Through-Bond and Through-Space Interactions in [2,2]Cyclophanes

Abstract

The interpretation of the distortions of the electron distribution in [2,2]cyclophanes (22-CPs) is controversial. Some studies indicate that there is an accumulation of electron density (ρ) outside the cavity of 22-CPs. The nature of through-space (ts) interaction is still under debate. The relative importance of ts and through-bond (tb) is an open question. In an attempt to clarify these points, we have investigated five 22-CPs and their corresponding toluene dimers by molecular orbitals analysis, electron density difference analysis, some topological analysis of ρ (quantum theory of atoms in molecules (QTAIM), electron localization function (ELF) and noncovalent interactions (NCI)), and energy decomposition analysis with natural orbitals for chemical valence (EDA-NOCV). ρ is concentrated inside the inter-ring region. All the analyses indicated that ts is predominant. The ts is composed by attractive dispersion and Pauli repulsion, with a small covalent contribution. Except for 1 and 6, all the compounds present inter-ring bond paths.

Structural and thermodynamic insights into the coordination preference of norbornadiene with the initiator complex [RuCl2(PPh3)2(piperidine)] in polymerization via olefin metathesis

“…In EDA*, variations in steric interaction energy (Δ E ster ) correspond to the sum of the electrostatic energy terms with the exchange repulsion energy (Pauli repulsion) and the orbital interaction energy (Δ E orb ) reflect the terms related to the transfer of charge (donor/acceptor interactions, between occupied orbitals of a fragment with empty orbitals of another fragment), as well as polarization (mixture of unoccupied/occupied orbitals). 44 In each case, the complex was decomposed into two fragments, one ligand (PPh 3 , the amine or the NBD) and the remaining part of the complex. The (*) in EDA* is used to differentiate the EDA* method from ethyl diazoacetate.…”

Utilization of the through-space effect to design donor–acceptor systems of pyrrole, indole, isoindole, azulene and aniline

“…72 In contrast, the term throughspace effect (TSE) pertains to electronic interactions between atoms or groups of atoms that are not directly bonded to each other, but exert influence on one another through threedimensional space. More recent research studies [73][74][75][76] have demonstrated that the TSE predominates in many situations that were previously assumed to be produced primarily by the TBE. Many attempts have been made in the past to evaluate the TSE using a wide range of substituents.…”

Compact CPL emitters based on a [2.2]paracyclophane scaffold: recent developments and future perspectives

“…The conformational stiffness and proximity of the two p systems favours transannular through-space and throughbond interactions that confer on pCps intriguing electronic properties. 12,13 These molecules show a unique reactivity [14][15][16][17][18][19][20] and an unusual spectroscopic behaviour. 21,22 The absorption spectrum of commercially available pCp is characterized by a low-intensity band with a maximum around 302 nm which is rarely observed for more common benzene derivatives.…”