Exploring the catalytic and anticancer activity of gold(I) complexes bearing 1,3,5-triaza-7-phosphaadamantane (PTA) and related ligands

A series of water-soluble gold(i) complexes bearing phosphine ligands, [AuCl(L)] {where L = 1,3,5-triaza-7-phosphaadamantane, PTA (1); 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane, DAPTA (2); or 1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane-3,7-diylbisphenylmethanone, DBPTA (3)} and [AuCl(L)]X {where L is either PTA-CH2-C6H4-p-COOH and X = Br (4) or PTA-CH2-C6H3-p-OH-m-CHO and X = Cl (5)}, were synthesized under mild conditions and characterized with multinuclear (1H, 13C and 31P) nuclear magnetic resonance (NMR) spectroscopy, attenuated total reflection - Fourier transform infrared (ATR-FTIR) spectroscopy, matrix-assisted laser desorption/ionization - mass spectrometry (MALDI-MS) and elemental analysis. The catalytic activity of the complexes was evaluated in the peroxidative oxidation of cyclohexane to cyclohexanol and cyclohexanone. Homogeneous reactions were conducted in aqueous media, while heterogeneous reactions were performed after immobilizing the complexes on porous carbon supports, including activated carbon (AC), carbon nanotubes (CNT) and their oxidized derivatives (AC-ox, AC-ox-Na, CNT-ox and CNT-ox-Na). The results demonstrated a better catalytic performance, in terms of yields and selectivity, under heterogeneous conditions depending on the nature of the carbon support. Finally, complexes 1-5 showed remarkable cytotoxicity against a selection of ovarian, lung and colon cancer cell lines, with IC50 values comparable to (or even better than) those of cisplatin. Interestingly, the most promising complexes exhibited good to excellent cytotoxicity against cancer cells while demonstrating substantial inactivity against normal ones.

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Funding Information: Centro de Química Estrutural (CQE) acknowledges the financial support of Fundação para a Ciência e Tecnologia (FCT) through projects UIDB/00100/2020 (DOI: 10.54499/UIDB/00100/2020), UIDP/00100/2020 (DOI: 10.54499/UIDP/00100/2020), and LA/P/0056/2020 (DOI: 10.54499/LA/P/0056/2020). N. R. C. acknowledges the financial support from Research fellowship BL2/2020_IST-ID of CQE (project 1801P.00974.1.01.01, UIDB/00100/2020) and Programa Doutoral FCT “Catalysis and Sustainability” (PD/00248/2012). A. G. M. acknowledges FCT for the international call of Scientific Employment Stimulus (2023.06724.CEECIND) DOI: 10.54499/2023.06724.CEECIND/CP2836/CT0005. FCT/MCTES is also acknowledged for projects DOIs: 10.54499/LA/P/0008/2020, 10.54499/UIDB/50006/2020 and 10.54499/UIDP/50006/2020 (LAQV), and bilateral project Portugal-Germany 5625-DRI-DAAD-2020/21. S. A. C. C. also acknowledges FCT for the Scientific Employment Stimulus – Institutional Call (DOI: 10.54499/CEECINST/00102/2018/CP1567/CT0026). Concerning the biological part, this research was funded by Fondazione AIRC per la Ricerca sul Cancro, IG23566. We acknowledge the supervision of Dr J. Gross for the HR-MS experiments conducted at the Chemistry Department of Heidelberg University. Publisher Copyright: © 2025 The Royal Society of Chemistry.