Conformational study of C24 cyclic polyyne clusters

Polyynes were first synthesized before the year 1900, and isolated and characterized after 2000. Cyclic polyynes are of particular interest since possess a high order of symmetry. Furthermore, some studies reported special mechanical properties of the condensed polyyne bulks. The optimal size of polyynes to form rings has been previously investigated and was found to be 24 with a stable cluster of crossing four C24 cyclic polyynes. We investigated in this study the conformation of clusters of polyynes (nC24) by the pattern previously identified to stabilize the cluster. Clusters of 4C24, 10C24, 22C24, 46C24, and 94C24 were designed and subjected to energy minimization. The main finding is the preservation of the symmetry for the nC24 cluster with the increase of its size. The study revealed that 4C24, 10C24, and 22C24 preserve a high symmetry and the calculations suggest an excellent increasing of the cluster stability with the increase of the number of polyyne rings. A 22C24 derived cluster namely 28C24 was found as the one likely to limit the growth of the polyyne clusters. An approach to form nC24 clusters has been developed and implemented in FreePascal along with an algorithm able to minimize the geometry of the cluster as prestep in geometry optimization at the (Post‐)Hartree–Fock theory levels. A new simplified way to analyze large molecular ensembles was used by treating the cluster as the second level of the molecular topology. With this approach, stable 4C24, 10C24, 22C24, 46C24, 94C24, and 28C24 clusters are obtained.