Determining stability constants of uranyl complexes with thei principal functional groups in siderophores and identifying stability series s of great importance to predict which siderophore classes preferentially bind to U'l and, hence, impact uranium speciation in the environment. It also helps to develop resins for scavenging U" from aqueous solutions. Here, we apply a recently developed computational approach to calculate log /3 values ti for a set of geochemically relevant uranium organometallic complexes using Density Functional Theory (DFT). We determined the stability series for catecholate, hydroxamate, a-hydroxycarlzioxi,rlate, a-annnocarborylate, hydroxy-phenylo)cazolonate, and a-hydro3cyimidazole with the uranyl cation. In this work, the stability constants (log filla) of Cl-hYdrcocYjmidazolate and hYdrox)r-PheilYloxazoloriate are calculated for the first Ourapproach employed the B3LYP density functional approximation, aug-cc-pVDZ basis set for ligand atoms, MII)F60 ECP for 'I and the IEFPCM solvation model. DFT calculated log)311, were corrected using a preifiously established fitting equation. We find that the siderophore functional groups stability decreases in the order: tr-hyclrolzycarbolcylate bound via the a-hydrolcy and carboxylate groups (log = 17.08), a-hydrolzyimidazolate (log = 16.55), catecholate (log fill, = 16.43), hydro)camate (log = 9.00), hydroxy-phenyloxazolonate (log fiii, = 8.43), a-hydrolcycarbolzylate bound via the carbolzylate group (log /31,0 = 7.51) and a-aminocarboxylate (loglio 4.73).We confirm that the stability for the binding mode of the functional groups decrease in the order: bidentate, monodentate via ligand 0 atoms, and rnonodentate via ligand N atoms. The stability series strongly suggests that a-hydro)c),iiiiidazolate is an important functional group that needs to be included when assessing uranyl mobility and removal from aqueous solutions.