Solution-Phase Synthesis and Isolation of An Aza-Triangulene and Its Cation in Crystalline Form

摘要

Synthesis of triangulene and its derivatives is challenging due to their intrinsic high spin nature. Herein, we report solution-phase synthesis and isolation of a nitrogen-doped triangulene (i.e., aza-triangulene) (NT) and its cation (NT~+) in single-crystal form. Notably, the cation NT~+ can be regarded as an isoelectronic structure of the corresponding all-carbon triangulene. Both NT and NT~+ show reasonable stability due to kinetic blocking by bulky and electron-withdrawing aryl substituents, and intramolecular donor-acceptor interaction. Bond length analysis, magnetic measurements and theoretical calculations reveal that the neutral NT has a doublet ground state with a zwitterionic character, while the cation NT~+ exhibits a triplet ground state with a singlet-triplet energy gap of + 0.84 kcal mol~(-1). This study provides a rational strategy to access high-spin systems by heteroatom doping of pure π-conjugated polycyclic hydrocarbons.