AM1-MO study on the structure and electron properties of squaraine dyes

The structure and electron properties of 8 bis(5-substitutent-2,3,3-trimethylindolen-2-ylidene)squaraines in ground state and singlet state were studied by AMI calculation. The (+), (-) sparkles were introduced in order to stimulate the solvent interaction. The absorption maximum value was estimated by AM1-Cl, and the results were close to the experimental values. The substituent effect on the absorption was discussed by comparing the difference of atomic charge densities between the s(D) and s(1) states. Redox potential in cyclic voltammetry exhibited two revevsible oxidation potentials, they are increased as the 5-substituent electron-donating ability. A good linear relationship was found between the first oxidation potential and the calculated ionization potential, and between the corrected experimental values and calculated values of electron affinity.