Exploration of Carbon Allotropes with Four-membered Ring Structures on Quantum Chemical Potential Energy Surfaces.

The existence of a new carbon allotrope family with four-membered rings as a key unit has been recently predicted with quantum chemical calculations. This family includes carbon allotropes in prism-, polymerized prism-, sheet-, tube-, and wavy-forms. An atypical bond property has been observed in this series of carbon structures, which differs from the typical sp3 , sp2 , and sp hybridizations. The lowest energy barrier from some of the equilibrium states of the carbon structures has been determined with the SHS-ADDF (scaled-hypersphere-search combined with the anharmonic downward distortion following) method within the GRRM software program package. The height of the barriers indicates that the well is deep enough for the carbon structures to exist. This class of carbon allotropes is expected to be energy-reservoirs with extra energy of 100-350 kJ mol-1 per one carbon atom. This article presents the structures, energies and reactivity of the carbon allotropes with four-membered ring structures as well as the background of the findings in the context of the global exploration of potential energy surfaces. © 2018 Wiley Periodicals, Inc.

Reply to the 'Comment on "Theoretical studies on a carbonaceous molecular bearing: association thermodynamics and dual-mode rolling dynamics"' by E. M. Cabaleiro-Lago, J. Rodriguez-Otero and A. Gil, Chem. Sci., 2016, 7, DOI: 10.1039/C5SC04676A.

We reply to the comments raised by Cabaleiro-Lago et al. on our article (H. Isobe et al., Chem. Sci., 2015, 6, 2746-2753). Here we appreciate the common views we share and welcome the clarity this gives, and we discuss and question some of their criticisms of the original piece and clarify our opinion in this area. The most important answer can be found in the equation, ΔG = ΔH - TΔS, derived from one of the best established fields in physics.

Theoretical studies on a carbonaceous molecular bearing: association thermodynamics and dual-mode rolling dynamics.

The thermodynamics and dynamics of a carbonaceous molecular bearing comprising a belt-persistent tubular molecule and a fullerene molecule have been investigated using density functional theory (DFT). Among ten representative methods, two DFT methods afforded an association energy that reasonably reproduced the experimental enthalpy of -12.5 kcal mol-1 at the unique curved π-interface. The dynamics of the molecular bearing, which was assembled solely with van der Waals interactions, exhibited small energy barriers with maximum values of 2-3 kcal mol-1 for the rolling motions. The dynamic motions responded sensitively to the steric environment and resulted in two distinct motions, precession and spin, which explained the unique NMR observations that were not clarified in previous experimental studies.