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Understanding the Relationship Between Photolysis Efficiency and Metal Binding Using ArgenCast Photocages
Author(s) -
Mbatia Hannah W.,
Kennedy Daniel P.,
Burdette Shawn C.
Publication year - 2012
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.2012.01136.x
Subject(s) - chemistry , aniline , electrophile , photodissociation , quantum yield , photochemistry , metal , trifluoromethanesulfonate , lone pair , thioether , protonation , chromophore , medicinal chemistry , stereochemistry , molecule , organic chemistry , catalysis , ion , fluorescence , physics , quantum mechanics
ArgenCast‐1 ( 1 ), a photocage for silver utilizing acyclic polythioether 3,6,12,15‐tetrathia‐9‐azaheptadecane receptor and 4,5‐dimethoxy‐2‐nitrobenzyl (DMNB) chromophore has been prepared using trimethylsilyl trifluoromethanesulfonate‐assisted electrophilic aromatic substitution. Metal binding studies with ArgenCast‐1 reveal interactions with Ag + , Hg 2+ and Cu + , but only Ag + coordinates in both aqueous and organic solvents. The uncaging mechanism of ArgenCast‐1 metal complex involves a photoreaction that converts the nitrobenzydrol into the electron withdrawing nitrosobenzophenone that participates in a resonance interaction with a metal‐bound aniline nitrogen atom. The structural change following photolysis decreases availability of the nitrogen lone pair for Ag + coordination, but strong interactions between Ag + and the thioether ligands mitigates metal ion release. A resonance interaction with a key aci ‐nitro intermediate reduces the photolysis quantum yield of ArgenCast‐1, so several naphthyl‐based nitrobenzyl groups were screened as alternatives to DMNB. The naphthyl Ag + photocages, ArgenCast‐2 and ‐3, exhibit nearly identical quantum yield to ArgenCast‐1 owing to the dominance of resonance between aci ‐nitro intermediate and the aniline nitrogen atom.