The mysterious blue emission around 440 nm in carbonyl-based aliphatic clusteroluminogens

Nonconjugated and nonaromatic heteroatoms-based structures are discovered with visible emission at clustering state, namely clusteroluminogens (CLgens). Such kind of luminescence is termed clusteroluminescence (CL) which could not be explained by the traditional molecular photophysical theories constructed upon through-bond conjugation, so investigation on CL has great theoretical significance. In this perspective, we summarize a general feature for C=O bond-based CLgens that a magic blue emission around 440 nm widely exists in different systems such as natural protein, polyamide, polyester, and polyketone. Comprehensive analysis of the reported works suggests that the (n, pi*) transition of carbonyl group most likely generates the 440 nm CL. This perspective aims to draw researchers' attention to the common features and general photophysical theories of CL, and shine new light on aggregate photophysics.

Automated summary

Nonconjugated and nonaromatic heteroatoms-based structures have been found to exhibit visible emission at the clustering state, known as clusteroluminogens. The origin of this clusteroluminescence (CL) cannot be explained by traditional molecular photophysical theories, making investigation on CL significant. A common feature of C=O bond-based clusteroluminogens is the blue emission around 440 nm, which has been observed in various systems such as natural proteins, polyamide, polyester, and polyketone. The (n, pi*) transition of carbonyl group is suggested to be the most likely contributor to the 440 nm CL emission.