Two new Zn(II) complexes with tridentate hydrazone-based ligands (condensation products of 2-acetylthiazole) were synthesized and characterized by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy and single crystal X-ray diffraction methods. The complexes 1, 2 and recently synthesized [ZnL³(NCS)₂] (L³ = (E)-N,N,N-trimethyl-2-oxo-2-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)ethan-1-aminium) complex 3 were tested as potential catalysts for the ketone-amine-alkyne (KA²) coupling reaction. The gas-phase geometry optimization of newly synthesized and characterized Zn(II) complexes has been computed at the density functional theory (DFT)/B3LYP/6–31G level of theory, while the highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO and LUMO) energies were calculated within the time-dependent density functional theory (TD-DFT) at B3LYP/6-31G and B3LYP/6-311G(d,p) levels of theory. From the energies of frontier molecular orbitals (HOMO–LUMO), the reactivity descriptors, such as chemical potential (μ), hardness (η), softness (S), electronegativity (χ) and electrophilicity index (ω) have been calculated. The energetic behavior of the investigated compounds (1 and 2) has been examined in gas phase and solvent media using the polarizable continuum model. For comparison reasons, the same calculations have been performed for recently synthesized [ZnL³(NCS)₂] complex 3. DFT results show that compound 1 has the smaller frontier orbital gap so, it is more polarizable and is associated with a higher chemical reactivity, low kinetic stability and is termed as soft molecule.

The reaction between [(C ₅ Me ₅ )TiF ₃ ] or [(C ₅ Me ₄ Et)TiF ₃ ] respectively in the presence of CaF ₂ (prepared in situ) resulted in the formation of [{(C ₅ Me ₅ )TiF ₃ } ₄ CaF ₂ ] 1 or [{(C ₅ Me ₄ Et)TiF ₃ } ₄ CaF ₂ ] 2, an X-ray study of compound 2 showed it to possess a core analogous to a crown ether.

The recrystallization of [{Ti(C₅Me₅)F₃}₄CaF₂] 1 and [{Ti(C₅Me₄Et)F₃}₄CaF₂] 2 in the presence of an excess of hmpa (hexamethylphosphoramide) resulted in the formation of [{Ti(C₅Me₅)F₃}₄(CaF₂)(hmpa)] 3 and [{Ti(C₅Me₄Et)F₃}₄(CaF₂)(hmpa)] 4, respectively. The adducts 3 and 4 were spectroscopically characterized and the molecular structure of 4 was determined, showing a co-ordination of calcium by eight fluorine atoms from two [Ti₂(C₅Me₄Et)₂F₇]^– moieties and by an oxygen atom of an hmpa ligand. Adduct formation and solution behavior of 2 in different solvents was studied by ¹H and ¹⁹F NMR and variable-temperature NMR. A temperature dependent equilibrium between 2 and a solvated form 2·solv (solv = solvent molecule) is proposed. With increase of the temperature the equilibrium between 2 and 2·solv was observed to be entropy-shifted to the non-solvated form.

In the title compound, C₁₆H₁₃NO₂, the quinoline system is approximately planar with a maximum deviation from the least-squares plane of 0.059 (1) Å for the N atom. The phenyl ring is rotated by 62.16 (4)° with respect to the plane of the quinoline system. In the crystal, O—H...O hydrogen bonds link molecules into infinite chains running along theb-axis direction.

In the title hydrate, C(12)H(13)NO(4)·H(2)O, the piperidine ring that is fused to the benzene ring is in a sofa conformation with the chiral C atom lying 0.4084 (18) Å out of the plane of the nine fused-ring atoms. In the crystal, O-H⋯O and N-H⋯O hydrogen bonds link the organic mol-ecules and water mol-ecules into chains running along the b-axis direction. The chains are further connected into layers parallel to the bc plane by π-π inter-actions between inversion-related benzene rings [centroid-centroid distance = 3.8846 (9) Å].

In the title compound, C(12)H(13)NO(3), the quinoline ring system is approximately planar with a maximum deviation from the least-squares plane of 0.058 (2) Å. In the crystal, N-H⋯O and O-H⋯O hydrogen bonds link the mol-ecules into chains running along the b-axis direction. The chains also feature π-π inter-actions between pyridine and benzene rings of inversion-related mol-ecules [centroid-centroid distance = 3.609 (2) Å].