Reactions Of Metal Complexes Research Articles

Tuning of the Electronic Structure and Reactivity of Metal Complexes with Redox‐Active Guanidine Ligands

AbstractRedox‐active ligands change more drastically the electronic structure of metal complexes than non‐redox‐active ligands, with consequences on the magnetic and optical properties as well as the (redox) reactivity. In this work, redox‐active guanidine ligands are integrated in cobalt and copper complexes. The variations in the electronic structures of cobalt complexes, in particular the relative energies of the states corresponding to high‐spin CoII or low‐spin CoIII, in dependence of the redox‐active o‐diguanidine ligand manifest themselves in different magnetic properties. Moreover, the electron transfer rates for copper complexes with two redox‐active diguanidino‐benzene ligands (self‐exchange betweeen a monocationic CuI complex and the corresponding dicationic complex) were varied systematically over two orders of magnitude by choice of the redox‐active diguanidine ligand, realizing redox pairs with intermediate or record‐high rates.

Efficient Cleavage of pUC19 DNA by Tetraaminonaphthols.

In an attempt to create models of phosphodiesterases, we previously investigated bis(guanidinium) naphthols. Such metal-free anion receptors cleaved aryl phosphates and also plasmid DNA. Observed reaction rates, however, could not compete with those of highly reactive metal complexes. In the present study, we have replaced the guanidines by ethylene diamine side chains which accelerates the plasmid cleavage by compound 13 significantly (1 mM 13: t1/2=22 h). Further gains in reactivity are achieved by azo coupling of the naphthol unit. The electron accepting azo group decreases the pKa of the hydroxy group. It can also serve as a dye label and a handle for attaching DNA binding moieties. The resulting azo naphthol 17 not only nicks (1 mM 17: t1/2~1 h) but also linearizes pUC19 DNA. Although the high reactivity of 17 seems to result in part from aggregation, in the presence of EDTA azo naphthol 17 obeys first order kinetics (1 mM 17: t1/2=4.8 h), reacts four times faster than naphthol 13 and surpasses by far the former bis(guanidinium) naphthols 4 and 5.

Constructing Co4(SO4)4 Clusters within Metal-Organic Frameworks for Efficient Oxygen Electrocatalysis.

Multinuclear metal clusters are ideal candidates to catalyze small molecule activation reactions involving the transfer of multiple electrons. However, synthesizing active metal clusters is a big challenge. Herein, on constructing an unparalleled Co4(SO4)4 cluster within porphyrin-based metal-organic frameworks (MOFs) and the electrocatalytic features of such Co4(SO4)4 clusters for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is reported. The reaction of CoII sulfate and metal complexes of tetrakis(4-pyridyl)porphyrin under solvothermal conditions afforded Co4-M-MOFs (M═Co, Cu, and Zn). Crystallographic studies revealed that these Co4-M-MOFs have the same framework structure, having the Co4(SO4)4 clusters connected by metalloporphyrin units through Co─Npyridyl bonds. In the Co4(SO4)4 cluster, the four CoII ions are chemically and symmetrically equivalent and are each coordinated with four sulfate O atoms to give a distorted cube-like structure. Electrocatalytic studies showed that these Co4-M-MOFs are all active for electrocatalytic OER and ORR. Importantly, by regulating the activity of the metalloporphyrin units, it is confirmed that the Co4(SO4)4 cluster is active for oxygen electrocatalysis. With the use of Co porphyrins as connecting units, Co4-Co-MOF displays the highest electrocatalytic activity in this series of MOFs by showing a 10mAcm-2 OER current density at 357mV overpotential and an ORR half-wave potential at 0.83V versus reversible hydrogen electrode (RHE). Theoretical studies revealed the synergistic effect of two proximal Co atoms in the Co4(SO4)4 cluster in OER by facilitating the formation of O─O bonds. This work is of fundamental significance to present the construction of Co4(SO4)4 clusters in framework structures for oxygen electrocatalysis and to demonstrate the cooperation between two proximal Co atoms in such clusters during the O─O bond formation process.

Synthesis and Reactivity of the Rare-Earth Metal Complexes Bearing the Indol-2-yl-Based NCN Pincer Ligand.

The pincer rare-earth dialkyl complexes [κ3-LRE(CH2SiMe3)2 (RE = Lu(1a), Yb(1b), Er(1c), Y(1d), Dy(1e))] with the indol-2-yl-based NCN pincer ligand were synthesized by the reactions of the proligand HL (L = 1-Me2NCH2CH2-3-(2-iPrC6H5N═CH)C8H4N) with RE(CH2SiMe3)3(THF)2. These complexes exhibited a variety of reactivities toward organic compounds such as amines, triphenylphosphine ylide, N-phenylimidazole, pyridine derivatives, and o-carborane leading to σ-bond metathesis, migration insertion, and redox reaction products. The reactions of the dialkyl rare-earth metal complexes with o-carborane afforded the novel NCN pincer-ligated carboryne-based metallacyclopropanes which reacted with diphenyl ketone to give insertion products of the RE-C2-ind and one of the RE-Ccage bonds, while the reaction of the carboryne-based metallacyclopropanes with diphenyldiazomethane produced the di-aza-metallacyclopentanes via the insertions of the N═N bond of the diphenyldiazomethane into two RE-Ccage bonds and the RE-C2-ind bond. The reactions of the dialkyl complexes with 2 equiv of 2,2'-bipyridine afforded the pincer-ligated bis(2,2'-bipyridyl monoanionic radical) complexes via the homolytic redox reaction.

Exploring the molecular structure and in vitro biological potential of newly synthesized Fe(III), Co(II), and Ni(II) coordination compounds with 2-(pyridin-2-yl)-1H-benzimidazole and phenylalanine ligands

This study presents a thorough investigation into the synthesis, characterization, computational analysis, and biological evaluation of FePBZPHA, CoPBZPHA, and NiPBZPHA mixed-ligand complexes. They were synthesized in high yields via reactions between chloride salts of Iron, Cobalt, or Nickel with 2-(pyridin-2-yl)-1H-benzimidazole (PBZ) and Phenylalanine (PHA). They underwent extensive spectroscopic, elemental, conductivity, magnetic, and thermal analysis to confirm their formation. Molar conductivity measurements indicated their non-electrolytic nature, with UV–vis spectra revealing distinct absorption bands for PBZ and PHA ligands, shifting significantly upon metal ion coordination. Stoichiometry determination confirmed the 1:1:1 (M:PBZ:PHA) ratio, while FT-IR spectra comparison elucidated intricate binding modes, supported by mass spectra and elemental analysis. Thermal analysis revealed their thermal stability and decomposition pathways. DFT calculations unveiled octahedral coordination geometries and enhanced electron affinity, electronegativity, and reactivity of metal complexes. Biological evaluation showcased significantly enhanced efficacy of metal complexes in antimicrobial, anti-inflammatory, and antioxidant activities, with FePBZPHA exhibiting the highest potency. Molecular docking analysis highlighted their potential as therapeutic agents, with metal complexation enhancing binding affinity and interaction versatility. Overall, this study provides comprehensive insights into the synthesis, characterization, computational analysis, and biological evaluation of FePBZPHA, CoPBZPHA, and NiPBZPHA mixed-ligand complexes, suggesting promising applications in biomedicine and materials science.

Coupled redox cycling of arsenic and sulfur regulates thioarsenate enrichment in groundwater

High‑arsenic groundwater is influenced by a combination of processes: reductive dissolution of iron minerals and formation of secondary minerals, metal complexation and redox reactions of organic matter (OM), and formation of more migratory thioarsenate, which together can lead to significant increases in arsenic concentration in groundwater. This study was conducted in a typical sulfur- and arsenic-rich groundwater site within the Datong Basin to explore the conditions of thioarsenate formation and its influence on arsenic enrichment in groundwater using HPLC-ICPMS, hydrogeochemical modeling, and fluorescence spectroscopy. The shallow aquifer exhibited a highly reducing environment, marked by elevated sulfide levels, low concentrations of Fe(II), and the highest proportion of thioarsenate. In the middle aquifer, an optimal ∑S/∑As led to the presence of significant quantities of thioarsenate. In contrast, the deep aquifer exhibited low sulfide and high Fe(II) concentration, with arsenic primarily originating from dissolved iron minerals. Redox fluctuations in the sediment driven by sulfur‑iron minerals generated reduced sulfur, thereby facilitating thioarsenate formation. OM played a crucial role as an electron donor for microbial activities, promoting iron and sulfate reduction processes and creating conditions conducive to thioarsenate formation in reduced and high‑sulfur environments. Understanding the process of thioarsenate formation and the influencing factors is of paramount importance for comprehending the migration and redistribution of arsenic in groundwater systems.

Late-stage diversification of bacterial natural products through biocatalysis.

Bacterial natural products (BNPs) are very important sources of leads for drug development and chemical novelty. The possibility to perform late-stage diversification of BNPs using biocatalysis is an attractive alternative route other than total chemical synthesis or metal complexation reactions. Although biocatalysis is gaining popularity as a green chemistry methodology, a vast majority of orphan sequenced genomic data related to metabolic pathways for BNP biosynthesis and its tailoring enzymes are underexplored. In this review, we report a systematic overview of biotransformations of 21 molecules, which include derivatization by halogenation, esterification, reduction, oxidation, alkylation and nitration reactions, as well as degradation products as their sub-derivatives. These BNPs were grouped based on their biological activities into antibacterial (5), antifungal (5), anticancer (5), immunosuppressive (2) and quorum sensing modulating (4) compounds. This study summarized 73 derivatives and 16 degradation sub-derivatives originating from 12 BNPs. The highest number of biocatalytic reactions was observed for drugs that are already in clinical use: 28 reactions for the antibacterial drug vancomycin, followed by 18 reactions reported for the immunosuppressive drug rapamycin. The most common biocatalysts include oxidoreductases, transferases, lipases, isomerases and haloperoxidases. This review highlights biocatalytic routes for the late-stage diversification reactions of BNPs, which potentially help to recognize the structural optimizations of bioactive scaffolds for the generation of new biomolecules, eventually leading to drug development.

Mechanistic Aspects of Redox Reactions of Transition Metal Complexes in Aqueous Media

Mechanistic Aspects of Redox Reactions of Transition Metal Complexes in Aqueous Media

Sensing Mechanism of Cysteine Specific Fluorescence Probes and Their Application of Cysteine Recognition.

Due to the biological importance of cysteine (Cys), the development of organic fluorescence probes for Cys has been a wide, potent, and outstanding research field in most recent years. It has been used as a biomarker in treating various diseases; therefore, developing a sensing mechanism for detecting Cys is very important. In this Review, we focus on and summarize the specific results of recent exciting literature regarding the sensing mechanism of Cys-specific fluorescence probes and their applications in Cys recognition. Moreover, a design strategy of the sensing mechanism of Cys can be classified into seven reaction mechanisms, including the aromatic substitution rearrangement reaction, cyclization of aldehyde, Michael addition reaction, Se-N or S-S or bond cleavage reaction, addition cyclization of acrylate, metal complex reaction, and nucleophilic substitution reaction. In all sections, discussions have corresponded to Cys-specific sensing mechanisms, which consist of emission, color changes, and detection limits and deal with the application and recognition sites of molecules. Future directions and challenges have been proposed for the preparation of Cys-specific probes.

New inorganic inhibitors derived from cefotaxime to enhance corrosion resistance of mild steel in 3% NaCl

To overcome the threat of corrosion and its cost, a new Schiff base was prepared and utilized to synthesize inorganic inhibitors to enhance corrosion resistance and reduce current density. The Schiff base was obtained from the interaction of cefotaxime with acetylacetone, while 1H NMR and IR spectra were used to confirm the preparation. Moreover, FeIII, CoII, NiII and CuII metal salts were reacted with the Schiff base to give the corresponding complexes. Meanwhile, the non-ionic behavior of the observed complexes in solutions was proved from the conductance results. In addition, the octahedral geometry and the postulated structure of complexes were determined from CHNM%, IR spectroscopy, UV-visible spectra, and TGA analysis. Also, the energy of molecular orbitals (HOMO and LUMO) and other quantum mechanics parameters were calculated using the DFT method. The observed results indicated the reactivity of metal complexes and their ability to donate electrons more than the Schiff base. Furthermore, the corrosion rate of a steel sample under various concentrations of inhibitors was calculated by a potentiodynamic polarization test. The obtained data displayed that metal complexes declined the corrosion rate more than the Schiff base; therefore, the binding between the metal ion and the Schiff base improved the inhibition efficiency.

Two birds with one stone: An innovative fluorescent cellulose polyacrylamide-hydrogel modified by born/nitrogen-doped carbon dots with sensitive visual sensing and superior extraction capacity toward Ag+

Since the last decade, water pollution by silver ions (Ag+) has been a serious potential threat to environmental protection and an enormous research effort has been put into the detection and removal of environmental Ag+. Here, we report a novel fluorescent cellulose polyacrylamide-hydrogel (FCPH) modified by boron/nitrogen doped carbon dots (BN-CDs) for sensitive visual detection and efficient extraction of Ag+. In addition, the introduction of BN-CDs in the cross-linking process promotes the formation of 3D network structures with more ionic adsorption sites in FCPH. On the one hand, the FCPH exhibits an excellent sensing performance in the range of 0–300 μM with a limit detection of 51 nM. On the other hand, the adsorption experiments confirm that the FCPH exhibits an excellent Ag+ extraction performance of over 251.4 mg‧g−1, and the adsorption results accord well with the pseudo-second-order model and the Langmuir model. Detailed mechanism characterizations reveal that the excellent adsorption capacity of FCPH is caused by the redox reaction and formation of metal complexes between the surface functional groups of BN-CDs and Ag+ in FCPH. Hence, this work fabricates a bifunctional hydrogel and provides a convenient “two birds with one stone” strategy for the visual sensing and extraction of Ag+.

Spontaneous ligand loss by soft landed [Ni(bpy)3]2+ ions on perfluorinated self-assembled monolayer surfaces.

Transition metal (TM) complexes are widely used in catalysis, photochemical energy conversion, and sensing. Understanding factors that affect ligand loss from TM complexes at interfaces is important both for generating catalytically-active undercoordinated TM complexes and for controlling the degradation pathways of photosensitizers and photoredox catalysts. Herein, we demonstrate that well-defined TM complexes prepared on surfaces using ion soft landing undergo substantial structural rearrangements resulting in ligand loss and formation of both stable and reactive undercoordinated species. We employ nickel bipyridine (Ni-bpy) cations as a model system and explore their structural reorganization on surfaces using a combination of experimental and computational approaches. The controlled preparation of surface layers by mass-selected deposition of [Ni(bpy)3]2+ cations provides insights into the chemical reactivity of these species on surfaces. Both surface characterization using mass spectrometry and electronic structure calculations using density functional theory (DFT) indicate that [Ni(bpy)3]2+ undergoes a substantial geometry distortion on surfaces in comparison with its gas-phase structure. This distortion reduces the ligand binding energy and facilitates the formation of the undercoordinated [Ni(bpy)2]2+. Additionally, charge reduction by the soft landed [Ni(bpy)3]2+ facilitates ligand loss. We observe that ligand loss is inhibited by co-depositing [Ni(bpy)3]2+ with a stable anion such as closo-dodecaborate dianion, [B12F12]2-. The strong electrostatic interaction between [Ni(bpy)3]2+ and [B12F12]2- diminishes the distortion of the cation due to interactions with the surface. This interaction stabilizes the soft landed cation by reducing the extent of charge reduction and its structural reorganization. Overall, this study shows the intricate interplay of charge state, ion surface interactions, and stabilization by counterions on the structure and reactivity of metal complexes on surfaces. The combined experimental and computational approach used in this study offers detailed insights into factors that affect the integrity and stability of active species relevant to energy production and catalysis.

Uncovering Nitrosyl Reactivity at N-Heterocyclic Carbene Center.

N-heterocyclic carbenes (NHCs) have garnered much attention due to their unique properties, such as strong σ-donating and π-accepting abilities, as well as their transition-metal-like reactivity toward small molecules. In 2015, we discovered that NHCs can react with nitric oxide (NO) gas to form radical adducts that resemble transition metal nitrosyl complexes. To elucidate the analogy between NHC and transition metal NO adducts, here we have undertaken a systematic investigation of the electron- and proton-transfer chemistry of [NHC-NO]• (N-heterocyclic carbene nitric oxide radical) compounds. We have accessed a suite of compounds, comprised of [NHC-NO]+, [NHC-NO]-, [NHC-NOH]0, and [NHC-NHOH]+ species. In particular, [NHC-NO]- was isolated as potassium and lithium ion adducts. Most interestingly, a monomeric potassium [NHC-NO]- compound was isolated with the assistance of 18-crown-6, which is the first instance of a monomeric alkali N-oxyl compound to the best of our knowledge. Our results demonstrate that [NHC-NO]• exhibits redox behavior broadly similar to metal nitrosyl complexes, which opens up more possibilities for utilizing NHCs to build on the known reactivity of metal complexes.

SERS study of classical and newly β-lactams-metal complexation based on in situ laser-induced coral reefs-like silver photomicroclusters: In vitro study of antibacterial activity

The influence of metal complexation of two polar β-lactam antibiotics was investigated using surface enhanced Raman spectroscopy (SERS) technique. SERS method was applied to track the structural changes and the degradation behaviour of the studied compounds upon Zinc (II) ions-complexation. In situ laser-induced coral reefs-like photomicroclusters have been utilized as a SERS platform. The produced coral reefs-like photomicroclusters were characterized using scanning electron microscopy (SEM) and transmission electron microscope (TEM). The antibacterial efficiency of the antibiotics was investigated and compared before and after metal complexation using two techniques; agar well diffusion and growth curve. To provide a detailed elucidation of the complexation reaction, mass fragmentation of metal- antibiotics complexes was investigated using liquid chromatography/mass spectrometric (LC/MS) technique. It was found that metal complexation of classical β-lactam antibiotic (Ticarcillin) promoted the rate of its degradation, leading to a decrease of the antibacterial efficiency. On the other side, the antibacterial activity of the newly developed β-lactam (Faropenem) has been greatly enhanced via metal-complexation reaction.

Efficient carbon-neutral cycle reactions catalyzed by N-substituted biomimetic [Ru–Ru]-Based H-clusters

Herein, we report two biomimetic [Ru–Ru] analogs (Ru2ADTX(CO)6, X = Ts or Cbz), which contain the N-substituted azadithiolate (ADT) moiety of the native H-cluster, and their differential reactivity to the formic acid/carbon dioxide-hydrogen (FA/CO2–H2) “carbon-neutral cycle” reaction. The results show that the strongly electron-withdrawing tosyl-substituted Ru2ADTTs(CO)6 (1) exhibits a higher preference for CO2 hydrogenation, while the donor-inductive carboxybenzyl-substituted Ru2ADTCbz(CO)6 (2) favors FA dehydrogenation, supporting electronically- or sterically-substituted pendant amine bases in influencing the entry and exit of protons from the Ru–Ru active site and subsequent H2 oxidation and generation. Furthermore, the propensity of TEA in FA dehydrogenation and DBU in CO2 hydrogenation support the role of bases as sacrificial electron donors and co-reagents, respectively. In the CO2 hydrogenation reaction, the P-ligands with more phosphorus atoms exhibited higher reactivity and final CO2 conversion efficiency, indicating that the number of phosphorus atoms and the different electronic but isosteric substitutions on the P-ligands have significant effects on the reactivity of metal complexes. These results support the combination of the FA dehydrogenation of complex 2 and the CO2 hydrogenation capability of complex 1 to construct an efficient FA/CO2–H2 reversible reaction for a sustainable supply of energy and environmental CO2 control.

Synthesis and Characterization of Photoanode by Immobilisation of Pyridyl Complexes on ITO for Photo-Conversion System

Increasing developments on the application of copper complexes as dyes are due to their dual function in dye-sensitized solar cells (DSSCs) as redox mediators and dye sensitizers. The economical (abundance, low cost) and environmentally friendly properties of copper motivate researchers on the use of copper complexes for replacement of ruthenium-based dyes in solar cells. A novel [Cu(I)(2,9-dmp)(phen-dione)]PF6 (A2) bearing polypyridyl ligands, 1,10- phenanthroline-5,6-dione (phen-dione), 2,9-dimethyl-1,10-phenanthroline (dmp) was prepared by metal complexation reaction. The photofunctionality of A2 as a promising photosensitizer in DSSCs was studied. Interestingly, A2 exhibited two absorption peaks, one is detected in the ultraviolet region due to pi-pi* transition and the other is a metal-to-ligand charge transfer (MLCT) band at 405nm in the visible region. A2 was compared to the same complex with Cu(II) ion as the metal centre which only absorbed light in the ultraviolet region thereby implying limited use of Cu(II) complex in its light harvesting application. The photofunctionality of A2 was studied by employing it as an active material for photoelectric conversion by engaging it with ITO to create a photoanode. Upon light irradiation, an anodic current was observed. In conclusion, introduction of Cu(I), instead of Cu(II), in polypridyls ligands resulted in successful enhancement of photophysical properties of A2, making the photoanode of A2 suitable for light harvesting applications.

Development of Amphiphilic Short Peptides to Control Drug Inclusivity through Metal Complexation Reactions

We previously reported that amphiphilic peptides containing one Lys and two His in the hydrophilic domain—KHHAAAAAA7 (KHHA7)—formed ternary complexes with intermediate metal ions and a poorly water-soluble anticancer drug—paclitaxel (Ptx)—which improved the water dispersibility of Ptx. In this study, the effect of ternary complexes of KHHA7 on cell viability is evaluated in vitro using HeLa cells. The ternary complexes reduced the cell viability by approximately 60%, suggesting that complex formation enhanced the cytotoxicity by increasing the water dispersibility of Ptx. Furthermore, the novel amphiphilic short peptides KHHAAAAAAW (KHHA6W) and KHHAAAWAAA (KHHA3WA3) were synthesized by Fmoc solid phase synthesis as dispersants for Ptx. These peptides differed from KHHA7 owing to the presence or absence of Trp and its position. The change in amino acid residues from Ala to Trp and the position of Trp in the hydrophobic domain of the amphiphilic peptide had little effect on the water dispersibility of Ptx.

Efficient degradation of tetracycline in FeS-based SR-AOPs process at basic pHs: The overlooked role of metal complexation and redox reaction in persulfate activation

Herein, mackinawite (FeS) was employed for activation of persulfate (PS) to remove tetracycline (TTC). The effect of the coexistence of Cu(II) on TTC degradation was explored at different initial pHs. Nearly 100% removal in 5 min at an initial pH of 3 was achieved with/without Cu(II). No less than 90% of TTC removal was achieved in a 60 min reaction at initial pH of 5, 7 and 9 where the Fe(II) leaching was small. More surprisingly, compared to FeS/PS/TTC system, up to a three-fold increase in degradation rates of TTC was observed in the FeS/PS/TTC-Cu system at initial pH of 9. Cu(I) produced by TTC-Cu associated with PS activation at initial pH of 5, 7 and 9 was thought to result in the apparent increase in TTC degradation efficiency. By further comparing the TTC degradation processes involving oxidizing complexed Cu(II), oxidizing non-complexed Cr(VI), non-oxidizing complexed Zn(II) and Pb(II), respectively, we determined the contribution of the complexation and redox processes of metal ions to TTC degradation. In addition, free radicals were detected in the FeS/PS/TTC-Cu system, in which SO4•− played the dominant role in the TTC degradation. Meanwhile, the structural Fe(II) was presumed as the primary form of Fe(II) improving to the activation of PS under basic conditions based on the theoretical calculations. These findings emphasize the importance of the complexation and redox reaction of metals at basic pH in the FeS/PS system, which may broaden the application of FeS/PS system.

Anticancer activity and DNA interaction of bis(pyridyl)allene-derived metal complexes

Abstract The constant need for novel drugs has prompted the scientific community to explore alternative structures to natural products and small and medium size organic compounds used in classic medicinal and pharmaceutical chemistry. Since the discovery of cisplatin, organometallic compounds have revealed great potential as metallodrugs and their development has exponentially grown in recent years. In this manuscript, we describe our efforts towards the synthesis of new metallodrugs by reaction of bis(pyridyl)allenes and metal complexes. Two classes of compounds are presented: one in which the allene structure is intact and the metal (Pd(II), Pt(IV) or Au(III)) coordinates to the pyridine-nitrogens; and another, in which one of the pyridines cyclises into a gold-activated allene to form β-N-stabilised gold carbenes. Both classes of compounds are active catalysts in important organic reactions, and are also promising antimicrobial, antifungal and anticancer agents. In this work, we describe the promising anticancer activity, against breast cancer cells, of the gold carbene complexes, and preliminary studies of their interaction with DNA, including non-canonical DNA structures. Our results have revealed an unusual selective stabilisation of hTeloC i-motif by one of the Au(III) carbene complexes, that opens up exciting opportunities for further development of novel DNA-binding metallodrugs.

An energy decomposition and extrapolation scheme for evaluating electron transfer rate constants: a case study on electron self-exchange reactions of transition metal complexes.

A simple approach to the analysis of electron transfer (ET) reactions based on energy decomposition and extrapolation schemes is proposed. The present energy decomposition and extrapolation-based electron localization (EDEEL) method represents the diabatic energies for the initial and final states using the adiabatic energies of the donor and acceptor species and their complex. A scheme for the efficient estimation of ET rate constants is also proposed. EDEEL is semi-quantitative by directly evaluating the seam-of-crossing region of two diabatic potentials. In a numerical test, EDEEL successfully provided ET rate constants for electron self-exchange reactions of thirteen transition metal complexes with reasonable accuracy. In addition, its energy decomposition and extrapolation schemes provide all the energy values required for activation-strain model (ASM) analysis. The ASM analysis using EDEEL provided rational interpretations of the variation of the ET rate constants as a function of the transition metal complexes. These results suggest that EDEEL is useful for efficiently evaluating ET rate constants and obtaining a rational understanding of their magnitudes.