The Divergent Dimerization Behavior of N‐Substituted Dicyanomethyl Radicals: Dynamically Stabilized versus Stable Radicals

Abstract

Herein, we demonstrate that the dimerization behavior of amine‐substituted dicyanomethyl radicals can be switched from σ‐ to π‐dimerization simply by varying the electron‐donating substituents. For dicyanomethyl radicals with a 4,4′‐ditolylamine (DT.) or a phenothiazine (PT.) substituent, the monomeric radical form and the corresponding dimer connected by a reversible C−C bond (σ‐dimer) are in equilibrium in solution. On the other hand, the radical with the julolidine skeleton (JD.) does not undergo σ‐dimerization and was isolated as a stable radical in spite of the absence of bulky protecting groups. X‐ray single‐crystal analysis revealed that JD. forms the π‐dimer in the crystalline state, and variable‐temperature spectroscopy showed that JD. is in equilibrium with the π‐dimer in toluene solution. DFT calculations point to the importance of electrostatic interactions as a driving force for the π‐dimerization of JD. because of its polarized structure.

Tunable Redox Chemistry and Stability of Radical Intermediates in 2D Covalent Organic Frameworks for High Performance Sodium Ion Batteries

“…Therefore, controllable modulation of the stability of the radical intermediates is of vital importance to optimize the performance of the organic electrode materials. Previous reports − and our work , showed that π–π and p−π conjugation interactions could contribute to delocalize the energy density of the unpaired electrons and the steric effect could restrict intermolecular electron self-exchange behavior. On the basis of this idea, rigid aromatic rings (such as formazanate complexes, trioxotriangulene, and triphenylmethane) were often used as blocks to provide conjugation structure and steric effect to tune the stability of the radical intermediates.…”

A de novo strategy to develop NIR precipitating fluorochrome for long-term in situ cell membrane bioimaging

“…As is known, the combination of donor-acceptor interaction and π-conjugation may efficiently redshift the fluorescence of fluorochrome (24,25). Meanwhile, the good planarity could promote intermolecular π−π stacking interaction (26,27), thereby decreasing the solubility and realizing antidiffusion imaging.…”

Pragmatic Improvement of Magnetic Exchange Couplings from Subsystem Density-Functional Theory through Orthogonalization of Subsystem Orbitals

“…The corresponding CCDC identifier and label used in this work are listed below the radical dimer. The following crystal structures were used: SAXPOW01, , SAXPOW05, , SAXPOW06, , ITULIT01, , JASKEW03, , and DESJET , …”

“…For the Wu−Yang potential reconstructions the following convergence criteria were used: First, the overall integrated density error is below 1.0 × 10 −5 electrons. Second, The following crystal structures were used: SAXPOW01, 62,63 SAXPOW05, 64,65 SAXPOW06, 64,66 ITULIT01, 67,68 JASKEW03, 28,69 and DESJET 70,71 The Journal of Physical Chemistry C the density error between two iterations changes less than 1.0 × 10 −7 electrons. The van Leeuwen−Baerends reconstruction was limited to 5000 cycles.…”