Visible Light-Assisted Coordination of a Rh(III)-BODIPY Complex to Guanine

Abstract

Most photodynamic therapeutics (PDTs) used in cancer treatment require oxygen to work efficiently to terminate cancer cells. These PDTs do not efficiently treat tumors in hypoxic conditions. Rh(III) polypyridyl complexes have been reported to have a photodynamic therapeutic effect in hypoxic conditions when exposed to UV light. UV light can damage tissue and cannot penetrate deep to reach cancer cells. This work proposes the coordination of a BODIPY fluorophore to a rhodium metal center to form a Rh(III)-BODIPY complex that enhances the reactivity of the rhodium under visible light. This complex formation is facilitated with the BODIPY as the highest occupied molecular orbital (HOMO), while the lowest unoccupied molecular orbital (LUMO) is localized on the Rh(III) metal center. Irradiation of the BODIPY transition at ∼524 nm can cause an indirect electron transfer from the orbital of the BODIPY-centered HOMO to the Rh(III)-centered LUMO, populating the dσ* orbital. In addition, photo binding of the Rh complex covalently coordinated to the N (7) position of guanine in an aqueous solution was also observed by mass spectrometry after chloride dissociation upon irradiation with green visible light (532 nm LED). Calculated thermochemistry values of the Rh complex reaction in methanol, acetonitrile, water, and guanine were determined using DFT calculations. All enthalpic reactions and Gibbs free energies were identified as endothermic and nonspontaneous, respectively. This observation supports the chloride dissociation using 532 nm light. This Rh(III)-BODIPY complex expands the class of visible lightactivated Rh(III) photocisplatin analogs that may have potential photodynamic therapeutic activity for the treatment of cancers in hypoxic conditions.

Ru(II) Phenanthroline-Based Oligothienyl Complexes as Phototherapy Agents

“…In addition, PDT can induce hypoxia as oxygen is consumed during irradiation. , Decreased generation of ROS limits damage to cancerous cells. To address this, there is motivation to develop light-triggered compounds that exploit oxygen-independent mechanisms for phototoxicity. − In this context, metal complexes such as Ru(II) polypyridyl systems have attracted considerable attention. ,,,− Judicious choice of ligand–metal combinations provides access to a variety of excited-state configurations with characteristic photophysical properties and reactivities. Strategies have included photorelease of bulky ligands to reveal phototoxic metals and/or ligands, ,,,,,− photocaging of chemotherapeutics and enzyme inhibitors, ,,,,,− …”

N^N^C-Cyclometalated rhodium(iii) complexes with isomeric pyrimidine-based ligands: unveiling the impact of isomerism on structural motifs, luminescence and cytotoxicity

“…These reactions do not require inert atmosphere which is often used for the synthesis or rhodium complexes. [94][95][96][97][98] The identity and purity of the complexes was established by elemental analysis, IR spectroscopy, X-ray single crystal and powder diffraction (ESI, Fig. S5-S8, S15-S20, S23 and S24 †).…”

“…In this manuscript we focus on the investigation of the coordination behaviour of HL 2,5 and HL 2,6 toward rhodium(III) chloride and on unveiling the impact of isomerism on structures and properties. Our particular interest to rhodium complexes stems partly from our experience in rhodium chemistry [82][83][84] and partly from appealing properties this metal shows in the C-H bond activation and catalysis, [85][86][87][88][89][90][91] photochemistry [92][93][94][95][96][97][98][99][100][101][102][103][104][105][106][107] and bioinorganic chemistry. Along with the synthesis of HL 2,5 and HL 2,6 and their rhodium(III) complexes [RhL 2,5 (Solv)Cl 2 ]•nEtOH and [RhL 2,6 (Solv)Cl 2 ]•nEtOH, here we report the impact of isomerism on molecular and supramolecular structures of these compounds, on the photophysical properties of the rhodium(III) complexes and on the cytotoxic activity of the ligands and complexes.…”