Tuning Second-Order Optical Nonlinearities in Push-Pull Benzimidazoles

✍ Scribed by Antonio Carella; Roberto Centore; Alain Fort; Andrea Peluso; Augusto Sirigu; Angela Tuzi

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 146 KB
• Volume: 2004
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/ejoc.200300786

✦ Synopsis

Abstract

The synthesis and full characterization of new chromophores with second order optical nonlinearities containing the 2‐phenyl‐(5,6)‐nitrobenzimidazole group is reported. Starting from 2‐{4‐[(4‐N,N‐dihydroxyethylamino)phenylazo]phenyl}‐5(6)‐nitrobenzimidazole, a combined theoretical and experimental approach, including theoretical computations of second order nonlinear optical activity (MNDO/AM1), X‐ray structural analysis and synthetic strategies, has led to a significant optimization (more than 50%) of the NLO activity of related chromophores. The results indicate that 6‐nitro‐substituted compounds are more active than 5‐nitro‐substituted ones and that a further increase of NLO activity can be achieved by insertion of a carbon−carbon double bond between the benzimidazole and 2‐phenyl rings. Calculations also suggest that an additional improvement of the nonlinearity should be expected upon functionalization of the N1 atom of the 6‐nitrobenzimidazole with electron‐withdrawing groups. Experimental nonlinearities (EFISH technique, μβ/10^−48^ esu, λ = 1.907 μm, DMF solution) between 940 and 1550 were measured. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)