Two cyclic carbaporphyrin arrays (trimer 6 and tetramer 7) were synthesized from a dibrominated carbaporphyrin precursor (5) via a one-pot Yamamoto-type coupling. Single-crystal X-ray diffraction analyses revealed that 6 and 7 contain three and four covalently linked carbaporphyrin (formally dicarbacorrole) units, respectively. Trimer 6 adopts a roughly planar conformation and tetramer 7 adopts an up-and-down zig-zag conformation. Both 6 and 7 contain a [n]cyclo-meta-phenylene ([n]CMP) core, namely, - and CMP for 6 and 7, respectively. Transient absorption (TA) anisotropy and pump-power-dependent excited-state decay studies provided evidence for excitation energy transfer (EET) within both trimer 6 and tetramer 7. The exciton energy hopping (EEH) times were estimated to be 18 and 35 ps for 6 and 7, respectively, as inferred from pump-power-dependent TA measurements. Since the center-to-center distances between adjacent carbaporphyrin units are similar in 6 and 7, the different EEH times are attributed to differences in the orientation of the transition dipoles in these two congeneric arrays. The orientation factor κ2, the key parameter defining the Förster resonance energy transfer efficiency, was calculated to be 2.15 and 1.03 for 6 and 7, respectively, a finding that supports the shorter excitation energy hopping time seen in the case of trimer 6. To our knowledge, this is the first time that covalently linked cyclic carbaporphyrin arrays were synthesized using a single carbaporphyrin as the starting point and that EET between carbaporphyrin subunits constrained within a well-defined polycyclic framework has been correlated with structural differences.
|Number of pages||8|
|Journal||Journal of the American Chemical Society|
|Publication status||Published - 2023 Feb 8|
Bibliographical noteFunding Information:
The work at Beijing Normal University (BNU) was supported by startup funding (Grant 312232114 to X.-S.K.). The work at Yonsei University was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean Government (MSIT) (no. 2020R1A5A1019141). The quantum mechanical calculations were performed with the supercomputing resources of the Korea Institute of Science and Technology Information. The work in Austin was supported by the Robert A. Welch Foundation (F-0018 to J.L.S.). We would like to thank Prof. Guofu Zi for his help with the X-ray data collection.
© 2023 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry