Issue 29, 2014

Tuning of the HOMO–LUMO gap of donor-substituted symmetrical and unsymmetrical benzothiadiazoles

Abstract

This article reports the design and synthesis of donor-substituted symmetrical and unsymmetrical benzothiadiazoles (BTDs) 5–12 of type D–π–A–D, D1–π–A–D2, D1–A1–A2–D2, D–A1–A2–D and D–A1–A2–A1–D by Ullmann, Suzuki and cycloaddition–retroelectrocyclization reactions. The photophysical, electrochemical and computational properties were studied and show substantial donor–acceptor interaction. Their single photon absorption show strong charge transfer bands in the near-infrared (NIR) region and the electrochemical reduction show multiple reduction waves. The optical HOMO–LUMO gap of BTDs 5–12 was found to be a function of the number and nature of the acceptors. Computational studies reveal that strong cyano-based acceptors, dicyanoquinodimethane (DCNQ) and tetracyanobutadiene (TCBD) lower the LUMO level in BTDs 7–12, which results in a low HOMO–LUMO gap compared to acetylene linked BTDs 5 and 6. The BTDs with carbazole and single TCBD and DCNQ acceptors show better thermal stability.

Graphical abstract: Tuning of the HOMO–LUMO gap of donor-substituted symmetrical and unsymmetrical benzothiadiazoles

Supplementary files

Article information

Article type
Paper
Submitted
25 Mar 2014
Accepted
13 May 2014
First published
13 May 2014

Org. Biomol. Chem., 2014,12, 5448-5457

Tuning of the HOMO–LUMO gap of donor-substituted symmetrical and unsymmetrical benzothiadiazoles

R. Misra and P. Gautam, Org. Biomol. Chem., 2014, 12, 5448 DOI: 10.1039/C4OB00629A

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