Planar\nand Curved π‑Extended Porphyrins\nby On-Surface Cyclodehydrogenation

Recent advancements\nin on-surface synthesis have enabled the reliable\nand predictable preparation of atomically precise low-dimensional\nmaterials with remarkable properties, which are often unattainable\nthrough traditional wet chemistry. Among these materials, porphyrins\nstand out as a particularly intriguing class of molecules, extensively\nstudied both in solution and on surfaces. Their appeal lies in the\nability to fine-tune their unique chemical and physical properties\nthrough central metal exchange or peripheral functionalization. However,\nthe synthesis of π-extended porphyrins featuring unsubstituted\nanthracenyl groups has remained elusive. Herein, we report an <i>in vacuo</i> temperature-controlled cyclodehydrogenation of\nbis- and tetraanthracenyl Zn(II) porphyrins on a gold(111) surface.\nBy gradually increasing the temperature, sequential dehydrogenation\nleads to the formation of fused anthracenyl porphyrin products. Notably,\nat high molecular coverage, the formation of bowl-shaped porphyrins\noccurs, along with transmetalation of Zn with Au. These findings open\nthe door to a variety of π-extended anthracenyl-containing porphyrin\nproducts via cyclodehydrogenation and transmetalation, offering significant\npotential in the fields of molecular (photo/electro)catalysis, (opto)electronics,\nand spintronics.