Developing strong NIR absorption materials through linear planar π-conjugated cyclopalladated complex dimers†
a
and
Jiangbin
Xia
*ab
Abstract
Near-infrared absorption metal complexes (NIRMCs) have been traditionally associated with the π-expanded macrocycle structure. However, macrocyclic ligands suitable for NIRMCs require a laborious synthetic route, and are a limited few. Herein, we report a kind of NIRMC based on linear large planar π-conjugated cyclopalladated dimers, which can be obtained by a facile base-induced dimerization of corresponding monomers. These dimers show an intense absorption in the NIR region with ε770 nm = 2.5 × 105 cm−1 M−1, and display a fluorescence emission peak at ca. 910 nm. Quinoid thiophene methine (QTM) and the cyclopalladated structure are speculated to be the key factors for their strong NIR absorption, which provides a different perspective of preparing NIR absorption metal complexes.
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