Does the Presence of a Bond Path Really Mean Interatomic Stabilization? The Case of the Ng@Superphane (Ng = He, Ne, Ar, and Kr) Endohedral Complexes

Using a fairly structurally flexible and, therefore, very suitable for this type of research, superphane molecule, we demonstrate that the inclusion of a noble gas atom (Ng = He, Ne, Ar, and Kr) inside it and, thus, the formation of the Ng@superphane endohedral complex, leads to its ‘swelling’. Positive values of both the binding and strain energies prove that encapsulation and in turn ‘swelling’ of the superphane molecule is energetically unfavorable and that the Ng⋯C interactions in the interior of the cage are destabilizing, i.e., repulsive. Additionally, negative Mayer Bond Orders indicate the antibonding nature of Ng⋯C contacts. This result in combination with the observed Ng⋯C bond paths shows that the presence of a bond path in the molecular graph does not necessarily prove interatomic stabilization. It is shown that the obtained conclusions do not depend on the computational methodology, i.e., the method and the basis set used. However, on the contrary, the number of bond paths may depend on the methodology. This is yet another disadvantageous finding that does not favor the treatment of bond paths on molecular graphs as indicators of chemical bonds. The Kr@superphane endohedral complex features one of the longest C–C bonds ever reported (1.753 Å).

Possibility of using fullerene C240 as the carrier of steroid hormones

Fullerene molecules are created entirely of carbon and form orbicular or ellipsoidal cage shape similar to a hollow tube. The derivatives of fullerenes are classified into the following categories according to their functionalization: endohedral fullerenes with active molecules residing inside the carbon cage, exohedral with wide variety of both inorganic and organic groups existing outside and connected to the fullerenes’ exterior and heterofullerenes when one or more carbon atoms that form the fullerene carbon cage are replaced by a non-carbon atom, i.e. a heteroatom. Fullerene C240belongs to the family of giant fullerenes and is characterized by a greater stability than that of the well-known fullerene C60. This has been proved by observing an increased formation heat that accompanied the decreasing of the carbon cage size.In order to determine the fullerene C240 ability to transport the steroid hormones: estradiol, progesterone, androsterone and their basic structures: estrone, androstane and pregnane, the following parameters, inter alia, have been calculated: energies of stabilization, interaction and deformation of each endohedral complex. The calculations for all chosen structures were carried out with the use of the molecular modeling technique. Based on all available studies, it can be stated that fullerene C240 could be a solution for problems faced by medicine and pharmacy.

Possibility of using fullerene C240 as the carrier of steroid hormones

Fullerene molecules are created entirely of carbon and form orbicular or ellipsoidal cage shape similar to a hollow tube. The derivatives of fullerenes are classified into the following categories according to their functionalization: endohedral fullerenes with active molecules residing inside the carbon cage, exohedral with wide variety of both inorganic and organic groups existing outside and connected to the fullerenes’ exterior and heterofullerenes when one or more carbon atoms that form the fullerene carbon cage are replaced by a non-carbon atom, i.e. a heteroatom. Fullerene C240belongs to the family of giant fullerenes and is characterized by a greater stability than that of the well-known fullerene C60. This has been proved by observing an increased formation heat that accompanied the decreasing of the carbon cage size.In order to determine the fullerene C240 ability to transport the steroid hormones: estradiol, progesterone, androsterone and their basic structures: estrone, androstane and pregnane, the following parameters, inter alia, have been calculated: energies of stabilization, interaction and deformation of each endohedral complex. The calculations for all chosen structures were carried out with the use of the molecular modeling technique. Based on all available studies, it can be stated that fullerene C240 could be a solution for problems faced by medicine and pharmacy.