Mixed ligand complexes of copper(II), cobalt(II), nickel(II) and zinc(II) with thiocyanate and pyrazole based tetradentate ligand: Syntheses, characterizations and structures

Facile synthesis of acridine-based nickel(II) complexes via metal-mediated rearrangement of diphenylamine derivative and application in H2 evolution reaction

In this study, the formation of acridine-based metal complexes from rearrangement of diphenylamine-2,2'-dicarboxaldehyde (2,2'-dpadc) in the presence of transition metal ions was investigated. As a result, two novel isomorphic nickel(II) complexes bearing acridine-based Schiff-base ligand [NiLACR](X)2·CH3CN (X = BF4 (1), ClO4 (2), LACR = (E)-N1-(2-((acridin-4-ylmethylene)amino)ethyl)-N1-(2-aminoethyl)ethane-1,2-diamine) were successfully synthesized via a one-pot condensation of 2,2'-dpadc and tris(2-aminoethyl)amine (TREN) with a satisfactory yield of approximately 60%. These complexes were fully characterized by X-ray crystallography, UV-vis spectroscopy and CHN elemental analysis. Additionally, their thermal stability (thermogravimetric analysis) and electrochemical properties were also determined. A plausible mechanism for the nickel(II)-mediated rearrangement of 2,2'-dpadc to form the acridine-based nickel(II) complex was proposed. To demonstrate their potential applications, complex 1 was explored in the realm of electrocatalysis. It exhibited moderate activity towards hydrogen evolution reaction (HER). During 1-h controlled-potential electrolysis (CPE) experiments, H2 production (16 micromole) was observed with faradaic efficiency of 40% when the reaction was conducted in a TBAPF6/DMF solution at -2.1 V vs. Fc/Fc+ in the presence of acetic acid as a proton source. The facile synthesis of these acridine-based nickel(II) complexes reported herein may stimulate further development of novel acridine-based ligands and their corresponding metal complexes for a wide range of applications.

Synthesis of water-soluble Ni(II) complexes and their role in photo-induced electron transfer with MPA-CdTe quantum dots

Photocatalytic water splitting using solar energy for hydrogen production offers a promising alternative form of storable and clean energy for the future. To design an artificial photosynthesis system that is cost-effective and scalable, earth abundant elements must be used to develop each of the components of the assembly. To develop artificial photosynthetic systems, we need to couple a catalyst for proton reduction to a photosensitizer and understand the mechanism of photo-induced electron transfer from the photosensitizer to the catalyst that serves as the fundamental step for photocatalysis. Therefore, our work is focused on the study of light driven electron transfer kinetics from the quantum dot systems made with inorganic chalcogenides in the presence of Ni-based reduction catalysts. Herein, we report the synthesis and characterization of four Ni(II) complexes of tetradentate ligands with amine and pyridine functionalities (N2/Py2) and their interactions with CdTe quantum dots stabilized by 3-mercaptopropionic acid. The lifetime of the quantum dots was investigated in the presence of the Ni complexes and absorbance, emission and electrochemical measurements were performed to gain a deeper understanding of the photo-induced electron transfer process.