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Synthesis of <i>trans</i>-A<sub>2</sub>B<sub>2</sub>-Porphyrins Bearing Phenylethynyl Substituents
Nowak-Kró,l, Agnieszka,Koszarna, Beata,Yoo, Su Yeon,Chromiń,ski, Jan,Wȩ,cławski, Marek K.,Lee, Chang-Hee,Gryko, Daniel T. American Chemical Society 2011 Journal of organic chemistry Vol.76 No.8
<P>Efficient and convenient conditions for the preparation of <I>trans</I>-A<SUB>2</SUB>B<SUB>2</SUB>-porphyrins bearing two phenylethynyl moieties directly from phenylpropargyl aldehydes and dipyrromethanes of diversified lipophilicity and reactivity have been developed. This new procedure allows the preparation of a library of porphyrins of this architecture with a wide range of substituents. Thanks to the identification of the reagent solubility as one of the key factors influencing the yield of the porphyrinogens, we were able to improve yields to ca. 30%. The scope and limitations of two sets of conditions have been explored. The methodological advantage of this approach is its straightforward access to building blocks and the formation of the porphyrin core in the last step without the need for deprotection of the triple bond or bromination and consecutive coupling reaction, which often demands copper salts to proceed smoothly, especially with electron-deficient alkyne partners. Therefore, it prevents undesired copper porphyrin formation, as well as the need for utilizing expensive alkynes. A two-step method for the preparation of phenylpropargyl aldehydes has also been refined.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/joceah/2011/joceah.2011.76.issue-8/jo1025578/production/images/medium/jo-2010-025578_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jo1025578'>ACS Electronic Supporting Info</A></P>
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Kaufmann, Christina,Kim, Woojae,Nowak-Kró,l, Agnieszka,Hong, Yongseok,Kim, Dongho,Wü,rthner, Frank American Chemical Society 2018 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.140 No.12
<P>An adequately designed, bay-tethered perylene bisimide (PBI) dimer <B>Bis-PBI</B> was synthesized by Pd/Cu-catalyzed Glaser-type oxidative homocoupling of the respective PBI building block. This newly synthesized PBI dimer self-assembles exclusively and with high binding constants of up to 10<SUP>6</SUP> M<SUP>-1</SUP> into a discrete π-stack of four chromophores. Steady-state absorption and emission spectra show the signatures of H-type excitonic coupling among the dye units. Broadband fluorescence upconversion spectroscopy (FLUPS) reveals an ultrafast dynamics in the optically excited state. An initially coherent Frenkel exciton state that is delocalized over the whole quadruple stack rapidly (τ = ∼200 fs) loses its coherence and relaxes into an excimer state. Comparison with Frenkel exciton dynamics in PBI dimeric and oligomeric H-aggregates demonstrates that in the quadruple stack coherent exciton propagation is absent due to its short length of aggregates, thereby it has only one relaxation pathway to the excimer state. Furthermore, the absence of pump-power dependence in transient absorption experiments suggests that multiexciton cannot be generated in the quadruple stack, which is in line with time-resolved fluorescence measurements.</P> [FIG OMISSION]</BR>
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