An Open-Shell Functionalization of Inorganic Benzene

Area of Science:

• Inorganic Chemistry
• Materials Science
• Quantum Chemistry

Background:

• Borazine derivatives represent a class of inorganic aromatic compounds.
• Nitroxide radicals are stable organic radicals with unpaired electrons.
• Open-shell inorganic benzene analogs are of interest for their unique electronic and magnetic properties.

Purpose of the Study:

• To synthesize and characterize a novel borazine derivative functionalized with nitroxide free radicals.
• To investigate the magnetic interactions and spin states within the synthesized molecule.
• To explore the potential of this compound as an inorganic benzene analog.

Main Methods:

• Synthesis of N,N′,N″-(tris(4-Bromophenyl))-B,B′,B″-tris((2,6-dimethyl-4-(N-tert-butyl-N-oxyamino)phenyl) borazine (TriBNit).
• Single-crystal X-ray diffraction for structural determination.
• Temperature-dependent magnetic susceptibility measurements.
• Electron Paramagnetic Resonance (EPR) spectroscopy at variable temperatures.

Main Results:

• The crystal structure confirmed the grafting of three nitroxide radicals onto the borazine core.
• Magnetic susceptibility indicated weak intramolecular and strong intermolecular antiferromagnetic interactions.
• EPR spectroscopy revealed the coexistence of S = 1/2 and S = 3/2 ground-spin states at 80 K, attributed to radical orientation.
• At room temperature, EPR spectra averaged to an S = 1/2 ground-spin state due to radical mobility.

Conclusions:

• TriBNit serves as a significant example of an open-shell inorganic benzene analog.
• The interplay of intramolecular and intermolecular interactions dictates the magnetic properties.
• The observed spin states are dependent on temperature and radical mobility, offering tunable magnetic behavior.