TY - JOUR
T1 - A 24-crown-8 bearing naphthalene and naphthoquinone chromophores
AU - Hogan, C.F.
AU - Hutchison, J.A.
AU - Ghiggino, K.P.
AU - Langford, S.J.
AU - Latter, Melissa
AU - Lau, V.L.
AU - Murali, VV
PY - 2005
Y1 - 2005
N2 - The novel bichromophoric crown ether N24C8NQ 3 has been synthesised in good yield by the conjugate addition of a polyether diol 1 to 2,3-dichloronaphthoquinone in the presence of base. Crown ether 3 was further reacted with malononitrile in the presence of TiCl4 to prepare the tetracyano-1,4-napthoquinodimethane derivative 4. Electrochemical and photophysical studies on 3 and 4 have been undertaken. The addition of alkali metal cations to the crown ether 3 causes significant changes in the first and second reduction potentials of the naphthoquinone (NQ) chromophore. In the case of the first process, a correlation exists between the reversible potential and cation '' fit ''. Crown ethers 3 and 4 exhibit red-shifted absorption bands attributed to intramolecular charge transfer interactions between the chromophores. Fluorescence from the naphthalene chromophore in 3 and 4 is quenched substantially (> 80%) as compared to the model 5. The weak nature of the complex between 3 and the guest dibenzylammonium hexafluorophosphate (K-a < 50 M-1) was compared to another electron deficient crown, tetranitrodibenzo-24-crown-8, the results of which suggest that the oxygens within the crown ether macrocycle, bearing electron withdrawing chromophores, play an important role in stabilising such pseudorotaxane complexes.
AB - The novel bichromophoric crown ether N24C8NQ 3 has been synthesised in good yield by the conjugate addition of a polyether diol 1 to 2,3-dichloronaphthoquinone in the presence of base. Crown ether 3 was further reacted with malononitrile in the presence of TiCl4 to prepare the tetracyano-1,4-napthoquinodimethane derivative 4. Electrochemical and photophysical studies on 3 and 4 have been undertaken. The addition of alkali metal cations to the crown ether 3 causes significant changes in the first and second reduction potentials of the naphthoquinone (NQ) chromophore. In the case of the first process, a correlation exists between the reversible potential and cation '' fit ''. Crown ethers 3 and 4 exhibit red-shifted absorption bands attributed to intramolecular charge transfer interactions between the chromophores. Fluorescence from the naphthalene chromophore in 3 and 4 is quenched substantially (> 80%) as compared to the model 5. The weak nature of the complex between 3 and the guest dibenzylammonium hexafluorophosphate (K-a < 50 M-1) was compared to another electron deficient crown, tetranitrodibenzo-24-crown-8, the results of which suggest that the oxygens within the crown ether macrocycle, bearing electron withdrawing chromophores, play an important role in stabilising such pseudorotaxane complexes.
U2 - 10.1080/10610270500297056
DO - 10.1080/10610270500297056
M3 - Article
SN - 1061-0278
VL - 17
SP - 513
EP - 519
JO - Supramolecular Chemistry
JF - Supramolecular Chemistry
IS - 7
ER -