Exploring EPR and NMR parameters of benzothiazole metallic complexes with Rhenium: implications for new MRI probes

Abstract

Cancer is a leading cause of death worldwide, among all cancer types, breast cancer is one of the most common and has a high mortality rate. To avoid death cases, early diagnosis is essential to a successful treatment. In this case, Magnetic Resonance Imaging (MRI) techniques, which are often used for the diagnosis, need a contrast agent (CA) for improving the obtained images. The complex ReABT, which is the complex Re(CO)3(NNO) conjugated with 2-(4’-aminophenyl)benzothiazole, presented as a candidate for acting as a spectroscopic probe instead of the traditional CAs. In line with that scenario, this study was divided into two parts, the first one was focused on the Electronic Paramagnetic Resonance (EPR) parameters that modulate the MRI action of this complex. This part of the study was carried out by evaluating the influence of the rhenium nucleus on the hydrogen atoms of water molecules in different chemical environments (gas phase, solution, and inside PI3K enzyme active site) at the theoretical level using DFT methods. In addition, relativistic effects on the EPR results were evaluated using ZORA implementation and a thermodynamic analysis was performed to confirm the stability of ReABT. The second part of this work is focused on the study of the NMR parameters, shielding tensors (σ), of the complex ReABT. The best calculation protocol has been defined, by an HCA model, with the PEB0 functional and the ZORA implementation on the hamiltonian system and basis sets. The results indicate that ReABT can be used as spectroscopic probes, being promising for application in the nuclear medicine diagnosis of breast cancer.