Past DISIT Seminars

The study of metallopolymers with controllable helical sense remains in its infancy. Reports in the literature are rare and depict integration of the chiral element directly into the polymer backbone, leading to rigid, “static” helicity with high helix inversion barriers. “Dynamic” helical metallopolymers with low helix inversion barriers can potentially offer flexibility and adaptability, thus rendering them more amenable for development of functionality, but such systems have not been explored. Instigated by our previous work on shape-persistent coordination frameworks,1 we have described new luminescent poly(M-salphen)-alt-(m- and p-phenyleneethynylene)s (M = Pt, Zn) with coilable structures.2,3 Saccharide-functionalized conjugated metallopolymers that display mirror-image circular dichroism spectra for L- and D-sugar sidechains respectively, signifying ordered (helical) coiling of the polymer backbone with opposite screw-sense preferences, have been developed.4 The observation of different spectroscopic behavior and Cotton effects for a variety of solvents (in a reversible manner) and temperatures thus demonstrate the flexible, responsive and dynamic nature of the folded helical conformation in these systems. New advances and applications as bioactive materials will be presented.

1. (a) Shape-Persistent (Pt-salphen)2 Phosphorescent Coordination Frameworks: Structural Insights and Selective Perturbations, Z. Guo, S.-M. Yiu, M. C. W. Chan*, Chem. Eur. J. 2013, 19, 8937–8947
   (b) Mitochondria-Targeted Platinum(II) Complex: Dual Inhibitory Activities on Tumor Cell Proliferation and Migration/Invasion, J. Li, X. He, Y. Zou, D. Chen, L. Yang, J. Rao, H. Chen, M. C. W. Chan, L. Li, Z. Guo, L. W. Zhang, C. Chen*, Metallomics 2017, 9, 726–733.
2. Alternating Poly(Pt-salphen)-(p-phenyleneethynylene) as Phosphorescent Conjugated Linear-Rod and Coilable Sensory Materials, S. Sun, W.-L. Tong, M. C. W. Chan*, Macromol. Rapid Commun. 2010, 31, 1965–1969
3. Poly(Zn-salphen)-alt-(p-phenyleneethynylene)s as Dynamic Helical Metallopolymers: Luminescent Properties and Conformational Behavior, C. Zhao, S. Sun, W.-L. Tong, M. C. W. Chan*, Macromolecules 2017, 50, 6896–6902
4. Saccharide-Functionalized Poly(Zn-salphen)-alt-(m- and p-phenyleneethynylene)s as Dynamic Helical Metallopolymers, C. Zhao, S. Meng, H.-N. Chan, X. Wang, H.-W. Li*, M. C. W. Chan*,Angew. Chem. Int. Ed. 2022, 61, e202115712

Superoxide radical or its conjugated acid, the hydroperoxyl radical (HOO·), is the main radical species produced metabolically in living organisms and it is also released during the oxidation of some organic materials like aliphatic alcohols and amines, representing a chain-transfer process which propagates their oxidative degradation. In biological systems, it is considered a detrimental oxidizing species and is implicated in the on-setting of Ferroptosis [1]. We will show that it can also have opposite valence and it can work as potent co-antioxidant, acting as a sacrificial reducing agent that recycles chain-breaking antioxidants like phenols and particularly polyphenols, or it enables the chain-breaking behavior of persistent nitroxides [2-5].

Indeed, its generation by suitable precursors, such as gamma-terpinene or other compounds bearing the 1,4-cycloheadiene core, in the presence of persistent nitroxides like 2,2,6,6-tetramethylpyperidine-N-oxide (TEMPO) was show to boost unprecedented antioxidant performance, pairing the most potent natural or man-made chain-breaking antioxidants, while working in a catalytic fashion where TEMPO is continuously recycled [2]. Similarly, gamma-terpinene boosts the antioxidant performance of polyphenols, particularly catechols like synthetic 3-5-di-tert-butylcatechol or natural caffeic acid derivatives, or hydroxytyrosol (from olive) in the protection of vegetable lipids of interest in food science [4]. Based on the above chemistry lipophilic antioxidants bearing the catechol or TEMPO active core have been designed and tested under biomimetic settings, in combination with a source of hydroperoxyl/superoxide radical, seeking for a tool to modulate ferroptosis in biological systems [5]. The spontaneous release of hydroperoxyl/superoxide radical during the autoxidation of polyunsaturated lipids under mimetic settings has also been preliminarily investigated and its role will be discussed in the context of antioxidant strategies aimed at modulating Ferroptosis. 

1. L. Valgimigli. Biomolecules 2023, 13, 1291. Doi:10.3390/biom13091291
2. A. Baschieri, L. Valgimigli, S. Gabbanini, G. A. DiLabio, E. Romero-Montalvo, R. Amorati   J. Am. Chem. Soc. 2018, 140, 10354−10362
3. K.A. Harrison, E.A. Haidasz, M. Griesser, D.A. Pratt. Chem. Sci. 2018, 9, 6068–6079
4. Y. Guo, A. Baschieri, R. Amorati, L. Valgimigli. Food Chemistry, 2021, 345, 128468
5. Y. Guo, A. Baschieri, F. Mollica, L. Valgimigli, J. Cedrowski, G. Litwinienko, R. Amorati. Angew. Chem. Int. Ed. 2021, 60, 15220–15224
6. J.-F. Poon, O. Zilka, D.A. Pratt. J. Am. Chem. Soc. 2020, 142, 14331–14342

1. M. Raynal, P. Ballester, A. Vidal-Ferran, P. W. van Leeuwen, Chem. Soc. Rev. 2014, 43, 1734-1787
2. A. Casnati, R. Salvio, Coord. Chem. Rev. 2025, 531, 216479
3. Lisi, D.; Vezzoni, C. A.; Casnati, A.; Sansone, F.; Salvio, R., Chem. Eur. J. 2023, 29, e202203213
4. Vezzoni, C. A.; Casnati, A.; Orlanducci, S.; Sansone, F.; Salvio, R. ChemCatChem 2024, e202301477
5. D. Del Giudice, S. Di Stefano, Acc. Chem. Res. 2023, 56, 889-899