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.

Graphical abstractTwo 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 full-size imageDownload as PowerPoint slide