Investigation of Cobalt(III)‐Tetrachlorocatechol Complexes as Models for Catechol‐Based Anticancer Prodrugs

Abstract

Two novel cobalt(III) complexes, [Co(TPA)(TCC)]ClO4·H2O (1) and [Co(py2en)(TCC)]ClO4·2H2O (2), were synthesized and fully characterized by IR, UV/Vis and 1H NMR spectroscopy, ESI mass spectrometry, and X‐ray diffraction. Cyclic voltammetry experiments revealed an irreversible reduction of the Co3+ center for both complexes. The Co3+/Co2+ redox potential, –0.91 V for 1 and –1.15 V for 2 (vs. Fc/Fc+), was obtained by square wave voltammetry in DMSO. Reactions of 1 and 2 with ascorbic acid and sodium dithionite at pH 7.4 and 6.2 were carried out in argon and open‐air atmospheres, to simulate biological redox activation under hypoxia and normoxia. Neither the Co3+/Co2+ reduction nor the dissociation of TCC2– was observed. Thermodynamic parameters calculated for the Co3+/Co2+ reduction and substitution of the TCC2– ligand by water indicate an endothermic non‐spontaneous reaction.

Understanding the Origin of One- or Two-Step Valence Tautomeric Transitions in Bis(dioxolene)-Bridged Dinuclear Cobalt Complexes

“…34 The spectra of 2a and 3a both display a ligand-to-metal charge transfer (LMCT) band at 674 and 809 nm, respectively. 55 The LMCT band is shifted to lower energies in 3a due to the smaller separation of {Co III (Me n tpa)-cat} and {Co II (Me n tpa)-SQ} states for n = 2 than n = 0; this is consistent with the observation of solid-state VT in 3a but not 2a.…”

“…The visible absorption spectra of 2a and 3a are characteristic of LS-Co­(III)-cat species and confirm the solid state {Co III -cat-cat-Co III } charge distribution is retained in solution . The spectra of 2a and 3a both display a ligand-to-metal charge transfer (LMCT) band at 674 and 809 nm, respectively . The LMCT band is shifted to lower energies in 3a due to the smaller separation of {Co III (Me n tpa)-cat} and {Co II (Me n tpa)-SQ} states for n = 2 than n = 0; this is consistent with the observation of solid-state VT in 3a but not 2a .…”

Insights of Tris(2-pyridylmethyl)amine as anti-tumor agent for osteosarcoma: experimental and in silico studies

“…Several tripodal amines have been investigated as anticancer agents, alone or bounded to metal centers [18,19,20,21,22,23,24,25,26,27,28,29]. The family of tetradentate tripodal amines have a general structure consisting of a central donor atom of nitrogen attached to three independent arms, each one also containing at least one methylene group and a donor atom.…”