Synthesis, stereochemistry and antimicrobial activity of copper(II) and nickel(II) complexes of 4-phenylsemicarbazones

2-Acetylpyridine-(4-phenylsemicarbazone) and o-vanillin-(4-phenylsemicarbazone) have been prepared and characterized on the basis of elemental analyses, infrared, electronic, 1H and 13C NMR spectra. Several nickel(II) and copper(II) complexes have been obtained from these ligands. The IR spectra of the ligands as well as those of their complexes suggest that 2-acetylpyridine-(4-phenylsemicarbazone) is a neutral tridentate molecule while o-vanillin-(4-phenylsemicarbazone) is a monobasic tridentate molecule. On the basis of the analytical data, magnetic moments and spectral data, a square-planar geometry has been proposed for the nickel(II) and copper(II) complexes with these ligands. Some representative complexes of copper(II) and nickel(II) were found to have remarkable antifungal and antibacterial activity.KEY WORDS: 4-Phenylsemicarbazone, Metal complexes, Stereochemistry, Antimicrobial activity Bull. Chem. Soc. Ethiop. 2011, 25(3), 361-370

Synthesis, crystal and molecular structure of manganese (II) complex of 2-acetylpyridine N (4) ethylthiosemicarbazone

A novel Mn(II) complex with thiosemicarbazone derived from 2-acetylpyridine and N(4)-ethylthiosemicarbazide has been prepared. The single-crystal X-ray analysis of the Mn(II) complex showed a distorted octahedral MnN4S2 environment with the ligand chelating via the nitrogen and sulfur donor atoms in a tridentate manner. The triclinic form of the ligand which has crystallized in a monoclinic system in other works is also described. The basicity of  nitrogen atoms of the ligand was tested with its reaction with HNO3 and the structure of the salt obtained is reported. The result shows that the lone pair of the pyridine nitrogen is more available due to the delocalization of other nitrogen lone pair of electron. http://dx.doi.org/10.21060/cis.2016.41

Synthesis, crystal structure and magnetic properties of [Cu(mal)(abpt)(H2O)].3/2H2O and [Cu2(sq)(abpt) 2].2H2O (mal = malonate, sq = squarate, abpt =4-amino-3,5-di-2-pyridyl-4H-1,2,4 triazole)

Two new mixed-ligand complexes of formula [Cu(mal)(abpt)(H2O)].3/2H2O (1) and [Cu2(sq)(abpt) 2].2H2O (2) [mal = malonate, abpt = 4-amino-3,5-di-2-pyridyl-4H-1,2,4 triazole and sq = squarate], have been prepared and characterized by X-ray crystal structure determination and magnetic studies. Complex 1 crystallizes in the monoclinic system, space group C2/c, with a = 14.0086(2) Å, b = 10.0980(2) Å, c = 25.630(4) Å; β = 97.5900(10) o, and Z = 8. Complex 2 crystallizes in the triclinic system, space group P-1 with a = 7.5696(15) Å, b = 8.4697(17) Å, c = 11.049(2) Å; β = 93.00(3)o,  α = 96.98(3), γ = 90.111(3) and Z = 1. Complex 1 consist of a neutral mononuclear [Cu(mal)(abpt)(H2O)] unit and water molecule of crystallization in a distorted square pyramidal coordination sphere, while complex 2 is viewed as being made up of [Cu(sq)(abpt)2] units with the squarato ligand bridging the two copper(II) cations. Variable temperature magnetic behaviour of the complexes reveals the existence of weak antiferromagnetic interaction for complex 1 and weak ferromagnetic intrachain interaction for complex 2.KEY WORDS: Copper(II) complexes, Mixed-ligand, Magnetic properties, Malonate, Squarate, 4-Amino-3,5-di-2-pyridyl-4H-1,2,4 triazoleBull. Chem. Soc. Ethiop. 2011, 25(1), 53-60

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Vapor Sorption and Solvatochromism in a Metal–Organic Framework of an Asymmetric Pyridylcarboxylate

Two new metal–organic frameworks (MOFs) of cobalt­(II) and 3-(4-pyridyl)­benzoate (34pba) were prepared concomitantly under solvothermal conditions. Using dimethylformamide (DMF) as solvent, {[Co­(34pba)₂­(H₂O)]­·1/2DMF­·H₂O}_<i>n</i>, <b>1</b>, can be prepared as a pure phase in the presence of the templating molecules arginine or proline, neither of which is incorporated in the resulting structure. {[Co­(34pba)₂]­·2DMA}_<i>n</i>, <b>2</b>, (where DMA is dimethylacetamide) has the same framework formula as two previously reported MOFs and represents a third in this series of structural isomers. The activated phase of <b>1</b>, <b>1d</b> absorbs a number of solvent vapors, across a wide range of polarities, with accompanying phase changes and solvatochromic responses. The facile exchange of guest species within the framework of <b>1d</b> is explained by the low activation energy (59–69 kJ mol^–1) for the desorption of water from <b>1d</b>·<b>H</b>_<b>2</b><b>O</b>

3.3.2. Synthesis, crystal structure and biological activity of 1-(phthalazin-1(2H)-one)[(Pyridin-2-yl)ethylidene]hydrazone and its cobalt (III) complex

A new mononuclear complex of cobalt (III) (2) with 1-(phthalazin-1(2H)-one)[(Pyridin-2-yl) ethylidene] hydrazone ligand (1) has been synthesized and characterized by elemental analysis, IR and mass spectroscopic techniques. The crystal structures of the free ligand (1) and its complex (2) have been determined by single crystal X-ray diffraction technique. In complex 2 the hydrazone ligand chelates to the cobalt (III) ion through nitrogen atoms in a tridentate manner, giving an octahedral geometry where the cobalt (II) was oxidized to cobalt (III). The antifungal activity of ligand 1 and its complex 2 was studied against Aspergillus niger, Aspergillus flavus and Candida albicans. The results revealed modest activity of complex 2 against the tested organism with inhibition zones of 14, 15 and 14 mm, compared to the free ligand 1 with the inhibition zones of 12, 11 and 12 mm for A. niger, A. flavus, C. albicans respectively

Success or Failure of Chiral Crystallization of Similar Heterocyclic Compounds

Single crystals of two achiral and planar heterocyclic compounds, C9H8H3O(CA1) and C8H5NO2 (CA4), recrystallized from ethanol, were characterized by single crystal X-ray analysis, respectively, and chiral crystallization was observed only for CA1 as P212121 (# 19), whereas it was not observed for CA4P21/c (# 14). In CA1, as a monohydrate, the hydrogen bonds were pronounced around the water of crystallization (O4), and the planar cyclic sites were arranged in parallel to slightly tilted positions. On the other hand, an anhydride CA4 formed a dimer by hydrogen bonds between adjacent molecules in the crystal, which were aggregated by van der Waals forces and placed in parallel planar cyclic sites