Carbonyl compounds are widely explored in medicinal inorganic chemistry and have drawn attention due to their signaling functions in homeostasis. Carbon-monoxide-releasing molecules (CORMs) were developed with the purpose of keeping the CO inactive until its release in the intracellular environment, considering its biological relevance. However, for therapeutic applications, the mechanisms of photorelease and which electronic and structural variations influence its rates must be fully understood. In this work, four ligands containing a pyridine, a secondary amine, and a phenolic group with different substituents were used to prepare new Mn(I) carbonyl compounds. Structural and physicochemical characterization of these complexes was carried out and confirmed the proposed structures. X-ray diffractometry structures obtained for the four organometallic compounds revealed that the substituents in the phenolic ring promote only negligible distortions in their geometry. Furthermore, UV-Vis and IR kinetics showed the direct dependence of the electron-withdrawing or donating ability of the substituent group, indicating an influence of the phenol ring on the CO release mechanism. These differences in properties were also supported by theoretical studies at the DFT, TD-DFT, and bonding situation analyses (EDA-NOCV). Two methods were used to determine the CO release constants (k_CO,old and k_CO,new), where Mn-HbpaBr (1) had the greatest k_CO by both methods (K_co,old = 2.36 × 10⁻³ s⁻¹ and k_CO,new = 2.37 × 10⁻³ s⁻¹). Carbon monoxide release was also evaluated using the myoglobin assay, indicating the release of 1.248 to 1.827 carbon monoxides upon light irradiation.

Understanding the structure of metal‐ligand complexes is essential for catalyst design, materials development, and biochemical modeling. Metal carbonyls are especially relevant due to their diverse structures and electronic features. Here, we benchmarked seventeen density functionals (B3LYP, BP86, CAM–B3LYP, M06, M06L, PBE, PBE0, r²SCAN, r²SCAN–3c, revPBE, revTPSS, RPBE, TPSS, TPSS0, TPSSh, B97, and B97X) combined with three dispersion schemes (D3zero, D3BJ, D4) and also tested calculations without dispersion correction, totaling fifty‐four approaches. Their ability to reproduce geometries, structural parameters, and CO stretching frequencies was assessed for thirty‐four Mn(I) and Re(I) carbonyls obtained from the CCDC. Relative electronic energies were further compared using DLPNO‐CCSD(T) calculations, alongside evaluation of computational cost. Our results highlight that hybrid meta‐GGA and meta‐GGA functionals, particularly TPSSh(D3zero) and r²SCAN(D3BJ, D4), offer the best balance between accuracy and efficiency, providing reliable structures, vibration properties, and energetics consistent with high‐level DLPNO‐CCSD(T) references.

This study investigates CO photorelease using experimental and computational approaches, with organoselenium ligands featuring a free selenium moiety capable of stabilizing intermediates in situ .

To control biochemical processes, non-covalent interactions involving cations are activated by protons or electrons. In the present study, the bonding situation between: (i) carboxylic acid or (ii) ferrocene-functionalized crown ether derivatives and cations (Li⁺, Na⁺ or K⁺) has been elucidated and, mainly, tuned by the substitution of hydrogen atoms by electron donor (–NH₂) or acceptor (–NO₂) groups. The deprotonation of the carboxyl groups improves the interaction with the cations through more favorable electrostatic O⋯cation interactions. Reducing the ferrocene structures favors cationic recognition supported by a less unfavorable iron⋯cation binding. The receptors preferably interact with smaller cations because of more attractive electrostatic and orbital (σ or π) O⋯cation interactions. The presence of electron donor or acceptor groups in the carboxylic acid-functionalized crown ethers promotes less attractive interactions with the cations, mainly due to the less favorable electrostatic O⋯Na⁺ interactions. The –H → –NH₂ substitution in the ferrocene framework favors the cationic recognition. It is based on the strengthening of the electrostatic and σ O⋯Na⁺ and H₂N⋯Na⁺ bonds. The (i) absence of repulsive electrostatic iron⋯cation interactions, or (ii) the presence of oxygen atoms with large electron density, ensures carboxylic acid-functionalized crown ethers have more favorable interactions with cations than ferrocene compounds. Therefore, this work has demonstrated how cation recognition can be improved by structural changes in carboxylic acid- or ferrocene-functionalized crown ethers and has shown that the carboxylic acid molecules appear to be better candidates for cation recognition than ferrocene derivatives.

Ru-NE bonds (E = O, S, Se and Te) have been studied and the results show that upon one-electron reduction the Ru-NE interaction is weakened by 150–200 kcal mol⁻¹, favouring the lability of the NE group.