5,10-A2B2-type meso-substituted porphyrins--a unique class of porphyrins with a realigned dipole moment |
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Authors: | Senge Mathias O Ryppa Claudia Fazekas Marijana Zawadzka Monika Dahms Katja |
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Institution: | SFI Tetrapyrrole Laboratory, School of Chemistry, Trinity College Dublin, Dublin 2, Ireland. sengem@tcd.ie |
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Abstract: | Current applications in porphyrin chemistry require the use of unsymmetrically substituted porphyrins. Many current industrial interests in optics and biomedicine require systems with either push-pull (electron-donating and -withdrawing groups) or amphiphilic systems (hydrophobic and hydrophilic groups). In this context we present the class of 5,10-A(2)B(2)-type porphyrins for which two different substituents are positioned in diagonally opposite meso positions. Thus, the intramolecular dipole moment in these tetrapyrroles is positioned along a β-β vector passing through two pyrrole rings. This is opposite to the situation of the frequently used 5,15-A(2)BC porphyrins for which the dipole moment is oriented along a meso-meso axis. We have elaborated syntheses of the 5,10-A(2)B(2) porphyrins by using transition-metal-catalyzed transformations of 5,10-A(2) porphyrins or direct substitutions reactions thereof; this gives the target molecules in 22-77% overall yields. The compounds exhibit interesting structural, spectroscopic, and optical features and can serve as building blocks for new porphyrin arrays and applications. |
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Keywords: | macrocycles nitrogen heterocycles nonlinear optics porphyrinoids tetrapyrroles |
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