Phenalenyl-Fused Nickel(II) Norcorroles with Precisely Oxygen-Edited Skeletons: Tuning Aromaticity and Site-Selective Reactivity.

Abstract

Aromaticity governs molecular stability, electronic structure, and reactivity, yet its atomically precise control on surfaces remains challenging. Here, we synthesize phenalenyl-fused nickel(II) norcorrole and oxygen-edited porphyrinoids on Au(111) via surface-assisted cyclodehydrogenation of rationally designed precursors. Stepwise insertion of one or two oxygen atoms at pyrrole-pyrrole linkages yields <b>PLY-Nor</b>, <b>PLY-OxCor</b>, and <b>PLY-2OxPor</b>, enabling systematic modulation of their electronic structures and aromatic character. Scanning probe microscopy resolves their atomic backbones, while d<i>I</i>/d<i>V</i> spectroscopy reveals a progressive widening of the frontier-orbital gap with oxygen incorporation. Density functional theory calculations and complementary aromaticity analyses confirm an evolution from a fragmented aromatic framework toward a more delocalized aromatic character. Moreover, oxygen skeletal editing redistributes frontier electron density at the molecular edge, leading to distinct dimerization selectivity. Together, these findings demonstrate atomic skeletal editing as a powerful strategy for engineering of electronic structure, aromaticity, and on-surface reactivity with atomic precision in organic molecules and nanostructures.