Homo- and Hetero-Oligonuclear Complexes of Platinum Group Metals (PGM) Coordinated by Imine Schiff Base Ligands

Oligonuclear Metal Complexes with Schiff Base Ligands

As stated by two of the seven papers [...].

Novel Pyrazole-Based Transition Metal Complexes: Spectral, Photophysical, Thermal and Biological Studies

A novel bioactive Schiff base (HL) named 3-methyl-1-phenyl-5-((5-nitrosalicylidene)amino)pyrazole was prepared by condensing 5-amino-3-methyl-1-phenylpyrazole with 5-nitrosalicyldehyde in methanol on a heating mantle in refluxing condition for 1 h. Some transition metal complexes of the ligand in (1 : 1) and (1 : 2) have also been prepared by condensing the metal acetate salt with the synthesized Schiff base. The Schiff base and metal complexes were characterized by different physiochemical techniques, i. e., 1 H-NMR, InfraRed, mass spectroscopy, elemental analysis, Ultraviolet-Visible, Cyclic voltammetry, electronic spectra and Electron spin resonance. The presence of water molecules in the complexes have been calculated with the help of thermogravimetric analysis. Kinetic parameters such that entropy change, enthalpy change and activation energy have been calculated with the help of Coats-Redfern equations. Fluorescence spectra showed enhancement in the fluorescence signal of the metal complexes. Square planar geometry for the copper complexes and octahedral geometry for the other metal complexes have been proposed with help of various methods. Biological activities of all the compounds have been carried out and the results disclosed that the metal complexes have high biological activity than the Schiff base having MIC value in the range 25-3.12 μg/mL and mycelial growth inhibition 60.82-96.98 %.

Photofunctions in Hybrid Systems of Schiff Base Metal Complexes and Metal or Semiconductor (Nano)Materials

Composite materials very often provide new catalytic, optical or other physicochemical properties not observed for each component separately. Photofunctions in hybrid systems are an interesting topic of great importance for industry. This review presents the recent advances, trends and possible applications of photofunctions of hybrid systems composed of Schiff base metal complexes and metal or semiconductor (nano)materials. We focus on photocatalysis, sensitization in solar cells (DSSC-dye sensitized solar cell), ligand-induced chirality and applications in environmental protection for Cr(VI) to Cr(III) reduction, in cosmetology as sunscreens, in real-time visualization of cellular processes, in bio-labeling, and in light activated prodrug applications.

The Physical Chemistry and Chemical Physics (PCCP) Section of the International Journal of Molecular Sciences in Its Publications: The First 300 Thematic Articles in the First 3 Years

The Physical Chemistry and Chemical Physics Section (PCCP Section) is one of the youngest among the sections of the International Journal of Molecular Sciences (IJMS)—the year 2021 will only mark three years since its inception [...]

Nickel(II)-Based Building Blocks with Schiff Base Derivatives: Experimental Insights and DFT Calculations

We have recently reported a series of neutral square planar tridentate Schiff base (L) complexes of the general formula [(L)M(py)], showing relatively high first-order hyperpolarizabilities and NLO redox switching behavior. In the present study, new members of this family of compounds have been prepared with the objective to investigate their potential as building blocks in the on-demand construction of D-π-A push–pull systems. Namely, ternary nickel(II) building blocks of general formula [(L^A/D)Ni(4-pyX)] (4–7), where L^A/D stands for an electron accepting or donating dianionic O,N,O-tridentate Schiff base ligand resulting from the monocondensation of 2-aminophenol or its 4-substituted nitro derivative and β-diketones R-C(=O)CH₂C(=O)CH₃ (R = methyl, anisyl, ferrocenyl), and 4-pyX is 4-iodopyridine or 4-ethynylpyridine, were synthesized and isolated in 60–78% yields. Unexpectedly, the Sonogashira cross-coupling reaction between the 4-iodopyridine derivative 6 and 4-ethynylpyridine led to the formation of the bis(4-pyridyl) acetylene bridged centrosymmetric dimer [{(L^D)Ni}₂(µ²-py-C≡C-py)] (8). Complexes 4–8 were characterized by elemental analysis, FT-IR and NMR spectroscopy, single crystal X-ray diffraction and computational methods. In each compound, the four-coordinate Ni(II) metal ion adopts a square planar geometry with two nitrogen and two oxygen atoms as donors occupying trans positions. In 8, the Ni…Ni separation is of 13.62(14) Å. Experimental results were proved and explained theoretically exploiting Density Functional Theory calculations.

Decoding Directing Groups and Their Pivotal Role in C-H Activation

Synthetic organic chemistry has witnessed a plethora of functionalization and defunctionalization strategies. In this regard, C-H functionalization has been at the forefront due to the multifarious applications in the development of simple to complex molecular architectures and holds a brilliant prospect in drug development and discovery. Despite been explored tremendously by chemists, this functionalization strategy still enjoys the employment of novel metal catalysts as well metal-free organic ligands. Moreover, the switch to photo- and electrochemistry has widened our understanding of the alternative pathways via which a reaction can proceed and these strategies have garnered prominence when applied to C-H activation. Synthetic chemists have been foraging for new directing groups and templates for the selective activation of C-H bonds from a myriad of carbon-hydrogen bonds in aromatic as well as aliphatic systems. As a matter of fact, by varying the templates and directing groups, scientists found the answer to the challenge of distal C-H bond activation which remained an obstacle for a very long time. These templates have been frequently harnessed for selectively activating C-H bonds of natural products, drugs, and macromolecules decorated with multiple C-H bonds. This itself was a challenge before the commencement of this field as functionalization of a site other than the targeted site could modify and hamper the biological activity of the pharmacophore. Total synthesis and pharmacophore development often faces the difficulty of superfluous reaction steps towards selective functionalization. This obstacle has been solved by late-stage functionalization simply by harnessing C-H bond activation. Moreover, green chemistry and metal-free reaction conditions have seen light in the past few decades due to the rising concern about environmental issues. Therefore, metal-free catalysts or the usage of non-toxic metals have been recently showcased in a number of elegant works. Also, research groups across the world are developing rational strategies for directing group free or non-directed protocols that are just guided by ligands. This review encapsulates the research works pertinent to C-H bond activation and discusses the science devoted to it at the fundamental level. This review gives the readers a broad understanding of how these strategies work, the execution of various metal catalysts, and directing groups. This not only helps a budding scientist towards the commencement of his/her research but also helps a matured mind searching out for selective functionalization. A detailed picture of this field and its progress with time has been portrayed in lucid scientific language with a motive to inculcate and educate scientific minds about this beautiful strategy with an overview of the most relevant and significant works of this era. The unique trait of this review is the detailed description and classification of various directing groups and their utility over a wide substrate scope. This allows an experimental chemist to understand the applicability of this domain and employ it over any targeted substrate.

A Review on the Advancements in the Field of Metal Complexes with Schiff Bases as Antiproliferative Agents

Metal complexes play an essential role in pharmaceutical sciences for their multiple and important activities. Schiff bases are versatile pharmacophores able to form chelating complexes with several metals in different oxidation states. Complexes with Schiff bases are widely described in the literature for their multiple actions and numerous advantages, such as low cost and easy synthesis. They show multiple biological activities, including antimicrobial, antioxidant, antimalarial, antinflammatory and antitumor. Schiff bases may also form complexes with lanthanides and actinides acting as catalysts (e.g., in various synthetic processes) and antitumor agents. This review intends to extend on our previous paper regarding Schiff bases as antitumorals, highlighting the importance, in the field of the anticancer agents, of these tools as ligands of metal complexes.

Ultrasound-Assisted Synthesis and Crystal Structure of Novel 2D Cd (II) Metal–Organic Coordination Polymer with Nitrite End Stop Ligand as a Precursor for Preparation of CdO Nanoparticles

In the present research, a sonochemical approach was applied to prepare new cadmium(II) coordination 2D polymer, [Cd(L)(NO2)2]n (L = 1,2-bis(1-(pyridin-3-yl)ethylidene)hydrazine) and structurally characterized with various spectroscopic techniques including XRD, elemental analysis, SEM, and IR spectroscopy. The coordination number of cadmium (II) ions is seven (CdN2O5) by two nitrogen atoms from two organic Schiff base ligand and five oxygen of nitrite anions. The 2D sheet structures ended by nitrite anions and the nitrite anion displayed the end-stop role. The comprehensive system showed a three-dimensional structure with several weak interactions. The high-intensity ultrasound is regarded as an easy, environmentally-friendly, and flexible synthetic instrument for the compounds of coordination. CdO NPs was obtained by thermolysing 1 at 180 °C with oleic acid (as a surfactant). Further, the size and morphology of the produced CdO nanoparticles were investigated through SEM.

Imine-functionalized polysiloxanes for supramolecular elastomers with tunable mechanical properties

A series of imine-functionalized polysiloxanes were reported for the first time and used to build supramolecular coordination elastomers.