The bonding character, electron delocalization, and aromaticity of the cyclo [18]carbon (C 18 ) precursors, C 18 -(CO) n (n = 6, 4, and 2), have been studied by combining quantum chemical calculations and various electronic wavefunction analyses with different physical bases. It was found that C 18 -(CO) n (n = 6, 4, and 2) molecules exhibit alternating long and short CÀ C bonds, and have out-of-plane and in-plane dual π systems (π out and π in ) perpendicular to each other, which are consistent with the relevant characteristics of C 18 . However, the presence of carbonyl (-CO) groups significantly reduced the global electron conjugation of C 18 -(CO) n (n = 6, 4, and 2) compared to C 18 . Specifically, the -CO group largely breaks the extensive delocalization of π in system, and the π out system is also affected by it but to a much lesser extent; as a consequence, C 18 -(CO) n (n = 6, 4, and 2) with larger n shows weaker overall aromaticity. Mostly because of the decreased but still apparent π out electron delocalization in the C 18 -(CO) n (n = 6, 4, and 2), a notable diatropic induced ring current under the action of external magnetic field is observed, demonstrating the clear aromatic characteristic in the molecules. The correlation between C 18 -(CO) n (n = 6, 4, and 2) and C 18 in terms of the gradual elimination of -CO from the precursors showed that the direct elimination of two CO molecules in C 18 -(CO) n (n = 6, 4, and 2) has a synergistic mechanism, but it is kinetically infeasible under normal conditions due to the high energy barrier.

Organic−inorganic hybrid phase-transition materials have broad application prospects in aerospace, construction, military, and other fields due to their flexible and diverse structures and environmental friendliness. In this paper, we synthesized two organic−inorganic hybrids, (C 10 H 16 N) BF 4 (1) and (C 10 H 15 NF) BF 4 (2), and their phase-transition temperatures were 410.4 and 488.4 K, respectively. Through the confinement effect caused by the introduction of F atoms into the zero-dimensional structure, the phase-transition temperature was increased by 78.0 K and a hightemperature phase-transition compound was successfully obtained. In addition, 1 and 2 have energy gaps of 4.34 and 4.41 eV, respectively, which have potential applications as wide-band-gap semiconductor materials. In this study, the H/F-substitution regulation strategy provides feasibility for its practical application while optimizing the properties of organic−inorganic hybrid compounds.

No abstract

No abstract

No abstract