Evaluation of Chromium(II) and (III) Salen/Salpohen Complexes for Potential Near-IR Absorbance Introduction
Brendan T. Sperling, Masashi W. Kimura, Daniel P. Miller*
Normally, Salens and Salophens do not absorb in the Near-IR region based on our simulations and literature, but an exception with chromium(II) salens have been found computationally 1Bandini (1999). Literature exists that proves that the Cr(II) and Cr(III) Salens and Salophens do exist and are able to be made. In terms of application, near IR absorbing materials are used for deep optical imaging purposes 2Wang (2016). The inherent magnetism of the chromium was another reason why we found it worth inspecting as these chromium materials are also paramagnetic and can potentially guide to a magnetic region in the body to help target imaging better.
Results
Figure 2. Comparison of the UV-Vis spectra for the chromium(II) and (III) salens and salophens with ammonia ligands creating an octahedral geometry.
Cr(II) Salen
Cr(II) Salophen
Cr(III) Salen
Cr(III) Salophen
Figure 1. Depiction of salen and salophen (respectively) molecules.
Computational Details
ADF software package B3LYP-D3 hybrid functional and dispersion correction TZP basis set on all atoms Performed geometry optimizations (Molecular Orbitals) followed by single point TD-DFT calculations to generate UV-Vis spectra. We found all real frequencies on the salens/salophens from IR spectra simulations.
Conclusions and Future Work • •
The Chromium (II) salen absorbs in the Near-IR for this specific system; this is supported by the molecular orbitals showing Chromium’s involvement/mixing with the ligand vs. Chromium(III). For further investigation into this subject, we plan to synthesize the Chromium (II) Salen/Salophen. References 1 The First Catalytic Enantioselective Nozaki-Hiyama Reaction, Marco Bandini, et.al, 1999 2 Chromium(II)-catalyzed enantioselective arylation of ketones, Gang Wang, et.al, 2016
Figure 3. Comparison of the HOMO-LUMO of the salens and salophens in Figure 2. up above in their respective positions.
Cr(II) Salen
Cr(II) Salen
Cr(II) Salophen
Cr(III) Salen
Cr(III) Salen
Cr(III) Salophen
Cr(II) Salophen
Cr(III) Salophen