Chromophores exhibiting nonlinearity–transparency–thermal stability trade-off: synthesis and nonlinear optical properties of two-dimensional chromophores containing nitro acceptors

Nonlinear optical multipolar chromophores with nitro acceptors were designed and synthesized. The target compounds were characterized by NMR, IR, UV and melting point. The decomposition temperature was determined with differential scanning calorimetry, and the absorption spectra were measured. The first hyperpolarizability of the chromophore were calculated via solvatochromic methods. The nonlinear optical properties of five compounds were discussed. Especially, the first-order hyperpolarizabilities of chromophores 2 and 3 come from their two-dimensional structure, the length of the conjugation bridge and the intramolecular proton transfer. The strong dihydroxyl donor of chromophores 4 and 5 expanded the first-order hyperpolarizabilities. These NLO chromophores exhibit large optical nonlinearity, good transparency and thermal stability.