A Computational Study of Tetrafluoro-[2.2]Cyclophanes

Abstract

A computational study of the isomers of tetrafluorinated [2.2]cyclophanes persubstituted in one ring, namely F4-[2.2]paracyclophane (4), F4-anti-[2.2]metacyclophane (5a), F4-syn-[2.2]metacyclophane (5b), and F4-[2.2]metaparacyclophane (6a and 6b), was carried out. The effects of fluorination on the geometries, relative energies, local and global aromaticity, and strain energies of the bridges and rings were investigated. An analysis of the electron density by B3PW91/6-31+G(d,p), B3LYP/6-31+G(d,p), and MP2/6-31+G(d,p) was carried out using the natural bond orbitals (NBO), natural steric analysis (NSA), and atoms in molecules (AIM) methods. The analysis of frontier molecular orbitals (MOs) was also employed. The results indicated that the molecular structure of [2.2]paracyclophane is the most affected by the fluorination. Isodesmic reactions showed that the fluorinated rings are more strained than the nonfluorinated ones. The NICS, HOMA, and PDI criteria evidenced that the fluorination affects the aromaticity of both the fluorinated and the nonfluorinated rings. The NBO and NSA analyses gave an indication that the fluorination increases not only the number of through-space interactions but also their magnitude. The AIM analysis suggested that the through-space interactions are restricted to the F4-[2.2]metacyclophanes. In addition, the atomic properties, computed over the atomic basins, gave evidence that not only the substitution, but also the position of the bridges could affect the atomic charges, the first atomic moments, and the atomic volumes.

Stable‐Ion NMR Spectroscopy and GIAO‐DFT Study of Carbocations Derived from Multibridged [3n]Cyclophanes

“…Increased aromaticity can be seen in polycyclic compounds with cofacial benzene rings generally. [25][26][27][28] Upon monoprotonation, the opposite deck becomes less aromatic, in accord with favorable donor-acceptor interactions in the cyclophane carbocation. On the basis of NICS(1) zz , the outer face of the benzenium deck is no longer aromatic, whereas the inner face is still aromatic.…”

Design of Air and Moisture Stable Ruthenophane and Ruthenium(II)‐π Complexes and Study of Their Applications in Catalysis

“…Among the various ligands reported, the cyclophanes have been extensively investigated as selective catalysts, auxiliaries in asymmetric synthesis, and also in the preparation of artificial receptors ,. These ligands have the ability to coordinate strongly with the transition metal ions, wherein the cyclophane moiety acts as the π‐donor.…”

“…Among the various ligands reported, the cyclophanes have been extensively investigated as selective catalysts, auxiliaries in asymmetric synthesis, and also in the preparation of artificial receptors. [8,9] These ligands have the ability to coordinate strongly with the transition metal ions, wherein the cyclophane moiety acts as the p-donor. Furthermore, the ability of such complex formation depends mainly on the effective cation-p interactions exist between the metal ion and the aromatic surface of the ligand.…”

Synthesis of Highly Distorted π‐Extended [2.2]Metacyclophanes by Intermolecular Double Oxidative Coupling

“…We calculated strain energies of 2 a, 2 b, and 2 c by DFT calculations at the wB97XD/6-31G(d) level. [20] The strain energies were estimated as a reaction enthalpy on a homodesmotic reaction (Supporting Information, Scheme S1…”

“…We calculated strain energies of 2 a, 2 b, and 2 c by DFT calculations at the wB97XD/6-31G(d) level. [20] The strain energies were estimated as a reaction enthalpy on a homodesmotic reaction (Supporting Information, Scheme S1). The values are 30.8 kcal mol À1 for 2 a, 4.56 kcal mol À1 for 2 b, and 12.1 kcal mol À1 for 2 c. The distortion of the benzene rings is mitigated for the dimers with less bulky substituents.…”