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Praveen V.K.,CNR Institute for Organic Syntheses and Photoreactivity | Ranjith C.,University of Milan | Bandini E.,CNR Institute for Organic Syntheses and Photoreactivity | Ajayaghosh A.,Indian National Institute for Interdisciplinary Science and Technology | Armaroli N.,CNR Institute for Organic Syntheses and Photoreactivity
Chemical Society Reviews | Year: 2014

Oligo(phenylenevinylene)s (OPVs) are extensively investigated π-conjugated molecules that exhibit absorption and fluorescence in the UV-Vis spectral region, which can be widely tuned by chemical functionalisation and external control (e.g. solvent, temperature, pH). Further modulation of the optoelectronic properties of OPVs is possible by supramolecular aggregation, primarily driven by hydrogen bonding or π-stacking interactions. In recent years, extensive research work has been accomplished in exploiting the unique combination of the structural and electronic properties of OPVs, most of which has been targeted at the preparation of molecules and materials featuring photoinduced energy transfer. This review intends to offer an overview of the multicomponent arrays and self-assembled materials based on OPV which have been designed to undergo energy transfer by means of a thorough choice of excitation donor-acceptor partners. We present a few selected examples of photoactive dyads and triads containing organic moieties (e.g. fullerene, phenanthroline) as well as coordination compounds (Cu(i) complexes). We then focus more extensively on self-assembled materials containing suitably functionalised OPVs that lead to hydrogen bonded aggregates, helical structures, gels, nanoparticles, vesicles, mesostructured organic-inorganic hybrid films, functionalised nanoparticles and quantum dots. In most cases, these materials exhibit luminescence whose colour and intensity is related to the efficiency and direction of the energy transfer processes. This journal is © the Partner Organisations 2014. Source


Varughese S.,Indian National Institute for Interdisciplinary Science and Technology
Journal of Materials Chemistry C | Year: 2014

Switching and tuning solid state luminescence properties of molecular materials by modulating molecular packing through non-covalent routes is an attractive prospect. This strategy further makes it feasible to expand the utility of molecules of interest by obtaining a large array of solids - polymorphs, solvates, amorphous phase, nano/micro-crystals and as multi-component systems - with distinct fluorophore arrangement and hence emission characteristics. Because non-covalent interactions that determine the fluorophore arrangements in polymorphs or supramolecular complexes are weak and flexible, their making and breaking become more realistic under ambient conditions, thus having potential to achieve reversible transformations and hence external-stimuli-responsive and switchable molecular fluorescent materials. Recent advances in this context are highlighted in this review with the aid of illustrative examples and further emphasize the scope and relevance of interdisciplinary and multitechnique approaches to unravel the structure-optical property relationships and also to augment the foundations of factual knowledge. This journal is © the Partner Organisations 2014. Source


Varghese S.,Indian National Institute for Interdisciplinary Science and Technology | Das S.,Indian National Institute for Interdisciplinary Science and Technology
Journal of Physical Chemistry Letters | Year: 2011

The optical properties of π-conjugated organic molecules in their solid state are critically important in determining performance efficiencies of optoelectronic devices such as organic light-emitting diodes and organic thin-film transistors. This Perspective discusses some recent systematic explorations aimed toward arriving at an understanding of the role that molecular packing plays in determining these properties. © 2011 American Chemical Society. Source


George J.,Indian National Institute for Interdisciplinary Science and Technology | George Thomas K.,Indian National Institute for Interdisciplinary Science and Technology
Journal of the American Chemical Society | Year: 2010

(Figure Presented) Au nanoparticles grown on D- and L-isomers of diphenylalanine peptide nanotubes showed a bisignated CD signal at their surface plasmon frequency with positive and negative couplets, respectively. The surface plasmon coupled CD signal in these hybrid systems originates from the asymmetric organization of Au nanoparticles on peptide nanotubes. Mirror image relationship in the CD spectra clearly indicates that the chiral molecules on the nanotubes drive the organization of nanoparticles in two different ways. Copyright © 2010 American Chemical Society. Source


Sivakumar S.,Indian National Institute for Interdisciplinary Science and Technology | Reddy M.L.P.,Indian National Institute for Interdisciplinary Science and Technology
Journal of Materials Chemistry | Year: 2012

Luminescent lanthanide complexes (Eu 3+ (1) or Tb 3+ (2)) involving a highly fluorinated aromatic carboxylate, namely, 3,5-bis(perfluorobenzyloxy)benzoic acid which acts as an antenna chromophore and sensitizes the visible emitting lanthanides, have been synthesized and characterized and their photophysical properties investigated. The results demonstrated that the replacement of high-energy C-H vibrations with fluorinated phenyl groups in the 3,5-bis(benzyloxy)benzoate effectively improves the luminescence intensity and lifetimes of lanthanide complexes. It is interesting to note that the designed fluorinated carboxylate is well suited for the sensitization of Tb 3+ emission (Φ sen = 52%), thanks to a favorable position of the triplet state of the ligand as investigated in the Gd 3+ complex. On the other hand, the corresponding Eu 3+ complex shows weak luminescence efficiency (Φ sen = 24%) due to poor match of the triplet state of the ligand with the emissive excited states of the metal ion. In the present work, efforts have also been made to isolate luminescent molecular terbium plastic materials by combining the unique optical properties of lanthanides with the mechanical characteristics, thermal stability, flexibility and film-forming tendency of polymers (PMMA). The photoluminescence quantum yields of polymer-lanthanide hybrid materials are significantly enhanced (53-65%) as compared to that of the Tb 3+-3,5-bis(perfluorobenzyloxy)benzoate complex. © The Royal Society of Chemistry 2012. Source

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