The concept of variable stoichiometry cocrystallization is explored in halogen-bonded systems. Three novel cocrystals of 1,4-diiodotetrafluorobenzene and 3-nitropyridine with molar ratios of 1:1, 2:1, and 1:2, respectively, are prepared by slow evaporation methods. Single-crystal X-ray diffraction analysis reveals key differences between each of the nominally similar cocrystals. For instance, the 1:1 cocrystal crystallizes in the P21/n space group and features a single chemically and crystallographically unique halogen bond between iodine and the pyridyl nitrogen. The 2:1 cocrystal crystallizes in the P1- space group and features a halogen bond between iodine and one of the nitro oxygens in addition to an iodine-nitrogen halogen bond. The 1:2 cocrystal crystallizes with a large unit cell (V = 9896 Å3) in the Cc space group and features 10 crystallographically distinct iodine-nitrogen halogen bonds. Powder X-ray diffraction experiments carried out on the 1:1 and 2:1 cocrystals confirm that gentle grinding does not alter the crystal forms. 1H → 13C and 19F → 13C cross-polarization magic angle spinning (CP/MAS) NMR experiments performed on powdered samples of the 1:1 and 2:1 cocrystals are used as spectral editing tools to select for either the halogen bond acceptor or donor, respectively. Carbon-13 chemical shifts in the cocrystals are shown to change only very subtly relative to pure solid 1,4-diiodotetrafluorobenzene, but the shift of the carbon directly bonded to iodine nevertheless increases, consistent with halogen bond formation (e.g., a shift of +1.6 ppm for the 2:1 cocrystal). This work contributes new examples to the field of variable stoichiometry cocrystal engineering with halogen bonds.

The present study was conducted to investigate the distribution of selected metals (Fe, Zn, Cd, Pb, and Cu) in tissues of Nile Tilapia (Oreochromis niloticus) grown along El-Khadrawia drain-Mubark industrial Zone. The tissues analyzed included muscle and liver. Results showed metal concentrations in water followed a richness of: Fe> Zn> Cu> Pb >Cd mg/l (p < 0.05) while Fe> Cu > Zn > Pb > Cd mg/Kg dry wt. (p < 0.05) in muscles and liver tissues in winter season. Metal levels in muscles follow the level: Zn>Fe>Cu> Pb>Cd mg/Kg dry wt. (p < 0.05), while in liver they follow the level: Fe > Zn > Cu>Pb>Cd mg/Kg dry wt. (p < 0.05) in summer season. The presence of heavy metals led to significant decrease in nucleic acids (DNA & RNA) contents in liver tissue during summer season (p<0.05). So, the study showed that muscles of Nile Tilapia (Oreochromis niloticus) along El-Khadrawia drain are not safe from contamination with the metals investigated.