Co(ii) and Ni(ii) complexes based on anthraquinone-1,4,5,8-tetracarboxylic acid (H4AQTC): canted antiferromagnetism and slow magnetization relaxation in {[Co2(AQTC)(H2O)6]·6H2O}

Abstract

Three coordination polymers {[Co₂(AQTC)(H₂O)₆]·6H₂O}_n (1), {[M₂(AQTC)(bpym)(H₂O)₆]·6H₂O}_n (M = Co(2), Ni(3)) have been synthesized and structurally characterized, where H₄AQTC is anthraquinone-1,4,5,8-tetracarboxylic acid and bpym is 2,2′-bipyrimidine. Complex 1 features a 3-D structure, where layers of Co₂(AQTC) are cross-linked by Co–H₂O chains. Complexes 2 and 3 are isostructural and display 1-D chain structures. The chains are connected through hydrogen-bonding interactions to form 3-D supramolecular structures. Magnetic properties of these complexes are investigated. Compound 1 shows canted antiferromagnetism and slow relaxation below 4.0 K. For complexes 2 and 3, dominant antiferromagnetic interactions are observed. The luminescent properties of the three complexes are investigated as well.