ner_tags: O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O
tokens: to study the reactions of carbon atoms with anthracene and coronene. In our computational study, we were mainly interested in the investigation of the pathways found previously for the reaction of carbon with benzene (Krasnokutski Huisken 2014c ) and naphthalene. Hence, we focused on the formation of seven-membered carbon rings. Our computations predict the barrierless reaction of carbon atoms with anthracene molecules and the possibility of a ring opening for all three aromatic cycles, i.e., the formation of seven-membered carbon rings in the center as well as on the sides of the molecule. Thus, the calculations reveal the possibility of the same reaction pathways as observed for benzene and naphthalene. This is in line with the experimental results obtained for benzene, naphthalene, and anthracene molecules. However, similar to the case of naphthalene, the carbon atom cannot be inserted into the CC bond shared by two aromatic rings. Figure 8 shows the molecular structures of the initial associative complexes between coronene and the carbon atom. It can be seen from this figure that, similar to the cases of the other PAHs studied, the carbon atom lands on the top of the CC bonds. The binding of the carbon atom to the bonds of the central ring is the weakest, and increases when the carbon atom moves to the side of the coronene molecule. Similar to the previously studied PAH molecules, the carbon atom cannot be inserted into the CC bond shared by the two aromatic rings. Therefore, the formation of a seven-membered ring in the center of coronene is not possible. Such a structure was found to be a transition state, with negative binding energy of the carbon atom. The binding of the carbon atom to the coronene molecule was enhanced going from the initial triplet state to the singlet state of the system. The highest binding energy (186.2 kJ mol −1 ) was found for the carbon atom on top of the peripheral CC bonds in the singlet state. With a relatively small energy barrier, the carbon atom can be inserted into the peripheral CC bonds of the coronene molecule. In this case, the reaction pathway is the same as for the other molecules studied. However, in the case of coronene, there is a considerable increase in the number of CC bonds, which cannot be opened. Therefore, landing of carbon atoms on these sites would not lead to the formation of a seven-membered ring. Two of the four complexes shown in Figure 8 , namely complexes 1 and 2, have rather low binding energy. Moreover, the energy barrier for the formation of a seven-membered carbon ring was computed to be a little higher compared to the case of benzene and naphthalene molecules. Therefore, there is a higher chance that the initial associative complexes 3 and 4 could also be frozen inside the liquid helium droplets. This explains the results of the calorimetric measurements showing only low energy released in the reaction of carbon atoms with coronene molecules. Figure 8. Molecular