One-Pot Synthesis and Characterization of Three Chromotropic Supramolecular Isomeric Cu(II) Coordination Polymers as 1-D Zigzag or Helical Chains with Homochiral or Heterochiral Cu(II) Coordination Centres

The reaction of 1,10-phenanthroline (Phen) and 4′,4′''-(perfluoropropane-2,2-diyl) bis(([1,1′-biphenyl]-4-carboxylic acid)) (H₂L2) with Cu(CH₃COO)₂⋅H₂O in DMF/H₂O at 50 ∼ 90°C in capped glass vials afforded three products with distinctively different colours and shapes. Single crystal X-ray diffraction analysis revealed that the three products, namely {[Cu(phen)(L2)] ⋅ 1.25H₂O} (1) (teal acicula, KPI = 60.6%), {[Cu(phen)(L2)]⋅ H₂O⋅DMF}_n(2) (sapphire blue plate, KPI = 65.6%) and {[Cu(phen)(L2)]⋅0.31H₂O}_n (3) (cool grey plate, KPI = 66.8%) are 1-D supramolecular Cu(II) coordination polymers. Both 1 and 2 are composed of 1-D zigzag chains with 1 contains heterochiral Cu(II) (Λ- and Δ- alternatively) centres in the same chain and 2 contains homochiral Cu(II) (Λ- or Δ-) centres in the same chain, while 3, containing homochiral Cu(II) (Λ- or Δ-) centres, has a helical structure along a axis, with a rectangular channel of a size 19.61 × 16.61 Ų. Each helical turn spans 10.74 Å, composed of two [Cu(L2)(Phen)] units. With the largest KPI (∼66.3%), the highest thermal stability, highest formation energy from DFT calculations and lowest hygroscopicity, 3 can be obtained as the only product at higher temperature (95°C) and/or higher ratio of water (DMF/water (v/v) = 20:6), which implies that it is the thermodynamic product. 2 can be obtained at mediate temperature (60 ∼ 80°C) as the only product or co-exist with other products, while 1 only appeared at low temperature (60 and 70 °C) in the solvents of DMF/water (v/v) = 20:2 or 20:3 at a very small amount. The chromotropism of the three isomers was examined using UV-Vis spectroscopic technique, and the coordination geometry of Cu(II) was examined with Hathaway's tetragonality analysis and Continuous Shape Measures Calculation using SHAPE 2.1 programme. Linear correlations between the solid-state UV-Vis absorption maxima of the three isomers against the tetragonality (T) or the distortion percentage of the coordination geometry of Cu(II) from a perfect octahedral (D_oct) were observed. The three complexes were also analyzed by FT IR, TGA and DFT formation energy calculations. The thermodynamic stability and the thermal stability of the three isomer increases in order of 1 < 2 < 3, supported by the analysis of the metal-ligand coordination bonds and the intermolecular interactions, the study of chromotropism and crystal fields, the effects of solvent polarity and temperature to the formation of isomers, the close-packing theory (KPI calculations), the DFT calculations and the TGA analysis.