Crystal structure, spectroscopic characterization, and computational study of two new 4-aminobenzoic acid derived Schi base ligands

Two new Schi base ligands, (E)-4-(3-ethoxy-2-hydroxybenzylideneamino) benzoic acid (L1) and (E)-4-(3-methoxy-2-hydroxy-benzylideneamino)benzoic acid (L2), were synthesized and characterized by elemental analyses, FT-IR, NMR spectroscopy and single-crystal X-ray di raction analysis. The compound, L1, was crystallized in the triclinic system, space group P - 1, with a = 4:9897(3) A, b = 6:9109(5) A, c = 20:7694(15) A, = 83:690(4), = 84:855(4), = 78:698(4), V = 696:35(8) A3, and Z = 2. The compound L2 was crystallized in the orthorhombic system, non-centerosymmetric space group, P212121, with a = 4:7824(4) A, b = 10:2031(11) A, c = 30:516(3) A, V = 1489:0(3) A3, and Z = 4. Both L1 and L2 display a trans-con guration about the C=N double bond. The Density Functional Theory (DFT) and the Time-Dependent Density Functional Theory (TD-DFT) were used to study the ground state properties (molecular orbitals), and interpret the absorption spectra of these ligands, respectively. Electronic Di erence Density Maps (EDDMs) were calculated from the TD-DFT study, indicating the change of electron density in the singlet excited states.