Br Ligands Research Articles

Syntheses, characterization and antibacterial activity of mononuclear and dinuclear copper(II) complexes containing a hydrazone ligand

An aroylhydrazone compound (HL) was prepared and explored as a ligand (HL = N’-(2-hydroxy-4-methoxybenzylidene)-3-hydroxy-4-methoxybenzohydrazide). Reaction of the aroylhydrazone ligand with copper bromide and copper chloride afforded two new copper(II) complexes, [Cu2Br2L2] (1) and [CuL(DMF)]Cl (2), respectively. The aroylhydrazone ligand and copper complexes were characterized by CHN elemental analyses and infrared spectroscopy. Structures were further confirmed by single crystal X-ray diffraction experiments. The aroylhydrazone compound coordinates to Cu atoms through its phenolate oxygen, imino nitrogen and carbonyl oxygen. The Cu atom in 1 adopts a square pyramidal coordination, with three donor atoms of one L and one phenolate oxygen of a second L in the basal plane, and with one Br ligand at the apical position. The Cu atom in 2 is square pyramidal, with three donor atoms of one L and one oxygen of a DMF ligand in the basal plane, and with one Cl ligand at the apical position. Crystal structures of the aroylhydrazone and the copper complexes are stabilized by hydrogen bonds. The complexes possess antibacterial activities against B. subtilis, S. aureus and E. coli.

Engineering halogen ligand in Fe-based ionic liquid for elemental mercury removal from flue gas

The application of Fe-based ionic liquids (ILs) in elemental mercury (Hg0) removal from flue gas is limited by the low oxidative activity of the Fe(III) center. Here, a strategy of engineering halogen ligand to enhance the oxidative activity of Fe-based ILs for mercury removal was proposed. We developed a series of ionic liquids [Bmim][FeCl4-xBrx] (x = 0–4) with varying ratios of Cl− and Br− ligand substitutions. Mercury removal performance evaluations demonstrated a positive correlation between the oxidative activity towards Hg0 and the number of Br ligand substitutions in the ILs. [Bmim][FeBr4] achieved ∼99 % removal efficiency in the temperature range of 50–150 °C, with a saturated adsorption capacity reaching 205.4 mg/g (at 150 °C). In-situ Raman spectroscopy, DFT calculations, Hg-TPD, and XPS collectively revealed that the introduction of Br significantly lowered the excitation energy of the ligand–metal p-d orbital electron transitions, which facilitates the generation of active bromine species with unfilled 4p orbital, consequently enhancing the oxidative removal performance of Fe-based ILs for Hg0. This work provides an application of metal-based ILs in the realm of mercury removal and broadens the scope of ligand–metal interaction for IL design.

Kinetic study of the azo – Hydrazone photoinduced mechanism in complexes with a -Re(CO)3L0/+ core by flash photolysis

The photoprocesses of three rhenium(I) tricarbonyl complexes, fac-Re(NN)(CO)3L0/+, bearing an azo/hydrazone ligand, NN, and L = Cl, Br or CH3CN as axial ligand, were studied by time-resolved spectroscopic techniques. Flash irradiation of deaerated solutions of the complexes in acetonitrile photogenerated intermediates with intense optical absorptions in the UV–vis spectral region of the hydrazone ligand. The decay of the intermediates photogenerated with the Cl, Br and CH3CN ligands in the axial position proceeds by three different mechanisms. For the fac-Re(NN)(CO)3Cl, a three-step mechanism involving isomerization, tautomerization and rotation accounts for the spectroscopic transformations. In contrast to the flash photolysis result, the continuous photolysis of the complex in acetonitrile does not show spectroscopic changes associated with the generation of a stable product, i.e., the complex exhibits a photoreversible behavior. The first step observed in the flash irradiation of fac-Re(NN)(CO)3Cl, is missing in the decay of the photogenerated intermediates with fac-Re(NN)(CO)3Br and fac-[Re(NN)(CO)3CH3CN]+. A possible reason for this absence is that the process is too fast for the time-response of the flash photolysis set-up. Time-resolved spectra and associated reaction rate data for the Re(I) complexes are communicated and discussed. DFT calculations support a plausible E → Z mechanism with thermal back-isomerization mediated by tautomerization.

Exploring the Parameters Controlling Product Selectivity in Electrochemical CO2 Reduction in Competition with Hydrogen Evolution Employing Manganese Bipyridine Complexes.

Selective reduction of CO2 is an efficient solution for producing nonfossil-based chemical feedstocks and simultaneously alleviating the increasing atmospheric concentration of this greenhouse gas. With this aim, molecular electrocatalysts are being extensively studied, although selectivity remains an issue. In this work, a combined experimental-computational study explores how the molecular structure of Mn-based complexes determines the dominant product in the reduction of CO2 to HCOOH, CO, and H2. In contrast to previous Mn(bpy-R)(CO)3Br catalysts containing alkyl amines in the vicinity of the Br ligand, here, we report that bpy-based macrocycles locking these amines at the side opposite to the Br ligand change the product selectivity from HCOOH to H2. Ab initio molecular dynamics simulations of the active species showed that free rotation of the Mn(CO)3 moiety allows for the approach of the protonated amine to the reactive center yielding a Mn-hydride intermediate, which is the key in the formation of H2 and HCOOH. Additional studies with DFT methods showed that the macrocyclic moiety hinders the insertion of CO2 to the metal hydride favoring the formation of H2 over HCOOH. Further, our results suggest that the minor CO product observed experimentally is formed when CO2 adds to Mn on the side opposite to the amine ligand before protonation. These results show how product selectivity can be modulated by ligand design in Mn-based catalysts, providing atomistic details that can be leveraged in the development of a fully selective system.

Mechanistic studies of Ni-catalyzed electrochemical homo-coupling reactions of aryl halides.

Ni-catalyzed electrochemical arylation is an attractive, emerging approach for molecular construction as it uses air-stable Ni catalysts and efficiently proceeds at room temperature. However, the homo-coupling of aryl halide substrates is one of the major side reactions. Herein, extensive experimental and computational studies were conducted to examine the mechanism of Ni-catalyzed electrochemical homo-coupling of aryl halides. The results indicate that an unstable NiII(Ar)Br intermediate formed through oxidative addition of the cathodically generated NiI species with aryl bromide and a consecutive chemical reduction step. For electron-rich aryl halides, homo-coupling reaction efficiency is limited by the oxidative addition step, which can be improved by negatively shifting the redox potential of the Ni-catalyst. DFT computational studies suggest a NiIII(Ar)Br2/NiII(Ar)Br ligand exchange pathway for the formation of a high-valent NiIII(Ar)2Br intermediate for reductive elimination and production of the biaryl product. This work reveals the reaction mechanism of Ni-catalyzed electrochemical homo-coupling of aryl halides, which may provide valuable information for developing cross-coupling reactions with high selectivity.

Replenishment in the Family of Rhenium Chalcobromides; Synthesis and Structure of Molecular {Re4S4}Br8(TeBr2)4, Dimeric [{Re4S4}Br8(TeBr2)3]2, and Polymeric {Re4S4}Br8 Compounds Based on the {Re4S4}8+ Tetrahedral Cluster Core.

We have obtained three new rhenium(IV) chalcobromides belonging to the homologous series {Re4S4}Br8(TeBr2)n (n = 0, 3, 4): a molecular complex {Re4S4}Br8(TeBr2)4 (1), a dimeric complex [{Re4S4}(TeBr2)3Br7(μ-Br)]2 (2), and a two-dimensional (2D) polymeric compound {Re4S4}Br8 (3). Compound 1 is isotypic to the already known {Re4Te4}(TeBr2)4Br8, while 2 and 3 exhibit a new type of binding of tetrahedral clusters via μ-Br bridges. Compounds were characterized by X-ray single-crystal diffraction, X-ray powder diffraction, and thermal and elemental analyses. In compound 2, two tetrahedral cluster cores {Re4S4}8+ are linked together forming a dimer through two Re-μ-Br-Re bridges. Calculations of the electron localization function (ELF) showed that there is no covalent interaction between rhenium atoms of neighboring clusters. In compound 3, each rhenium atom of the {Re4S4}8+ core is coordinated by three Br ligands: one terminal Br and two bridging μ-Br ligands. As a result, eight bridging bromine atoms link {Re4S4}8+ cluster cores into goffered layers. {Re4S4}Br8 is the new stable rhenium(IV) thiobromide, the first discovered in the Re-S-Br system, along with the already known octahedral rhenium(III) thiobromides Re6S4+xBr10-2x (x = 0-4).

Spin-Crossover and Slow Magnetic Relaxation Behavior in Hexachlororhenate(IV) Salts of Mn(III) Complexes [Mn(5-Hal-sal2323)]2[ReCl6] (Hal = Cl, Br)

The cationic complexes of Mn(III) with the 5-Hal-sal2323 (Hal = Cl, Br) ligands and a paramagnetic doubly charged counterion [ReCl6]2− have been synthesized: [Mn(5-Cl-sal2323)]2[ReCl6] (1) and [Mn(5-Br-sal2323)]2[ReCl6] (2). Their crystal structures and magnetic properties have been studied. These isostructural two-component ionic compounds show a thermally induced spin transition at high temperature associated with the cationic subsystem and a field-induced slow magnetic relaxation of magnetization at cryogenic temperature, associated with the anionic subsystem. The compounds are the first examples of the coexistence of spin crossover and field-induced slow magnetic relaxation in the family of known [MnIII(sal2323)] cationic complexes with various counterions.

Halide-ligand-dependent Performance of AgBiS2Nanocrystal/ZnO Heterojunction Solar Cells

The carrier transport properties of solar cells fabricated with colloidal AgBiS2 nanocrystals (NCs) are affected by the type of ligands adsorbed on the nanoparticle surface, the coverage, and the coordination state. We focus on halide ions (F−, Cl−, Br−, and I−) to passivate the surface of AgBiS2 NCs and investigate their adsorption behavior using X-ray photoelectron spectroscopy (XPS) in this study. The adsorption strength of ligands was a useful figure of merit that could explain the correlation between the ligand type and solar cell performance. The Br ligand achieved the best NC passivation among the four halide ligands. Therefore, the cell with a Br ligand shows the highest solar cell performance.

Speciation of Ru Molecular Complexes in a Homogeneous Catalytic System: Fingerprint XANES Analysis Guided by Machine Learning

X-ray absorption spectroscopy is a powerful tool for the characterization of local atomic structure. Commonly, bond lengths and coordination numbers are extracted from the extended energy region of the spectrum (extended X-ray absorption fine structure, EXAFS). However, for many diluted systems, such as homogeneous catalysts, with a low concentration of the active component and under in situ or operando conditions, one cannot collect sufficient EXAFS data for a quantitative analysis. Considering the case of a homogeneous ruthenium-based catalyst, where the ligand surrounding the ruthenium atoms can change from Br to CO depending on the reaction conditions, we establish here an effective machine learning approach based on the descriptor analysis of spectral features. After the training procedure, the algorithm predicts both the ligand surrounding ruthenium and the distances to Br and CO ligands. The prediction quality of the approach was verified by means of a cross-validation procedure applied to the mixture of compounds and was validated for experimental spectra of reference RuBr3 and [RuBr2(CO)3]2 complexes. This work describes a practical route to improve classical fingerprint analysis and linear combination fit by more sophisticated data science algorithms.

Structural diversity in hybrid lead halides templated by 4-methylimidazolium

We present several new hybrid organic-inorganic lead(II) bromide materials with interesting polyhedral connectivity templated by [4-MeImH] ([4-MeImH] ​= ​4-methylimidazolium). These include two new examples of a 1D structure-type consisting of edge-sharing chains ([4-MeImH]PbBr3 and [4-MeImH]0.6[ImH]0.4PbBr3, [ImH] ​= ​imidazolium); the first example of a 2D layered material containing 7-coordinate Pb, and featuring edge- and face-sharing polyhedra ([4-MeImH]Pb2Br5) and two examples of materials consisting of corner- and face-sharing octahedra; [ImH]PbBr3, which has a 4H-perovskite structure and [4-MeImH]4[ImH]5Pb6Br21, which has a structural resemblance to the 4H-perovskite, but incorporates terminal Br ligands leading to a complex layered structure.

Crystal Structure and Magnetic Properties of 3,5-Pyridinedicarboxylate-Bridged Re(Ii)M(Ii) Heterodinuclear Complexes (M = Cu, Ni and Co)

The use of the mononuclear rhenium(II) precursor NBu 4 [Re(NO)Br 4 (H 2 pydc)]· i -PrOH ( 1 ) (H 2 pydc = 3,5-pyridinedicarboxylic acid) as a metalloligand towards Cu(II), Ni(II) and Co(II) afforded three new heterobimetallic complexes [Re(NO)Br 4 (μ-Hpydc)Cu(4,4’-dmbipy) 2 ]·(CH 3 ) 2 CO·0.25MeCN ( 2 ), [Re(NO)Br 4 (μ-Hpydc)Ni(dmphen) 2 ]·MeCN ( 3 ) and [Re(NO)Br 4 (μ-Hpydc)Co(dmphen) 2 ]·2H 2 O ( 4 ), respectively [4,4’-dmbipy = 4,4’-dimethyl-2,2’-bipyridine, dmphen = 2,9-dimethyl-1,10-phenanthroline and n -Bu 4 N + = tetra- n -butylammonium]. The crystal structures of 1 and 2 are reported herein together with the cryomagnetic investigation of 1 - 4 in the temperature range of 2.0-300 K. 1 is a mononuclear compound whose structure is made of [Re(NO)Br 4 (H 2 pydc)] - complex anions, tetra- n -butylammonium cations and isopropanol molecules of crystallization. Each rhenium(II) ion in 1 is six-coordinate with four bromide ligands in the equatorial positions and a nitrosyl group and one pyridyl-nitrogen atom from an H 2 pydc ligand filling the axial sites. 2 is a neutral heterobimetallic compound where the [Re(NO)Br 4 (Hpydc)] 2- complex anion acts as a monodentate ligand towards the [Cu(dmphen) 2 ] 2+ complex cation through one carboxylate-oxygen atom. The rhenium(II) ion is six-coordinate in a somewhat distorted octahedral surrounding similar to that in 1 . The copper(II) ion in 2 is five-coordinate with four nitrogen atoms from two bidentate 4,4’-dmbipy ligands and one carboxylate-oxygen atom, describing a surrounding intermediate between square pyramidal and trigonal bipyramidal. Compound 1 behaves as a quasi-magnetically isolated spin doublet with weak antiferromagnetic interactions through space Br⋯Br contacts, ligand field, spin-orbit coupling, tetragonal distortion, and covalence effects considered as variable parameters in a successful simulation of the magnetic data . Compounds 2 – 4 exhibit also weak intramolecular antiferromagnetic interactions ( J ) covering the range -0.60(1) to -1.50(1) cm -1 with the Hamiltonian being defined as H = - J S Re S M , M = Cu ( 2 ), Ni ( 3 ) and Co ( 4 ).

Bis(benzo[h]quinolin-10-olato-κ2 N,O)bromidomanganese(III).

The title compound, [MnBr(C13H8NO)2], consists of a manganese(III) atom, which is coordinated by one bromido and two benzo[h]quinolin-10-olato ligands. The MnIII complex exhibits a distorted square-pyramidal coordination geometry with the Br ligand in the apical position. Neighbouring complexes are held together by π-π inter-actions and weak C-H⋯Br hydrogen bonds.

Mechanistic Insights for Iodane Mediated Aromatic Halogenation Reactions

AbstractStable iodanes such as PhI(OAc)2 (Ac=acetyl) may be readily activated by electrophiles and salts for useful functional group transfer reactions under mild conditions, but the underlying reaction mechanism remains controversial. In this work, a general mechanism of iodane‐mediated aromatic halogenation is revealed by extensive DFT calculations using PhI(OAc)2 and anisole PhOMe as model iodane and aromatic substrate, respectively. It is shown that facile OAc/X (X=Cl, Br) ligand exchange with electrophiles can be induced by electrophilic attack at acetyl C=O groups of PhI(OAc)2 to form more reactive iodanes, especially the non‐symmetric iodanes PhI(X)OAc that can be activated by electrophiles to reach reactive iodonium PhIX+ for further electrophilic halonium X+ transfer to aromatic substrates. Direct anionic OAc−/X− exchange of iodane are 4∼7 kcal/mol endergonic, suggesting the crucial role of electrophilic iodane activation. Hetero‐ and homolytic I−X bond cleavages of neutral iodanes are more than 28 kcal/mol endergonic and thus unlikely under ambient conditions without electrophilic activation.

Halide effect on the electron distribution in oxovanadium complexes bearing side-on (η2) dioxygen ligands: A combined crystallographic and theoretical study

A Cambridge Crystallographic Database (CSD) search of oxovanadium complexes bearing side-on (η2) dioxygen ligands show 134 entries in the database. The OO bond distances were found to range from 1.141 to 1.479 Å suggesting that these complexes are predominantly peroxo complexes. Computational study at the density functional level of theory using a model pentagonal bipyramidal oxovanadium complex bearing side-on dioxygen and halide (F, Cl, Br) ligands reveals that the position of the halide significantly affects the bond orders of the V = O and the O = O bonds. Natural bond orbital (NBO) analyses reveal significant delocalization of σ-electrons from the dioxygen ligand into n* orbitals of the central vanadium ion which results in decreased order of the O = O bond. Analyses of the chemical reactivity of the complexes using the global chemical reactivity indices indicate that complexes with F ligands are the most stable with those of Br ligands being the most reactive.

Unravelling the Chemistry of the [Cu(4,7-Dichloroquinoline)2Br2]2 Dimeric Complex through Structural Analysis: A Borderline Ligand Field Case

Large dark prismatic crystals (P 1 ¯ ) consisting of closely packed centrosymmetric [Cu(4,7-dichloroquinoline)2]2Br4 binuclear units are formed when 4,7-dichloroquinoline (DCQ, C9H5NCl2) binds copper(II). Cu2+ adopts a strongly distorted square pyramidal coordination geometry, perturbed by electrostatic interactions with two axial μ–Br ligands acting as highly asymmetric bridges. It is shown that, as electronic states of ligands are higher in energy than the metal ones, antibonding orbitals bear significant ligand-like character and electronic charge is partially transferred from inner-sphere coordinated halogen atoms to copper. Overall, the title compound sits on the Hoffman’s border between main group and transition chemistry, with non-negligible contributions of the ligands to the frontier orbitals. The relative energy placement of metal and ligand states determines an internal redox process, where the metal is slightly reduced at the expense of partial oxidation of the bromide ligands. In fact, the crystal structure is partially disordered due to the substitution of some penta-coordinated Cu(II) centers with tetra-coordinated Cu(I) ions. The geometry of the complex is rationalized in terms of electrostatic-driven distortions from an ideal octahedral prototype. Implications on the reactivity of Cu(II)–quinoline complexes are discussed.

Synthesis, crystallographic studies, antibacterial and antifungal activities of mononuclear mercury(II) complexes derived from [PPh2(CH2)nPPh2CH2C(O)C6H4Cl)]Br ligands

This account describes our recent studies on zwitterionic mercury(II) complexes with two diphosphonium salts, [PPh2(CH2)nPPh2CH2C(O)C6H4Cl)]Br (n = 1 (S1) and 2 (S2)), derived from 1,2-bis(diphenyl-phosphino)methane (dppm) and 1,2-bis(diphenyl-phosphino)ethane (dppe). These complexes were synthesized through reactions between diphosphonium salts and HgX2 in equimolar ratio and characterized by elemental analysis, IR, 1H, 13C and 31P NMR spectroscopic methods. The structure of complex [HgI2Br(PPh2(CH2)2PPh2CH2C(O)C6H4Cl)] (6) was determined by a single crystal X-ray structural analysis. The results indicated that the mercury center in this complex is four-coordinated in a distorted tetrahedral configuration. The results confirmed that the coordination of ligand to metal occurred through the phosphine group (P-coordination mode). Furthermore, antibacterial/antifungal activities of the diphosphonium ligands and their complexes were tested against two Gram-negative bacteria Escherichia coli (ATCC 25922) and Pseudomonas aeruginosa (ATCC 9027) and two Gram-positive bacteria Staphylococcus aureus (ATCC 6538) and Bacillus subtilis (ATCC 6633) as well as two fungi (Geotrichum sp. and Candida albicans). It seems that the chemical compounds reported herein may be used for control of pathogenic bacteria/fungi.

Novel Brain-Tumor-Inhibiting Copper(II) Compound Based on a Human Serum Albumin (HSA)-Cell Penetrating Peptide Conjugate.

It is a great challenge to design drugs that penetrate the blood-brain barrier to inhibit brain tumor growth by acting against multiple targets and also improve their delivery efficacy and targeting ability to cancer cells. To overcome the above problems, we designed a multitarget metal agent for treating brain tumors based on an human serum albumin (HSA)-cell penetrating peptide conjugate. Thus, we rationally screened copper (Cu) and 2-acetyl-3-ethylpyrazine thiosemicarbazones to synthesize six compounds, and we investigated their structure-activity relationships and confirmed multiple mechanisms for brain glioma cells. The HSA-6b complex structure indicated that 6b binds to the IIA subdomain of HSA and His242 replaces the Br ligand in 6b in coordination with Cu2+. In vivo data suggested that both 6b and the HSA-6b-peptide conjugate penetrate the blood-brain barrier and inhibit brain tumor growth with few side effects. Furthermore, the HSA-peptide conjugate also improved the delivery efficacy and targeting ability of 6b in vivo.

Switching the Spin on a Ni Trimer within a Metal-Organic Motif by Controlling the On-Top Bromine Atom.

Controlling the spin of metal atoms embedded in molecular systems is a key step toward the realization of molecular electronics and spintronics. Many efforts have been devoted to explore the influencing factors dictating the survival or quenching of a magnetic moment in a metal-organic molecule, and among others, the spin control by axial ligand attachments is the most promising. Herein, from the interplay of high-resolution scanning tunneling microscopy imaging/manipulation and scanning tunneling spectroscopy measurements together with density functional theory calculations, we successfully demonstrate that a Ni trimer within a metal-organic motif acquires a net spin promoted by the adsorption of an on-top Br atom. The spin localization in the trimetal centers bonded to Br was monitored via the Kondo effect. The removal of the Br ligand resulted in the switch from a Kondo ON to a Kondo OFF state. The magnetic state induced by the Br ligand is theoretically attributed to the enhanced Br 4pz and Ni 3dz2 states due to the charge redistribution. The manipulation strategy reported here provides the possibility to explore potential applications of spin-tunable structures in spintronic devices.

Extended Assemblies of Ru(bpy)(CO)2X2 (X = Cl, Br, I) Molecules Linked by 1,4-Diiodotetrafluoro-Benzene (DITFB) Halogen Bond Donors

The ruthenium carbonyl compounds, Ru(bpy)(CO)2X2 (X = Cl, Br or I) act as neutral halogen bond (XB) acceptors when co-crystallized with 1,4-diiodotetrafluoro-benzene (DITFB). The halogen bonding strength of the Ru-X⋅⋅⋅I halogen bonds follow the nucleophilic character of the halido ligand. The strongest halogen bond occurs between the chlorido ligand and the iodide atoms of the DITFB. All three halogen bonded complexes form polymeric assemblies in the solid state. In Ru(bpy)(CO)2Cl2⋅DITFB (1) and in Ru(bpy)(CO)2Br2⋅DITFB (2) both halido ligands are halogen bonded to only one DITFB donor. In Ru(bpy)(CO)2I2⋅DITFB (3) only one of the halido ligands is involved in halogen bonding acting as ditopic center for two DITFB donors. The polymeric structures of 1 and 2 are isomorphic wave-like single chain systems, while the iodine complexes form pairs of linear chains attached together with weak F⋅⋅⋅O≡C interactions between the closest neighbors. The stronger polarization of the iodide ligand compared to the Cl or Br ligands favors nearly linear C-I⋅⋅⋅I angles between the XB donor and the metal complex supporting the linear arrangement of the halogen bonded chain.

Antitumor Platinium(IV) Prodrugs: A Systematic Computational Exploration of Their Reduction Mechanism by l-Ascorbic Acid.

The reduction mechanism of Pt(IV) anticancer prodrugs, still today a matter of debate, assisted by one of the dominant reductants in human plasma, that is l-ascorbic acid in its monodeprotonated form, has been computationally examined in this work. In order to check what should be the influence on the reduction rate of the identity of the ligands in axial and equatorial position, both cisplatin and oxaliplatin derivatives have been studied, varying the ligands in axial position in connection with the role they should play as bridges, trans leaving species, and proton acceptors. OH, OAc, Cl, and Br ligands have been tested as bridging/leaving ligands, whereas Cl and aspirin have been used as trans labile and less labile ligands, respectively. The most recent theoretical and experimental investigations have demonstrated that the generally adopted grouping of reduction mechanisms into inner- and outer-sphere does not properly take into account all the viable alternatives. Therefore, inner-sphere mechanisms, classified as ligand-bridged, ligand-bridged-H transfer and enolate β-carbon attack, have been explored for all the complexes under investigation. Concerning the outer-sphere mechanism, redox potentials have been calculated adopting a recently proposed procedure based on the separation between electrochemical and chemical events to evaluate their propensity to be reduced. Moreover, according to the hypothesis that the outer-sphere reduction mechanism involves the sequential addition of two electrons causing the formation of a Pt(III) intermediate, the possibility that singlet and triplet pathways can cross for the Pt(IV) cisplatin derivative having two chlorido ligands in axial position has been explored in detail. Results show that the mechanism indicated as base-assisted outer sphere can become competitive with respect to the inner one if two singlet-triplet spin inversions occur. Results presented here are helpful in addressing synthetic strategies as they show that Pt(IV) prodrugs propensity to be reduced can be properly tuned and give indications on how this aim can be accomplished.