RESUMEN
CONTEXT: In this work, in order to find new strategy to solve the safe problem of one famous high energy compound 1,3,5-trinitro-1,3,5-triazinane (RDX) under the impact and static electricity environment, cyclo[n]carbons (n = 10, C10; n = 14, C14; n = 18, C18) were employed to construct novel energetic composites (RDX@C10, RDX@C14, RDX@C18) with RDX for the first time. The investigated results showed that C10, C14 and C18 all can form stable composites with RDX through a exothermal process. Three cyclo[n]carbons could not only decrease the impact sensitivity of RDX by decreasing the positive ESP values and transferring the HPV region. But also could reduce the electrostatic sensitivity greatly by decreasing the energy gap, increasing the EHOMO and controlling the active electron-induced process and reaction. Among them, the desensitization effect by C18 and C14 was found to be much better than C10. In addition, three cyclo[n]carbons may be used as new sensors for the detection of RDX, due to the fast recovery time under different lights, and great change in the UV-Vis spectrum. These improvements may provide valuable insights for enhancing the safe performance of high energy compounds with similar structures to RDX, and broaden the application sphere of cyclo[n]carbons. METHODS: All of the calculations on the structures were carried out by using the Gaussian 09 software at the M06-2X/6-311G(d,p) level. In addition, further calculations on the properties and interactions were performed by using the Multiwfn software.
RESUMEN
Cyclo[n]carbon (Cn) is one member of the all-carbon allotrope family with potential applications in next-generation electronic devices. By employing first-principles quantum transport calculations, we have investigated the electronic transport properties of single-molecule junctions of Cn, with n = 14, 16, 18, and 20, connected to two bulk gold electrodes, uncovering notable distinctions arising from the varying aromaticities. For the doubly aromatic C14 and C18 molecules, slightly deformed complexes at the singlet state arise after bonding with one Au atom at each side; in contrast, the reduced energy gaps between the highest occupied and the lowest unoccupied molecular orbitals due to the orbital reordering observed in the doubly anti-aromatic C16 and C20 molecules lead to heavily deformed asymmetric complexes at the triplet state. Consequently, spin-unpolarized transmission functions are obtained for the Au-C14/18-Au junctions, while spin-polarized transmission appears in the Au-C16/20-Au junctions. Furthermore, the asymmetric in-plane π-type hybrid molecular orbitals of the Au-C16/20-Au junctions contribute to two broad but low transmission peaks far away from the Fermi level (Ef), while the out-of-plane π-type hybrid molecular orbitals dominate two sharp transmission peaks that are adjacent to Ef, thus resulting in much lower transmission coefficients at Ef compared to those of the Au-C14/18-Au junctions. Our findings are helpful for the design and application of future cyclo[n]carbon-based molecular electronic devices.
RESUMEN
Discovery of species with adaptive aromaticity (being aromatic in both the lowest singlet and triplet states) is particularly challenging as cyclic species are generally aromatic either in the ground state or in the excited state only, according to Hückel's and Baird's rules. Inspired by the recent realization of cyclo[18]carbon, here we demonstrate that cyclo[10]carbon possesses adaptive aromaticity by screening cyclo[n]carbon (n=8-24), which is supported by nucleus-independent chemical shift (NICS), anisotropy of the current-induced density (ACID), π contribution of electron localization function (ELFπ ) and electron density of delocalized bonds (EDDB) analyses. Further study reveals that the lowest triplet state of cyclo[10]carbon is formed by in-plane ππ* excitation. Thus, the major contribution to the aromaticity from out-of-plane π molecular orbitals does not change significantly in the lowest singlet state. Our findings highlight a crucial role of out-of-plane π orbitals in maintaining aromaticity for both the lowest singlet and triplet states as well as the aromaticity dependence on the number of the carbon in cyclo[n]carbon.