The synthesis and characterization of diaquabis[2-(2-hydroxyethyl)pyridine-κ² N,O)nickel(II) dinitrate, [Ni(C₇H₉NO)₂(H₂O)₂](NO₃)₂, under ambient conditions is reported and compared with catena-poly[[bis[2-(2-hydroxyethyl)pyridine-κ² N,O]copper(II)]-μ-sulfato-κ² O:O′], [Cu(C₇H₉NO)₂(SO₄)] _n [Zeghouan et al. (2016). Private communication (refcode 1481676). CCDC, Cambridge, England]. In the two complexes, the 2-(2-hydroxyethyl)pyridine ligands coordinate the metal ions through the N atom of the pyridine ring and the O atom of the hydroxy group, creating a chelate ring. The Ni^II or Cu^II ion lies on an inversion centre and exhibits a slightly distorted MO₄N₂ octahedral coordination geometry, build up by O and N atoms from two 2-(2-hydroxyethyl)pyridine ligands and two water molecules or two O atoms belonging to sulfate anions. The sulfate anion bridges the Cu^II ions, forming a polymeric chain. The photoluminescence properties of these complexes have been studied on as-synthesized samples and reveal that both compounds display a strong blue-light emission with maxima around 497 nm. From DFT/TDDFT studies, the blue emission appears to be derived from the ligand-to-metal charge-transfer (LMCT) excited state. In addition, the IR spectroscopic properties and thermogravimetric behaviours of both complexes have been investigated.

In the title salt, [Co(C7H9NO)2(H2O)2]Cl2, the Co(II) cation, located on an inversion center, is N,O-chelated by two hy-droxy-ethyl-pyridine ligands and coordinated by two water mol-ecules in a distorted O4N2 octa-hedral geometry. In the crystal, the Cl(-) anions link with the complex cations via O-H⋯Cl hydrogen bonds, forming a three-dimensional supra-molecular architecture. π-π stacking is observed between the pyridine rings of adjacent mol-ecules [centroid-centroid distance = 3.5810 (11) Å].

The title layered polymer, [Co(N3)2(C7H10N2)2] n , contains Co(II), azide and 4-(dimethyl-amino)-pyridine (4-DMAP) species with site symmetries m2m, 2 and m, respectively. The Co(2+) ion adopts an octa-hedral coordination geometry in which four N atoms from azide ligands lie in the equatorial plane and two 4-DMAP N atoms occupy the axial positions. The Co(II) atoms are connected by two bridging azide ligands, resulting in a chain parallel to the c axis.

The asymmetric unit of the title hydrated salt, C(6)H(14)NO(2) (+)·F(-)·H(2)O, contains a discrete cation with a protonated amino group, a halide anion and one water mol-ecule. The crystal structure is composed of double layers parallel to (010) held together by N-H⋯O, N-H⋯F, O-H⋯F and C-H⋯F hydrogen bonds, forming a two-dimensional network, and stacked along the c axis, viz. hydro-philic layers at z = 0 and 1/2 and hydro-phobic layers at z = 1/3 and 2/3.