Molecular and Polymeric Cadmium Nitrate Complexes with Bridging 3-Aminoquinoline: Synthesis, Structures, and Luminescence Properties

The reaction of Cd(NO3)2⋅4H2O with 3-aminoquinoline (3-Аq) affords the molecular and poly-meric complexes [Cd(NO3)2(H2O)(3-Аq)]⋅2MeCN (I) and {[Cd(NO3)2(3-Аq)2]⋅MeCN}n (II), respectively, depending on the ratio of the reagents and composition of the medium. Compounds I and II are studied by elemental analysis, X-ray structure analysis (CIF files CCDC nos. 2015059 (I) and 2015060 (II)), X-ray diffraction analysis, and luminescence investigation. In both cases, the environment of the cadmium atom is a pentagonal bipyramid. The 3-Аq molecules of dimer I are bridging ligands, and the monodentate mode of binding with Cd(II) along with the indicated function is observed in the polymer. Hydrogen bonds between the H atoms of the NH2 group and the N atom of the solvate MeCN molecule and the O atom of the NO3 group result in the formation of a three-dimensional supramolecular network, which is additionally strengthened by intermolecular stacking interactions between the aromatic fragments of 3-Аq of the adjacent molecules. Both compounds luminesce in the red spectral range. As compared to the spectrum of free 3-Аq, the shift of the emission bands of dimer I and polymer II in this range is 93 and 38 nm, respectively.