Fluorescent properties in solid-state and solution of novel tricyclic derivatives of chloro/bromophenylchromanones and 2-methylpyrazoline

In this work, we reported the synthesis and spectroscopic characterization of seven novel tricyclic compounds resulting from the reaction of 3-benzylidenechromanone with Cl or Br substituent in different positions and without halogen with methylhydrazine. The structural characterization of compounds was done through different techniques i.e., FTIR,1HNMR,a single and powder X-Ray diffraction. Moreover, fluorescence quantum yield and lifetime assessed their fluorescent properties in the solid state and various solvents. Derivatives with Cl or Br substituent in positions 2 and 4 are isostructural. 4-Cl, 4-Br and 3-Cl compounds exhibit fluorescence with moderate efficiency (quantum yield 0.11-0.26) in solid state due to specific arrangements, so-called π-stack brick stone with head-to-tail self-assembly. Other crystalline compounds (2-Cl, 2-Br and 3-Br) that exhibit negligible fluorescence quantum yield have crossed V-type arrangement. In the solution, the nonhalogenated compound shows the best fluorescence efficiency. In turn, the presence of halogen atoms results in fluorescence decreasing. TD-DFT study revealed that unsubstituted compound higher emissive in solution has a different electron density distribution at HOMO and LUMO levels than less emissive substituted compounds (A3 and A3).

Novel 'main-part' isostructuralism in metal complexes with 1-methylimidazole: crystal structures, energy calculations and magnetic properties

Two new transition metal complexes with 1-methylimidazole (1-MeIm) and azide as ligands, namely, [Co(1-MeIm)₄(N₃)₂] (1) and [Ni(1-MeIm)₄(N₃)₂] (2), have been synthesized and characterized by IR, Raman, UV-Vis and XPS spectroscopy. Their crystal structures were solved by single-crystal X-ray diffraction. The supramolecular self-assembly of the two complexes is governed by non-classical C-H⋯N hydrogen bonds and C-H⋯π interactions. Lattice energies and intermolecular interaction energies for various molecular pairs are quantified using the PIXEL method. DFT computational studies to assess the binding energy through modern tools like non-covalent interaction (NCI plots) analysis and reduced density gradient (RDG) analysis have also been carried out. A detailed analysis of geometric descriptors revealed the existence of quasi-isostructural pairs or 'main-part' isostructuralism in a series formed by 1, 2, and a related cadmium complex, being more evident in the 1/2 pair. DFT studies using theoretical models have been used to disclose the relative importance of the H-bond and C-H⋯π noncovalent interactions. Magnetic measurements for compound 1 show weak ferrimagnetic coupling between adjacent M(II) centers, mediated by H-bonding and C-H⋯π non-covalent interactions.