Experimental and DFT Study of the Photoluminescent Green Emission Band of Halogenated (-F, -Cl, and -Br) Imines.

The morphological, optical, and structural changes in crystalline chiral imines derived from 2-naphthaldehyde as a result of changing the -F, -Cl, and -Br halogen (-X) atoms are reported. Scanning electron microscopy (SEM), optical absorption, photoluminescence (PL), and powder X-ray diffraction (XRD) studies were performed. Theoretical results of optical and structural properties were calculated using the PBE1PBE hybrid functional and compared with the experimental results. Differences in surface morphology, absorbance, XRD, and PL of crystals were due to the change of halogen atoms in the chiral moiety of the imine. Absorption spectra exhibited the typical bands of the naphthalene chromophore located in the ~200-350 nm range. Observed absorption bands in the UV region are associated with π→π* and n→π* electronic transitions. The band gap energy was calculated using the Tauc model. It showed a shift in the ~3.5-4.5 eV range and the crystals exhibited different electronic transitions associated with the results of absorbance in the UV region. XRD showed the monoclinic→orthorhombic crystalline phase transition. PL spectra displayed broad bands in the visible region and all the samples have an emission band (identified as a green emission band) in the ~400-750 nm range. This was associated with defects produced in the morphology, molecular packing, inductive effect and polarizability, crystalline phase transition, and increase in size of the corresponding halogen atoms; i.e., changes presumably induced by -C-X…X-, -C-X…N-, -C-N…π, and -C-X…π interactions in these crystalline materials were associated with morphological, optical, and structural changes.

2-Amino-4-ferrocenyl-thia-zole.

The title compound, [Fe(C5H5)(C8H7N2S)], was synthesized by the direct reaction of acetyl-ferrocene, thio-urea and resublimed iodine. The structure shows one mol-ecule in the asymmetric unit. The amino-thia-zole ring makes an angle of 14.53 (13)° with the ferrocenyl ring to which it is attached. In the crystal, pairs of complex mol-ecules inter-act via inter-molecular N-H⋯N hydrogen bonds, forming a cyclic dimer which then inter-acts with other dimers through C-H⋯π inter-actions.

X-ray structure analysis of symmetrically substituted 1,1'-diformyl-ruthenocene.

1,1'-Di-formyl-ruthenocene, [Ru(C6H5O)2], crystallizes in the ortho-rhom-bic system in the P212121 space group at room temperature. There are two crystallographically independent mol-ecules in the asymmetric unit. The cyclo-penta-dienyl rings have eclipsed configuration. The mol-ecules self-assemble in a two-dimensional structure by C-H⋯O and C-H⋯π inter-actions with cisoid relative orientations of the two formyl groups. The crystal studied was refined as an inversion twin.

2-Methyl-1,4,5-triphenyl-1H-imidazole.

In 2-methyl-1,4,5-triphenyl-1H-imidazole, C(22)H(18)N(2), the three substituent phenyl groups are not delocalized with the imidazole moiety; the dihedral angles these phenyl groups form with the imidazole ring are in the range 25.90 (5)-63.49 (6) degrees.