Doping a Nanographene with a Formal Ni ^IV Center

A new nanographene ligand (<b>2</b>) was synthesized by incorporating a <i>meso</i>-oxo substituted carbaporphyrin(1.1.1.0) unit into the hexa-peri-hexabenzocoronene (HBC) backbone. Compound <b>2</b> features an adj-CCNN dianionic core and coordinates with a Ni^II cation to form organo-Ni^II complex <b>3</b>. Notably, complex <b>3</b> was readily oxidized to formal Ni^IV species <b>4</b> after treating with CuCl₂, as confirmed with X-ray photoelectron spectroscopy (XPS) and theoretical calculations. Complex <b>4</b> showed substantial stability in the solid state but reacted rapidly with water at room temperature to yield inner oxygen-inserted complex <b>5</b>. Demetalation of complex <b>5</b> with trifluoroacetic acid afforded an inner oxygen doped free base <b>6</b> containing a quinonoid-type ring. These new nanographene-containing compounds <b>2</b>-<b>6</b> were thoroughly characterized and studied using NMR spectroscopy, single-crystal X-ray diffraction analysis, UV-vis-NIR spectroscopy, and cyclic voltammetry as well as density functional theory (DFT) calculations. To the best of our knowledge, complex <b>4</b> represents the first example of a highly reactive Ni^IV nanographene complexes. The present work advances the development of metal doping chemistry of nanographenes, which in turn provide new access to postsynthetic heteroatom doping within the carbon networks of nanographenes.