Pyrazino-tetracyanonaphthoquinodimethanes: sterically deformed electron acceptors affording zwitterionic radicals
摘要:
The X-ray analyses of the title electron acceptors (1) revealed their butterfly-shaped deformed geometry, which is not affected by the pyridyl group attached at 2-position of the pyrazino-TCNNQ skeleton. Small differences between the first and second reduction potentials (ca. 0.1 V) in pyrazino-TCNNQs show that their anion radicals (1(-.)) are prone to disproportionate into the neutral (1) and dianionic (1(2-)) species. The thermodynamically unstable anion radical species based on the pyrazino-TCNNQ skeleton could be isolated as inner salts upon electrochemical reduction of the derivatives having an N-methylpyridinium moiety at 2-position (2(+)). The zwitterionic open-shell species (2) constitute a novel class of radicals that exhibit semiconducting behavior as a single component thanks to the high electrochemical amphotericity. (C) 2004 Elsevier Ltd. All rights reserved.
Single-Component Organic Semiconductors Based on Novel Radicals that Exhibit Electrochemical Amphotericity: Preparation, Crystal Structures, and Solid-State Properties of N,N‘-Dicyanopyrazinonaphthoquinodiiminides Substituted with an N-Alkylpyridinium Unit
摘要:
N,N'-Dicyanonaphthoquinodiimines fused with a pyrazine ring 1 were prepared from the corresponding quinones 4. The new accepters 1 have a planar pi -system and undergo reversible two-stage 1e-reduction. Quaternization of the pyridyl substituent in 1d-f gave pyridinium derivatives 2d(+), 2e(+), and R-3(+), respectively, which are stronger accepters that undergo three-stage le-reduction. Upon electrochemical. reduction of these cations, novel radicals 2d(.) 2e(.), and R-3(.) were generated and isolated as stable solids. The molecular geometries determined by X-ray analysis indicated that these radicals adopt a zwitterionic structure, in which the unpaired electron is located on the quinodiimine unit but not on the pyridyl group. These novel radicals undergo facile and reversible 1e-oxidation as well as two-stage le-reduction. The observed amphotericity endows the radicals with electrical conductivities (10(-5) to 10(-9) S cm(-1)), and these thus represent a new motif for single-component organic semiconductors.
The X-ray analyses of the title electron acceptors (1) revealed their butterfly-shaped deformed geometry, which is not affected by the pyridyl group attached at 2-position of the pyrazino-TCNNQ skeleton. Small differences between the first and second reduction potentials (ca. 0.1 V) in pyrazino-TCNNQs show that their anion radicals (1(-.)) are prone to disproportionate into the neutral (1) and dianionic (1(2-)) species. The thermodynamically unstable anion radical species based on the pyrazino-TCNNQ skeleton could be isolated as inner salts upon electrochemical reduction of the derivatives having an N-methylpyridinium moiety at 2-position (2(+)). The zwitterionic open-shell species (2) constitute a novel class of radicals that exhibit semiconducting behavior as a single component thanks to the high electrochemical amphotericity. (C) 2004 Elsevier Ltd. All rights reserved.
Single-Component Organic Semiconductors Based on Novel Radicals that Exhibit Electrochemical Amphotericity: Preparation, Crystal Structures, and Solid-State Properties of <i>N,N</i><i>‘</i>-Dicyanopyrazinonaphthoquinodiiminides Substituted with an <i>N</i>-Alkylpyridinium Unit
N,N'-Dicyanonaphthoquinodiimines fused with a pyrazine ring 1 were prepared from the corresponding quinones 4. The new accepters 1 have a planar pi -system and undergo reversible two-stage 1e-reduction. Quaternization of the pyridyl substituent in 1d-f gave pyridinium derivatives 2d(+), 2e(+), and R-3(+), respectively, which are stronger accepters that undergo three-stage le-reduction. Upon electrochemical. reduction of these cations, novel radicals 2d(.) 2e(.), and R-3(.) were generated and isolated as stable solids. The molecular geometries determined by X-ray analysis indicated that these radicals adopt a zwitterionic structure, in which the unpaired electron is located on the quinodiimine unit but not on the pyridyl group. These novel radicals undergo facile and reversible 1e-oxidation as well as two-stage le-reduction. The observed amphotericity endows the radicals with electrical conductivities (10(-5) to 10(-9) S cm(-1)), and these thus represent a new motif for single-component organic semiconductors.