Chiral Stilbazolium Chromophores: An Approach toward Multiproperty Materials Combining Conductivity and Second-Order Optical Nonlinearities

A new chiral cyanine dye, 4‘-[2-(methoxymethyl)pyrrolidinyl]-1-methylstilbazolium iodide (MPMS+I-) is reported. It crystallizes in the monoclinic P21 space group. a = 16.559(2) A, b = 6.263(1) A, c = 24.477(3) A, β = 109.20(1)°, Z = 2. The hyperpolarizability of MPMS+I- is compared versus that of 4‘-dimethylamino-1-methylstilbazolium iodide (DAMS+I-). MPMS+I- is phase matchable and exhibits an efficiency up to 80 times that of urea in second-harmonic generation (SHG). Both compounds (C+I-) react with tetracyanoquinodimethane (TCNQ), and the resulting C+(TCNQ2)- exhibit conductivities in the range 10-3−10-2 S cm-1. The possibility of combining conductivity and optical nonlinearities is discussed.