Enhanced intramolecular charge transfer in new type donor-acceptor substituted perylenes

Here we report the facile synthesis and physical characterization of new type N-(2,6-diisopropylphenyl)-3,4-perylenedicarboximides (PMI) with alkyl-substituted quinoline-4(1H)-ylidenemethyl or acridine-9(10H)-ylidenemethyl units as strong donors in the 9-position. When compared to parent PMI, these perylene dyes, 9-((1-methylquinoline-4(1H)-ylidene)methyl)-PMI, 9-((1-benzylquinoline-4(1H)ylidene)methyl)-PMI, 9-((1-heptylquinoline-4(1H)- ylidene)methyl)-PMI, and 9-((10-methylacridine-9(10H)-ylidene)methyl)-PMI, show a pronounced bathochromic shift of their electronic absorption with solvatochromism because of their intramolecular charge transfer. The solvatochromic behavior of these dyes is further confirmed by second-order nonlinear optical experiments. Remarkably high second-order nonlinear optical values (β up to 1300 ± 50 × 10 esu at 880 nm in dichloromethane) are obtained by femtosecond hyper-Rayleigh scattering. The one-step synthesis together with the spectroscopic, solvatochromic, and nonlinear optical characteristics qualify these new types of perylene dyes as promising candidates for solvent polarity probes, photovoltaics, or nonlinear optical applications.