Aqueous and Solid Phase Synthesis of [Ni(Me3en)(acac)]BPh4 and its Solvatochromic Properties: A Laboratory Experiment for First-Year Undergraduates

Abstract

A laboratory experiment that involves the aqueous and solid phase synthesis, characterization, and solvatochromic properties exploration of red complex [Ni(Mei3en)(acac)]BPh4 has been developed for first-year undergraduates in the College of Chemistry and Chemical Engineering at Xiamen University. In contrast to previously reported synthesis methods ( Fukuda, Y. Studies on mixed chelates─II Mixed nickel(II) chelates with N,N,N′,N′-tetramethylethylenediamine and β-diketones. J. Inorg. Nucl. Chem. 1972, 34, 2315-2328 ; Funasako, Y. Thermochromic and solvatochromic Nafion films incorporating cationic metal-chelate complexes. Chem. Comm 2013, 49, 4688-4690 ; Hosokawa, H. Colorimetric Humidity and Solvent Recognition Based on a Cation-Exchange Clay Mineral Incorporating Nickel(II)-Chelate Complexes. Langmuir 2015, 31, 13048-13053 ; Nguyen, T. N. Studies on Mixed Chelates. VII. Mixed Nickel(II) Chelates Containing N,N′- or N,N-Dialkylethylenediamines and Acetylacetone. Bull. Chem. Soc. Jpn. 1977, 50 (1), 154-157 ; Wei, X. J. Vis-Spectrum Investigation of Thermo-Solvatochromic Behaviors of a Mixed Diamine and β-Diketonate Ligand Ni(II) Complex in Different Alcoholic Solutions. Acta Phys.-Chim. Sin. 2009, 25 (7), 1449-1454 ; Inorganic and Analytical Chemistry Experiment Test of The 10th Chinese National Undergraduate Chemistry Laboratory Tournament https://chemlabs.nju.edu.cn/DFS/file/2019/08/26/20190826132901247mmvyr5.pdf?iid=2382 (accessed November 2023).), which using a large amount of organic solvents, the aqueous and solid phase synthesis methods described here are remarkably green, environmentally friendly, high efficiency and highly reproducible, and the complex [Ni(Me3en)(acac)]BPh4 showing a remarkable reversible solvatochromic phenomenon, so this experiment is very suitable as a classroom demonstration for first-year undergraduates in inorganic chemistry or general chemistry. By performing this experiment, students will gain experience in solid phase synthesis, purification, and UV-vis characterization of the complex. In addition, students will gain appreciation of how solvatochromism and thermochromism (in acetone) of the complex Ni(Me3en)(acac)]BPh4 and their mechanisms, and progress in the understanding of the effect of the configuration of a complex on crystal field splitting, and the effect of crystal field splitting on color.