Uzal-Varela, RocíoRodríguez-Rodríguez, AuroraLalli, DanielaValencia, LauraManeiro, MarcelinoBotta, MauroIglesias, EmiliaEsteban-Gómez, DavidAngelovski, GoranPlatas-Iglesias, Carlos2024-10-252024-10-252024-01-10Inorg. Chem. 2024, 63, 1575−15881520-510Xhttp://hdl.handle.net/2183/39818Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract]: We present the synthesis and characterization of a series of Mn(III), Co(III), and Ni(II) complexes with cross-bridge cyclam derivatives (CB-cyclam = 1,4,8,11-tetraazabicyclo[6.6.2]hexadecane) containing acetamide or acetic acid pendant arms. The X-ray structures of [Ni(CB-TE2AM)]Cl2·2H2O and [Mn(CB-TE1AM)(OH)](PF6)2 evidence the octahedral coordination of the ligands around the Ni(II) and Mn(III) metal ions, with a terminal hydroxide ligand being coordinated to Mn(III). Cyclic voltamme-try studies on solutions of the [Mn(CB-TE1AM)(OH)]2+ and [Mn(CB-TE1A)(OH)]+ complexes (0.15 M NaCl) show an intricate redox behavior with waves due to the MnIII/MnIV and MnII/MnIII pairs. The Co(III) and Ni(II) complexes with CB-TE2A and CB-TE2AM show quasi-reversible features due to the CoIII/CoII or NiII/NiIII pairs. The [Co(CB-TE2AM)]3+ complex is readily reduced by dithionite in aqueous solution, as evidenced by 1H NMR studies, but does not react with ascorbate. The [Mn(CB-TE1A)(OH)]+ complex is however reduced very quickly by ascorbate following a simple kinetic scheme (k0 = k1[AH–], where [AH–] is the ascorbate concentration and k1 = 628 ± 7 M–1 s–1). The reduction of the Mn(III) complex to Mn(II) by ascorbate provokes com-plex dissociation, as demonstrated by 1H nuclear magnetic relaxation dispersion studies. The [Ni(CB-TE2AM)]2+ complex shows significant chemical exchange saturation trans-fer effects upon saturation of the amide proton signals at 71 and 3 ppm with respect to the bulk water signal.engCC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/).http://creativecommons.org/licenses/by/3.0/es/IonsLigandsReaction productsRedox-responsiveTranstition metalsAgent basedContrast agentCross-bridgeCyclam derivativesHexadecaneOctahedral coordinationPendant armsSynthesis and characterizationsX-ray structurejournal articleopen access10.1021/acs.inorgchem.3c03486