Fixation of atmospheric CO2 as novel carbonate–(water)2–carbonate cluster and entrapment of double sulfate within a linear tetrameric barrel of a neutral bis-urea scaffold?

Dalton Transactions Pub Date: 2017-06-30 DOI: 10.1039/C7DT01697B

Abstract

A meta-phenylenediamine-based disubstituted bis-urea receptor L1 with electron-withdrawing 3-chloro and electron-donating 4-methylphenyl terminals has been established as a potential system to fix and efficiently capture atmospheric CO2 as air-stable entrapment of an unprecedented {CO32?–(H2O)2–CO32?} cluster (complex 1a) within its tetrameric long straight pillar-like assembly entirely sealed by n-TBA cations via formation of a barrel-type architecture. L1 and its isomeric 4-bromo-3-methyl disubstituted bis-urea receptor L2 have been found to entrap similar kinds of water-free naked sulfate–sulfate double anion (complexes 1b and 2a) by cooperative binding of urea moieties inside the two pairs of the inversion-symmetric linear tetrameric barrel of L1 and L2, respectively. On the other hand, in the presence of excess halides, L1 self-assembles to form hexa-coordinated fluoride complex 1c and tetra-coordinated bromide complex 1d, while L2 self-assembles to form penta-coordinated fluoride complex 2b in the solid state via semicircular receptor architectures and non-cooperative H-bonding interactions of urea moieties.

Graphical abstract: Fixation of atmospheric CO2 as novel carbonate–(water)2–carbonate cluster and entrapment of double sulfate within a linear tetrameric barrel of a neutral bis-urea scaffold
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