Highly NIR-II luminescent erbium porphyrinoids

Abstract

Erbium (Er[Formula: see text] ion exhibits efficient broadband emission at 1.53 [Formula: see text]m (4f optical transition 4I13/2 [Formula: see text] 4I15/2), which is promising to achieve better clarity and deeper penetration depth for biological imaging. However, because of the relatively low luminescent level (4I[Formula: see text], ca. 6500 cm[Formula: see text] and the tendency of being facile to be quenched by high-energy oscillators such as N-H, C-H, or O-H groups, achieving small molecular Er complexes with intense NIR-II luminescence has remained a challenge. In this work, a series of Er[Formula: see text] complexes of porphyrinoids and [Formula: see text]-perhalogenated derivatives caped with auxiliary deuterated Kläui ligands were prepared, namely X-1-Er, X-2-Er and X-cis/trans-3-Er (X = H, F, Cl, Br). Interestingly, most of the [Formula: see text]-perhalogenated Er complexes displayed high overall quantum yields ([Formula: see text] 0.1% in CH2Cl2 and CD2Cl2) and long lifetimes ([Formula: see text] 8 [Formula: see text]s in CH2Cl2 and 11 [Formula: see text]s in CD2Cl2).