On the structure refinement of metal complexes against 3D electron diffraction data using multipolar scattering factors.

This study examines various methods for modelling the electron density and, thus, the electrostatic potential of an organometallic complex for use in crystal structure refinement against 3D electron diffraction (ED) data. It focuses on modelling the scattering factors of iron(III), considering the electron density distribution specific for coordination with organic linkers. We refined the structural model of the metal-organic complex, iron(III) acetylacetonate (FeAcAc), using both the independent atom model (IAM) and the transferable aspherical atom model (TAAM). TAAM refinement initially employed multipolar parameters from the MATTS databank for acetylacetonate, while iron was modelled with a spherical and neutral approach (TAAM ligand). Later, custom-made TAAM scattering factors for Fe-O coordination were derived from DFT calculations [TAAM-ligand-Fe(III)]. Our findings show that, in this compound, the TAAM scattering factor corresponding to Fe3+ has a lower scattering amplitude than the Fe3+ charged scattering factor described by IAM. When using scattering factors corresponding to the oxidation state of iron, IAM inaccurately represents electrostatic potential maps and overestimates the scattering potential of the iron. In addition, TAAM significantly improved the fitting of the model to the data, shown by improved R1 values, goodness-of-fit (GooF) and reduced noise in the Fourier difference map (based on the residual distribution analysis). For 3D ED, R1 values improved from 19.36% (IAM) to 17.44% (TAAM-ligand) and 17.49% (TAAM-ligand-Fe3+), and for single-crystal X-ray diffraction (SCXRD) from 3.82 to 2.03% and 1.98%, respectively. For 3D ED, the most significant R1 reductions occurred in the low-resolution region (8.65-2.00 Å), dropping from 20.19% (IAM) to 14.67% and 14.89% for TAAM-ligand and TAAM-ligand-Fe(III), respectively, with less improvement in high-resolution ranges (2.00-0.85 Å). This indicates that the major enhancements are due to better scattering modelling in low-resolution zones. Furthermore, when using TAAM instead of IAM, there was a noticeable improvement in the shape of the thermal ellipsoids, which more closely resembled those of an SCXRD-refined model. This study demonstrates the applicability of more sophisticated scattering factors to improve the refinement of metal-organic complexes against 3D ED data, suggesting the need for more accurate modelling methods and highlighting the potential of TAAM in examining the charge distribution of large molecular structures using 3D ED.

QTAIM analysis of the bonding in anionic group 6 carbonyl selenide clusters: [Se2M3(CO)10]2- (M=Cr, Mo, W).

CONTEXT: This research aims to offer a deeper understanding of the bonding interactions between M-Se and M-CO and how these interactions change across the group 6 transition metal series: [Se2M3(CO)10]2- (M = Cr, Mo, W). It also seeks to explore the impact of carbonyl groups on M-M interactions within the clusters. Seven criteria, which are based on QTAIM properties, have been considered and compared with the corresponding criteria in other transition metal clusters. The results confirm that no such bond critical points or bond baths occur between transition metals, which instead have 5c-7e bonding interactions delocalized over their five-membered M3(µ-Se)2 ring, as evidenced by the non-negligible nonbonding delocalization indices. The topological properties of three bond clusters, Cr-Se, Mo-Se, and W-Se, resemble those of "intermediate closed shell characters," which combine covalent and electrostatic properties. Source function calculations indicated that the bonded Se atom contributed the most to each Cr-Se and Mo-Se bcp. The OCO atoms and nonbonded Se atoms also contributed to some extent. However, metal atoms act as sinks rather than as sources of electron density. In contrast, the majority of the metal atoms, both bonded and nonbonded, contribute to Cr-W bcps. Analysis of the delocalization indices δ(M…O) in the three clusters indicates that CO significantly contributes to Cr π-back donation in cluster 1. In contrast, no π-back donation occurs from CO to Mo or W in clusters 2 or 3, respectively. METHODS: The B3P86 hybrid functional was used for computations in the Gaussian 09 software. The LanL2DZ basis set was employed for Cr, Mo, and W, while the 6-31G (d, p) basis set was used for C, O, and Se atoms. We performed QTAIM analysis using the AIM2000 and Multiwfn packages, incorporating B3P86/WTBS for Cr, Mo, and W atoms. The 6-311++G(3df,3pd) basis set was used for C, O, and Se atoms. Additionally, we utilized the ELF and SF.

The impact of biomolecule interactions on the cytotoxic effects of rhenium(I) tricarbonyl complexes.

Rhenium complexes show great promise as anticancer drug candidates. Specifically, compounds with a Re(CO)3(NN)(py)+ core in their architecture have shown cytotoxicity equal to or greater than that of well-established anticancer drugs based on platinum or organic molecules. This study aimed to evaluate how the strength of the interaction between rhenium(I) tricarbonyl complexes fac-[Re(CO)3(NN)(py)]+, NN = 1,10-phenanthroline (phen), dipyrido[3,2-f:2',3'-h]quinoxaline (dpq) or dipyrido[3,2-a:2'3'-c]phenazine (dppz) and biomolecules (protein, lipid and DNA) impacted the corresponding cytotoxic effect in cells. Results showed that fac-[Re(CO)3(dppz)(py)]+ has higher Log Po/w and binding constant (Kb) with biomolecules (protein, lipid and DNA) compared to complexes of fac-[Re(CO)3(phen)(py)]+ and fac-[Re(CO)3(dpq)(py)]+. As consequence, fac-[Re(CO)3(dppz)(py)]+ exhibited the highest cytotoxicity (IC50 = 8.5 µM for HeLa cells) for fac-[Re(CO)3(dppz)(py)]+ among the studied compounds (IC50 > 15 µM). This highest cytotoxicity of fac-[Re(CO)3(dppz)(py)]+ are probably related to its lipophilicity, higher permeation of the lipid bilayers of cells, and a more potent interaction of the dppz ligand with biomolecules (protein and DNA). Our findings open novel avenues for rational drug design and highlight the importance of considering the chemical structures of rhenium complexes that strongly interact with biomolecules (proteins, lipids, and DNA).

Review on the Applications of Selected Metal-Based Complexes on Infectious Diseases.

Fatalities caused by infectious diseases (i.e., diseases caused by parasite, bacteria, and viruses) have become reinstated as a major public health threat globally. Factors such as antimicrobial resistance and viral complications are the key contributors to the death numbers. As a result, new compounds with structural diversity classes are critical for controlling the virulence of pathogens that are multi-drug resistant. Derivatization of bio-active organic molecules with organometallic synthons is a promising strategy for modifying the inherent and enhanced properties of biomolecules. Due to their redox chemistry, bioactivity, and structural diversity, organometallic moieties make excellent candidates for lead structures in drug development. Furthermore, organometallic compounds open an array of potential in therapy that existing organic molecules lack, i.e., their ability to fulfill drug availability and resolve the frequent succumbing of organic molecules to drug resistance. Additionally, metal complexes have the potential towards metal-specific modes of action, preventing bacteria from developing resistance mechanisms. This review's main contribution is to provide a thorough account of the biological efficacy (in vitro and in vitro) of metal-based complexes against infectious diseases. This resource can also be utilized in conjunction with corresponding journals on metal-based complexes investigated against infectious diseases.

Guest-Shuttling in a Nanosized Metallobox.

An iridium-conjoined long and narrow metallorectangle was obtained by combining a quinoxalinophenanthrophenazine-connected Janus-di-imidazolylidene ligand and pyrazine. The size and shape of this assembly together with the fused polyaromatic nature of its panels provides it with properties that are uncommon for other metallosupramolecular assemblies. For example, this nanosized 'slit-like' metallobox is able show very large binding affinities with planar organic molecules in such a way, that the cavity is asymmetrically occupied by the guest molecule. This unsymmetrical conformation leads to the existence of a large amplitude motion of these guests, which slide between the two sides of the cavity of the host, thus constituting rare examples of molecular shuttles.

Complexes of N-Confused Porphyrin Derivatives as Ortho-Metallating Ligands. Synthesis, Structure, Redox Properties, and Chirality.

A family of transition metal complexes of meso-aryl-2-aza-21-carbaporphyrin (N-confused porphyrin, NCP) derivatives acting as ortho-metallating ligands for ruthenium(II), rhodium(III), and iridium(III) is synthesized and characterized by XRD, spectroscopic, and electrochemical methods. The chirality of these systems is shown by the separation of the enantiomers and analyzed by circular dichroism and DFT. A preliminary catalytic study indicates the activity of the iridium(III) ortho-metallated complexes in the N-heterocyclization of primary amines with diols.

Identification of anti-cancer organometallic compounds by inhibition of BCL-2/Bax interactions.

Apoptosis is regulated by the BCL-2 family, which includes the anti-apoptotic and pro-apoptotic proteins (Bax, Bok, Bak, etc.). These proteins often interact in dimers and act as apoptotic switches. Anti-apoptotic proteins, such as BCL-2, block the functions of these pro-apoptotic proteins. The pro-apoptotic and anti-apoptotic protein-protein interactions must be inhibited to prevent tumor cells from escaping apoptosis. This method has been used to develop anticancer drugs by inhibiting BCL-2 with both natural and synthetic compounds. Metal-containing compounds were used as pharmaceuticals for human cancer patients for a long time, and cisplatin was the first candidate of this class. Drug design, however, needs to pay more attention to metal complexes. We have studied the X-ray crystal structure of the BCL-2 protein in detail and identified the hydrophobic nature of the site with two less solvent-accessible sites. Based on the hydrophobic nature of the compounds, 74 organometallic compounds with X-ray crystallographically characterized bioactivity (including anticancer activity) were selected from the Cambridge crystallographic database. For testing, molecular docking was used to determine which compound was most effective against the BCL-2 protein. Organometallic compounds (benzene)-chloro-(1-{[(9H-fluoren-2-yl)imino]methyl}naphthalen-2-olato)-ruthenium (2), (1-((1,1'-biphenyl)-4-yl)-2,3,4,5-tetramethylcyclopentadienyl)-chloro-(4,4'-dimethyl-2,2'-bipyridine)-rhodium hexafluorophosphate (37), (µ-1,1'-(butane-1,4-diyl)bis(3-oxy-2-methylpyridin-4(1H)-one))-dichloro-bis(pentamethyl-cyclopentadienyl)-di-rhodium tetrahydrate (46), (µ-1,1'-(butane-1,4-diyl)bis(3-oxy-2-methylpyridin-4(1H)-one))-dichloro-bis(pentamethyl-cyclopentadienyl)-di-iridium (47) etc are found to be important compounds in this study. The capability of different types of complex interactions was identified using Hirshfeld surface analysis of the complexes. A NCI plot was conducted to understand the nature of the interaction between complex amino acids and active-site amino acids. A DFT study was conducted to examine the stability and chemical reactivity of the selected complexes. Using this study, one suitable hydrophobic lead anti-cancer organometallic pharmaceutical was found that binds at the less solvent-accessible hydrophobic site of BCL-2.

Fragmentation of metal(II) bis(acetylacetonate) complexes induced by slow electrons.

Nowadays, organometallic complexes receive particular attention because of their use in the design of pure nanoscale metal structures. In the present work, we present results obtained from a series of studies on the degradation of metal(II) bis(acetylacetonate)s induced by low-energy electrons. These slow particles induce the formation of the acetylacetonate anion, [acac]-, and the parent anion as the most dominant species at incident electron energies near 0 eV. They also fragment the organometallic compounds via various competitive reaction channels that occur at higher energies via dissociative electron attachment. The reported data may contribute to a better understanding of the physical chemistry underlying the electron-molecule interactions, which is crucial for potential applications of these molecular systems in the deposition of nanoscale structures.

Thioredoxin Reductase and Organometallic Complexes: A Pivotal System to Tackle Multidrug Resistant Tumors?

Cancers classified as multidrug-resistant (MDR) are a family of diseases with poor prognosis despite access to increasingly sophisticated treatments. Several mechanisms explain these resistances involving both tumor cells and their microenvironment. It is now recognized that a multi-targeting approach offers a promising strategy to treat these MDR tumors. Inhibition of thioredoxin reductase (TrxR), a key enzyme in maintaining redox balance in cells, is a well-identified target for this approach. Auranofin was the first inorganic gold complex to be described as a powerful inhibitor of TrxR. In this review, we will first recall the main results obtained with this metallodrug. Then, we will focus on organometallic complexes reported as TrxR inhibitors. These include gold(I), gold(III) complexes and metallocifens, i.e., organometallic complexes of Fe and Os derived from tamoxifen. In these families of complexes, similarities and differences in the molecular mechanisms of TrxR inhibition will be highlighted. Finally, the possible relationship between TrxR inhibition and cytotoxicity will be discussed and put into perspective with their mode of action.

Probing the Influence of Novel Organometallic Copper(II) Complexes on Spinach PSII Photochemistry Using OJIP Fluorescence Transient Measurements.

Modern agricultural cultivation relies heavily on genetically modified plants that survive after exposure to herbicides that kill weeds. Despite this biotechnology, there is a growing need for new sustainable, environmentally friendly, and biodegradable herbicides. We developed a novel [CuL2]Br2 complex (L = bis{4H-1,3,5-triazino[2,1-b]benzothiazole-2-amine,4-(2-imidazole) that is active on PSII by inhibiting photosynthetic oxygen evolution on the micromolar level. [CuL2]Br2 reduces the FV of PSII fluorescence. Artificial electron donors do not rescind the effect of [CuL2]Br2. The inhibitory mechanism of [CuL2]Br2 remains unclear. To explore this mechanism, we investigated the effect of [CuL2]Br2 in the presence/absence of the well-studied inhibitor DCMU on PSII-containing membranes by OJIP Chl fluorescence transient measurements. [CuL2]Br2 has two effects on Chl fluorescence transients: (1) a substantial decrease of the Chl fluorescence intensity throughout the entire kinetics, and (2) an auxiliary "diuron-like" effect. The initial decrease dominates and is observed both with and without DCMU. In contrast, the "diuron-like" effect is small and is observed only without DCMU. We propose that [CuL2]Br2 has two binding sites for PSII with different affinities. At the high-affinity site, [CuL2]Br2 produces effects similar to PSII reaction center inhibition, while at the low-affinity site, [CuL2]Br2 produces effects identical to those of DCMU. These results are compared with other PSII-specific classes of herbicides.

A comparative study on the metal complexes of an anticancer estradiol-hydroxamate conjugate and salicylhydroxamic acid.

Hydroxamic acids bearing an (O,O) donor set are well-known metal-chelating compounds with diverse biological activities including anticancer activity. Since steroid conjugation with a pharmacophoric moiety may have the potential to improve this effect, a salicylhydroxamic acid-estradiol hybrid molecule (E2HA) was synthesized. Only minimal effect of the conjugation on the proton dissociation constants was observed in comparison to salicylhydroxamic acid (SHA). The complexation with essential metal ions (iron, copper) was characterized, since E2HA may exert its cytotoxicity through the binding of these ions in cells. UV-visible spectrophotometric and pH-potentiometric titrations revealed the formation of high-stability complexes, while the Fe(III) preference over Fe(II) was proved by cyclic voltammetry and spectroelectrochemical measurements. Complex formation with half-sandwich Rh(III)(η5-Cp*) and Ru(II)(η6-p-cymene) organometallic cations was also studied as it may improve the anticancer effect and the pharmacokinetic profile of the ligand. At equimolar concentration the speciation is complicated because of the presence of mononuclear and binuclear complexes. The complexes readily react with small molecules e.g. glutathione, 1-methylimidazole and nucleosides, having major effect on solution speciation, namely mixed-ligand complex formation and ligand displacement occur. These processes serve as models for the interactions with biomolecules in the body. E2HA exerted moderate anticancer activity (IC50 = 25-59 µM) in the tested three human cancer cell lines (Colo205, Colo320 and MCF-7), while being non-toxic on non-cancerous MRC-5 cells. Meanwhile, SHA was inactive in the same cells. Complexation with half-sandwich Rh(III) and Ru(II) cations had only a minor improvement on the cytotoxic effect of E2HA.

Unlocking a (Pseudo)-Mechanically Interlocked Molecule with a Coronene "Shoehorn".

Mechanically interlocked molecules (MIMs) have gained increasing interest during the last decades, not only because of their aesthetic appeal, but also because their unique properties have allowed them to find applications in nanotechnology, catalysis, chemosensing and biomedicine. Herein we describe how a pyrene molecule with four octynyl substituents can be easily encapsulated within the cavity of a tetragold(I) rectangle-like metallobox, by template formation of the metallo-assembly in the presence of the guest. The resulting assembly behaves as a mechanically interlocked molecule (MIM), in which the four long limbs of the guest protrude from the entrances of the metallobox, thus locking the guest inside the cavity of the metallobox. The new assembly resembles a metallo-suit[4]ane, given the number of protruding long limbs and the presence of the metal atoms in the host molecule. However, unlike normal MIMs, this molecule can release the tetra-substituted pyrene guest by the addition of coronene, which can smoothly replace the guest in the cavity of the metallobox. Combined experimental and computational studies allowed the role of the coronene molecule in facilitating the release of the tetrasubstituted pyrene guest to be explained, through a process that we named "shoehorning", as the coronene compresses the flexible limbs of the guest so that it can reduce its size to slide in and out the metallobox.

Organometallic Chemistry within the Structured Environment Provided by the Macrocyclic Cores of Carbaporphyrins and Related Systems.

The unique environment within the core of carbaporphyrinoid systems provides a platform to explore unusual organometallic chemistry. The ability of these structures to form stable organometallic derivatives was first demonstrated for N-confused porphyrins but many other carbaporphyrin-type systems were subsequently shown to exhibit similar or complementary properties. Metalation commonly occurs with catalytically active transition metal cations and the resulting derivatives exhibit widely different physical, chemical and spectroscopic properties and range from strongly aromatic to nonaromatic and antiaromatic species. Metalation may trigger unusual, highly selective, oxidation reactions. Alkyl group migration has been observed within the cavity of metalated carbaporphyrins, and in some cases ring contraction of the carbocyclic subunit takes place. Over the past thirty years, studies in this area have led to multiple synthetic routes to carbaporphyrinoid ligands and remarkable organometallic chemistry has been reported. An overview of this important area is presented.

Rhodium-Based MOF-on-MOF Difunctional Core-Shell Nanoreactor for NAD(P)H Regeneration and Enzyme Directed Immobilization.

An organometallic complex-catalyzed artificial coenzyme regeneration system has attracted widespread attention. However, the combined use of organometallic complex catalysts and natural enzymes easily results in mutual inactivation. Herein, we establish a rhodium-based metal-organic framework (MOF)-on-MOF difunctional core-shell nanoreactor as an artificial enzymatic NAD(P)H regeneration system. UiO67 as the core is used to capture rhodium molecules for catalyzing NAD(P)H regeneration. UiO66 as the shell is used to specifically immobilize His-tagged lactate dehydrogenase (LDH) and serve as a protection shield for LDH and [Cp*Rh(bpy)Cl]+ to prevent mutual inactivation. A variety of results indicate that UiO67@Rh@UiO66 has good activity in realizing NAD(P)H regeneration. Noteworthily, UiO67@Rh@UiO66@LDH maintains a high activity level even after 10 cycles. This work reports a novel NAD(P)H regeneration platform to open up a new avenue for constructing chemoenzyme coupling systems.

Palladium (II), platinum (II) and silver (I) complexes with oxazolines: Their synthesis, characterization, DFT calculation, molecular docking and antitumour effects.

Six new Pd(II), Pt(II) and Ag(I) complexes, (1);{Pd (L1)]2C6H4}2Cl4} (2); Pt(L2)(DMSO)Cl; 3; {PtL5]2C6H4}2·PhCOO-⋅11NO3-; 4; {[Pt(L4)]2C6H4}; the binuclear cyclometalated complex the polymer chain (5); {[PtL5]C6H4}·NO3-}; and the polymeric silver species (6); Zn(L6)2·AgNO3·CHCl3 were synthesized and thoroughly characterized using X-ray diffraction and spectroscopic techniques (L1=(S,S)-1,4-i-PrOx]2C6H4}2Cl4, L2=Di(2,2-bis(4R-isopropyl-4,5-dihydro-oxazol-2-yl)acetonitrile) zinc (II) (BR1);L3= 1,4-bis(4R-benzyl-4,5-dihydro-oxazol-2-yl)benzene (AR2); L4= 1,4-bis(4R-benzyl-4,5-dihydro-oxazol-2-yl)benzene，L5=1,4-bis(4R-benzyl-4,5-dihydro-oxazol-2-yl)-benzene，L6=Di(2,2-bis(4S-isopropyl-4,5-dihydrooxazol-2-yl)acetonitrile) zinc (II). Complexes 1-6 showed cytotoxic effects against human tumour cell lines, including a multidrug-resistant subline. Oxazoline and Pd complex 1 induced apoptosis in A549 cells. DFT calculations were also performed to exhibit the excellent bioactivity of complex 1 against A549, MDA-MB-231, and KB cells. Complex 1, with the best docking score and a stable interaction network within the binding site of the G-quadruplex, could stably interact with the G-quadruplex. Additionally, complex 1 was further used in the animal experiment of human lung adenocarcinoma cells in nude mice. By comparing with the model control group, the tumour volume, relative tumour volume and relative tumour proliferation rate T/C decreased significantly in the cisplatin group and compound 1 (complex 1) group.

Water-Soluble Carbon Monoxide-Releasing Molecules (CORMs).

Carbon monoxide-releasing molecules (CORMs) are promising candidates for producing carbon monoxide in the mammalian body for therapeutic purposes. At higher concentrations, CO has a harmful effect on the mammalian organism. However, lower doses at a controlled rate can provide cellular signaling for mandatory pharmacokinetic and pathological activities. To date, exploring the therapeutic implications of CO dose as a prodrug has attracted much attention due to its therapeutic significance. There are two different methods of CO insertion, i.e., indirect and direct exogenous insertion. Indirect exogenous insertion of CO suggests an advantage of reduced toxicity over direct exogenous insertion. For indirect exogenous insertion, researchers are facing the issue of tissue selectivity. To solve this issue, developers have considered the newly produced CORMs. Herein, metal carbonyl complexes (MCCs) are covalently linked with CO molecules to produce different CORMs such as CORM-1, CORM-2, and CORM-3, etc. All these CORMs required exogenous CO insertion to achieve the therapeutic targets at the optimized rate under peculiar conditions or/and triggering. Meanwhile, the metal residue was generated from i-CORMs, which can propagate toxicity. Herein, we explain CO administration, water-soluble CORMs, tissue accumulation, and cytotoxicity of depleted CORMs and the kinetic profile of CO release.

Theoretical Analysis of Polynuclear Zinc Complexes Isolobally Related to Hydrocarbons.

Based on the isolobal analogy of ZnCp (Cp = η5-C5H5) and ZnR (R = alkyl or aryl group) fragments with hydrogen atom and fragment [Zn(CO)2] with a CH2 carbene, the following complexes [(ZnCp)2{µ-Zn(CO)2}], 1, [(ZnPh)2{µ-Zn(CO)2}], 2, [(ZnPh){µ-Zn(CO)2}(ZnCp)], 3, [(ZnCp)2{µ-Zn2(CO)4}], 4, [(ZnPh)2{µ-Zn2(CO)4}], 5, [(ZnPh){µ-Zn(CO)2}2(ZnCp)], 6, [Zn3(CO)6], 7 and [Zn5(CO)10], 8, were built. These polynuclear zinc compounds are isolobally related to simple hydrocarbons (methane, ethane, cyclopropane and cyclopentane). They have been studied by density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM) to compare the nature and topology of the Zn-Zn bond with previous studies. There are bond critical points (BCPs) between each pair of adjacent Zn centers in complexes 1-8 with Zn-Zn distances within the range 2.37-2.50 Å. The nature of the Zn-Zn bond in these complexes can be described as polar rather than pure covalent bonds. Although in a subtle way, the presence of different ligands and zinc oxidation states introduces asymmetry and polarity in the Zn-Zn bond. In addition, the Zn-Zn bond is delocalized in nature in complex 7 whereas it can be described as a localized bond for the remaining zinc complexes here studied.

Redox-Switchable Behavior of Transition-Metal Complexes Supported by Amino-Decorated N-Heterocyclic Carbenes.

The coordination chemistry of the N-heterocyclic carbene ligand IMes(NMe2)2, derived from the well-known IMes ligand by substitution of the carbenic heterocycle with two dimethylamino groups, was investigated with d6 [Mn(I), Fe(II)], d8 [Rh(I)], and d10 [Cu(I)] transition-metal centers. The redox behavior of the resulting organometallic complexes was studied through a combined experimental/theoretical study, involving electrochemistry, EPR spectroscopy, and DFT calculations. While the complexes [CuCl(IMes(NMe2)2)], [RhCl(COD)(IMes(NMe2)2)], and [FeCp(CO)2 (IMes(NMe2)2)](BF4) exhibit two oxidation waves, the first oxidation wave is fully reversible but only for the first complex the second oxidation wave is reversible. The mono-oxidation event for these complexes occurs on the NHC ligand, with a spin density mainly located on the diaminoethylene NHC-backbone, and has a dramatic effect on the donating properties of the NHC ligand. Conversely, as the Mn(I) center in the complex [MnCp(CO)2 ((IMes(NMe2)2)] is easily oxidizable, the latter complex is first oxidized on the metal center to form the corresponding cationic Mn(II) complex, and the NHC ligand is oxidized in a second reversible oxidation wave.

Automated Search For The Low-Lying Energy Isomers of Rhamnolipids and Related Organometallic Complexes.

Rhamnolipids (RMLs) are a widely studied biosurfactant due to their high biodegradability and environmentally friendly production. However, the knowledge of the structure-property relationship of RMLs is imperative for the design of highly efficient applications. Aiming to a better understanding of it at a molecular level, we performed an automated search for low energy structures of the most abundant RMLs, namely, Rha-C10 , Rha-C10 -C10 , Rha-Rha-C10 and Rha-Rha-C10 -C10 and their respective C2 -congeners. Besides that, selected neutral metal complexes were also considered. We found that several low-energy congeners have internal hydrogen bonds. Moreover, geometries in "closed" conformation were always more stable than "open" ones. Finally, the energy diferences between open and closed conformations of K+ , Ni2+ , Cu2+ and Zn2+ complexes were found to be 23.5 kcal mol-1 , 62.8 kcal mol-1 , 24.3 kcal mol-1 and 41.6 kcal mol-1 , respectively, indicating a huge structural reorganization after the complex formation.

NIR-II J-Aggregated Pt(II)-Porphyrin-Based Phosphorescent Probe for Tumor-Hypoxia Imaging.

The luminescence of traditional phosphorescence-based hypoxia probes is limited to the visible and first near-infrared wavelength regions (<1000 nm), which has defects of higher light scattering and lower penetration depth in contrast with the second near-infrared wavelength window (NIR-II, 1000-1700 nm) for optical bioimaging. Herein, 5,15-bis(2,6-bis(dodecyloxy)phenyl)-porphyrin platinum(II) (PpyPt) with J-aggregation induced NIR-II phosphorescence is reported. J-aggregates of PpyPt are confirmed by the X-ray diffraction data in the crystalline state. Moreover, the emission and excitation spectra of PpyPt in the solid states reveal NIR-II luminescence feature of PpyPt in J-aggregates. More importantly, by preparation of water-soluble PpyPt nanoparticles (PpyPt NPs4.76 ) with J-aggregates, it has NIR-II phosphorescent lifetime of microseconds and good oxygen-sensitivity in water. Moreover, the good biological hypoxia-sensing potential of PpyPt NPs4.76 is demonstrated in cells and 4T1-tumor-bearing mice. This study provides an efficient strategy to design NIR-II phosphorescent probe for sensitive tumor-hypoxia detection through the construction of J-aggregates.