Synthesis and properties of long conjugated organic optical limiting materials with different π-electron conjugation bridge structure

Three novel organic optical materials, 4′-(N,N-dihydroxyethylamino),4-(pyridine-4-vinyl)stilbene (8a), N-((4-N,N-dihydroxyethylamino)benzylidene)-4-(pyridine-4-vinyl)aniline (8b) and 4′-(N,N-dihydroxyethylamino),4-(pyridine-4-vinyl)azobenzene (8c), were synthesized and characterized by FT-IR, UV, ¹H NMR and elementary analysis. Their optical properties were evaluated by optical limiting and nonlinear optical analyses. The results show that these compounds possess good optical limiting and large nonlinear optical properties, which are attributed to the long D-π-A conjugated electron structure of molecules, and the π-electron conjugated bridge structure affects the nonlinear optical and optical limiting properties of D-π-A conjugation compounds. The compound 8a with C{double bond, long}C double bond as conjugation bridge shows better optical limiting property than compounds 8b and 8c with C{double bond, long}N or N{double bond, long}N double bond under the same linear transmittance, while compound 8c with N{double bond, long}N double bond as conjugation bridge is superior in nonlinear optical properties to compounds 8a and 8b with C{double bond, long}C or C{double bond, long}N double bond as conjugation bridge.