Fig. 4: UV/vis/NIR absorption spectra of the dimers and monomers considered in this study as recorded in CH₂Cl₂.

The inset shows photographs of the corresponding solutions in CH₂Cl₂ (1.0 × 10⁻⁵ M for all compounds). Here the numbers 1–6 refer to FHP, D, MD1, MD2, FHPO₂, and FHPMO, respectively.