In the past few years, a series of progresses (Nat. Chem., 2013, 5, 698; Nat. Commun., 2014, 5, 3265; Angew. Chem. Int. Ed., 2014, 53, 6232; Angew. Chem. Int. Ed., 2015, 54, 3102) on the project of metallapentalyne have been published our group. Recently, we found that two anti-aromatic systems could be stabilized by one metal fragment simultaneously. This research has been published on Angew. Chem. Int. Ed. (2015, 54, 6181-6185) entitled “Stabilizing Two Classical Antiaromatic Frameworks: Demonstration of Photoacoustic Imaging and the Photothermal Effect in Metalla-aromatics”. In addition, due to the excellent evaluations from the reviewers, this article has been selected as the cover story of issue 21.

   Anti-aromatic compounds with 4n π electrons are difficult to prepare and isolate because of their high instability. Recently, we incorporated a transition metal into an anti-aromatic framework, leading to the first isolation of metallapentalynes (Nature Chemistry, 2013, 5, 597) and metallapentalenes (Nature Communications, 2014, 5, 3265). However, such stabilization resulting from a metal fragment has been limited to single anti-aromatic species in all previous cases. In this project, we overcomed a greater challenge and reported the first example of the simultaneous stabilization of two anti-aromatic frameworks (cyclobutadiene and pentalene) by one metal fragment, just as “Killing two birds with one stone”. In addition, this is also the first example of a [2+2] cycloaddition reaction between a late transition metal carbyne with alkynes, a key process for alkyne metathesis, which allows for the exploration of the possibility of using late transition metal carbyne complexes as catalysts for alkyne metathesis.

    On the other hand, calculations done by the group of Jun Zhu revealed that the metal fragment significantly reduces the anti-aromaticity in cyclobutadiene and pentalene simultaneously, leading to air- and moisture-stable products. Unique structures lead to unique properties. In cooperation with Prof. Gang Liu in School of Public Health of Xiamen University, we found that these novel metalla-aromatics show broad absorption in the ultraviolet-visible-near-infrared region, thus resulting in significant photoacoustic and photothermal effect of metalla-aromatics for the first time. These results will encourage further efforts to the exploration of organometallics for photoacoustic image-guided photothermal therapy.

    This research was supported by the National Basic Research Program of China, the National Science Foundation of China and the Program for New Century Excellent Talents in University.

    URL link for article: http://onlinelibrary.wiley.com/doi/10.1002/anie.201501349/abstract
    URL link for cover: http://onlinelibrary.wiley.com/doi/10.1002/anie.201503578/epdf