Intermolecular pi-dimer of oxoverdazyl radicals with long-distance multicenter (2e/8c) bonding via nitrogen atoms

摘要

The 1,5-dimethyl-6-oxoverdazyl radical's solid-state structure shows distinct pi-dimeric units with close interplanar separations (3.10 angstrom) between the head-over-tail cofacial moieties and several interatomic contacts shorter than the sums of the van der Waals radii. Evaluations of the frontier orbitals of monomeric oxoverdazyl and its pi-dimer reveal that interaction of the radical SOMOs (concentrated on the nitrogen atoms) leads to the formation of the supramolecular orbital involving four equivalent bonding (N center dot center dot center dot N) segments between two oxoverdazyl moieties. As such, this pi-dimer represents a rare example of nitrogen-based multicenter (2e/8c) long-distance bonding and emphasizes the universal character of this phenomenon in organic (ion-) radical systems. Copyright 2009 John Wiley & Sons, Ltd.