Self-Assembly Snapshots Of A 2 X 2 Copper(I) Grid

Self-assembled 2x2 grids have been characterised as high-fidelity species produced when the correct stoichiometric ratios are met, but rarely are the individual steps leading to and from their formation characterised. Here, we present such a study using equilibrium-restricted factor analysis to model a set of UV-vis spectra starting from a bis-bidentate ligand to the assembly of a 2x2 grid complex upon titration with 1equiv. of [Cu(MeCN)(4)](PF6) and to disassembly upon further titration. Intermediate species [CuL2](+), [Cu2L3](2+), [Cu3L2](3+) and [Cu2L](2+) are evidenced along the assembly and disassembly pathways. Complementary H-1 NMR titrations are consistent with the rich set of complexes and equilibria involved. Given the nature of the assembly process, the assembly is entropy driven and likely enthalpy driven as well. The disassembly process is both enthalpy and entropy driven according to the standard free energy values derived from the modelling of the spectrophotometric titration data.