A Design of Copper(II) Coordination Polymers with l‑Homoserine: Structural, Spectroscopic, and Biological Studies

Five copper-(II) coordination polymerstrans-[Cu-(μ-l-hser)-(l-hser)] _n (1a), {cis-[Cu-(μ-l-hser)₂]·H₂O} _n (1b·H₂O), {[Cu-(μ-l-hser)-(H₂O)-(bpy)]₂SO₄·2H₂O} _n (2·2H₂O), {[Cu-(μ-l-hser)-(H₂O)-(bpy)]₂SO₄·3H₂O} _n (2·3H₂O), and {[Cu-(μ-l-hser)-(H₂O)-(bpy)]₂SO₄·4H₂O} _n (2·4H₂O)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, 1a and 1b·H₂O, polymerization is achieved through the hydroxyl group of the l-homoserinate side chain. In contrast, all ternary compounds (2·2H₂O, 2·3H₂O, and 2·4H₂O) achieved polymerization through the carboxylate group of l-homoserinate. Successful solid-state transformation of 2·2H₂O into 2·4H₂O was established at higher relative humidity values. Copper-(II) centers adopt a square-pyramidal geometry in 1a and a distorted octahedral geometry in all other investigated compounds. Spectroscopic studies suggest that 1a retains its solid-state geometry in solution, while 2·2H₂O and 2·3H₂O exhibit slight changes. Among the compounds, 2·2H₂O exhibited moderate antiproliferative activity against H460 (lung), MCF-7 (breast), and HCT116 (colon) cancer cell lines, and demonstrated antibacterial activity against Moraxella catarrhalis ATCC 23246. Absorption and fluorescence spectra suggested a lower binding affinity of 2·2H₂O to the double-stranded DNA dodecamer ds-(CGCGAATTCGCG).