LINEARLY EXTENDED PYRYLIUM SALTS (LEPS) AND LINEARLY EXTENDED THIOPYRYLIUM SALTS (LETS) AS ORGANIC SEMICONDUCTORS
type: CreativeWork
description: Research focused on the development of a new class of n-type organic semiconductors called linearly extended pyrylium salts (LEPS) and linearly extended thiopyrylium salts (LETS). While a lot of progress has been made on p-type organic semiconductors over the last decade, less attention has been paid to n-type organic semiconductors. Pyrylium and thiopyrylium cations are aromatic structures akin to benzene but with one methine carbon (CH) replaced by either a positively charged oxygen or sulfur atom, respectively. This makes these aromatic π-systems very electron-deficient. With pentacene-like backbones, LEPS and LETS compounds combine linearly conjugated π-systems of acenes with the highly electron-deficient nature of pyrylium and thiopyrylium salts. The LEPS and LETS compounds described here were synthesized efficiently using new reactions. Their properties were calculated through high-level computation and studied experimentally by UV-Vis-NIR spectroscopy, cyclic voltammetry, single crystal X-ray diffraction, ESR and variable temperature NMR (VT-NMR) experiments. The LEPS and LETS compounds described here show moderate to high solubilities in organic solvents like acetonitrile and dichloromethane. While they are resistant to oxidation due to their electron-deficient backbones, they are sensitive to nucleophiles like water. LEPS and LETS compounds with a mesityl or 2’,6’-dimethylphenyl substituent have much higher resistance to moisture compared to other LEPS and LETS compounds due to shielding of the reactive site via the o-methyl groups of the phenyl substituents. LEPS and LETS compounds have broad absorptions in the UV-Vis-NIR region and possess small HOMO-LUMO gaps close to that of pentacene. They also exhibited reversible electrochemical behavior including remarkably easy reductions. Single crystal X-ray diffraction studies show that LEPS and LETS compounds form intermolecular face-to-face π-π stacking thin films. Broad and indiscernible NMR signals in the ar…
abstract: Research focused on the development of a new class of n-type organic semiconductors called linearly extended pyrylium salts (LEPS) and linearly extended thiopyrylium salts (LETS). While a lot of progress has been made on p-type organic semiconductors over the last decade, less attention has been paid to n-type organic semiconductors. Pyrylium and thiopyrylium cations are aromatic structures akin to benzene but with one methine carbon (CH) replaced by either a positively charged oxygen or sulfur atom, respectively. This makes these aromatic π-systems very electron-deficient. With pentacene-like backbones, LEPS and LETS compounds combine linearly conjugated π-systems of acenes with the highly electron-deficient nature of pyrylium and thiopyrylium salts. The LEPS and LETS compounds described here were synthesized efficiently using new reactions. Their properties were calculated through high-level computation and studied experimentally by UV-Vis-NIR spectroscopy, cyclic voltammetry, single crystal X-ray diffraction, ESR and variable temperature NMR (VT-NMR) experiments. The LEPS and LETS compounds described here show moderate to high solubilities in organic solvents like acetonitrile and dichloromethane. While they are resistant to oxidation due to their electron-deficient backbones, they are sensitive to nucleophiles like water. LEPS and LETS compounds with a mesityl or 2’,6’-dimethylphenyl substituent have much higher resistance to moisture compared to other LEPS and LETS compounds due to shielding of the reactive site via the o-methyl groups of the phenyl substituents. LEPS and LETS compounds have broad absorptions in the UV-Vis-NIR region and possess small HOMO-LUMO gaps close to that of pentacene. They also exhibited reversible electrochemical behavior including remarkably easy reductions. Single crystal X-ray diffraction studies show that LEPS and LETS compounds form intermolecular face-to-face π-π stacking thin films. Broad and indiscernible NMR signals in the ar…
author: Zhao, Jianyu
keywords: Chemistry
date published: 2016-01-01T08:00:00Z
date modified: 2026-07-24T05:23:15Z
provider: University of New Hampshire
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of New Hampshire