Donor-Substituted Heptaazaphenalene as a Nonlinear Optically Active Molecule with Multiple Charge-Transfer Transitions

The synthesis of a novel nonlinear optical (NLO) chromophore with threefold symmetry − 2,5,8‐tris(diethylamino)‐1,3,4,6,7,9,9b‐heptaazaphenalene (4) − is reported. Compound 4 was synthesized from 2,5,8‐trichloro‐1,3,4,6,7,9,9b‐heptaazaphenalene (3) through a nucleophilic aromatic substitution, its structural assignment was confirmed by X‐ray investigations, and its second‐order polarisability (β) was determined by hyper Rayleigh scattering (HRS). Compound 4 shows a very high absorbance coefficient in the UV and a remarkably large β value despite its short‐wavelength absorption. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)