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

Two new schi base ligands, (e)-4-(3-ethoxy-2-hydroxybenzylideneamino) benzoic acid (l^1) and (e)-4-(3-methoxy-2-hydroxy-benzylideneamino)benzoic acid (l^2), were synthesized and characterized by elemental analyses, ft-ir, nmr spectroscopy and single-crystal x-ray diffraction analysis. the compound, l^1, was crystallized in the triclinic system, space group ρ-1, with a = 4.9897(3) å, b = 6.9109(5) å, c = 20.7694(15) å, α = 83.690(4)°, β = 84.855(4)°, γ = 78.698(4)°, v = 696.35(8) å^3, and z = 2. the compound l^2 was crystallized in the orthorhombic system, non-centerosymmetric space group, p2_1 2_1 2_1, with a = 4.7824(4) å, b = 10:.2031(11) å, c = 30.516(3) å, v = 1489.0(3) å^3, and z = 4. both l^1 and l^2 display a trans-configuration 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 difference density maps (eddms) were calculated from the td-dft study, indicating the change of electron density in the singlet excited states.