<p>Shiv Nadar University is a comprehensive, multidisciplinary, research-focused, and student-centric University offering a full range of academic programs at the undergraduate, postgraduate and doctoral level. With state-of-the-art infrastructure, the University comprises of academic wings, sophisticated labs, international standard sports facilities, amphitheaters, auditorium, conference rooms and smart classrooms. The University&rsquo;s goal is to become internationally recognized for the quality of its research and creative endeavors and their applicability to improving quality of life, generating new insights and expanding the boundaries of human knowledge creativity. Committed to excellence in teaching, research and service, the University aims to serve the higher education needs of India and the world beyond.</p>

Shiv Nadar University

The performance attained by electronic devices incorporating more than a single molecule is in part limited by weak electronic coupling between molecules. By implementing designed supramolecular interactions, chemists have begun taking control of the nanoscale ordering of the active layer in an effort to move beyond the trial and error tuning of the device morphology. This review describes current progress in solid-state devices in which the molecular components possess designed supramolecular interactions - as opposed to non-specific cohesive forces - used to instill or modify functionality. Supramolecular organic devices for applications in solar energy conversion, light-emitting diodes, field-effect transistors, storage and logic functions are covered. © 2010 Elsevier B.V.

World University root node

Chemistry

(SoNS) School of Natural Sciences

Coordination Chemistry Reviews

Harnessing supramolecular interactions in organic solid-state devices: Current status and future potential

The anisotropy of the electronic interactions between fullerenes in crystalline solids was examined using a confocal fluorescence microscope by probing the polarization of the fluorescence emission arising from fullerene excimer-like emitting states. Crystals of C60 obtained by vacuum-sublimation or from chloroform solution exhibited no or little polarization (p = 0 or 0.11, respectively), as expected from the high symmetry of the C60 fcc lattice or the low degree of anisotropy induced by included solvent molecules. The use of hydrogen-bonding to supramolecularly control interfullerene electronic interactions was explored using a fullerene derivative (1) combining a solubilizing 3,4-di-tert-butylbenzene group and a barbituric acid hydrogen-bonding (H-B) moiety. The crystal structure of 1 establishes the existence of fullerene H-B tapes along which interfullerene electronic interactions are expected to be large. In agreement with this, we observe very strong polarization of the fullerene excimer-like emission (p = 0.78), indicative of a high degree of anisotropy in the fullerene interactions. The charge-carrier mobility of 1 as determined from OFET devices was found to be lower than that of C60 (1.2 × 10-4 vs 1.2 × 10-2 cm2/s V), which is rationalized on the basis of the reduced dimensionality of 1 as a wire-like semiconductor and variations in the morphology of the device active layer revealed by AFM measurments. © 2010 American Chemical Society.

Journal of the American Chemical Society

Self-assembly of supramolecular fullerene ribbons via hydrogen-bonding interactions and their impact on fullerene electronic interactions and charge carrier mobility

Two coumarin derived dyes (compounds La and L) have been synthesized in high yields by Schiff base condensation. On probing with a femtosecond laser, none of these compounds show any two-photon activity in the wavelength range, 760-860 nm. However, La in presence of Zn(II) and L in presence of Mg(II), exhibit large two-photon absorption as well as emission in the same wavelength range. Theoretical calculations at the B3LYP functional with 6-31G and LanL2DZ mixed basis set under DFT formalism support experimental results. © 2010 Elsevier B.V. All rights reserved.

Inorganica Chimica Acta

Coumarin derived chromophores in the donor-acceptor-donor format that gives fluorescence enhancement and large two-photon activity in presence of specific metal ions

Two new chromophores in the format, donor-acceptor-donor, have been synthesized in high yields from easily available starting materials. These compounds do not show any two-photon absorption (TPA) cross-section in the wavelength range, 780-900 nm when probed by the Z-scan technique with a femtosecond laser. However, in presence of Zn(II), Ca(II) or Mg(II) ion, each compound gives exceptionally large TPA cross-section in the same wavelength range. © 2008 Elsevier B.V. All rights reserved.

Journal of Luminescence

Acyclic donor-acceptor-donor chromophores for large enhancement of two-photon absorption cross-section in the presence of Mg(II), Ca(II) or Zn(II) ions

Two azine molecules, [3-{4-(dimethylamino)phenyl}prop-2-en-1-ylidene] hydrazone (HL) and [4-(dimethylamino)benzylidene]hydrazone (LL) synthesized via Schiff base condensation, show an absorption band due to intra-ligand charge transfer (ILCT). Both ligands show weak emission in the absence of a metal ion as input. When Ag+ ions are added to either compound in THF, the metal ion gets bonded to the azine moiety resulting in a high intensity emission (∼400 fold). While Cu+ shows a slight enhancement of emission, other first-row transition, alkali or alkaline-earth metal ions do not show any emission allowing Ag+ ions to be detected in the presence of these metal ions. Both the Ag+ complexes were characterised by X-ray crystallography and show solid-state spectra similar to their solution spectra. Time-resolved fluorescence measurements done on the complexes show two excited-state lifetimes. © The Royal Society of Chemistry 2009.

Fulltext

Dalton Transactions

Ag(i) induced emission with azines having donor-acceptor-donor chromophore

Two different coumarin derivatives have been connected via an imine linkage to obtain a new fluorescence signaling system. This compound itself does not show any emission due to rapid isomerization around the C=N bond. However, in the presence of a Mg(II) ion, this isomerization is stopped because of bonding to the metal ion resulting in high-intensity (∼550-fold) emission. Other metal ions like Li(I), Ca(II), and Zn(II) show very little emission, while biologically relevant transition-metal ions do not show any emission. In this way, the Mg(II) ion can be detected in the presence of these ions. © 2008 American Chemical Society.

Inorganic Chemistry

A coumarin-derived fluorescence probe selective for magnesium

The laterally nonsymmetric aza cryptand Lo readily forms mononuclear inclusion complexes with metal ions like CuII, Ni II, AgI, TlI, and so forth. However, when the secondary amines present in the three bridges are substituted by a cyanomethyl group to yield a new cryptand L, its metal-binding properties are drastically altered. Thus, while Lo binds AgI at the tren end, showing AgN4 coordination, in L, the bridgehead nitrogen atoms are pulled inside to form a two-coordinate complex of AgI and none of the O or N atoms present in the three bridges are involved in coordination. This is probably the first example where the two bridgehead atoms are pulled inside to the maximum to bind the metal ion. Likewise, the TlI ion shows TlN4 coordination with Lo, while in L it is loosely bound at the tren end, showing TlN3 coordination. Upon treatment with a AgI salt, the TlI can be replaced almost instantaneously. On the other hand, with copper(II) tetrafluoroborate salt in moist DMF, two of the cyanide groups in L are converted to carboxylic acid groups and bind the metal ion from outside. The CuII ion in this complex shows distorted octahedral coordination where the two O atoms from the two carboxylic acid groups and the two corresponding N atoms in the two bridges are bound equatorially. The two axial sites are occupied by the nearby bridgehead N atom and the O atom of a DMF molecule. All five complexes and the free ligands are characterized by spectroscopic and X-ray crystallographic studies. © Wiley-VCH Verlag GmbH &amp; Co. KGaA, 2006.

European Journal of Inorganic Chemistry

Alteration in the binding property of a laterally nonsymmetric aza cryptand toward CuII, AgI, and TlI ions upon derivatization with a cyanomethyl group