A Design of Copper(II) Coordination Polymers with <scp>l</scp>-Homoserine: Structural, Spectroscopic, and Biological Studies

Five copper-(II) coordination polymers<i>trans</i>-[Cu-(μ-l-hser)-(l-hser)] <i>_n</i> (<b>1a</b>), {<i>cis</i>-[Cu-(μ-l-hser)₂]·H₂O} <i>_n</i> (<b>1b·H₂O</b>), {[Cu-(μ-l-hser)-(H₂O)-(bpy)]₂SO₄·2H₂O} <i>_n</i> (<b>2·2H₂O</b>), {[Cu-(μ-l-hser)-(H₂O)-(bpy)]₂SO₄·3H₂O} <i>_n</i> (<b>2·3H₂O</b>), and {[Cu-(μ-l-hser)-(H₂O)-(bpy)]₂SO₄·4H₂O} <i>_n</i> (<b>2·4H₂O</b>)were synthesized via solution-based and/or mechanochemical methods (l-hser = l-homoserinate, bpy = 2,2'-bipyridine). The compounds were characterized in the solid state (using single-crystal and powder X-ray diffraction (SCXRD and PXRD), EPR, Raman and IR spectroscopy, and thermogravimetric analysis (TGA)) and in solution (using UV-vis spectroscopy, EPR, Raman spectroscopy, and fluorimetry). In the binary bis-(homoserinato)-copper-(II) compounds, <b>1a</b> and <b>1b·H₂O</b>, polymerization is achieved through the hydroxyl group of the l-homoserinate side chain. In contrast, all ternary compounds (<b>2·2H₂O</b>, <b>2·3H₂O</b>, and <b>2·4H₂O</b>) achieved polymerization through the carboxylate group of l-homoserinate. Successful solid-state transformation of <b>2·2H₂O</b> into <b>2·4H₂O</b> was established at higher relative humidity values. Copper-(II) centers adopt a square-pyramidal geometry in <b>1a</b> and a distorted octahedral geometry in all other investigated compounds. Spectroscopic studies suggest that <b>1a</b> retains its solid-state geometry in solution, while <b>2·2H₂O</b> and <b>2·3H₂O</b> exhibit slight changes. Among the compounds, <b>2·2H₂O</b> exhibited moderate antiproliferative activity against H460 (lung), MCF-7 (breast), and HCT116 (colon) cancer cell lines, and demonstrated antibacterial activity against <i>Moraxella catarrhalis</i> ATCC 23246. Absorption and fluorescence spectra suggested a lower binding affinity of <b>2·2H₂O</b> to the double-stranded DNA dodecamer ds-(CGCGAATTCGCG).