Synthesis, crystal structures, luminescence and magnetic property of two complexes based on 5-nitroisophthalic acid

Based on 5-nitroisophthalic acid (5-H2nip) and bis(4-pyridyl)amine (dpa), the complexes {[Cd6(5-nip)6(dpa)4]·EtOH}n (1) and [Co5(5-nip)2(dpa)2(OH)2(SO4)2(H2O)2]n (2) have been synthesized and characterized by elemental analysis, single-crystal X-ray diffraction, IR spectroscopy, thermal gravimetry analysis, fluorescence and magnetic susceptibility. The carboxylate groups of the 5-nip2− adopt three different bridging modes [bis(chelate-bidentate), bis(bidentate) and bis(monodentate)]. The 5-nip2− anions and dpa play as linkers, which connect Cd(II) or Co(II) ions to form the three-dimensional structures of 1 and 2. Moreover, 1 exhibits intense solid-state luminescence emissions centered at 402 nm at room temperature, which mainly originates from the intraligand π–π* transitions of 5-nip2−. Magnetic susceptibility measurement indicates that 2 shows antiferromagnetic interactions between the Co(II) ions.