Persistent oxidation dications of dialkyl- and tetraalkyl-perylenes and dibenzo[cd,lm]perylene; charge distribution mode, substituent effects and conformational aspects

Abstract

Starting with appropriate alkylnaphthalenes, 3,10-dimethyl- 2, 3,10-diethyl- 3, 2,3,10,11-tetramethyl- 4 and 3,4,9,10-tetramethyl-perylene 5 were synthesized by a sequence of radical cation and radical anion coupling steps. Persistent oxidation dications of parent perylene 1, alkylperylenes 2–5 and dibenzo[cd,lm]perylene 6 were generated in SbF₅–SO₂ClF.Based on 1D- and 2D-NMR experiments combined with AMl calculations the charge delocalization mode in the dications was deduced. The total deshielding (ΣΔδ¹³C), substituent effects, conformational/geometrical changes and tropicity in the dications are examined.Whereas alkylperylene dications represent 18π electron Hückel dictations with a diamagnetic ring current (more diatropic than their neutral precursors), the 24π (20π periphery) dication of dibenzoperylene exhibits a paramagnetic ring current which greatly shields its protons (more paratropic than neutral hydrocarbon).