eq) following literature procedure with necessary respectively, with decent colour quality (Fig. S9c-f, ESI†).
L-F, TbL-F,




a
modification (Scheme S5, ESI†).58 This complex was Interestingly, it was also possible to bend the coated films
characterized by 1H NMR and HR-MS spectroscopy. The without losing any emission intensity of the resulting films (Fig.
complex displayed emission in blue region with two band S9c-f, Inset, ESI†).
maxima at 459 and 484 nm (λex = 385 nm) in MeCN (1.0 × 10-5
M) (Fig. S8a, ESI†). Next, a definite amount of this blue emitting
[IrIII(F2ppy)2(biimid)]PF6 (Ir) complex was doped into red
emitting Eu
(Eu L-F-Ir/ Eu
(Fig. 4). The CIE coordinates of the corresponding gels were
evaluated (Eu L-F-Ir: 0.28, 0.35 and Eu L-Cl-Ir: 0.31, 0.35) and
these values were close to that of pure white light (0.33, 0.33)
(Fig. 6f). The emission spectra of Eu L-F-Ir/ Eu L-Cl-Ir (λex = 330

L-F/ EuL-Cl gel component and the assembly


L-Cl-Ir gel) showed a nearly white light emission




nm) gel displayed ligand centred band at 374 (L-F) or 384 nm (L-
Cl), a broad band at 490 nm (blue-green region) from
IrIII(F2ppy)2(biimid)]+ and three sharp bands at 595, 620, and 695
nm (red region) that were characteristic of the Eu(III)-centred
emissions (Fig. 6d,e). This eventually covered the entire visible
spectrum and resulted in a white-light emission. We also
prepared
blue
emitting
Ir-L-X
gels
by
doping
[IrIII(F2ppy)2(biimid)]PF6 into the L-X gel component (Fig. 4).
Luminescence spectrum of Ir-L-F gel supported the blue
emission (CIE coordinates: 0.23, 0.30) with a broad band at 490
nm (Fig. S8b, ESI†).
Fig.7 (a) The UV–vis transmittance spectra of neat PMMA, Eu
PMMA and Eu L-F-Ir-PMMA films. (b) Eu L-F-PMMA, Tb L-F-PMMA and Eu
Ir-PMMA films placed over a printed script ‘CSMCRI’ depicting the transparency of
the film in daylight and (c) Eu L-F-PMMA, (d) Tb L-F-PMMA, (e) Eu L-F-Ir-PMMA
films under UV light irradiation after bending.

L-F-PMMA, Tb

L-F-




L-F-
Table 1. Photophysical properties of mixed gels obtained from DMF solvent.



[L-X]:[Ln]
Emission
colour
CIE
coordinates
Mixed gels
([Ln]=
[Eu]:[Tb]
Further, PMMA/Ln
following casting method. Poly(methyl methacrylate) (PMMA)
was dissolved in toluene and then Eu L-F or Tb L-F or Eu L-F-Ir
L-F composite films were prepared by
[Eu]+[Tb])
EuL-F-
TbL-F
EuL-F-
2(TbL-F)
EuL-Cl-
TbL-Cl
1:1
1:2
1:1
1:2
Near white
Yellow
0.31, 0.36
0.36, 0.45
0.34, 0.36
0.30, 0.41



sols (1 wt%) was added under stirring condition. Homogeneous
solution was casted on a petri dish for solvent evaporation and
subsequently dried in a vacuum oven to achieve respective
1:1
Near white
Yellow
EuL-Cl-
2(TbL-Cl)
colourless transparent film (Fig. 7b), which emitted red (Eu
L-F-
PMMA) or green (Tb L-F-PMMA) or white (Eu L-F-Ir-PMMA) on


exposure to an UV-irradiation (Fig. 7c-e). Prepared films were
flexible and could be folded to provide different shapes with
retention of their optical properties (Fig. 7c-e). PMMA was
chosen as a matrix due to its transparent thermoplastic nature
which often used as a shatterproof substitute for glass.
Interestingly, these transparent hybrid films displayed notable
Optical applications
These soft gels are also well suited for generating coated
surfaces or thin-films. We have applied these gels on a
nonfluorescent glass plate to print ‘CSIR-CSMCRI’ having blue,
green, yellow, orange, and red-light emission under UV light
with excellent colour quality using different combinations of the
gels discussed in the previous section (Fig. S9a, ESI†). Next, we
UV-shielding properties. UV–vis transmittance spectra of Eu
L-
F-PMMA, Tb L-F-PMMA and Eu L-F-Ir-PMMA hybrid films


have written ‘CSMCRI’ on a silica gel plate using EuL-F gel
showed that the transmitting efficacy of the films was very less
in UV region up to 360 nm, which supported their excellent UV
cut-off performance (Fig. 7a). Thus, these hybrid films have
potential application in UV-shielding glasses and window films.
The solid-state emitting capabilities and easy material
processabilities of these gel materials can be exploited for other
which remained colourless and imperceptible to the naked eye
on irradiation with normal visible light. However, under UV light
irradiation (λex = 365 nm) the alphabets emitted red light and
became visible (Fig. S9b, ESI†). This demonstrates the possibility
of using such gel for security purposes, where gel materials can
be used as an invisible security ink for writing secret codes. With
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 7 of 12
Journal of Materials Chemistry C
Please do not adjust margins
Journal Name
ARTICLE
probable optical applications such as the production of coated Rheological properties of gels
View Article Online
Rheological experiments (strain and freDqOuIe:n10c.y10s3w9/eCe8pTCs)03w48e7rGe
performed for investigating the mechanical properties of these
supramolecular gels (Fig. 9 and Fig. S11, ESI†). The oscillatory
light-emitting diodes (LED), specific secret barcode systems and
thin-films for use in tamper seals.
Morphological properties of gels
The morphologies of the gels were examined by recording field strain sweep measurements for all the gels exhibited nonlinear
emission scanning electron microscopic (FESEM) images of the behaviour of the storage modulus (G′, the contribution of
corresponding xerogel to gain insight into the self-assembly elastic) and loss modulus (Gʺ, the contribution of viscous) to a
process. The FESEM micrographs of L-F xerogel in DMF fixed frequency (f = 1 Hz) by varying the strain amplitude (Fig.
demonstrated the formation of multi brunched entangled tree 9a,b,c). At low strain amplitudes, the storage modulus remained
like fibrous network with fibre at about micrometer in length constant and the response was solid-like (G′ > Gʺ). However,
and width ranging from ~ 390 - 820 nm (Fig. 8a). The after reaching the yield strain, G′ was decreased rapidly,
corresponding metallo xerogels (Eu
L-F, TbL-F, EuL-F-TbL-F, suggesting that the gel network was collapsed and became sol.
Ir-L-F, and Eu L-F-Ir) in DMF showed a similar type of fibrous After determination of linear viscoelastic region by strain-

network in FESEM micrograph (Fig. 8c-g). In comparison to the sweep measurements, frequency sweep measurements were
fibers of L-F (~ 390 - 820 nm), the fibres obtained from performed. All the gels showed little frequency dependence of
metallogels were thick in nature (~ 0.95–3.94 µm).
the storage modulus (G′) to a fixed small amplitude of strain
(0.1%). G′ exceeded G′′ by almost an order of magnitude in all
the cases, thereby suggesting elastic nature of the gels (Fig.
9d,e,f and Fig. S11, ESI†). While the overall behaviour of the G′
(b)
(e)
(h)
(c)
(f)
(i)
(a)
(d)
(g)
and G′′ were similar for all the gels, the G′ of metallogels (Tb
L-
F, Eu L-F, Eu L-F-Tb L-F and Eu L-F-Ir) were an order of




magnitude larger compared to the G′ of the ligand gel (L-F). This
confirms higher rigidity of metallogels compared to L-F gel.
Moreover, mixed Eu
to be softer compared to the pure Tb
Stimuli-responsiveness of the metallogels
We explored stimuli-responsive properties of the red emitting
Eu L-F and mixed metal white light emitting Eu L-F-Tb L-F gels.

L-F-Tb

L-F and Eu

L-F-Ir gels were found

L-F and Eu

L-F gels.



Upon exposure to the vapor of trifluoroacetic acid (TFA), a
distinct gel-to-sol transition was observed with subsequent
change in emission spectra (Fig. 10a,b). This phenomenon was
ascribed to the dissociation of the Ln(III)-terpyridyl complexes,
which was induced by the diffusion of TFA vapor into the gel
matrix and the subsequent protonation of the nitrogen atoms
of the terpyridine ligand. The corresponding emission spectrum
Fig. 8 FESEM micrographs of (a) L-F xerogel showing multi brunched tree like
fibrous network, (b) L-Cl xerogel showing network of helical fibers, (c-i) Eu L-F,
Tb L-F, Eu L-F-Tb L-F, Ir-L-F, Eu L-F-Ir, Eu L-Cl, and Tb L-Cl metallo xerogels
showing fibrous structures.







of the TFA exposed Eu
435 nm, attributed to the free protonated terpyridine ligand
(Fig. 10b). Similarly, TFA exposed Eu L-F sol displayed a broad
L-F-TbL-F sol displayed a broad band at
L-Cl xerogel in DMF unveiled a network of helical fibres,
comprised of thin fibres of nanometer diameter (100 - 200 nm)
and micrometer in length (Fig. 8b). Presumably, the observed
helical nature of the fibers occurred due to the interwinding of
thin fibers during the assembly process. However, FESEM

band at 436 nm with the low-intensity Eu(III)-centred peaks (Fig.
S12, ESI†). However, the sol was re-converted to gel state on
exposure to the vapor of triethylamine (NEt3). Triethylamine
(Et3N+H: pKa = 10.75) would induce deprotonation of the
images of EuL-Cl and TbL-Cl xerogel showed simple fibers
protonated terpyridine (pKa
coordinate to the respective Eu(III)/Tb(III) ion. FESEM
micrographs revealed that actual Eu L-F-Tb L-F gel (Fig. 10c)
<
Et3N+H),61 which further
instead of helical fibers that were observed in the L-Cl gel (Fig.
8h,i). Energy-dispersive X-ray spectroscopy (EDXS) analysis
confirmed the presence of Eu(III), Tb(III) and Ir(III) in the above-
mentioned xerogels.
Fluorescence microscopy also revealed that the respective gel
of EuL-F, TbL-F, EuL-F-2(TbL-F) and Ir-L-F was composed of


and the corresponding re-converted gel (Fig. 10d) following
reversible stimuli conversion possessed almost similar fibrous
structures.
red, green, yellow and blue light-emitting self-assembled fibres
(Fig. S10, ESI†).
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 8 of 12
ARTICLE
Journal Name
View Article Online
DOI: 10.1039/C8TC03487G
Fig. 9. Oscillatory rheology measurements of L-F, Tb

L-F and Eu
L-F-Tb

L-F-Tb

L-F gels obtained from DMF. Strain sweeps at frequency = 1 Hz of the storage modulus G′ (
■)
and loss modulus Gʺ (●) for (a) L-F, (b) Tb

L-F and (c) Eu


L-F gels. Frequency sweeps at 0.1% strain amplitude for (d) L-F, (e) Tb

L-F and (f) Eu L-F-Tb L-F gels


Furthermore, a white-luminescent coating on a silica matrix of and mixed Eu(III)/Tb(III) or Eu(III)/Ir(III) in DMF solvent. The
a TLC plate (thickness of 0.2 mm, 60 Å pore size, coated on the individual homometallic gels exhibited bright red (Eu-gels) and
aluminium plate) was developed by drop-casting a solution of green (Tb-gels) fluorescence upon exposure to UV light (λex
=
Eu L-F-Tb L-F and this was found to be responsive towards pH 365 nm). Coordinated terpyridine moiety acted as an antenna


5
alteration. The white-luminescent coating was transformed to by populating the lowest DJ excited state of Eu(III) and Tb(III)
blue upon exposure to aqueous HCl (pH < 7) due to the through energy transfer and subsequently deactivation to the
protonation of the nitrogen atoms of the terpyridine ligand and 7FJ ground states. Careful tuning of the stoichiometric ratio of
subsequent dissociation of Ln−N(terpyridine) coordination Eu(III) and Tb(III) helped in achieving gels that provided various
bond. Similarly, the white-luminescent coating was altered to emission colours, including white light. Furthermore, we also
blue upon acquaintance to aqueous ammonia solution (pH > 7) perceived near white light emission by doping a blue emissive
as a consequence of the hydrolysis of Ln(III) ions (Fig. 10e).
Ir(III) complex [IrIII(F2ppy)2(biimid)]PF6 to the red emissive Eu
L-
F/Cl gel. These gel materials can be used to fabricate
luminescent agarose gel by simple drop casting procedure and
also transparent luminescent PMMA films by incorporating into
poly(methyl methacrylate) (PMMA) polymer matrix without
altering the optical properties of the metallogels. Moreover,
LnL-F-PMMA and EuL-F-Ir-PMMA films exhibited excellent
UV-shielding performance, which is important for developing
transparent luminescent PMMA films with excellent UV-
shielding properties. Besides, the lanthanide-based gels showed
chemo/vapo-chromism
based
on
Ln−N(terpyridine)
coordination dynamics, which could offer a suitable pathway for
future engineering of stimuli-responsive gel materials.
Experimental section
Materials
Fig. 10 (a) Stimuli-responsive emission colour changes of Eu
UV light, (b) Assessment of luminescence spectra of (A) Eu L-F-Tb
exposed Eu L-F-Tb L-F sol generated after gel−sol transition, (c and d) FESEM
micrographs of Eu L-F-TbL-F gel and the corresponding re-converted gel, (e)

L-F-Tb
L-F gel under


L-F and (B) TFA



All chemicals and solvents used for synthesis were purchased
from commercial sources and were used as received without
further purification. For spectroscopic measurements and
gelation tests HPLC grade solvents were used. 2,2´-biimidazole
(biimid)59 and iridium dimer Tetrakis(4,6-difluorophenyl
pyridine-C2,N')(µ-dichloro)diiridium [(F2ppy)2Ir(µ-Cl)]2 were
synthesized following the literature protocols.59,60
White-luminescent coating on a silica matrix of a TLC plate from the Eu
F and its pH-responsive colour change
L-F-TbL-
Conclusions
60
In summary, we have demonstrated that the appropriate halo-
substituted terpyridine ligands could be used for developing a
series of luminescent supramolecular gels with Eu(III), Tb(III),
Instruments
8 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 9 of 12
Journal of Materials Chemistry C
Please do not adjust margins
Journal Name
ARTICLE
1H NMR (500 MHz) spectra for the synthesized ligands were The crude material was purified by column chromatography
View Article Online
recorded on a Bruker AX 500 spectrometer (500 MHz) and was (silica gel, CH2Cl2: MeOH, 97:3) to obtainDpOuIr:e10l.i1g0a3n9d/Cs8aTsCa03n4o87ffG-
calibrated with respect to the internal standard white solid. Detailed characterization of L-F and L-Cl are
tetramethylsilane (TMS). Chemical shifts were quantified in provided in the supporting information (Page 2, ESI).
ppm with CDCl3 solvent as the internal reference. FT-IR spectra L-X gel formation
on KBr disks (4000−
400 cm-1) were recorded with a Perkin- A weighted amount of L-X (4.9 × 10−2 M) (X = F and Cl) was added
Elmer 883 spectrometer. High-resolution mass spectra (HRMS) to MeCN (1 mL) and sonicated for 2-3 min followed by heating
were recorded on Agilent 6545 Q-TOF LC/MS. UV−Vis till the clear solutions obtained, which eventually resulted in
absorption spectra measurements were performed in 1 cm stable white opaque gels upon cooling to room temperature
quartz cuvettes using a Varian Cary 500 spectrometer. within 2-5 h. The gel formation was confirmed by an inverted
Fluorescence spectra were recorded at room temperature using vial method. Gelation was also found in DMF and mixed solvent
either on a Quanta Master 400, PTI spectrofluorometer or a MeCN/DMF (1:1, v/v).
Fluorolog Horiba Jobin Yvon spectrophotometer.
Formation of Eu•L-X and Tb•L-X gels
X-ray diffraction data on appropriate single crystal of L-F were To the DMF solution of L-X (X = F and Cl; 6.25 × 10−2 M, 500 μL),
collected on a BRUKER SMART APEX (CCD) diffractometer 500 μL DMF solution of Eu(NO3)3·6H2O or Tb(NO3)3·6H2O (6.25
equipped with a graphite monochromator and Mo-Kα radiation × 10−2 M, 500 μL) were mixed and the mixture was sonicated
(λ = 0.71073 Å) at 150 K. Data collection and reduction were and heated until the clear solutions attained. Next, the solutions
accomplished using the SMART and SAINT software packages.62 were left undisturbed for few hours at ambient temperature
Multiscan empirical absorption corrections were applied to the resulted in a stable metallogel of Eu
data using the program SADABS.63 The structure was solved by stable upon inversion of the vials.
L-X and TbL-X, which were
direct methods SHELXTL and was refined on F2 by the full- Selected FTIR bands: (KBr, cm−1, vs = very strong, br = broad, s =
matrix least-squares technique.64 Crystallographic data strong and m = medium) Eu
L-F: 3422 (br), 1650 (s), 1608 (s),
(excluding structure factors) of L-F have been deposited in the 1583 (s), 1513 (vs), 1465 (m), 1382 (vs), 1225 (m), 1162 (m), 832
Cambridge Crystallographic Data Centre as supplementary (s), 786 (vs), 732 (s).
publications with CCDC no-1837781
Powder X-ray diffraction (PXRD) patterns were recorded at (vs), 1228 (m), 1164 (m), 834 (m), 786 (s), 734 (m).
room temperature on Philips X’pert X-ray powder Formation of mixed-metallic Eu•L-X-Tb•L-X, Eu•L-X-2(Tb•L-X)
diffractometer using Cu-Kα radiation (λ = 1.5418 Å) over 2θ and Eu•L-X-Ir gels (X = F, Cl)
range of 5–50°. Mixed-metallic Eu L-X-Tb
TbL-F: 3420 (br), 1651 (s), 1606 (s), 1510 (s), 1466 (m), 1382
a

L-X gels were prepared by mixing
Field emission-scanning electron microscopy (FE-SEM) images Eu(NO3)3·6H2O (6.25 × 10−2 M, 250 μL) and Tb(NO3)3·6H2O (6.25
were collected using a JEOL JSM-7100F instrument operated at × 10−2 M, 250 μL) to L-X (6.25 × 10−2 M, 500 μL) in DMF solvent.
18 kV accelerating voltage. A small portion of the synthesized Similarly, EuL-X-2(TbL-X) gels were synthesized by mixing
gels was scooped out with a spatula and diluted with DMF and Eu(NO3)3·6H2O (2.08 × 10−2 M, 250 μL) and Tb(NO3)3·6H2O (4.17
the resulting solutions were drop-casted on a silicon wafer and × 10−2 M, 250 μL) to 500 μL solution of L-X (6.25 × 10−2 M) in
allowed to dry under desiccator for overnight.
DMF solvent.
Rheological measurements were performed on a Rheoplus Eu•L-X-Ir gels were obtained by adding a weighted amount (16
MCR302 (Anton Paar) rheometer with parallel plate geometry. mg) of the Ir(III) complex [IrIII(F2ppy)2(biimid)]PF6 into the Eu
After placing the sample, the gap size between the plates was X sol (6.25 × 10−2 M, 1mL).
L-
fixed at 0.5 mm. The oscillatory strain sweep measurements In all the cases, the formation of gels was confirmed by
were performed at a fixed frequency (f = 1 Hz) by increasing the inversion test methodology.
strain amplitude from 0.1% up to 100% at 25 °C. Frequency
sweep measurements were performed from 0.1 to 100 Hz at a Preparation of [IrIII(F2ppy)2(biimid)]PF6
fixed small amplitude of strain (0.1%) at 25 °C.
The complex was synthesized following a literature procedure
The Fluorescent microscope images were taken using an with slight modifications.58 A 0.84 mmol (2.4 equiv) amount of
Olympus BX53 fluorescence microscope.
General procedure for the synthesis of 4′-p-halophenyl-2,2′:6′,2′′-
terpyridine:
2,2´-biimidazole (biimid)59 was added to the ethanolic solution
(10 mL) iridium dimer [(F2ppy)2Ir(µ-Cl)]260 (0.35 mmol (1 equiv))
and the reaction mixture was refluxed for 16 h under nitrogen.
After cooling to ambient temperature, a saturated aqueous of
KPF6 (3 mmol, 0.48 gm) was added with stirring and the solution
was stirred for 30 min. The appeared precipitate was filtered off
using a glass frit and washed with cold methanol and water for
further purification and then dried in a desiccator. Yield: 0.32
gm, 38%. 1H NMR (600 MHz, CDCl3) δ 13.27 (s, 2H), 8.25 (d, J =
8.5 Hz, 2H), 7.76 (t, J = 7.8 Hz, 2H), 7.64 (t, J = 10.2 Hz, 2H), 7.15
(d, J = 17.8 Hz, 2H), 7.03 (t, J = 6.6 Hz, 2H), 6.57 – 6.36 (m, 4H),
5.76 (dd, J = 8.5, 2.0 Hz, 2H). HRMS (ESI): calcd for C28H18N6F4Ir
[M]+ 707.1158 found 707.1203.
These derivatives were synthesized following previously
reported procedures with necessary modification.50,51 2-
Acetylpyridine (5.42 mL, 48 mmol) was added into the EtOH
solution (120 mL) of p-fluoro/chloro-benzaldehyde (24 mmol),
followed by addition of KOH pellets (3.70 g, 48 mmol) and aq
NH3 (70 mL, 60 mmol) to the reaction mixture. Further, the
reaction mixture was stirred at r.t. for 5 h. The off-white solid
generated in due course of the reaction was collected by
filtration and washed with EtOH and then dried in a desiccator.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 9
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 10 of 12
ARTICLE
Journal Name
24 P. Sutar and T. K. Maji, Inorg. Chem., 2017, 56, 9417-9425.
Conflicts of interest
There are no conflicts to declare.
25 C. Kim, K. Y. Kim, J. H. Lee, J. Ahn, K. SaDkuOrI:a1i,0S.1.0S3V.9iLe/Cwe8eATratCicn0led3O4Jn8.l7iHnGe.
Jung, ACS Appl. Mater. Interfaces, 2017, 9, 3799-3807.
26 W. K.-L., L. G.-L., Y. Y.-Y. and W. W.-T., Adv. Mater., 2006, 18
,
1051-1054.
27 P. Sutar and T. K. Maji, Chem. Commun., 2016, 52, 8055-8074.
28 S. Mohapatra, S. Adhikari, H. Riju and T. K. Maji, Inorg. Chem.,
2012, 51, 4891-4893.
Acknowledgments
T.S.M. acknowledge SERB (India) Grant PDF/2016/002461 for
funding and fellowship. A. D. acknowledges SERB (India)
(EMR/2016/001850,
(ERIP/ER/1502249/M/01)
29 W.-X. Feng, S.-Y. Yin, M. Pan, H.-P. Wang, Y.-N. Fan, X.-Q. Lü
and C.-Y. Su, J. Mater. Chem. C, 2017, 5, 1742-1750.
&
JCB/2017/000004) and DRDO
Grants for funding. SKP
30 P. Kumar, S. Soumya and E. Prasad, ACS Appl. Mater.
Interfaces, 2016, , 8068-8075.
8
acknowledges Grant SERB (PDF/2015/000745) for funding and
fellowship. Authors acknowledge Dr. Suresh K. Jewrajka (CSIR-
CSMCRI) for providing us the poly(methyl methacrylate)
(PMMA) for our experiments.
31 P. Coppo, M. Duati, V. N. Kozhevnikov, J. W. Hofstraat and L.
D. Cola, Angew. Chem., Int. Ed., 2005, 44, 1806-1810.
32 D. Sykes, I. S. Tidmarsh, A. Barbieri, I. V. Sazanovich, J. A.
Weinstein and M. D. Ward, Inorg. Chem., 2011, 50, 11323-
11339.
33 D. Sykes, S. C. Parker, I. V. Sazanovich, A. Stephenson, J. A.
Weinstein and M. D. Ward, Inorg. Chem., 2013, 52, 10500-
10511.
34 J. A. Kaplan, P. Barthelemy and M. W. Grinstaff, Chem.
Commun., 2016, 52, 5860-5863.
References
1
2
3
A. R. Hirst, B. Escuder, J. F. Miravet and D. K. Smith, Angew.
Chem., Int. Ed., 2008, 47, 8002-8018.
P. Chen, Q. Li, S. Grindy and N. Holten-Andersen, J. Am. Chem.
Soc., 2015, 137, 11590-11593.
35 C. Giansante, G. Raffy, C. Schäfer, H. Rahma, M.-T. Kao, A. G.
L. Olive and A. Del Guerzo, J. Am. Chem. Soc., 2011, 133, 316-
325.
36 J. F. Galisteo-Lopez, S. Gomez-Esteban, B. Gomez-Lor and C.
J. A. Foster, K. K. Damodaran, A. Maurin, G. M. Day, H. P. G.
Thompson, G. J. Cameron, J. C. Bernal and J. W. Steed, Chem.
Lopez, J. Mater. Chem. C, 2015, 3, 5764-5768.
37 L. Yongguang, W. K. Man‐Chung, T. A. Yiu‐Yan, W. Lixin and Y.
V. Wing‐Wah, Chem. Eur. J, 2010, 16, 8690-8698.
Sci., 2017,
J. A. Foster, M.-O. M. Piepenbrock, G. O. Lloyd, N. Clarke, J. A.
K. Howard and J. W. Steed, Nat. Chem., 2010, , 1037.
8, 78-84.
4
38 J. Y. R. Silva, L. L. da Luz, F. G. M. Mauricio, I. B. Vasconcelos
Alves, J. N. d. S. Ferro, E. Barreto, I. T. Weber, W. M. de
Azevedo and S. A. Júnior, ACS Appl. Mater. Interfaces, 2017,
2
5
6
P. Dastidar, Chem. Soc. Rev, 2008, 37, 2699-2715.
A. Maity, F. Ali, H. Agarwalla, B. Anothumakkool and A. Das,
Chem. Commun., 2015, 51, 2130-2133.
Z. Yang, G. Liang and B. Xu, Acc. Chem. Res., 2008, 41, 315-
326.
Y. Zhou, H.-Y. Zhang, Z.-Y. Zhang and Y. Liu, J. Am. Chem. Soc.,
2017, 139, 7168-7171.
9
, 16458-16465.
39 Y. Cui, H. Xu, Y. Yue, Z. Guo, J. Yu, Z. Chen, J. Gao, Y. Yang, G.
Qian and B. Chen, J. Am. Chem. Soc., 2012, 134, 3979-3982.
40 D. Ananias, F. A. A. Paz, D. S. Yufit, L. D. Carlos and J. Rocha, J.
Am. Chem. Soc., 2015, 137, 3051-3058.
7
8
9
41 A. J. McConnell, C. S. Wood, P. P. Neelakandan and J. R.
Nitschke, Chem. Rev, 2015, 115, 7729-7793.
42 Y. Sagara and T. Kato, Nat. Chem., 2009, 1, 605.
43 J. H. v. Esch and B. L. Feringa, Angew. Chem., Int. Ed., 2000,
39, 2263-2266.
A. Y.-Y. Tam and V. W.-W. Yam, Chem. Soc. Rev, 2013, 42
1540-1567.
,
10 J. W. Steed, Chem. Soc. Rev, 2010, 39, 3686-3699.
11 V. K. Praveen, C. Ranjith and N. Armaroli, Angew. Chem., Int.
Ed., 2014, 53, 365-368.
44 S. Yagai, T. Nakajima, K. Kishikawa, S. Kohmoto, T. Karatsu and
A. Kitamura, J. Am. Chem. Soc., 2005, 127, 11134-11139.
45 S.-k. Ahn, R. M. Kasi, S.-C. Kim, N. Sharma and Y. Zhou, Soft
12 S. S. Babu, V. K. Praveen and A. Ajayaghosh, Chem. Rev, 2014,
114, 1973-2129.
13 G. Yu, X. Yan, C. Han and F. Huang, Chem. Soc. Rev, 2013, 42
,
Matter, 2008, 4, 1151-1157.
6697-6722.
46 T. Z. Grove, C. O. Osuji, J. D. Forster, E. R. Dufresne and L.
14 S. Y.-L. Leung, S. Evariste, C. Lescop, M. Hissler and V. W.-W.
Regan, J. Am. Chem. Soc., 2010, 132, 14024-14026.
Yam, Chem. Sci., 2017,
15 A. Harada, R. Kobayashi, Y. Takashima, A. Hashidzume and H.
Yamaguchi, Nat. Chem., 2010, , 34.
8, 4264-4273.
47 P. T. Mather, Nat. Mater., 2007, 6, 93.
48 Q. Zhu, L. Zhang, K. Van Vliet, A. Miserez and N. Holten-
Andersen, ACS Appl. Mater. Interfaces, 2018, 10, 10409-
10418.
3
16 A. Sorrenti, R. Rodriguez-Trujillo, D. B. Amabilino and J.
Puigmartí-Luis, J. Am. Chem. Soc., 2016, 138, 6920-6923.
17 J. R. Moffat, G. J. Seeley, J. T. Carter, A. Burgess and D. K.
Smith, Chem. Commun., 2008, 4601-4603.
18 M. Martínez-Calvo, O. Kotova, M. E. Möbius, A. P. Bell, T.
McCabe, J. J. Boland and T. Gunnlaugsson, J. Am. Chem. Soc.,
2015, 137, 1983-1992.
19 K. Oxana, D. Ronan, d. S. C. M. G., B. Markus, K. P. E., B. J. J.
and G. Thorfinnur, Angew. Chem., Int. Ed., 2012, 51, 7208-
7212.
49 M. C. Heffern, L. M. Matosziuk and T. J. Meade, Chem. Rev,
2014, 114, 4496-4539.
50 J. Wang and G. S. Hanan, Synlett, 2005, 2005, 1251-1254.
51 A. Maron, A. Szlapa, T. Klemens, S. Kula, B. Machura, S.
Krompiec, J. G. Malecki, A. Switlicka-Olszewska, K. Erfurt and
A. Chrobok, Org. Biomol. Chem, 2016, 14, 3793-3808.
52 H. Agarwalla, K. Jana, A. Maity, M. K. Kesharwani, B. Ganguly
and A. Das, J. Phys. Chem. A., 2014, 118, 2656-2666.
53 T. S. Mahapatra, S. Chaudhury, S. Dasgupta, V. Bertolasi and
D. Ray, New J. Chem., 2016, 40, 2268-2279.
54 S. Petoud, J.-C. G. Bünzli, K. J. Schenk and C. Piguet, Inorg.
Chem., 1997, 36, 1345-1353.
55 K. Sénéchal-David, A. Hemeryck, N. Tancrez, L. Toupet, J. A. G.
Williams, I. Ledoux, J. Zyss, A. Boucekkine, J.-P. Guégan, H. Le
Bozec and O. Maury, J. Am. Chem. Soc., 2006, 128, 12243-
12255.
20 D. E. Barry, D. F. Caffrey and T. Gunnlaugsson, Chem. Soc. Rev,
2016, 45, 3244-3274.
21 G. Tumpa and U. Maitra, Angew. Chem., Int. Ed., 2017, 56
,
10730-10734.
22 S. Banerjee, R. Kandanelli, S. Bhowmik and U. Maitra, Soft
Matter, 2011, 7, 8207-8215.
23 P. Sutar, V. M. Suresh and T. K. Maji, Chem. Commun., 2015,
51, 9876-9879.
10 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 11 of 12
Journal of Materials Chemistry C
Please do not adjust margins
Journal Name
ARTICLE
56 B. Ahrens, S. A. Cotton, N. Feeder, O. E. Noy, P. R. Raithby and
S. J. Teat, J. Chem. Soc., Dalton Trans., 2002, 2027-2030.
View Article Online
DOI: 10.1039/C8TC03487G
57 H. Nozary, C. Piguet, P. Tissot, G. Bernardinelli, J.-C. G. Bünzli,
R. Deschenaux and D. Guillon, J. Am. Chem. Soc., 1998, 120
,
12274-12288.
58 J. C. Freys, G. Bernardinelli and O. S. Wenger, Chem. Commun.,
2008, DOI: 10.1039/B806175K, 4267-4269.
59 J.-C. Xiao and J. n. M. Shreeve, J. Org. Chem., 2005, 70, 3072-
3078.
60 S. Sprouse, K. A. King, P. J. Spellane and R. J. Watts, J. Am.
Chem. Soc., 1984, 106, 6647-6653.
61 K. L. Cheng, K. Ueno, T. Imamura, CRC Handbook of Organic
Analytical Reagents, 2nd ed., CRC Press, Florida, 1992
.
62 G. M. Sheldrick, SAINT 5.1 ed.; Siemens Industrial Automation
Inc., Madison, WI, 1995.
63 SADABS, Empirical Absorption Correction Program; University
of Göttingen, Göttingen, Germany, 1997.
64 G. M. Sheldrick, SHELXTL Reference Manual: Version 5.1;
Bruker AXS, Madison, WI, 1997.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 11
Please do not adjust margins

Journal of Materials Chemistry C
Page 12 of 12
View Article Online
DOI: 10.1039/C8TC03487G
Table of contents:
Text:
Lanthanide-based light-emitting supramolecular thermoreversible metallogels with
tunable luminescence by controlling the stoichiometry of L-X/EuIII•L-X/TbIII•L-X or L-
X/EuIII•L-X/[IrIII(F2ppy)2(biimid)]PF6.
Graphic: