The dynamics of a carbonaceous molecular bearing were investigated by DFT methods to reveal dual-mode motions with a minute energy barrier.

A novel diacetylene derivative, N,N 0 -bis[5-(3-tolylaminocarbonyloxy)-1,3-pentadiynyl]-N,N 0 -diphenyl-1,4-phenylenediamine (1), was prepared, where two diacetylene groups were connected by a 1,4phenylenediamine moiety. The molecules stacked one-dimensionally and showed solid-statepolymerization reactivity above 80 C. The decay of the monomers at 100 C proceeded gradually without a marked induction period and was fully completed after 400 h. The obtained polymer was a crystalline solid judged by powder X-ray diffraction (PXRD) patterns and SEM imaging. The conjugated p-system of the obtained polymer was classified as a two-legged conjugated ladder. The polymer showed a broad absorption from the visible to the near IR region, indicating a decrease in the optical band gap of ca. 1.0 eV, because of the expansion of the p-conjugated system from a onedimensional system to a ladder. The ladder polymer showed high conductivity after I 2 doping from s 293K ¼ 5 Â 10 À12 S cm À1 to 1.2 Â 10 À5 S cm À1 . The conductivity depended heavily on the pressure of iodine and reached s 373K ¼ 2.3 Â 10 À1 S cm À1 . The activation energy of the ladder polymer was also estimated as 360 meV.

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.

We reply to the comments raised by Cabaleiro-Lago et al. on our article (H. Isobe et al., Chem. Sci., 2015, 6, 2746–2753).

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