Azonia aromatic heterocycles as a new acceptor unit in D-π-A+ vs D-A+ nonlinear optical chromophores.
1. Departamento de Química Orgánica y Química Inorgánica, Universidad de Alcalá, 28871, Alcalá de Henares, Madrid, Spain. 2. Department of Physics, Skidmore College, Saratoga Springs, NY, United States. 3. Department of Chemistry, University of Leuven, Celestijnenlaan 200 D, 3001, Leuven, Belgium. 4. Departamento de Química Analítica, Química Física e Ingeniería Química, Universidad de Alcalá, 28871, Alcalá de Henares, Madrid, Spain.
A comparison of D-π-A+ and D-A+ cationic chromophores based on the quinolizinium system as new acceptor units is reported along with the results of studies into their linear and non-linear optical properties and electrochemical data. Experimental and theoretical data show that quinolizinium-based chromophores may provide a new generation of second-order non-linear materials with enhanced performance. The first hyperpolarizabilities were measured by Hyper-Rayleigh scattering experiments and the experimental data are supported by a theoretical analysis. In some chromophores the absence of a bridge (D-A+) between the donor and acceptor fragments enhances the NLO properties and the single crystal structure of such a material has been determined by X-ray diffraction.