Work

Host–Guest Complexes of Cyclopentadienyl Iron Dicarbonyl (CpFe(CO) 2 ) CO-Releasing Molecules with Cucurbit[7]uril

Year: 2025

Type: article

Abstract: Iron(II) cyclopentadienyl carbonyl complexes are promising as CO-releasing molecules (CORMs) for therapeutic applications. In common with other metallodrugs, the practical application of Fe-CORMs may require their conjugation with biocompatible carriers to improve their bioavailability and protect them from premature degradation. Here, we show that the CO-releasing properties of the complexes [CpFe(CO) 2 Cl] ( 1 ) and [CpFe(CO) 2 CH 2 CONH 2 ] ( 2 ) are retained when noncovalently encapsulated within cucurbit[7]uril (CB7), a well-established drug-enhancing excipient. The inclusion compounds were characterized in the solid-state by single-crystal and powder XRD, ATR-IR spectroscopy, Raman spectroscopy, TGA, and 13 C{ 1 H} CP MAS NMR. In the crystal structure of 2 @CB7, there are two crystallographically independent [ 2 @CB7] binary complexes that differ in the orientation of the guest molecules inside the CB cavity. High-resolution ESI-MS and 1 H NMR studies verified the formation and stability of 1:1 2 @CB7 inclusion complexes in an aqueous solution. In a physiological buffer, complex 2 is stable in the dark, but releases ca. 1.4 equiv of CO when irradiated with low-power cold white light, with a half-life ( t 1/2 ) of 19.2 ± 1.9 min. The photodecarbonylation behavior of the complexes is largely maintained in the inclusion compounds, with t 1/2 of 10.0 ± 0.6 and 21.1 ± 1.9 min for encapsulated 1 and 2 .

Source: Organometallics

DOI: 10.1021/acs.organomet.4c00469