Surface-assisted Dehydrogenative Homocoupling of Porphine Molecules
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- 作者：Alissa Wiengarten ; Knud Seufert ; Willi Auw盲rter ; David Ecija ; Katharina Diller ; Francesco Allegretti ; Felix Bischoff ; Sybille Fischer ; David A. Duncan ; Anthoula C. Papageorgiou ; Florian Klappenberger ; Robert G. Acres ; Thien H. Ngo ; Johannes V. Barth
- 刊名：Journal of the American Chemical Society
- 出版年：2014
- 出版时间：July 2, 2014
- 年：2014
- 卷：136
- 期：26
- 页码：9346-9354
- 全文大小：465K
- ISSN：1520-5126
文摘
The templated synthesis of porphyrin dimers, oligomers, and tapes has recently attracted considerable interest. Here, we introduce a clean, temperature-induced covalent dehydrogenative coupling mechanism between unsubstituted free-base porphine units yielding dimers, trimers, and larger oligomers directly on a Ag(111) support under ultrahigh-vacuum conditions. Our multitechnique approach, including scanning tunneling microscopy, near-edge X-ray absorption fine structure and photoelectron spectroscopy complemented by theoretical modeling, allows a comprehensive characterization of the resulting nanostructures and sheds light on the coupling mechanism. We identify distinct coupling motifs and report a decrease of the electronic gap and a modification of the frontier orbitals directly associated with the formation of triply fused dimeric species. This new on-surface homocoupling protocol yields covalent porphyrin nanostructures addressable with submolecular resolution and provides prospective model systems towards the exploration of extended oligomers with tailored chemical and physical properties.