Precise Internal Postsynthetic Oxygen-Doping of Metallonanographenes

Heteroatom doping has the potential to alter the electronic
structure
and optical properties of nanographenes, thereby expanding the scope
of their utility in various applications. In this work we demonstrate
a strategy to introduce an oxygen atom directly and precisely into
backbone of the already formed metal-nanographene complexes. Treating
metal-nanographene complexes HBCP-M (M = Cu, Ag, Au)
with Davis’ oxaziridine produces oxygen-doped complexes HBCP-OM (M = Cu, Ag, Au) with adj-CONN coordination
in one step. Compared with original metal complexes, the electronic
structure, photophysical properties and molecular conformations of HBCP-OM show sharp changes, as indicated by steady and fs-transient
absorption (TA) spectroscopies, DFT calculations and crystal structure
analysis. Moreover, the reduction of coordination cavity of HBCP-OM due to oxygen insertion affects the metal–ligand
interaction. This leads that HBCP-OCu, possessing a relatively
small Cu(III) cation, exhibits an extended near-infrared (NIR) absorption
beyond 1300 nm that is not observed in HBCP-OAg and HBCP-OAu.