3-Carbaldehyde-substituted 2,3'-biimidazo[1,2-a]pyridin-2'-one radicals: Interesting pi-stacking structures and magnetic properties

摘要

A new 3-formyI-2,3'-biimidazo[1,2-a]pyridm-2'-one radical was synthesized via Vilsmeier reaction under mild conditions, which exists as 1D double-stranded chain formed by lateral close contacts between pi-dimers. Its perchlorate salt exists as 1D slipped pi-stacking chain. The different stacking structures obviously affect their magnetic and photoluminescence properties in solid state. Neutral radical shows a dominant antiferromagnetic interaction between radicals and the magnetic phase transition at ~72 K, while radical salt exhibits a strong irreversibility between FC and ZFC states, attributed to the anisotropic contraction and nonuniform slippage of pi-stacking chain.