Abstract
We report a new boron dipyrromethene (BODIPY)-bridged bisphenoxyl diradicaloid (2), which showed closed-shell diamagnetic character in less polar solvents such as dichloromethane but open-shell diradical character with paramagnetic activity in the very polar solvent N,N-dimethylformamide. X-ray crystallographic analysis of 2 revealed an anti-parallel stacked dimer structure via intermolecular dipole–dipole interaction, and the observed solvent-dependent diradical character can be explained by the different dihedral angles between the phenoxyl units and the BODIPY bridge, and structural flexibility of the molecule in different solvents. Compound 2 also exhibited solvent-dependent optical and electrochemical properties.
Highlights
Recent theoretical and experimental studies on open-shell singlet diradicaloids showed promising applications of this type of material for organic electronics, photonics, and spintronics [1,2,3,4,5,6]
It is of importance to obtain stable materials, and it is expected that electron-deficient spacers can further improve the stability of diradicaloids by lowering their usually high lying HOMO energy level
We report a new boron dipyrromethene (BODIPY)-bridged bisphenylquinone 2 (Figure 1), which displayed very unusual solvent-dependent diradical character and physical properties
Summary
Recent theoretical and experimental studies on open-shell singlet diradicaloids showed promising applications of this type of material for organic electronics, photonics, and spintronics [1,2,3,4,5,6]. The parent extended quinones are very reactive, and various modifications have been conducted to obtain kinetically and thermodynamically stabilized quinone-based diradicaloids with different spacers, e.g., oligothiophenes [10], corannulene [11], perylenes [12,13], porphyrin [14], hexa-peri-hexabenzocoronene [15], naphthalene bisimide [16], and isoindigo [17]. A few relatively stable BODIPY-containing organic radicals have been reported by us, such as quinodimethane-bridged BODIPY dimers [21] and BODIPY-blocked anthroxyl radicals [22] In this context, we report a new BODIPY-bridged bisphenylquinone 2 (Figure 1), which displayed very unusual solvent-dependent diradical character and physical properties. 1. Chemical structures of oligo-para-phenyl quinones (1), and a boron dipyrromethene (BODIPY)-bridged (2) in closed-shell open-shell diradical. Results and Discussion resonance forms. bisphenoxyl diradicaloid (2) in closed-shell quinoidal and open-shell diradical (BODIPY)-bridged resonance forms
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