Effects of Temperature and Host Concentration on the Supramolecular Enantiodifferentiating 4 + 4 Photodimerization of 2-Anthracenecarboxylate through Triplet-Triplet Annihilation Catalyzed by Pt-Modified Cyclodextrins

摘要

Visible-light-driven photocatalytic supramolecular enantiodifferentiating dimerization of 2-anthracenecarboxylic acid (AC) through triplet-triplet annihilation (TTA), mediated by the Schiff base Pt(II) complex (>Pt-1, >Pt-2, and >Pt-3) was studied. The host concentration and the temperature effects on the stereoselectivity were comprehensively investigated. Increasing the concentration of sensitizers/hosts significantly enhanced the conversion of the photoreaction but led to reduced enantioselectivities of the chiral photodimers >2 and >3 when the photoreaction was triggered by a 532 nm laser, which was in contrast with the results obtained by direct irradiation of AC with a 365 nm light-emitting diode (LED) lamp, due to the aggregation of the sensitizer/host in water. The cyclization of AC through triplet-triplet annihilation displayed significant temperature dependency when >Pt-3 was employed as the sensitizer/host. Increasing the temperature from 0 °C to 30 °C with 5% equiv. of >Pt-3 led to a great increase of the ee of >2 from 2.1% to 31.6%. However, hardly any temperature dependency was observed when the photodimerization was mediated by other sensitizers and/or hosts, or the photoreaction was triggered directly with a 365 nm LED lamp.