TITLE:
Metal-Dependent UV-Vis Response of Resorcinol in Alkaline Media: Comparative Study of Mg2+, Ni2+, Cu2+, Zn2+, and Fe2+
AUTHORS:
Ram Krishna Hona, Carl White
KEYWORDS:
Resorcinol, UV-Vis Spectroscopy, Metal Selectivity, Ligand-Field Effects, Jahn-Teller Distortion
JOURNAL NAME:
Journal of Materials Science and Chemical Engineering,
Vol.14 No.3,
March
10,
2026
ABSTRACT: The time-dependent UV-Vis response of resorcinol in alkaline solution (NH4OH) was investigated in the presence of divalent metal ions Mg2+, Ni2+, Cu2+, Zn2+, and Fe2+ in order to elucidate the origin of metal-specific optical behavior and assess intrinsic selectivity. Distinct spectral responses were observed depending on the electronic structure of the metal ion. Mg2+ produced a pronounced, time-dependent visible absorption band accompanied by a bathochromic shift, indicative of ligand-centered chromophore formation. Ni2+ exhibited characteristic metal-centered d-d transitions with a small red shift attributed to gradual ligand-field modulation. In contrast, Cu2+ and Zn2+showed no measurable red shift, displaying only intensity changes consistent with Jahn-Teller-dominated (Cu2+) or spectroscopically silent (Zn2+, d10) behavior. Fe2+ showed no discernible absorption features beyond the blank, indicating the absence of either ligand-centered chromophore formation or stable metal-centered transitions under the experimental conditions. These results demonstrate that metal selectivity in the resorcinol-NH4OH system is governed primarily by electronic structure rather than coordination alone, enabling clear differentiation among metal ions based on their spectral signatures.