Two different 4,5-dichlorophthalate-extended Cu(II) 1D coordination polymers. Crystal structures, solvatochromism, and magnetic studies

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A new 1D Cu-coordination polymer with formula {[Cu2(tmeda)2(dcpa)2(H2O)]·H2O}∞, 1 (tmeda=N,N,N´,N´-tetramethylethylenediamine, dcpa=4,5-dichlorophthalate) has been synthesized by a self-assembly solution reaction between the aqua complex [Cu(tmeda)(H2O)x](ClO4)2 and the salt K2dcpa. The use of piperidinium (Pip) salt of dcpa under the same conditions induced the crystallization of a different 1D polymer {[Cu(tmeda)(dcpa)]·Pip(ClO4)}∞, 2. The 1D Cu-polymers-based 1–2 were structurally analyzed by single-crystal X-ray diffraction, Hirshfeld surfaces, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and multiple spectroscopic tools. X-ray analysis showed that the unusual inclusion of the ionic pair (PipClO4) into the single-crystal of 2 modified the Cu(II)…Cu(II) distances, Cu(II) geometries, supramolecular interactions, UV–Vis absorptions, and magnetic properties compared to 1.Polymer 1 consists of dinuclear Cu2 units bridged by deprotonated dcpa ligands with weak antiferromagnetic interactions (C = 0.74 emu K/mol, θ= −3.89 K). In contrast, polymer 2 is formed by mononuclear Cu units with antiferromagnetic interactions (C = 0.35 emu K/mol, θ= −4.49 K).Polymer 1 shows solvatochromism in the presence of non-protic solvents, and the solvent-dependent absorption maxima in the visible region (λmax = 637–685 nm) has a linear behavior as a function of the dielectric constant. The visible absorption bands of 1 originated from a combination of d-d transitions and ligand-to-metal charge transfers, as is evidenced by time-dependent density-functional theory calculations.