Cu/Cd heterometallic solids with the [Cu(Hdea)(H2dea)]22+ motif (H2dea = diethanolamine): Exchange interactions through hydrogen bonding

The novel hybrid composites [Cu(Hdea)(H2dea)]2[CdX4], X = Br (1), I (2) have been prepared in reactions of zero-valent copper with cadmium halide in air-exposed solution containing the corresponding ammonium salt and diethanolamine (H2dea). X-ray crystallographic analysis reveals ionic solids of non-symmetric H-bonded dimeric [Cu(Hdea)(H2dea)]22+ cations and perhalocadmate anions. Further hydrogen bonding joins the dimers into ‘zig-zag’ like tetramers with copper–copper distances of about 5 Å for 1 and forms columns of the dimeric cations propagated along the b axis in 2 (copper–copper separations within the column are of ∼4.5 and 6 Å). In the crystal structure of 1, tetrahedral CdBr42- anions alternate with cationic tetramers in three dimensions, whereas CdI42- anions form sheets parallel to the ab plane in 2. The exchange interactions between paramagnetic centres in the solid state, revealed by the triplet EPR spectra measured at X-band frequency, occur along the Cu–OH···O–Cu pathways, being mediated by hydrogen bonds established between OH and alkoxo groups of diethanolamine ligands.

Two new solids built of non-symmetric H-bonded dimeric [Cu(Hdea)(H2dea)]22+ cations and perhalocadmate anions have been synthesized in mild conditions starting from zero-valent copper and cadmium halide. The exchange interactions between paramagnetic centres in the solid state, that occur along the Cu–OH···O–Cu pathways, are not identical in the two compounds.Figure optionsDownload as PowerPoint slide