Air Stable Chalcogen-Doped Rubicenes with Diradical Character

Abstract

Air stable diradicaloid polycyclic aromatic hydrocarbons (PAHs) materials possess unique electronic and magnetic properties for various applications. In general, it is required to elongate conjugated distances between two radicals center to improve the air stability, complexing the synthetic procedures. Herein, the chalcogen containing rubicenes (O-, S-, and Se-rubicenes) were systematically investigated to understand the chalcogen effects on their physicochemical properties. Impressively, these rubicenes presented unprecedented diradical characters within one simple benzene ring and excellent air stabilities. Their diradical characters are manifested by single-crystal X-ray studies, variable temperature-nuclear magnetic resonance

Thermally Induced Persistent Covalent-Organic Frameworks Radicals

“…However, after heat treatment, a net spin of 0.77 × 1/2ℏ was generated for CityU-4-heat with an open-shell radical form (Figure 5b), where the singlet/triplet ratio of COFs radical is 0.237/0.763 due to radicals with spin polarization. 39 Moreover, the total energies of CityU-4 and CityU-4-heat are −494.97 and −496.69 eV, respectively, illustrating that the transition from CityU-4 with a higher energy to CityU-4-heat with a lower energy was favorable when increasing the temperature. The energy difference between CityU-4 and CityU-4-heat was much larger than thermal energy; thus, CityU-4-heat could not spontaneously transfer back to CityU-4 when decreasing the temperature.…”

“…Herein, taking advantage of the effect of temperature on structural conformation, , the modulated electronic structures with perturbed resonance forms can be realized through thermal treatment to generate persistent COF radicals. ,− Besides, covalent triazine frameworks (CTFs) typically with high porosity and good thermal and chemical stability were judiciously designed with arylamine based COFs as comparison. In a typical procedure, we synthesized three crystalline COFs (named as CityU-4 , CityU-5 , and CityU-6 ) containing p -phenylenediacetonitrile building units as electronic isolation units for the stabilization of radicals .…”

The design, synthesis and application of rubicene based polycyclic aromatic hydrocarbons (PAHs)

“…7). Meanwhile, these rubicenes presented diradical character and excellent air stabilities, 18,26 which were manifested by single-crystal X-ray studies, variable-temperature nuclear magnetic resonance (VT-NMR), and electron spin resonance (Fig. 7c).…”

“…11 Although the synthesis of rubicene-based p-functional materials has been a long standing challenge, the rubicene PAHs have become an important and active field in the chemistry and materials community due to their unique physicochemical properties. [24][25][26][27][28] In this review, we summarized the progress on the design, synthesis, and applications of rubicene-based p-functional materials. First, synthetic routes of rubicene PAHs are briefly introduced.…”

“…4c). 24,26 Based on the mechanism studies, it was noticed that this method started from closing the six-membered rings, followed by forming the fivemembered rings. Overall, these chalcogen doped rubicenes were synthesized under slightly different Scholl oxidation conditions in modest to good yields.…”