Abstract
Environmental pollution with chiral organic compounds is an emerging problem requiring innovative sensing methods. Amino-functionalized thioureas, such as 2-(dimethylamino)cyclohexyl-(3,5-bis(trifluoromethyl)phenyl)thiourea (Takemoto’s catalyst), are widely used organocatalysts with virtually unknown environmental safety data. Ecotoxicity studies based on the Vibrio fischeri luminescence inhibition test reveal significant toxicity of Takemoto’s catalyst (EC50 = 7.9 mg/L) and its NH2-substituted analog (EC50 = 7.2–7.4 mg/L). The observed toxic effect was pronounced by the influence of the trifluoromethyl moiety. En route to the porphyrin-based chemosensing of Takemoto-type thioureas, their supramolecular binding to a series of zinc porphyrins was studied with UV-Vis and circular dichroism (CD) spectroscopy, computational analysis and single crystal X-ray diffraction. The association constant values generally increased with the increasing electron-withdrawing properties of the porphyrins and electron-donating ability of the thioureas, a result of the predominant Zn⋯N cation–dipole (Lewis acid–base) interaction. The binding event induced a CD signal in the Soret band region of the porphyrin hosts—a crucial property for chirality sensing of Takemoto-type thioureas.
Highlights
Amino-functionalized thioureas (1a–d, Figure 1b) were screened for toxicity using a Vibrio fischeri 30-min kinetic luminescent bacteria test according to the Flash-test protocol
This bioassay data have widely been used for the quantitative structure–activity relationship (QSAR) models analysis to predict the toxicity of organic chemicals by their chemical structures [92]
Given the toxic effect revealed for 3,5-bis(trifluoromethyl)phenyl)-substituted thioureas
Summary
The production of chiral chemicals is rapidly growing to satisfy the continuously increasing demand in various industrial and medicinal fields. Pure compounds often show improved bioactivity, fewer adverse effects, and increased selectivity over their achiral or racemic counterparts. More than 50% of pharmaceuticals and around. 30% of pesticides are chiral, and their numbers are steadily growing [1,2,3]. An adverse effect of this process has increased the amount of pollution caused by chiral chemicals, representing a potential threat for ecosystems [4,5,6,7]. Noteworthy ecotoxicology data are frequently unavailable and the environmental fate remains unclear for numerous artificial
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