Self-Assembly of “Chalcone” Type Push-Pull Dye Molecules into Organic Single Crystalline Microribbons and Rigid Microrods for Vis/NIR Range Photonic Cavity Applications

Article abstract of DOI:10.1002/cphc.201600756

A novel supramolecular fluorescent donor–acceptor type dye molecule, (2E,4E)-1-(2-hydroxyphenyl)-5-(pyren-1-yl)penta-2,4-dien-1-one (HPPD) self-assembles in a mixture of ethanol/chloroform through intermolecular π–π stacking (distance ca. 3.384 ?) to form J-aggregated single-crystalline microribbons displaying Fabry–Pèrot (F-P) type visible-range optical resonance. The corresponding borondifluoride dye (HPPD-BF), with a reduced HOMO–LUMO gap, self-assembles into crystalline microrods acting as an F-P type resonator in the near-infrared (NIR) range.

Full text of DOI:10.1002/cphc.201600756

Accepted Article
Title: Self-Assembly of ”Chalcone” Type Push-Pull Dye Molecules into Organic Sin-
gle Crystalline Micro-Ribbons and Rigid Micro-Rods for Vis-NIR-Range Photo-
nic Cavity Applications
Authors: Radhika Vattikunta; Dasari Venkatakrishnarao; Mahamad Ahamad Mohid-
don; Rajadurai Chandrasekar
This manuscript has been accepted after peer review and the authors have elected
to post their Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by using the Digital
Object Identifier (DOI) given below. The VoR will be published online in Early View as
soon as possible and may be different to this Accepted Article as a result of editing.
Readers should obtain the VoR from the journal website shown below when it is pu-
blished to ensure accuracy of information. The authors are responsible for the content
of this Accepted Article.
To be cited as: ChemPhysChem 10.1002/cphc.201600756
Link to VoR: http://dx.doi.org/10.1002/cphc.201600756
A Journal of
www.chemphyschem.org

ChemPhysChem
10.1002/cphc.201600756
ARTICLE
Self-Assembly of “Chalcone” Type Push-Pull Dye Molecules into
Organic Single Crystalline Micro-Ribbons and Rigid Micro-Rods
for Vis-NIR-Range Photonic Cavity Applications
Radhika Vattikunta,[a] Dasari Venkatakrishnarao,[a] Mahamad Ahamad Mohiddon,[b] and Rajadurai
Chandrasekar[a]*
Abstract: Novel supramolecular fluorescent donor-acceptor type
dye molecule, (2E,4E)-1-(2-hydroxyphenyl)-5-(pyren-1-yl)penta-2,4-
dien-1-one
(HPPD)
self-assemble
in
a
mixture
of
methanol/chloroform via inter molecular - stacking (distance ~
3.384 Å) to form J- aggregated single crystalline micro-ribbons
displaying Fabry-Pèrot (F-P) type visible range optical resonance,
whereas its borondifluoride dye (HPPD-BF) with a reduced HOMO-
LUMO gap self-assemble into crystalline micro-rods acting as F-P
type resonator in the near infrared (NIR) range.
Introduction
Self-assembled organic optical structures are emerging as
promising photonic materials for fundamental understanding of
light-matter interaction and miniaturized device applications.[1-10]
Fluorescent (FL) organic molecules with supramolecular
properties (van der Waals, H-bond, - interactions, etc.) act as
key building blocks for the construction of shape-defined organic
assemblies via solution processing technique. Despite
numerous reports on self-assembled organic solids, only a few
research reports explored the single particle level light-matter
interaction properties. Self-assembly is one of the economical
ways to realize photonic organic particles with various
geometries such as tubes,[6-8] rods,[9,10] rings,[11] spheres,[12,13]
hemispheres,[14,15] fibers[16] etc. Here, in addition to molecular
constituents, the geometry of the organic particle also plays a
crucial role to realize various photonic materials such as
Scheme 1. Syntheses of push-pull type HPPD molecule and its BF2 (HPPD-
BF) complex.
photonic cavity effect in the FL emission spectrum suitable for
various applications.
To create self-assembled photonic particles with readily tunable
optical band width and high quantum yield, organic donor (D)
and acceptor (A) type FL molecular systems are ideal
candidates. To achieve supramolecular interactions, chalcone
type D-A push-pull dye molecules functionalized with -
stacking units are advantageous, since it can induce long range
molecular ordering in the solid state. Furthermore the boron
complexes of 2’-hydroxy-substituted chalcone analogues owing
to their enhanced push-pull character might display larger stoke
shift, decreased optical band gap and solution/solid state
emission in the NIR range.[18] Therefore this paper presents the
synthesis, crystal structure, optical properties of a novel FL
waveguides,[3-6,8]
lasers,[10,13,15a-c]
resonators,[7,12,14,16]
circuits,[16,17] modulators,[9] etc. Amongst the reported particle
geometries, to our knowledge, one of the missing shapes is
elongated flexible micro-ribbons with optical wave resonating
characteristics. Upon electronic excitation, it is expected that an
organic micro-ribbon with high refractive index (n) might trap the
FL light and through F-P type optical interference it might display
molecule,
namely
(2E,4E)-1-(2-hydroxyphenyl)-5-(pyren-1-
yl)penta-2,4-dien-1-one (HPPD) and its borondifluoride dye
(HPPD-BF). Further molecules HPPD and HPPD-BF readily self-
assemble into micro-ribbons and -rods, respectively under slow
solvent evaporation conditions and display single particle optical
cavity effect in the Vis-NIR region of the electromagnetic
spectrum.
[a]
[b]
R. Vattikunta, D. Krishnarao, Prof. Dr. R. Chandrasekar
Functional Molecular Nano/Micro Solids Laboratory
School of Chemistry, University of Hyderabad
Gachibowli, Hyderabad - 500046, Telangana, INDIA
E-mail: r.chandrasekar@uohyd.ac.in /
chandrasekar100@yahoo.com
Prof. Dr. M. A. Mohiddon
Department of Science and Humanities, National Institute of
Technology, Tadepalligudem 534101, Andhra Pradesh, India
Supporting information for this article is given via a link at the end of
the document.
Result and Discussion
This article is protected by copyright. All rights reserved

ChemPhysChem
10.1002/cphc.201600756
ARTICLE
Figure 2. A and B) Solution (in DMF, black lines) and solid state (red lines)
absorbance and emission properties of HPPD and HPPD-BF complex,
respectively.
the 19F-NMR spectrum displayed two peaks at -148.07 ppm and
-148.12 ppm, indicating the coordination of BF2 to HPPD. In
comparison to HPPD, the FTIR spectrum of HPPD-BF displayed
reduction of the >C=O band (1630 cm-1) intensity signifying the
formation of B-O bond. Further HPPD-BF exhibited two new
sharp peaks at 609 cm-1 and 638 cm-1 (Fig. S2). The Raman
spectrum (He-Ne 785 laser) of HPPD exhibited two intense
peaks at 1063 cm-1 and 1244 cm-1 (Fig. S3), however HPPD-BF
showed highly intense FL at all excitation frequencies [488 (Ar+),
532 (Nd-YAG), 633 (He-Ne) and 785 nm], devoid of any Raman
signals due to its extended absorption till ~800 nm (Fig. S4).
Figure 1. A) Single crystal structure of HPPD molecule. B) A HPPD dimer
displaying – stacking and intramolecular H-bond. C and D) Packing of –
stacked molecules along the crystallographic c-axis.
HPPD molecules
aggregate in
a
mixture of
methanol/chloroform (1:2) via weak intermolecular forces
forming tape like crystals. Examination of the single crystal X-ray
structure (monoclinic; P21/c; CCDC No. 1479670) (Fig. 1)
revealed presence of intramolecular hydrogen bond interaction
between the carbonyl oxygen and the hydroxyl group
[O(1)···H(24) = 2.537 Å] and intermolecular – stacking of
pyrene units C(9)···C(18) ~3.384 Å (Fig. 1B). In the solid state
the whole HPPD molecule was in the planar state with a transoid
conformation of 1,4-Diaryl-1,3-butadiene segment. The solid
state molecular packing clearly indicates a slipped ladder type J-
type aggregation of HPPD (Fig. 1C). The 1-D π–π stacks are
about 45 to the crystallographic b-axis and they grow along the
crystallographic c-axis. Unfortunately, the HPPD-BF crystals
suitable for single crystal diffraction were not obtained.
The donor-acceptor unit HPPD and its boron complex were
prepared in four steps (Scheme 1). At first, pyrene was
transformed to 1-bromopyrene 1 using NBS and it was further
converted to corresponding pyrene acrylaldehyde 2 as per the
reported procedure.[18,19] Subsequently compound
2
was
condensed with 2-hydroxyacetophenone via Claisen–Schmidt
reaction to get a red colored HPPD dye with 54% yield (Scheme
1
1). The H and 13C-NMR spectroscopy studies (in DMSO-d6)
exhibited chemical shift () value of 12.09 ppm for -OH proton,
and 193.5 ppm for the carbonyl carbon, respectively. The
downfield shifted –OH peak is indicative of the intramolecular H
bond in the solution state. Further, the ESI-TOF-MS analysis
clearly confirmed (m/z 413.228 [M+K]) the formation of HPPD
molecule. In the FTIR studies, the –OH and >C=O stretching
frequencies of HPPD appeared at ~3450 cm-1 (broad), and 1630
cm-1 (sharp), respectively. Finally to reduce the HOMO-LUMO
gap, borondifluoride complex of HPPD (HPPD-BF) was
synthesized from HPPD ligand using BF3·Et2O reagent in DCM
solvent as black color solid. The 1H NMR spectrum of HPPD-BF
in DMSO-d6 showed disappearance of -OH proton peak of
HPPD ligand (Fig. S1). The 11B-NMR spectrum (DMSO-d6) of
HPPD-BF showed two peaks at 0.81 ppm and -1.35 ppm and
A N,N”-dimethylformamide (DMF) solution (c ~10-5 M) of
HPPD showed multiple absorbance maxima at 276/326/432 nm
(Fig. 2A). Amongst these peaks, the 432 nm peak looked highly
intense and broad and appeared with a high energy shoulder at
~402 nm. To understand the origin of these absorbance peaks it
is important to look at the molecular structure carefully. The
electronic structure of HPPD unit comprises of electron
accepting 2-hydroxyacetonphenone type segment connected to
pyrene unit through 1,3-butadiene -coupler. In the coplanar
structure the intra-molecular hydrogen bond also helps to
This article is protected by copyright. All rights reserved

ChemPhysChem
10.1002/cphc.201600756
ARTICLE
In case of HPPD-BF the solution state (DMF; c ~10-5 M)
absorbance spectrum showed pyrene features (242, 278, 349
nm) and two additional broad bands, one at 421 nm with a 402
nm shoulder and another band at 556 nm. The emission
maximum, which occurred at 672 nm slightly shifted towards low
energy red side and displayed a Stoke shift of 122 nm. In the
solid state HPPD-BF displayed a red shifted (compared to
solution state) broad absorbance and emission maxima at 622
nm and 743 nm, respectively. The large Stoke shift of 122 nm
indicates the strong dipolar character of the BF2-complex. In
comparison to solution state, a profound change of the emission
energy of a highly intense band, points to the HPPD-BF
chromophores in their – stacked J-aggregated state. It is
worth to note that the solid state emission band width of HPPD-
BF appeared in the range of ~620 nm to 950 nm covering most
of the NIR region. It is possible that dipolar HPPD-BF molecules
have strong molecular ordering and tight packing in the solid
state favoring NIR emission. Both HPPD and HPPD-BF
molecules in DMF solution exhibited FL decay life time () of
0.97 ns and 1.97 ns, respectively (Fig. S7), hinting the fast
excited state dynamics of HPPD molecule compared to HPPD-
BF.
Figure 3. A) Confocal optical micrograph of micro-ribbons. B and C)
FESEM image of flexible and straight micro-ribbons. D) A close-view of
the ribbon tip (shown in red box in C) displaying the presence of
individual nano fibres along its growth axis. E) TEM image of a single
crystalline micro-ribbon and (F) its corresponding SAED pattern. G) AFM
image of a single micro-ribbon displaying its thickness (T) and width (W)
profiles.
To achieve supramolecular
interaction mediated
nano/micro scale aggregated structures (particles), bottom-up
self-assembly was adopted. Initially micro-crystals were grown
by dissolving 1 mg of HPPD in CHCl3/EtOH solvent mixture (2:1)
and subsequently keeping the solution at 0C for a day. Latter a
100 L solution of mother liquor from the tube containing single
crystals was drop-casted on a clean cover-slip and subjected to
slow solvent evaporation. Initial confocal microscope
examination of the sample exhibited formation of micro-ribbons
like structures with linear and bent geometries indicating their
flexible nature (Fig. 3 A). Further FESEM images of the same
sample showed presence of flexible micro ribbons of varying
lengths (L), widths (W) and thicknesses (T) (Fig. 3 B, C). A
close-up view of one of the ribbon ends showed that each ribbon
is composed of several anisotropically stacked nano-fibres with
their growth in the extended axis of the tape (Fig. 3 D). TEM
micrographs of a selected single ribbon exhibited a dark contrast
due to its large thickness (Fig. 3 E). SAED pattern exhibited
clear bright diffraction spots confirming the single crystalline
nature of the microribbon (Fig. 3 F). The micro-ribbons primarily
formed because of the – stacking interactions of pyrene units
of neighboring molecules developing nano-fibers, which
subsequently aggregate into flexible microribbon like structures.
To understand this premise, the dissolution or dis-assembly
mechanism of individual microribbons was investigated by
adding several drops of acetonitrile/EtOH or acetonitrile to the
microribbon sample and monitored directly under confocal
microscope. Interestingly during dissolution several nano-fibers
split apart from microribbons produced brush like structures.
This observation clearly specified that the microribbon super-
structure is formed as a result of several stacked nano-fibers
(Fig. S8).
increase the -conjugation of the aromatic -systems by
restricting the rotation of C21 and C22 bond. Further it has been
shown that pyrene can acts as either A or D depending upon the
substituents.[20] The absorbance spectral feature of HPPD is
different from compounds 1, 2 and 2-hydroxyacetophenone (Fig.
S5). In HPPD, the origin of low energy band at 432 nm with a
shoulder at 402 nm is possibly due to intra-molecular charge
transfer (ICT) mechanism. Compound
1 in DMF solvent
exhibited spectral features similar to pyrene, while 2 showed red
shifted bands, notably an intense band at 382 nm together with
a shoulder at 414 nm. These features could be as a result of π-
π* transition and acceptor nature of carbonyl group favoring ICT.
This further supports the origin of red shifted 440 nm band,
which appeared together with a shoulder in HPPD. To check the
possibility of any excited state intramolecular charge transfer
(ICT) in HPPD, solvatochromic studies in non-polar and polar
aprotic solvents (hexane, diethylether, THF, ethylacetate,
acetone, acetonitrile) of different polarity were performed (Fig
S6). Electronic excitation (λex= 435 nm) of HPPD displayed a
Gaussian type featureless emission with a peak maximum (λmax
)
centered at 607 nm with a Stoke shift of 172 nm (Fig. 2A).
During the solvatochromic studies, although the absorption band
shifted slightly to the low energy side the emission band showed
a drastic ~50 nm red shift while changing the solvent from
hexane to acetonitrile, indicating the possibility of ICT process.
In comparison to solution state, the HPPD solid state maximum
absorbance appeared at ~442 nm and emission at 712 nm with
a large Stoke shift of 270 nm. From the spectral data we were
not able to identify the characteristics J band expected from the
solid state HPPD packing; this could be as a result of a very
weak electronic coupling between the molecules.
Atomic force microcopy (AFM) topography image of a
selected microribbon exhibited thickness (T) and width (W)
parameters in range of 1.2 m and 20 m, respectively
This article is protected by copyright. All rights reserved

ChemPhysChem
10.1002/cphc.201600756
ARTICLE
Figure 4. A) Powder XRD data of micro-ribbons, power HPPD, and
calculated spectrum from the single crystal data. B) Packing of HPPD
molecules within the unit cell. C) Polarized optical microscopy images of
HPPD microribbons (white crossed arrow illustrate the crossed-
polarizers)
confirming the ribbon-like structure (Fig.
3 G). Further
comparison of the powder XRD data of microribbons with the
calculated spectrum (from the single crystal data) showed three
intense and matching diffraction peaks at 2 (hkl) values 10.04
(200), 12.16 (210), and 13.5 (020). The recorded intensity of
the 200 peak was much higher compared to the calculated value.
The powder sample showed nearly matching peak positions and
intensities with the calculated data (Fig. 4A). This result
established the existence of similar molecular packing both in
microribbons and single crystals. The microribbon growth
direction is plausibly in the direction of – stacking of pyrene
units, which is crystallographic c-axis (001 plane) (Fig. 4B). The
single crystalline microribbon was examined under polarized
optical microscope to study its intrinsic molecular ordering and
optical anisotropy. Under cross-polarizer set-up the ribbons
which are aligned parallel and perpendicular appeared dark,
whereas maximum birefringence was observed when the
ribbons were oriented nearly 45 to the direction of the
polarizer, implying the direction of the optical axis (Fig. 4C).
To investigate the photonic properties of microribbons,
single particle -FL spectroscopy was performed on a laser
confocal microscope set-up at ambient conditions. For example,
when the center of a single microribbon segment placed on a
cover slip (Fig. 5A) was electronically excited with a 488 Ar+
laser (objective: 150x; NA: 0.95), no FL wave propagation (or
wave guiding) was observed along the ribbon growth axis (Fig.
5B), but propagation in the lateral direction (distance ~7 m) was
recorded[15d] signifying optical anisotropy of the microcrystalline
ribbon (Fig. 5C,D and Fig. S9). Interestingly the corresponding
Figure 5. A) Bright-field and FL confocal micrographs of a single
microribbon. B) Excitation of microribbon tip with 488 nm Ar+ laser shows
no light propagation along the fibre axis. C and D) Excitation along the
corners shows light propagation in the transverse direction. The inset
shows the cartoon depicting the F-P type cavity action. E) Single particle

-fluorescence spectra of three micro-ribbons of varying widths. F) A plot
of FSR versus 1/W. G) A plot of Q factor versus W. H) 2D and 3D FL
intensity maps of microribbon and the corresponding excitation position
dependent F-P modes. The dotted lines indicate mirror-like surfaces
supporting F-P cavity resonance.
between peaks (Δ) or free spectral range (FSR) periodically
increased towards the higher wavelength region (up to 850 nm).
This result shows the mirror-like reflection action of microribbon
surfaces, which encourage multiple FL wave interferences via F-
P resonance action. To confirm this finding, similar experiments
were conducted for several microribbons with varying W. A
selected spectral data for three microribbons (W = 25, 15.6, and
7.2 m - estimated from the confocal microscope images) are
single particle spectrum (collected in
a reflection mode)
exhibited a Gaussian type FL band together with series of
wavelength dependent intensity modulated peaks indicating the
resonating action of the single microribbon. The separation
This article is protected by copyright. All rights reserved

ChemPhysChem
10.1002/cphc.201600756
ARTICLE
excitation positions. As one can see the 2D FL image recorded
in a reflection mode configuration displayed strong lateral
position (a-d) dependent spectral patterns (number of modes)
due to variation of the density of modes per unit volume at
different positions of the microribbons.
To unravel the NIR photonic behavior of HPPD-BF, its self-
assembly (1 mg/mL) was performed by sonication in CHCl3
followed by drop casting the dispersion on a cover slip to get
micro particles. FESEM examination of the particles confirmed
the rectangular feature of the microrods (Fig. 6A). The EDS of
each microrod revealed the existence of B, O, C and F elements
confirming the microrods chemical composition (Fig. 6A,B).
Single particle FL -PL spectroscopy studies on the microrods
displayed its F-P type resonance behavior by displaying wave
length dependent intensity modulated peaks. Similar to its solid
state emission, the HPPD-BF microrods exhibited a red shift of
the resonance band width (650-900 nm) covering most of the
NIR region of the electromagnetic spectrum (Fig. 6C). The
FWHM of the peaks were rather broad compared to HPPD
microribbons indicating the weak optical confinement within
these rods. A plot of FSR values of selected microrods of
varying cross sections confirmed the increase of the FSR value
upon decreasing the width confirming F-P type resonance action
(Fig. 6D).
Figure 6. A) FESEM image of a single crystalline HPPD-BF microrod
and its EDS elemental map. B) EDS data exhibiting distribution of B, C,
O, and F elements in the microrod. C) Single particle FL spectrum of a
selected microrod displaying F-P type photonic cavity resonance. D)
FSR versus 1/W plot.
presented in Fig. 5E. Here upon decreasing width of the
microribbons the FSR value correspondingly increased to 8.1,
14.8, and 29.7 nm, respectively. A plot of FSR versus 1/W
clearly in line with the relation FSR ~ 1/W (Fig. 5F),[14] which
further confirms the F-P type resonance action of each
microribbon wherein the two opposite lateral facets act like
mirrors by reflecting the FL waves via total internal reflection
(TIR). In the plot the variation of the FSR values for different W
values point out varying microribbon T values, which is difficult
to measure under the confocal microscope set-up for individual
microribbons. The variation of the FSR value also possibly due
to slight variation in the excitation and collection points (see Fig.
5H).
The quality factor Q (Q = /Δ; where Δ is the line width
of a peak at FWHM and  is the wave length of the guided light)
of optical resonator indicates the amount of light energy stored
within the ribbons during its multiple reflections between the
mirror-like flat surfaces; high Q value indicates superior mirror-
like surface of the resonators and its photonic quality. The
estimated best Q factor of microribbons was about 400 (Fig. 5G).
In the plot shown in Fig. 5G, the scattered Q factor values
indicate a disparity in the optical quality of the microribbons
leading to varied optical power loss during repeated reflections
affecting the FWHM of resonance peaks. It is also imperative to
mention here that sharp resonance lines emitted by the
microribbons covered both visible (Vis) and near infrared (NIR)
regions. To study the enhancement of the electric field and its
distribution within the microribbons, FL intensity mapping was
performed on a selected microribbon segment (Fig. 5H).
Interestingly, the 3D FL intensity map exhibited increased FL
signal intensity along the mirror like walls compared to rest of
Conclusions
In summary we have synthesized a new donor-acceptor type
chalcone ligand, HPPD and its BF2 complex. In the crystalline
state HPPD J-aggregate via intermolecular – stacking (~3.384
Å) of pyrene units. Ligand HPPD and its boron complex HPPD-
BF formed visible emitting micro- ribbons and NIR emitting
micro-rods, respectively upon solvent-assisted self-assembly.
The powder state emission of HPPD was relatively weaker then
the HPPD-BF complex matching with the pervious results.[18]
Single particle (micro-ribbon) -FL spectroscopy studies
revealed the F-P type resonating behavior of these particles.
Further FL intensity map confirmed the lateral direction of F-P
cavity by displaying enhanced FL. On the other hand the
microribbons demonstrated enhanced FL single due to optical
cavity effect. The HPPD micro ribbons and HPPD-BF are the
first of its kind in organic crystalline photonic resonators.
Experimental Section
Pyrene acrylaldehyde: Compound 3 was synthesized according to the
following literature procedure.[19]
(2E,4E)-1-(2-hydroxyphenyl)-5-(pyren-1-yl)
penta-2,
4
dien-1-one
(HPPD): To a stirred solution of compound 3 (188 mg, 0.73 mmol) and 2-
hyroxyacetophenone (100 mg, 0.73 mmol) in EtOH /MeOH, a solution of
NaOH (73 mg, 1.8 mmol) in water (1mL) was added and the stirring
continued for 16 h at 60 C. After cooling to room temperature, the
solution was neutralised with 1N HCl and extracted with EtOAC. The
organic layer was dried over Na2SO4 and evaporated under reduced
pressure. Column chromatography of the crude product on silica gel
using EtOAC/hexane (5:95) gave product HPPD as red solid: Yield 150
the areas, which indirectly implied
a high electric field
concentration along the lateral side of the microribbon resonator
(Fig. 5H, top). The F-P modes and the FSR values which appear
in a FL spectrum of a resonator are very much sensitive to the
This article is protected by copyright. All rights reserved

ChemPhysChem
10.1002/cphc.201600756
ARTICLE
mg (54%). 1H NMR (400 MHz, CDCl3, 298 K) δ/ppm: 12.98 (s, 1H), 8.42-
8.39 (d, 3J (H,H) = 9.31Hz, 1H), 8.31-8.29 (d, 3J (H,H) = 8.14Hz, 1H),
8.19-8.14 (m, 5H), 8.08-8.05 (s ,1H), 8.03-8.01(m,2H), 7.96-7.93(m,1H),
7.86-7.89 (m,1H), 7.50 (t, 3J (H,H) = 7.83Hz,1H), 7.34-7.28 (m,2H), 7.05
(dd, 3J (H,H) = 8.50Hz, 1H), 6.94 (t, 3J (H,H) = 7.63Hz, 1H).13C NMR
(100 MHz, CDCl3, 298 K) δ/ppm: 193, 163, 145, 139, 136, 132, 131, 130,
129.6, 129.3, 129, 128.8, 128.3, 128.2, 127, 126, 125.8, 125.5, 124.9,
124.6, 124.5, 123.5, 123.3, 122, 119, 118.6, 118.4. FT-IR (KBr; υ in
cm−1): 1632, 1556, 1487, 1437, 1380, 1302, 1261, 1237, 1187, 1152,
1023, 993, 837, 801, 747, 712. HR-MS (m/z): Calculated: 413.228.
Found: 413.265. Elemental analysis (%) Calcd for C27H18O2: C, 86.61; H,
4.85. Found C, 86.52; H, 4.91.
Synthesis of HPPD-BF2: To a stirred solution of HPPD (20 mg, 0.05
mmol) in DCM (10 mL), BF3•Et2O (0.06 mmol) was added and the
solution was heated to reflux at 40 C for 2h. The solution was
concentrated in a rotary solvent evaporator, cooled down to precipitate
the product. The precipitate was filtered off, rinsed with Et2O and air dried
to yield HPPD-BF as black solid with 38% yield. 11B NMR (160 MHz,
DMSO-d6, 298 K) δ/ppm: 0.81 ppm and -1.35. 19F NMR (470 MHz,
DMSO-d6, 298 K) δ/ppm: -148.07 ppm and -148.12. FT-IR (NEAT; υ in
cm−1): 1630, 1618, 1588, 1555, 1472, 1404, 1286, 1188, 1123, 1072, 982,
844, 758, 638, 610.Elemental analysis (%) Calcd for C27 H17 B F2 O2 :
Calculated C, 76.80; H, 4.06. Found C, 76.69; H, 4.12.
Solid state absorbance studies: The solid state absorbance spectra were
collected from a Shimadzu UV-3600 spectrometer in a diffuse reflectance
UV-visible (DR-UV-vis) mode. The reflectance spectra were converted to
an absorbance spectra using Kubelka-Munk function.
Electron microscopy studies: Size and morphology of the sample were
examined by using a Zeiss field emission scanning electron microscope
(FESEM) operating at 5 kV. Transmission electron microscope (TEM)
measurements were performed on a Tecnai G2 FEI F12 instrument
operating at an accelerating voltage of 200 kV. Carbon coated TEM grids
(200 Mesh Type–B) were purchased from Ted Pella Inc. USA.
The authors acknowledge funds from UGC-UPE 2, and SERB -
New Delhi (EMR/2015/000186) projects. RC thanks the Centre
for Nanotechnology (CFN), UoH for the SNOM and TEM
facilities. RV and DK thank CSIR-New Delhi for SRFs. We
acknowledge Prof. S. Dhara, School of Physics, UoH for
polarization microcopic studies.
Keywords: self-assembly • donor-acceptor • micro-ribbons •
resonators • near infrared emission
[1] (a) V. K. Praveen, C. Ranjith, E. Bandini, A. Ajayaghosh, and N.
Armaroli, Chem. Soc. Rev. 2014, 43, 4222. (b) M. Urdampilleta, S.
Klyatskaya, J-P. Cleuziou, M. Ruben, W. Wernsdorfer, Nat. Mater.
2011, 10, 502. (c) H. -J. Kim, T. Kim, M. Lee, Acc. Chem. Res., 2011
,
44, 72. (d) E. N. Savariar , K. Krishnamoorthy, S. Thayumanavan, Nat.
Nanotech. 2008, 3, 112.
[2] J. Gierschner, S. Varghese, S. Y. Park, Adv. Opt. Mater, 2016, 3, 348.
[3] Y. S. Zhao,H. Fu, A. Peng, Y. Ma, D. Xiao, J. Yao, Adv. Mater. 2008, 20,
2859.
[4] C. Zhang, Y. S. Zhao, J. Yao, Phys. Chem. Chem. Phys. 2011, 13, 9060.
[5] R. Chandrasekar, Phys. Chem. Chem. Phys. 2014, 16, 7173.
[6] N. Chandrasekhar, M. A. Mohiddon, R. Chandrasekar, Adv. Opt.
Mater. 2013, 1, 305.
[7] U. Venkataramudu, D. Venkatakrishnarao, N. Chandrasekhar, M. A.
Mohiddon, R. Chandrasekar, Phys. Chem. Chem. Phys. 2016, 18,
15528.
[8] P. Hui, R. Chandrasekar, Adv. Mater., 2013, 25, 2963.
[9] D. Venkatakrishnarao, M. A. Mohiddon, N. Chandrasekhar, R.
Chandrasekar, Adv. Opt. Mater. 2015, 3, 1035.
[10] C. Zhang, C. –L. Zou, Y. Yan, R. Hao, F. –W. Sun, Z. –F. Han, Y. S.
Zhao, J. Yao, J. J. Am. Chem. Soc., 2011, 133, 7276.
[11] N. Chandrasekhar, R. Chandrasekar, Angew. Chem. Int. Ed. 2012
51, 3556.
,
[12] YSLV. Narayana, D.Venkatakrishnarao, M. A. Mohiddon, A. Biswas,
N. Viswanathan, R. Chandrasekar, ACS Appl. Mater. Inter, 2016, 8,
952.
Atomic force microscopy studies: Atomic force microscopy (AFM) was
carried out on NT-MDT Model Solver Pro M microscope. All calculations
and image processing were carried out by using NOVA 1.0.26.1443
software provided by the manufacturer. The images were recorded in a
semi-contact mode using a super sharp silicon cantilever (NSG 10_DLC)
with a diamond like carbon tip (NT-MDT, Moscow). The dimension of the
tip is as follows: Cantilever length = 100 (±5) µm, Cantilever width 35
(±5) µm, and Cantilever thickness = 1.7-2.3 µm, Resonate frequency =
190-325 kHz, Force constant = 5.5-22.5 N/m, Chip size = 3.6×1.6×0.4
mm, Reflective side = Au, Tip height = 10-20 µm, and DLC Tip curvature
radius = 1-3 nm.
[13] C. Wei, M.Gao, F. Hu, J. Yao, Y. S. Zhao, Adv. Opt. Mater. 2016
,
DOI: 10.1002/adom.201600048.
[14] D. Venkatakrishnarao, R. Chandrasekar, Adv. Opt. Mater. 2016, 4,
112.
[15] (a) X. Wang, Q. Liao, H. Li, S. Bai, Y. Wu, X. Lu, H. Hu, Q. Shi, H. Fu,
J. Am. Chem. Soc. 2015, 137, 9289-9295. (b) X. Lu, X. Wang, Q.
Liao, H. Fu, J. Phys. Chem. C. 2015, 119, 22108. (c) X. Wang, Q.
Liao, X. Lu, H. Li, Z. Xu, H. Fu, Sci. Rep, 2014, 4, 7011. (d) X.
Wang, Q. Liao, Z. Xu, Y. Wu, L. Wei, X. Lu, H. Fu, ACS
Photonics, 2014, 1, 413–420.
Confocal Raman and single particle micro-spectroscopy studies: Raman
spectra of the samples were recorded on a WI-Tec confocal Raman
spectrometer equipped with a Peltier-cooled CCD detector. Using a 600
grooves/mm grating BLZ = 500 nm, the accumulation time was typically
20 s and integration time was typically 1.0 s. Twenty accumulations was
performed for acquiring a single spectrum. A 785 nm (Diode laser) was
used as an excitation source for the Raman spectroscopy studies. All
measurements were collected in air.The optical spectra of single
spherical particles were recorded on a WI-Tec alpha 300 AR confocal
spectrometer equipped with a Peltier-cooled CCD detector. Argon ion
(Ar+) laser operating at 488 nm, and (He-Ne) 633 nm, were used as an
excitation source. A 150× objective was used for the measurements.
[16] K. Takazawa, J. Inoue, K. Mitsuishi,. T. Kuroda, Adv. Funct. Mater,
2013, 23, 839–845.
[17] C. Zhang, C. –L. Zou, Y. Zhao, C. -H. Dong, C. Wei, H. Wang, Y. Liu,
G. –C. Guo, J. Yao, Y. S. Zhao, Sci. Adv. 2015, doi:
10.1126/sciadv.1500257.
[18] A. D’Aléo, D. Gachet, V. Heresanu, M. Giorgi, F. Fages, Chem. Eur. J.
2012, 18, 12764.
[19] S. Noel, C. Luo, C. Pinel, L. Djakovitch, Adv. Synth. Catal. 2007, 349,
1128.
[20] S. –W. Yang, A. Elangovan, K. –C. Hwang, T.-I. Ho, J. Phys. Chem. B
2005, 109, 16628.
.
Acknowledgements
This article is protected by copyright. All rights reserved

ChemPhysChem
10.1002/cphc.201600756
ARTICLE
Entry for the Table of Contents (Please choose one layout)
Layout 1:
ARTICLE
Novel supramolecular fluorescent
donor-acceptor type dye molecule
(2E,4E)-1-(2-hydroxyphenyl)-5-(pyren-
1-yl)penta-2,4-dien-1-one (HPPD) and
its BF2 complex self-assemble to form
single crystalline micro-ribbons and
R.Vattikunta, D. Venkatakrishnarao,M.
A.Mohiddon and R. Chandrasekar*
Page No. – Page No.
Self-assembly
Self-assembly of “Chalcone” Type
Push-Pull Dye Molecules into Organic
Single Crystalline Micro-Ribbons and
Rigid Microrods for Vis-NIR range
Photonic Cavity Applications
F-P Cavity
rods displaying Fabry-Pèrot (F-P) type
visible-NIR range optical resonance
Vis-NIR
 (nm)
This article is protected by copyright. All rights reserved