Two novel nickel(ii) and cobalt(ii) metal–organic frameworks based on a rigid aromatic multicarboxylate ligand: syntheses, structural characterization and magnetic properties

Abstract

Two novel metal–organic frameworks, formulated as [Ni₃(qptc)₂(H₂O)₃]·3.5H₂O·3Me₂NH (1) and [Co₃(qptc)₂(H₂O)₄]·5H₂O (2) (H₄qptc = 1,1′:4′,1′′:4′′,1′′′-quaterphenyl-2,4,2′′′,4′′′-tetracarboxylic acid), have been hydrothermally constructed based on a rigid aromatic multicarboxylate ligand. The single-crystal X-ray diffraction analysis shows that complex 1 crystallizes in the triclinic crystal system with space group P and possesses a 4,8-connected 3D open framework including trinuclear nickel Ni₃ SBUs, which belongs to an scu topology with the point symbols (4¹⁶·6¹²) and (4⁴·6²). Complex 2 belongs to the monoclinic crystal system with space group C2/c and exhibits a 3D framework containing Co₃ SBUs, which is a flu topology with the point symbols (4¹²·6¹²·8⁴) and (4⁶). Furthermore, the variable-temperature magnetic susceptibilities of complexes 1 and 2 have been investigated. Both complexes show weak ferromagnetic coupling between metal ions estimated by using a linear trinuclear model for 1 in the range of 2–300 K and the PHI program for 2 in the range of 20–300 K taking the orbital contribution into consideration.