TY - JOUR
T1 - Control of chromophore symmetry by positional isomerism of peripheral substituents
AU - Shimizu, Soji
AU - Haseba, Yu
AU - Yamazaki, Mariko
AU - Kumazawa, Genji
AU - Kobayashi, Nagao
PY - 2014/4/14
Y1 - 2014/4/14
N2 - The first example of the control of porphyrinoid chromophore symmetry based on the positional isomerism of peripheral substituents has been achieved by preparing tetraazaporphyrins (TAPs) with C4h, D2h, C 2v, and Cs symmetry due to the relative arrangement of peripheral tert-butylamino and cyano groups as push and pull substituents, respectively. The four structural isomers were successfully isolated and characterized by 1H NMR spectroscopy and X-ray crystallography. The band morphology in the Q-band region varies depending on the molecular symmetry due to the significant perturbation introduced into the chromophore by the push and pull substituents. The C4h and C2v isomers exhibit a single Q band, whereas the Q bands of the D2h and Cs isomers show a marked splitting. The magnetic circular dichroism spectra indicate that the push-pull TAPs retain the properties of the 16-membered 18π-electron perimeter generally observed for porphyrinoids. Theoretical calculations have demonstrated that the perturbation introduced by the substituents lowers the D4h symmetry of the parent TAP π-conjugated system, and this results in significant spectral changes. A novel approach to the fine-tuning of the spectral properties of porphyrinoids based on changes in the chromophore symmetry is described. Symmetry control: Control of porphyrinoid chromophore symmetry based on the positional isomerism of peripheral substituents has been achieved by preparing tetraazaporphyrins (TAPs) with C4h, D2h, C2v, and Cs symmetry as a result of the relative arrangement of peripheral substituents (see figure). A new approach to the fine-tuning of the spectral properties of porphyrinoids based on changes in the chromophore symmetry is described.
AB - The first example of the control of porphyrinoid chromophore symmetry based on the positional isomerism of peripheral substituents has been achieved by preparing tetraazaporphyrins (TAPs) with C4h, D2h, C 2v, and Cs symmetry due to the relative arrangement of peripheral tert-butylamino and cyano groups as push and pull substituents, respectively. The four structural isomers were successfully isolated and characterized by 1H NMR spectroscopy and X-ray crystallography. The band morphology in the Q-band region varies depending on the molecular symmetry due to the significant perturbation introduced into the chromophore by the push and pull substituents. The C4h and C2v isomers exhibit a single Q band, whereas the Q bands of the D2h and Cs isomers show a marked splitting. The magnetic circular dichroism spectra indicate that the push-pull TAPs retain the properties of the 16-membered 18π-electron perimeter generally observed for porphyrinoids. Theoretical calculations have demonstrated that the perturbation introduced by the substituents lowers the D4h symmetry of the parent TAP π-conjugated system, and this results in significant spectral changes. A novel approach to the fine-tuning of the spectral properties of porphyrinoids based on changes in the chromophore symmetry is described. Symmetry control: Control of porphyrinoid chromophore symmetry based on the positional isomerism of peripheral substituents has been achieved by preparing tetraazaporphyrins (TAPs) with C4h, D2h, C2v, and Cs symmetry as a result of the relative arrangement of peripheral substituents (see figure). A new approach to the fine-tuning of the spectral properties of porphyrinoids based on changes in the chromophore symmetry is described.
KW - UV/Vis spectroscopy
KW - chromophores
KW - porphyrinoids
KW - positional isomerism
KW - substituent effects
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U2 - 10.1002/chem.201304043
DO - 10.1002/chem.201304043
M3 - Article
AN - SCOPUS:84898908805
VL - 20
SP - 4822
EP - 4828
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
SN - 0947-6539
IS - 16
ER -