Synthesis, Spectroscopy, and Theoretical Details of Uranyl Schiff-Base Coordination Complexes

Abstract

Two uranyl Schiff-base coordination complexes, UO2L­(MeOH) and UO2Cl2( H2L ) {L = N,N′-bis­[(4,4′-diethylamino)­salicylidene]-1,2-phenylenediamine}, have been synthesized that feature a rigid phenyl backbone. These complexes have been characterized by structural, spectroscopic, and theoretical analysis to offer an electronic structure basis to explain the bonding parameters and stability. Single-crystal X-ray analysis reveals that UO2L­(MeOH) adopts the typical “soft taco confirmation” characteristic of uranyl salophen complexes, whereas UO2Cl2( H2L ) features an unusual neutral ligand coordination that contains an internal hydrogen bond between the phenol and imine. Rate constants calculated from electrochemical experiments confirm a quasi-reversible UO2 2+/UO2 + couple. Single-configurational and multiconfigurational methods were used to explore the bonding in UO2L­(MeOH) and UO2Cl2( H2L ). For UO2Cl2( H2L ), the U–Cl bond exhibits more covalent contributions than U–OL.

The Effect of Guest Metal Ions on the Reduction Potentials of Uranium(VI) Complexes: Experimental and Theoretical Investigations

“…For complexes 1 and 2,t he peaks are observed at potentials E c = À1.604 and À1.560 V, respectively,o nf orward cathodic scan for reduction processes at the electrode surface, whereas on reverses can, anodicp eaks are observed at potentials E a = À1.538 and À1.478 V, respectively,a ta100 mV s À1 scan rate. [26] After the separate addition of equimolecular redox-inac- tive monopositivem etal ions to solutionso fc omplex 2,t he cyclic voltammograms of the mixtures were recorded. The reduction processesf or both 1 and 2 are nearly reversible, and the appearance of peaks are due to the reduction of U VI to U V in the uranyl complexes.…”

“…However,f or complex 1 as mall peak appearsp ossibly for other reasonsb ecause it does not form a complex with Na + .N otably,t his feature is less pronouncedf or 1 than for 2.S uch as mall feature for the reductiono fo ther U VI complexes hasa lso been observedb ya nother group andh as been ascribed to the presence of as mall "unknown impurity". [26] After the separate addition of equimolecular redox-inac- www.chemeurj.org tive monopositivem etal ions to solutionso fc omplex 2,t he cyclic voltammograms of the mixtures were recorded. In these cyclic voltammograms, the corresponding reduction potentials of the U VI /U V couple are observed at more positive potentials than that of complex 2.T he peaks are observed at E c = À1.328, À1.391,a nd À1.436 Vo nf orward scan after the addition of Li + ,N a + ,a nd K + ,r espectively.O nr everse scan, the corresponding anodic peaks are observed at E a = À1.242, À1.261, and À1.341 V. Peak separation values (DE pc )a re À0.086, À0.130,a nd À0.095 Vw ith E 1/2 values of À1.285, À1.326, and À1.388 Vf or the mixture of complex 2 with Li + ,N a + ,a nd K + , respectively,a ss hown in Figure 7a nd FiguresS23-S25 (Supporting Information).…”

“…[21][22][23][24][25][26][27] The studies of these properties of uranium are helpful for waste managementi nn uclear reactors to prevent water and soil pollution.Uranium forms stable com-plexes with multidentate organic ligands, af act that is exploited in the detection and separation of uranium from nuclear slag, ground water,a nd seawater. [21][22][23][24][25][26][27] The studies of these properties of uranium are helpful for waste managementi nn uclear reactors to prevent water and soil pollution.Uranium forms stable com-plexes with multidentate organic ligands, af act that is exploited in the detection and separation of uranium from nuclear slag, ground water,a nd seawater.…”

“…The interest in coordinationcomplexes of uranium in current researchi sg rowing as ar esult of their significant photoluminescent, photocatalytic, electrochemical, optical, and molecular magnetic properties. [21][22][23][24][25][26][27] The studies of these properties of uranium are helpful for waste managementi nn uclear reactors to prevent water and soil pollution.Uranium forms stable com-plexes with multidentate organic ligands, af act that is exploited in the detection and separation of uranium from nuclear slag, ground water,a nd seawater. [28][29][30][31] It shows multiple oxidation states, varying from + III to + VI;h owever,i na erobic conditions the commono xidation state is + VI, which is stabilized as the uranyl dication (UO 2 2 + ).…”

Oligonuclear Actinoid Complexes with Schiff Bases as Ligands—Older Achievements and Recent Progress

“…Actinoid-Schiff base complexes are useful in the knowledge and grasp of fundamental An bonding trends and coordination preferences [59,60], Such complexes have thus attracted the intense interest of theoretical chemists, who have been trying to understand the bonding and the electronic structure trends across the 5f-metal series and how the changes in ligand binding may impact speciation and separation selectivity to different metal ions. For example, there are only few comparisons of isostructural molecular complexes with the metals in the IV oxidation state.…”