Electrochemical, Spectroscopic, and¹O₂Sensitization Characteristics of 10,10-Dimethylbiladiene Complexes of Zinc and Copper

Abstract

The synthesis, electrochemistry, and photophysical characterization of a 10,10-dimethylbiladiene tetrapyrrole bearing ancillary pentafluorophenyl groups at the 5- and 15-meso positions (DMBil1) is presented. This nonmacrocyclic tetrapyrrole platform is robust and can serve as an excellent ligand scaffold for Zn2+ and Cu2+ centers. X-ray diffraction studies conducted for DMBil1 along with the corresponding Zn[DMBil1] and Cu[DMBil1] complexes show that this ligand scaffold binds a single metal ion within the tetrapyrrole core. Additionally, electrochemical experiments revealed that all three of the aforementioned compounds display an interesting redox chemistry as the DMBil1 framework can be both oxidized and reduced by two electrons. Spectroscopic and photophysical experiments carried out for DMBil1, Zn[DMBil1], and Cu[DMBil1] provide a basic picture of the electronic properties of these platforms. All three biladiene derivatives strongly absorb light in the visible region and are weakly emissive. The ability of these compounds to sensitize the formation of 1O2 at wavelengths longer than 500 nm was probed. Both the free base and Zn2+ 10,10-dimethylbiladiene architectures show modest efficiencies for 1O2 sensitization. The combination of structural, electrochemical, and photophysical data detailed herein provides a basis for the design of additional biladiene constructs for the activation of O2 and other small molecules.

Electrochemical, Spectroscopic, and1O2Sensitization Characteristics of Synthetically Accessible Linear Tetrapyrrole Complexes of Palladium and Platinum

“…Figure 2 compares the cyclic voltammograms obtained for 1.0 mM solutions of Pd [ DMBil1 ] and Pt [ DMBil1 ] with those obtained previously for Zn [ DMBil1 ] and the free base DMBil1 . 25 DPVs recorded for Pd [ DMBil1 ] and Pt [ DMBil1 ] are reproduced in the Supporting Information (Figure S3), and the apparent redox potentials for each of these four compounds are listed in Table 3. All four biladiene derivatives show two 1e − reductions and two 1e − oxidations which are reported versus Ag/AgCl.…”

“…DMBil1 and Zn [ DMBil1 ] can sensitize 1 O 2 with quantum yields of Φ Δ < 5%; 25 however, the evidence of a heavy atom effect imparted by the presence of the Pd II and Pt II centers of Pd [ DMBil1 ] and Pt [ DMBil1 ] ( vide supra ) suggested that these two complexes may be more efficient photosensitizers for 1 O 2 production. These hopes were buoyed by the observation that phosphorescence of Pd [ DMBil1 ] and Pt [ DMBil1 ] is actively quenched in the presence of oxygen.…”

“…The DMBil1 ligand was prepared using published methods. 25–29 Solvents for synthesis were of reagent grade or better. Anhydrous solvents were dried by passage through activated alumina and then stored over 4 Å molecular sieves prior to use.…”

“…In addition to probing the basic light absorbing and redox properties of the DMBil platform, we also showed that this platform can ligate zinc(II) and copper(II) centers. 5 …”

Evaluating Nanoshells and a Potent Biladiene Photosensitizer for Dual Photothermal and Photodynamic Therapy of Triple Negative Breast Cancer Cells

“…Pd[DMBil1]-PEG 750 was synthesized using methods described previously [ 28 , 38 , 39 , 40 , 41 ]. Reactions requiring an inert atmosphere were carried out in oven-dried round bottomed flasks fitted with Suba-seal rubber septa purchased from Chemglass and maintained under positive nitrogen pressure using standard schlenk techniques.…”