In [Fe(ebbtr)₂(CH₃CN)₂](CF₃SO₃)₂·4CH₃CN spin crossover is associated with the occurrence of “normal” and “reverse” hysteresis loops separated by a region of stable HS form. This results from trans–trans → gauche–trans conformational changes of ebbtr molecules and anion reorientation, which occur in different ways during cooling and during heating.

In the two dimensional coordination network [Fe(ebbtr)₂(CH₃CN)₂](ClO₄)₂·4CH₃CN a sequence of LS → HS → LS → HS transitions occurs.

Analysis of the crystal packing of the title porphyrin derivative (C₇₂H₅₄N₄O₄) suggests no classical hydrogen bonds between neighbor molecules. X-ray crystal structure shows that all benzyl units of this porphyrin have close C–H⋯π weak contacts with phenyl or porphyrinyl units forming a network of porphyrin rings. Also C–H⋯O and parallel aromatic–aromatic weak interactions play an important role in structure extension. All of these interactions control the crystal packing of molecules. X-ray diffraction was used to perform single crystal analysis. The structure was solved in the triclinic space group P-1, with unit cell parameters: a = 8.0597(3) Å, b = 11.6862(4) Å, c = 14.2572(5) Å, α = 96.173(3)°, β = 93.150(4)°, and γ = 93.679(3)°, V = 1329.72(8) ų, Z = 1.

A series of 5,8-quinolinedione derivatives containing one or two alkoxy groups was synthesized and characterized by ¹H- and ¹³C-NMR, IR and MS spectra. X-ray diffraction was used to investigate the crystal structures of 6-chloro-7-(2-cyjanoethoxy)-5,8-quinolinedione and 6,7-di(2,2,2-trifloroethoxy)-5,8-quinolinedione. All studied compounds were tested in vitro for their antiproliferative activity against three human cancer cell lines and human normal fibroblasts. Most of the compounds showed higher cytotoxicity than the starting compound, 6,7-dichloro-5,8-quinolinedione, and cisplatin, which was used as a reference agent.

A new approach to the synthesis of selected quinolinecarbaldehydes with carbonyl groups located at C5 and/or in C7 positions is presented in this paper in conjunction with spectroscopic characterization of the products. The classical Reimer-Tiemann, Vilsmeier-Haack and Duff aldehyde synthesis methods were compared due to their importance. Computational studies were carried out to explain the preferred selectivity of the presented formylation transformations. A carbene insertion reaction based on Reimer-Tiemann methodology is presented for making 7-bromo-8-hydroxyquinoline-5-carbaldehyde. Additionally, Duff and Vilsmeier-Haack reactions were used in the double formylation of quinoline derivatives and their analogues benzo[h]quinolin-10-ol, 8-hydroxy-2-methylquinoline-5,7-dicarbaldehyde, 8-(dimethylamino) quinoline-5,7-dicarbaldehyde and 10-hydroxybenzo[h]quinoline-7,9-dicarbaldehyde. Four Schiff base derivatives of 2,6-diisopropylbenzenamine were prepared from selected quinoline-5-carbaldehydes and quinoline-7-carbaldehyde by an efficient synthesis protocol. Their properties have been characterized by a combination of several techniques: MS, HRMS, GC-MS, FTIR, electronic absorption spectroscopy and multinuclear NMR. The electrochemical properties of 8-hydroxy-quinoline-5-carbaldehyde, 6-(dimethylamino)quinoline-5-carbaldehyde and its methylated derivative were investigated, and a strong correlation between the chemical structure and obtained reduction and oxidation potentials was found. The presence of a methyl group facilitates oxidation. In contrast, the reduction potential of methylated compounds was more negative comparing to non-methylated structure. Calculations of frontier molecular orbitals supported the finding. The structures of 8-hydroxy-2-methylquinoline-5,7-dicarbaldehyde and four Schiff bases were determined by single-crystal X-ray diffraction measurements.