Easily
accessible green-light activatable (>500 nm) photocages
based on red-shifted, π-extended coumarin scaffolds are developed
with uncaging efficiencies similar to those of recently introduced
BODIPY derivatives. The photocages possess increased aqueous solubility,
high absorption coefficients within the 450–600 nm range, and
exceptionally high two-photon cross sections.
We describe a new strategy to generate non-coordinating anions using zwitterionic metal-organic frameworks (MOFs). By assembly of anionic inorganic secondary building blocks (SBUs) ([In(CO2)4](-)) with cationic metalloporphyrin-based organic linkers, we prepared zwitterionic MOFs in which the complete internal charge separation effectively prevents the potential binding of the counteranion to the cationic metal center. We demonstrate the enhanced Lewis acidity of Mn(III)- and Fe(III)-porphyrins in the zwitterionic MOFs in three representative electrocyclization reactions: [2 + 1] cycloisomerization of enynes, [3 + 2] cycloaddition of aziridines and alkenes, and [4 + 2] hetero-Diels-Alder cycloaddition of aldehydes with dienes. This work paves a new way to design functional MOFs for tunable chemical catalysis.
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