CO2 Fixation and Transformation by a Dinuclear Copper Cryptate under Acidic Conditions

Abstract CO 2 fixation and transformation by metal complexes continuously receive attention from the viewpoint of carbon resources and environmental concerns. We found that the dinuclear copper(II) cryptate [Cu 2 L 1 ](ClO 4 ) 4 ( 1 ; L 1 =N[(CH 2 ) 2 NHCH 2 ( m ‐C 6 H 4 )CH 2 NH‐(CH 2 ) 2 ] 3 N) can easily take up atmospheric CO 2 even under weakly acidic conditions at room temperature and convert it from bicarbonate into carbonate monoesters in alcohol solution. The compounds [Cu 2 L 1 (μ ‐ O 2 COH)](ClO 4 ) 3 ( 2 ), [Cu 2 L 1 (μ‐O 2 COR)](ClO 4 ) 3 ( 3 : R=CH 3 ; 4 : R=C 2 H 5 ; 5 : R=C 3 H 7 ; 6 : R=C 4 H 9 ; 7 : R=C 5 H 11 ; 8 : R=CH 2 CH 2 OH), [Cu 2 L 1 (μ ‐ O 2 CCH 3 )](ClO 4 ) 3 ( 9 ), and [Cu 2 L 1 (OH 2 )(NO 3 )](NO 3 ) 3 ( 10 ) were characterized by IR spectroscopy and ESI‐MS. The crystal structures of 2 – 6 and 10 were studied by single‐crystal X‐ray diffraction analysis. On the basis of the crystal structures, solution studies, and DFT calculations, a possible mechanism for CO 2 fixation and transformation is given.