Cubic Octa-Carbon: Quantum-Chemical Design of Molecular Structure and Potential Way of Its Synthesis from Cubane.

Denis V Chachkov,Oleg V Mikhailov

doi:10.3390/ijms222112067

Abstract

Quantum-chemical calculation of most important parameters of molecular and electronic structures of octa-carbon C8 having cubic form (bond lengths, bond and torsion angles) using CCSD(T)/QZVP and DFT B3PW91/QZVP methods, has been carried out. NBO analysis data and HOMO/LUMO images for this compound are presented, too. Good agreement was found between the structural data obtained using the above two quantum-chemical methods and, also, with corresponding experimental data. Also, the standard thermodynamic parameters of formation of cubic C8 considered here, and namely standard enthalpy ΔfH0(298K), entropy Sf0(298K) and Gibbs’ energy ΔfG0(298K) of formation for this compound were calculated. By using this data, a theoretically possible variant of the synthesis of this compound by dehydrogenation of cubane C8H8 is considered, and the thermodynamic characteristics of each of the four stages of this process have been calculated. It is noted that each of the four stages of this process is characterized by a very high (about 500 kJ/mol) enthalpy of activation, as a result of that, for their realization within a sufficiently short time, the use of appropriate catalysts is necessary.

Highlights

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The quantum-chemical calculation of molecular structures of octa-carbon molecule having C8 composition was carried out using the coupled-cluster method (CCSD)(T)/QZVP method, combining the having C8 composition was carried out using the CCSD(T)/QZVP method, combining the common QZVP extended quadruple zeta split-valence basis set [33,34] and the coupled common QZVP extended quadruple zeta split-valence basis set [33,34] and the coupled cluster method, using both single and double substitutions, including triple excitation cluster method, using both single and double substitutions, including triple excitation non-iterative CCSD(T) [35,36,37,38]
For comparison, we calculated the parameters of the molecular structure of with this, for comparison, we calculated the parameters of the molecular structure

Summary

Introduction

Alone, among all chemical elements is known to be the only one whose atoms’ number of valence orbitals, number of valence electrons and maximum possible coordination numbers of each coincide with each other Due to this unique circumstance, it can form long homochain structures containing many hundreds and thousands of atoms. One of the most interesting modifications of this type is octa-carbon C8 , for the molecular structure of which the cubic form seems to be the most probable This substance can serve as a very useful precursor for the organic synthesis of a number of cubane derivatives, for example, polycyclic framework compounds containing articulated cubane fragments; seems to be very promising for use in a number of branches of technology, in particular, as “building blocks” for new nanodevices, Int. J. Sci. 2021, 22, 12067 for use in a number of branches of technology, in particular, as “building blocks” for new nanodevices, which, in turn, can be implemented to create digital memory systems; the which, inthe turn, can beofimplemented createphysicochemical digital memory processes systems; the possibility of using it in creation catalysts for to various is possibility of using it in theof creation catalysts for varioushas physicochemical processes is not excluded

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