A Thorough Theoretical Exploration of Intriguing Characteristics of Cyclo[18]carbon: Geometry, Bonding Nature, Aromaticity, Weak Interaction, Reactivity, Excited States, Vibrations, Molecular Dynamics and Various Molecular Properties

Abstract

Although cyclo[18]carbon has been theoretically and experimentally investigated since long time ago, only very recently it was prepared and directly observed by means of STM/AFM in condensed phase (Kaiser et al., <i>Science</i>, <b>365</b>, 1299 (2019)). The unique ring structure and dual 18-center π delocalization feature bring a variety of unusual characteristics and properties to the cyclo[18]carbon, which are quite worth to be explored. In this work, we present an extremely comprehensive and detailed investigation on almost all aspects of the cyclo[18]carbon, including (1) Geometric characteristics (2) Bonding nature (3) Electron delocalization and aromaticity (4) Intermolecular interaction (5) Reactivity (6) Electronic excitation and UV/Vis spectrum (7) Molecular vibration and IR/Raman spectrum (8) Molecular dynamics (9) Response to external field (10) Electron ionization, affinity and accompanied process (11) Various molecular properties. We believe that our full characterization of the cyclo[18]carbon will greatly deepen researchers' understanding of this system, and thereby help them to utilize it in practice and design its various valuable derivatives.

Influence of Small Molecular Property on Antibody Response

“…As shown in Tables S4 and S5, only descriptors related to hydrophobicity, such as dipole moment, Log P , PSA, and MPI, were observed to be directly proportional to the antibody response. MPI is defined for quantitatively measuring the polarity of molecules based on the ESP on their van der Waals surface, representing the uniformity of ESP distribution, which is expressed as follows: where the A is the area of the van der Waals surface, S denotes the integration is performed over the molecular surface, and V ( r ) stands for ESP . Compared to the dipole moment, Log P , and PSA, MPI may be a better indicator of a hapten ability to induce an antibody response since it has a more explicit algorithm and can appropriately represent the molecular hydrophobicity in most cases…”

TAO-DFT investigation of electronic properties of linear and cyclic carbon chains

“…On the other hand, cyclic carbon chains (for brevity, denoted as c-CC[n] (see Fig. 1b)), which are the monocyclic isomers of linear carbon chains, have also attracted considerable attention in recent years [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] . Note that c-CC [n] (where the carbon atoms are also sp-hybridized) are hypothesized to be the building blocks of fullerenes in the initial stages of growth 21 .…”

“…Among them, c-CC [18] has recently been synthesized 26 , and some of the electronic properties of c-CC [18] have been reported. There are also a few theoretical studies on the electronic properties and applications of c-CC [18] and other cyclic carbon chains 22,[27][28][29][30][31][32][33][34][35][36][37][38] . For example, c-CC [18] has been found to possess electron-acceptor properties, and can be dubbed as the smallest all-carbon electron acceptor 28 .…”

Comparative Quantum Chemistry Study on the Unimolecular Decomposition Channels of Pyrazole and Imidazole Energetic Materials

“…Due to the structure of the cyclic electronic conjugation of pyrazoles and imidazoles, it is difficult to divide them into fragments to calculate the BDE. Therefore, the linear fitting between the LBOs and the experimental BDEs of C–C, C–N, and N–N bonds was also performed to predict the BDE of pyrazoles and imidazoles, which have been applied in some cyclic systems. , The relationships and the calculated BDEs are shown in Figure and Table , respectively.…”

“…Therefore, the linear fitting between the LBOs and the experimental BDEs 30 of C−C, C− N, and N−N bonds was also performed to predict the BDE of pyrazoles and imidazoles, which have been applied in some cyclic systems. 25,31 The relationships and the calculated BDEs are shown in Figure 3…”