Enhancement of Intermolecular Magnetic Exchange through Halogen···Halogen Interactions in Bisadeninium Rhenium(IV) Salts

• Published in: Crystal growth & design 2017-10, Vol.17 (10), p.5342-5348
• Main Authors: Armentano, Donatella, Barquero, Miguel A, Rojas-Dotti, Carlos, Moliner, Nicolas, De Munno, Giovanni, Brechin, Euan K, Martínez-Lillo, José
• Format: Article
• Language: English
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/acs.cgd.7b00841

Two novel ReIV salts of general formula [H2ade]2[ReIVX6]­X2·4H2O [H2ade2+ = 9H-adenine-1,7-diium; X = Cl­(1) and Br­(2)] have been synthesized and magnetostructurally characterized. 1 and 2 are isostructural salts that crystallize in the orthorhombic system with space group Fdd2. Both compounds are made up of discrete mononuclear [ReIVX6]2– and X– anions and doubly protonated adenine cations. The six-coordinate rhenium­(IV) ion is bonded to six halide ligands [X = Cl (1) and Br (2)] in an octahedral geometry. Short intermolecular ReIV–X···X–ReIV interactions, as well as ReIV–X···H–N­(H2ade) and ReIV–X···H–Ow hydrogen bonds, are present in the crystal lattice of 1 and 2. Magnetic susceptibility measurements on polycrystalline samples of 1 and 2 in the temperature range 2.0–300 K show the occurrence of significant intermolecular antiferromagnetic interactions in both compounds, resulting in the observation of maxima in χM at ca. 6.0 (1) and 12.0 K (2). The larger spin delocalization from the ReIV ion onto the peripheral bromide ligands when compared to the chloride ligands accounts for the enhancement of the magnetic exchange observed in 2.