VisibIe Color Change of Copper (Ⅱ) CompIexes in Reversible SCSC Transformation: The Effect of Structure on Color
A comprehensive 8-hour chemical experiment was devised around the single crystal-to-single crystal (SCSC) transformation, an emerging method in solid-phase inorganic synthesis. By employing a direct additive process technology, the green complexes (H3O)[K(15C5)2][CuCl4] (1) were synthesized in both powder and macro-single crystal forms. Upon temperature induction, complex 1 transitions to the red complex [K(15C5)2][CuCl3] (2), a shift attributed to the restricted dimerization of [CuCl3]− resulting from steric repulsion effects in the solid phase. Notably, complex 2 can revert back to complex 1 when exposed to hydrochloric steam through an SCSC transformation. This SCSC transformation between complexes 1 and 2 is vividly demonstrated on filter paper, showcasing dynamic color changes, either as texts or drawings. This rapid and visually engaging process is poised to spark students' curiosity. Furthermore, learners can bridge theory with practice, recognizing that the distinct colors of the two complexes arise from varying coordination numbers of copper (Ⅱ), grounded in the crystal field theory of inorganic chemistry. Characterization of the complexes was achieved using single crystal X-ray diffraction, powder X-ray diffraction, UV-visible spectroscopy, and Fourier transform infrared spectroscopy, confirming the differentiation of the complexes and the successful SCSC transformation. This aspect of the experiment allows students to hone their skills with the Cambridge crystal structure database and enhance their data analysis capabilities, fostering proficiency in operating large-scale instruments safely and accurately. With its streamlined design, modular teaching approach, and cost-effective reagents, this experiment is primed for integration into undergraduate curriculum for chemistry and related disciplines.
Single-crystal to single-crystal transformationCopper (Ⅱ) complexSteric repulsion effectCrystal field theoryComprehensive chemical experiment
万方数据
维普
