Biomimetic molecular organization of naphthalene diimide in the solid state: tunable (chiro-) optical, viscoelastic and nanoscale properties

Pandeeswar, M and Khare, Harshavardhan and Ramakumar, Suryanarayanarao and Govindaraju, T (2014) Biomimetic molecular organization of naphthalene diimide in the solid state: tunable (chiro-) optical, viscoelastic and nanoscale properties. In: RSC ADVANCES, 4 (39). pp. 20154-20163.

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Abstract

The interfacing of aromatic molecules with biomolecules to design functional molecular materials is a promising area of research. Intermolecular interactions determine the performance of these materials and therefore, precise control over the molecular organization is necessary to improve functional properties. Herein we describe the tunable biomimetic molecular engineering of a promising n-type organic semiconductor, naphthalene diimide (NDI), in the solid state by introducing minute structural mutations in the form of amino acids with variable Ca-functionality. For the first time we could achieve all four possible crystal packing modes, namely cofacial, brickwork, herringbone and slipped stacks of the NDI system. Furthermore, amino acid conjugated NDIs exhibit ultrasonication induced organogels with tunable visco-elastic and temperature responsive emission properties. The amino acid-NDI conjugates self-assemble into 0D nanospheres and 1D nanofibers in their gel state while the ethylamine-NDI conjugate forms 2D sheets from its solution. Photophysical studies indicated the remarkable influence of molecular ordering on the absorption and fluorescence properties of NDIs. Interestingly, the circular dichroism (CD) and X-ray diffraction (XRD) studies revealed the existence of helical ordering of NDIs in both solution and solid state. The chiral amino acids and their conformations with respect to the central NDI core are found to influence the nature of the helical organization of NDIs. Consequently, the origin of the preferential handedness in the helical organization is attributed to transcription of chiral information from the amino acid to the NDI core. On account of these unique properties, the materials derived from NDI-conjugates might find a wide range of future interdisciplinary applications from materials to biomedicine.

Item Type:	Journal Article
Publication:	RSC ADVANCES
Publisher:	ROYAL SOC CHEMISTRY
Additional Information:	Copyright for this article belongs to the ROYAL SOC CHEMISTRY, THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	24 Jun 2014 09:18
Last Modified:	24 Jun 2014 09:18
URI:	http://eprints.iisc.ac.in/id/eprint/49339

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