FULL PAPER
DOI: 10.1002/chem.201103855
Wide-Range Light-Harvesting Donor–Acceptor Assemblies through Specific
Intergelator Interactions via Self-Assembly
Suman K. Samanta[a] and Santanu Bhattacharya*[a, b]
Abstract: We have synthesized two
new low-molecular-mass organogela-
tors based on tri-p-phenylene vinylene
derivatives, one of which could be des-
ignated as the donor whereas the other
one is an acceptor. These were pre-
pared specifically to show the inter-
organic solvents. Evidence for inter-
AHCTUNGTRENNgGUN elator interactions was acquired from
of four chromophores was built up by
inclusion of two known dyes (anthra-
cene and rhodamine 6G) for the
energy-transfer studies. Interestingly,
an energy-transfer cascade was ob-
served in the assembly of four chromo-
phores in a particular order (anthra-
cene-donor-acceptor-rhodamine 6G),
and if one of the components was re-
moved from the assembly the energy
transfer process was discontinued. This
allowed the build up of a light-harvest-
ing process with a wide range. Excita-
tion at one end produces an emission
at the other end of the assembly.
various spectroscopic, microscopic,
thermal, and mechanical investigations.
Due to the photochromic nature of
these molecules, interesting photophys-
ical properties, such as solvatochrom-
ism and J-type aggregation, were clear-
ly observed. An efficient energy trans-
fer was exhibited by the mixture of
donor–acceptor assemblies. An array
ACHTUNGTRENNUNGgelator interactions at the molecular
level by using donor–acceptor self-as-
sembly to achieve appropriate control
over their macroscopic properties. In-
termolecular hydrogen-bonding, p-
stacking, and van der Waals interac-
tions operate for both the individual
components and the mixtures, leading
to the formation of gels in the chosen
Keywords: chromophores · donor–
acceptor systems · energy transfer ·
gels · reversible reactions
Introduction
important for addressing fundamental questions in the
energy-transfer process but is also of great interest in devel-
oping advanced materials, including optoelectronic devices,
organic light emitting diodes (OLEDs), and solar cells.[8]
Thus, developing light-harvesting systems comprised of suit-
able chromophore arrays holds considerable potential and
challenge for emerging new directions.
Natural photosynthesis occurs with the absorption of sun-
light and the manifestation of a continuous unidirectional
energy transfer process between chromophores plays a
significant role in the efficient light-harvesting process.[1]
The organization of dye assemblies at suitable distances and
in a specific orientation triggered by noncovalent interac-
tions is responsible for the fast migration of excitation
energy.[2] The phenomena of natural-light harvesting are
best understood through synthetically designed molecular
systems in which supramolecular interactions play a signifi-
cant role in the chromophore assembly in appropriate orien-
tations.[3] The supramolecular assemblies used to design arti-
ficial light-harvesting systems include molecular arrays,[4]
The supramolecular self-assembly of low-molecular-mass
gelators (LMMG)[9] gives rise to physical gels that provide
an exceptional opportunity to assist the energy-transfer
process.[10] The self-assembly brought about by dipole–
dipole, hydrogen-bonding, van der Waals, and p-stacking in-
teractions between appropriate chromophoric molecules
provide a novel chromophore assembly.[11] Interesting photo-
physical properties were observed in oligo(p-phenylene vi-
nylene)-based chromophores and research to this end has
ACHTUNGTRENNUNG
supramolecular complexes,[5] dendrimers,[6] and light-
harvesting antennae.[7] This self-assembly process is not only
been spearheaded by Meijer[12] and Ajayaghosh et al.[13]
A
number of cases has been studied by using synthetic donors
and acceptors to modify the efficiency of energy transfer
mostly in binary composites.[14] However, there are relatively
few chromophore arrays containing more than two mole-
cules interacting through noncovalent interactions that lead
to energy transfer mentioned in the literature.[15] Herein, we
discuss the donor–acceptor interactions in terms of hydro-
gen bonding and energy transfer between two new organo-
gelators (D and A, Scheme 1) based on a central tri(p-phen-
[a] Dr. S. K. Samanta, Prof. Dr. S. Bhattacharya
Department of Organic Chemistry
Indian Institute of Science
Bangalore 560012, Karnataka (India)
Fax : (+91)80-23600529
[b] Prof. Dr. S. Bhattacharya
Chemical Biology Unit
Jawaharlal Nehru Centre for Advanced Scientific Research
Bangalore 560064, Jakkur (India)
AHCTUNGTREGyNNUN lene vinylene) (TPV) moiety. As per the proposed model
reported earlier,[16] we successfully demonstrate herein an
extended energy-transfer array that depends on the choice
Supporting information for this article is available on the WWW
Chem. Eur. J. 2012, 18, 15875 – 15885
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
15875