Photoinduced Charge-Transfer Association of Tetracyanoquinodimethane with Aminobiphenyls
TL;DRAbstract
The molecular association of acceptors with electron donors is studied in the highly-polar solvent <TEX>$CH_3CN$</TEX>. Tetracyanoquinodimethane (TCNQ) forms a stable charge-transfer complex with donor molecules such as 4- aminobiphenyl (4-AB), benzidine (BD) and 2-aminobiphenyl (2-AB) with high association constants. The complexes of TCNQ with 4-AB or BD show new absorption bands at around 800 and 500 nm, which can be identified as reduced <TEX>$TCNQ^{{\bullet}-}$</TEX> and <TEX>$TCNQ^{2-}$</TEX> species, respectively. These bands grow quickly upon photoirradiation, implying that the charge-transfer complexes are easily formed in an excited state. Conversely, a small spectral manifestation of the charge transfer was observed in the case of 2-AB complex. It is demonstrated that the structural orientation between the geminate ion pairs could play an important role in building a stable complex.
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The molecular association of acceptors with electron donors is studied in the highly-polar solvent <TEX>$CH_3CN$</TEX>. Tetracyanoquinodimethane (TCNQ) forms a stable charge-transfer complex with donor molecules such as 4- aminobiphenyl (4-AB), benzidine (BD) and 2-aminobiphenyl (2-AB) with high association constants. The complexes of TCNQ with 4-AB or BD show new absorption bands at around 800 and 500 nm, which can be identified as reduced <TEX>$TCNQ^{{\bullet}-}$</TEX> and <TEX>$TCNQ^{2-}$</TEX> species, respectively. These bands grow quickly upon photoirradiation, implying that the charge-transfer complexes are easily formed in an excited state. Conversely, a small spectral manifestation of the charge transfer was observed in the case of 2-AB complex. It is demonstrated that the structural orientation between the geminate ion pairs could play an important role in building a stable complex.
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