Enhanced Intramolecular Charge Transfer in New Type Donor–Acceptor Substituted Perylenes

Here we report the facile synthesis and physical characterization of new type <i>N</i>-(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_HRS up to 1300 ± 50 × 10^–30 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

Theoretical and experimental investigation of electric field induced second harmonic generation in tetrathia 7 helicenes

In this paper, we report the first systematic experimental and theoretical investigation of the electric field induced second harmonic response of some tetrathia[7]helicene-based NLOphores. We studied six model compounds carrying the NO2, CH=CHCN, and COCF3 units as accepting groups on both the terminal thiophene positions as well as on the central benzene ring of the helicene backbone. These groups, known to be of medium and medium-strong accepting strength, allow tuning of both the electronic and structural properties of the helicenes studied. This experimental/theoretical study should set a milestone in addressing new structure-properties relationship of this class of nonconventional chiral chromophores able to show second order as well as third order NLO phenomena