Synthesis and Characterization of Cyclen Cored Photoactive Star Compounds and Their Cu(I) and Cu(II) Complexes. Effect of the Valence and Ligand Size on Their Molar Extinction Coefficient

Abstract Two novel cyclen-cored star compounds were functionalized with pyrene moieties on the periphery and used as ligands to produce the corresponding Cu(I) and Cu(II) complexes. The complexation of both ligands was comparatively studied by UV-vis spectroscopy. The Cu(I) and Cu(II) complexes were characterized in chloroform solution by different spectroscopic techniques. These studies suggested that the Cu(I) is coordinated to the four nitrogens of the cyclen ring exhibiting a tetrahedral conformation, while the Cu(II) complexes are coordinated in a similar manner to the nitrogen atoms of the cyclen ligand and to one or two of the carbonyl groups of the dendrons, in a distorted square pyramidal and octahedral geometries. The coordination environment generated species with enhanced photosensitive properties compared to the free ligands, due to the stereochemistry of the complexes induced by the copper.