A novel pyrazole derivative ligand, BTA（BTA = bis-（4-ethoxy-phenyl）-[4-（tripyrazol-1-yl-methyl）-phenyl]-amine）, was synthesized and fully characterized by 1H-NMR, MALDI-TOF-MS spectra and single-crystal X-ray diffraction analysis. It crystallizes in triclinic, space group P1, with a = 11.827（1）, b = 16.000（2）, c = 16.527（2）A, α = 108.510（1）, β = 91.116（5）, γ = 101.734（1）°, V = 2894.5（6） A3, Z = 1, Dc = 1.262 g/m^3, F（000） = 1162, Μr = 545.63, μ = 0.083 mm-1, the final R = 0.0728 and w R = 0.2213 for 7541 observed reflections with I 〉 2（I）. The structural analysis revealed that three pyrazole units are attached to the same carbon atom connected with bis-（4-ethoxy-phenyl）-phenyl-amine group. UV-vis spectral features of the ligand in various solutions were explained by time dependent density functional theory（TD-DFT）. It was also found that the ligand（BTA） exhibits an exclusively selective and sensitive response toward Fe3＋ using UV-vis spectroscopic method.
