Circular dichroism and optical absorption spectra of mononuclear and trinuclear chiral Cu(II) amino-alcohol coordinated compounds: A combined theoretical and experimental study

• Pseudoephedrine derivatives display absorption and optical activity in the UV region.
• Cu(II) complexes show absorption and optical activity in the UV and visible regions.
• TDDFT calculated oscillator and rotatory strengths are in agreement with experiments.
• Ligand to metal and metal to ligand charge transfer, and d–d transitions were found.
• Transitions in mono and trinuclear complexes mainly involve beta-spin orbitals.

Studies on the physicochemical properties of biomimetic compounds of multicopper oxidases are fundamental to understand their reaction mechanisms and catalytic behavior. In this work, electronic, optical, and chiroptical properties of copper(II) complexes with amino-alcohol chiral ligands are theoretically studied by means of time-dependent density functional theory. The calculated absorption and circular dichroism spectra are compared with experimental measurements of these spectra for an uncoordinated pseudoephedrine derivative, as well as for the corresponding mononuclear and trinuclear copper(II)-coordinated complexes. This comparison is useful to gain insights into their electronic structure, optical absorption and optical activity. The optical absorption and circular dichroism bands of the pseudoephedrine derivative are located in the UV-region. They are mainly due to transitions originated from n to π anti-bonding orbitals of the alcohol and amino groups, as well as from π bonding to π anti-bonding orbitals of carboxyl and phenyl groups. In the case of the mononuclear and trinuclear compounds, additional signals in the visible spectral region are present. In both systems, the origin of these bands is due to charge transfer from ligand to metal and d–d transitions.

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