Several dyes containing 1H-pyrazolo[3,4-b]quinoline skeleton have been synthesized and evaluated as the novel photoinitiators for free radical polymerization induced in the UV region with the argon-ion laser. The kinetic study of photoinitiated polymerization, performed for viscous monomeric formulation with the use of thiophenoxyacetic acid has shown that the tested dyes are good dyeing photoinitiators. The results have shown that there is a linear relationship between the rate of polymerization and the square root of efficiency of the singlet oxygen formation. This finding clearly indicates that the electron transfer process between the tested dyes and electron donors occurs via triplet state. In the paper, it is also shown that the structure of the dye has a strong effect on its polymerization photoinitiation ability. The dyes tested were prepared in a way that allows, firstly, the elimination of the rotational freedom of selected parts of molecule and secondly, to increase the quantum yield of the triplet state formation. The latest was achieved by introducing to the molecule a heavy atom. The tested dyes absorb at the boundary of UV and visible region, therefore they might be considered as the potential photoinitiators for dental application.