A chromophore for nonlinear optics with extended conjugation has been synthesized, and its structure determined from X-ray diffraction data. The compound crystallizes in the monoclinic system with the space group P2(1)/n and Z = 4. The unit cell parameters are a = 10.7826(4) angstrom, b = 14.5943(5) angstrom, c = 15.3792(5) angstrom and beta = 96.213(2)degrees. A thin film containing 5% of the chromophore in amorphous polycarbonate when poled at 180 degrees C and 60 V/mu m yields a maximum r(33) value of 206 pm/V. This is seven times higher than the value found for the archetypical inorganic material, lithium niobate.