Synthesis and optical nonlinear property of NLO chromophores with alkoxy chains of different lengths using 8-hydroxy-1,1,7,7-tetramethyl-formyljulolidine as donor

• Three chromophores had been synthesized and systematically investigated.
• The chromophores that had longer alkoxy chains had lower energy between ground state and excited state.
• The chromophores that had longer alkoxy chains resulted in relatively larger r33.

Three chromophores ZR1, ZR2 and ZR3 based on the electron donor bearing different lengths of alkoxy chains, the same π-electron bridge and tricyanofuran acceptor, have been synthesized and systematically investigated. Density Functional Theory calculations and cyclic voltammetry measurements suggested that ZR2 (with hexyloxy) and ZR3 (with octoxy) had relatively small energy gaps between ground state and excited state than ZR1 (with butoxy) due to the auxiliary electron-donating ability and steric hindrance of their longer alkoxy chains on the donor. The electro-optic coefficient of poled films containing 20% wt of the new dyes doped in amorphous polycarbonate afforded values of 48, 62 and 65 pm/V at 1310 nm for ZR1, ZR2 and ZR3 respectively. These results indicated that the introduction of the longer alkoxy chains on the donor could effectively reduce the intermolecular electrostatic interactions and aid the alignment of the chromophores. This conclusion is conducive to future molecular design.

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