摘要:
                                This paper presents the synthesis of a series of push-pull and quadrupolar pi-conjugated structures incorporating pro-aromatic methylenepyran electron-donor groups and various electron-attracting groups. Some of the methylenepyran derivatives were oxidized by I-2 to give, after reduction by Na2S2O3, bismethylenepyran compounds via successive steps.The electrochemical redox properties of methylenepyrans 5-9 and extended bismethylenepyrans 10, 14, and 15 determined by cyclic voltammetry indicate the formation of redox bistable systems with high bistability. Oxidation of the dimers obtained from 5 to 9 was also described. All compounds are colored and slightly fluorescent (except some bismethylenepyran derivatives). Some compound second-order nonlinear optical properties were investigated, and large positive values of mu beta were obtained. A positive dimer effect was also observed for bispyran derivatives. (C) 2013 Elsevier Ltd. All rights reserved.