Exploring the spectral properties and potential applications of dimethylamine-modified porphyrin and chlorin dyes

Abstract

The synthesis, structural characterization, and optical properties of new free-base and metalated dimethylamine-based porphyrin (1, 1a) and chlorin (2, 2a) derivatives are presented. The synthetic approach is based on the peripheral substitution of the para-fluor atoms of the commercially available 5,10,15,20-tetrakis(pentafluorophenyl)-21H,23H-porphyrin (H2TPPF20) by dimethylamine (H2Por 1), following the preparation of the analogous chlorin dye (H2Chl 2) using N-methylglycine and p-formaldehyde. Both compounds were then metalated with zinc acetate to perform the corresponding ZnPor 1a and ZnChl 2a dyes. Several photophysical parameters were determined, including absorption and emission features at 298 K (e.g., molar absorptivity coefficients, λ absorption maxima of Soret and/or Q bands, λemission maxima, and ratio of long- to short-wavelength emission intensity), fluorescence quantum yield (ФF), stability (under dark conditions), and photostability (under white light exposure at irradiance of 50 mW.cm−2). The photophysical results were determined and compared for the type of meso-substituted scaffold selected – A4-type – of free-base (1, 2) and zinc(II) complex (1a, 2a). The four compounds exhibit high dark stability in DMF (absorption reduction intensity < 3 %). The Pors 1 and 1a have also high photostability (absorption reduction intensity < 1.5 %), but H2Chl 2 and ZnChl 2a present a considerable absorption reduction, 14.3 % and 22.3 %, respectively. The ФF of the ZnPor 1a (ФF = 0.02) and H2Por 1 (ФF = 0.02) are lower than those of ZnChl 2a (ФF = 0.06) and H2Chl 2 (ФF = 0.09). The developed compounds present potential applications in nonlinear optics, biomarkers, and/or solar cells.