Photophysical properties of a series of 4-aryl substituted 1,4-dihydropyridines

In this article, a series of Hantzsch 1,4-dihydropyridines with different substituted aryl groups were synthesized and its spectral data obtained by UVVis absorption and fluorescence emission spectroscopies in solution. The dihydropyridines present absorption located around 350 nm and fluorescence emission in the bluegreen region. A higher Stokes shift could be observed for the derivative 3b because of an intramolecular charge transfer in the excited state from the dimethylaniline to the dihydropyridine chromophores, which was corroborated by a linear relation of the fluorescence maxima (nu max) versus the solvent polarity function (?f) from the LippertMataga correlation. A comparison between the experimental data and time-dependent density functional theory-polarizable continuum model calculations of the vertical transitions was performed to help on the elucidation of the photophysics of these compounds. For these calculations, the S0 and S1 states were optimized using Becke, three-parameter, Lee-Yang-Parr/6-31G* and Configuration Interaction Singles/6-31G*, respectively. The predicted absorption maxima are in good agreement with the experimental; however, the theoretical fluorescence emission maxima do not match the experimental, which means that the excited specie cannot be related to neither a locally excited state nor to an aromatized structure. Copyright (c) 2012 John Wiley & Sons, Ltd.