Search

Lithium trialkylzincate‐mediated I/Zn exchange reaction has been revisited computationally through a microsolvation approach. A never yet investigated iodoaryl derivative bearing a potential bulky para‐directing group, namely 4‐iodobenzyl mesylate, was considered as a substrate. THF as typical solvent and Et3ZnLi have also been considered for the first time in such a reaction. Three mechanistic pathways have been calculated, including (1) a literature‐inspired pathway with full preservation of the synergic character of the reagent as well as a complementary mesylate group‐directed pathway, (2) a THF‐solvated open complex‐promoted pathway and (3) an anionic pathway. While the anionic pathway appeared to be unlikely, pathway involving a THF‐solvated open zincate complex turned out to be the most energetically favored. Equivalent thermodynamic profiles were found for both complementary pathways with preservation of the synergic character of the reagent, albeit a slight preference could be attributed to that occurring with initial chelation of Li to the mesylate group (OMs) through microsolvation approach. The I/Zn exchange was shown to proceed through a lithium‐assisted aryl shuttle‐like process. The iodoaryl substrate is first converted into ArLi intermediate which in turns reacts with the remaining diorganozinc reagent. [ABSTRACT FROM AUTHOR]

Significant effort focused on developing photoactivatable theranostics for localized image guided therapy of cancer by thermal ablation. In this context iron complexes were recently identified as photoactivatable theranostic agents with adequate biocompatibility and body clearance. Herein, a series of FeII complexes bearing polypyridine or N‐heterocyclic carbenes is reported that rely on rational complex engineering to red‐shift their MLCT based excited‐state deactivation via a straightforward approach. The non‐radiative decay of their MLCT upon irradiation is exploited for theranostic purposes by combining both tracking in photoacoustic imaging (PA) and photothermal therapy (PTT). The influence of structural modifications introduced herein on the solubility and stability of the complexes in biorelevant aqueous media is discussed. The relationship between complexes' design, production of contrast in photoacoustic and photothermal efficiency are explored to develop tailored PA/PTT theranostic agents. [ABSTRACT FROM AUTHOR]

2‐MeTHF (2‐methyltetrahydrofuran) promotes the zincate‐mediated remote functionalisation of p‐iodobenzyl derivatives through metallotropy with a broad scope. This biosourced solvent remarkably impacted all the key elementary steps involved in the tandem reaction. The method tolerates a wide range of sensitive functionalities within the substrates as well as enolisable and activated or deactivated aromatic aldehydes as reaction partners. A challenging benzyl naphthalene derivative was even reacted through an original dearomatisation/rearomatisation/metallotropy chain. [ABSTRACT FROM AUTHOR]

The use of polypyridyl Ru complexes to inhibit metastasis is a novel approach, and recent studies have shown promising results. We have reported recently that Ru (II) complexes gathering two 4,7-diphenyl-1,10-phenanthroline (dip) ligands and the one being 2,2′-bipyridine (bpy) or its derivative with a 4-[3-(2-nitro-1H-imidazol-1-yl)propyl (bpy-NitroIm) or 5-(4-{4′-methyl-[2,2′-bipyridine]-4-yl}but-1-yn-1-yl)pyridine-2-carbaldehyde semicarbazone (bpy-SC) moieties can alter the metastatic cascade, among others, by modulating cell adhesion properties. In this work, we show further studies of this group of complexes by evaluating their effect on HMEC-1 endothelial cells. While all the tested complexes significantly inhibited the endothelial cell migration, Ru-bpy additionally interrupted the pseudovessels formation. Functional changes in endothelial cells might arise from the impact of the studied compounds on cell elasticity and expression of proteins (vinculin and paxillin) involved in focal adhesions. Furthermore, molecular studies showed that complexes modulate the expression of cell adhesion molecules, which has been suggested to be one of the factors that mediate the activation of angiogenesis. Based on the performed studies, we can conclude that the investigated polypyridyl Ru (II) complexes can deregulate the functionality of endothelial cells which may lead to the inhibition of angiogenesis. [ABSTRACT FROM AUTHOR]

Iron complexes are promising candidates for the development of sustainable molecular photoactive materials as an alternative to those based on precious metals such as Ir, Pt or Ru. These compounds possess metal‐ligand charge transfer (MLCT) transitions potentially of high interest for energy conversion or photocatalysis applications if the ultrafast deactivation via lower‐lying metal‐centred (MC) states can be impeded. Following an introduction describing the main design strategies used so far to increase the MLCT lifetimes, we review some of our latest contributions to the field regarding bidentate Fe(II) complexes comprising N‐heterocyclic carbene ligands. The discussion covers all aspects from their synthesis to their characterization via photophysical, electrochemical and computational techniques. The impact of bidentate coordination together with the configuration (facial and meridional isomers) is analysed, finally highlighting the current challenges in this promising area. [ABSTRACT FROM AUTHOR]

The enantioselective deprotometalation of alkyl ferrocenecarboxylates (FcCO2R) using mixed lithium-zinc or lithium-cadmium bases is described. By using FcCO2Me as the substrate, chiral lithium alkyl-amidozincates prepared from exo-(αR)- or endo-(αS)-N-(α-phenylethyl)bornylamine (H-exo-born-R or H-endo-born-S) were tested; the best results (27% yield and 62% ee in favor of the RP enantiomer) were obtained by using Bu2(endo-born-S)ZnLi in tetrahydrofuran (THF) at −30 °C before iodolysis. Due to the low compatibility of FcCO2Me with alkyl-containing lithium zincates, 1 : 1 mixtures of lithium and zinc amides were tested. Chiral (H-exo-born-R or H-endo-born-S) or/and achiral (lithium 2,2,6,6-tetramethylpiperidide or lithium diisopropylamide) secondary amines gave good results, the best (81% yield and 44% ee in favor of the RP enantiomer) being obtained by using (endo-born-S)3ZnLi in THF at room temperature. Among other secondary amines also prepared and/or tested, commercial (S,S)-bis(α-phenylethyl)amine (H-PEA-S) proved promising. After optimization of the reaction conditions, the best enantioselectivity (26% yield and 80% ee in favor of the RP enantiomer) was observed by treating a THF solution of FcCO2Me and Zn(PEA-S)2 with Li-PEA-S at −80 °C before iodolysis. That no reaction took place with cadmium instead of zinc suggests the formation of 'ate complexes upon treatment of Cd(PEA-S)2 by Li-PEA-S while Zn(PEA-S)2 and Li-PEA-S would rather work in tandem (Li-PEA-S as the base and Zn(PEA-S)2 as the in situ trap for the formed ferrocenyllithium). While FcCO2Me, FcCO2tBu and FcCO2iPr could be converted into their racemic 2-iodinated derivatives with a yield of 84 to 87% by employing LiTMP (2 equiv.) in the presence of ZnCl2·TMEDA (1 equiv.) as an in situ trap, their enantioselective deprotometalation rather required Li-PEA-S together with Zn(PEA-S)2 to produce the enantio-enriched derivatives with yields of 45–82% and 71% ee. [ABSTRACT FROM AUTHOR]

A series of six new Fe(II)NHC‐carboxylic sensitizers with their ancillary ligand decorated with functions of varied electronic properties have been designed with the aim to increase the metal‐to‐ surface charge separation and light harvesting in iron‐based dye‐sensitized solar cells (DSSCs). ARM130 scored the highest efficiency ever reported for an iron‐sensitized solar cell (1.83 %) using Mg2+ and NBu4I‐based electrolyte and a thick 20 μm TiO2 anode. Computational modelling, transient absorption spectroscopy and electrochemical impedance spectroscopy (EIS) revealed that the electronic properties induced by the dimethoxyphenyl‐substituted NHC ligand of ARM130 led to the best combination of electron injection yield and spectral sensitivity breadth. [ABSTRACT FROM AUTHOR]

Phthalides, also called isobenzofuranones, are widespread in many biologically active compounds and natural products. To date, most of their synthetic routes are non‐convergent. Herein we report a convergent route using a metal halogen exchange (MHE) strategy. Indeed MHE of easily available 2‐iodobenzoate derivatives, using the bimetallic organomagnesiate complex (rac)‐(BIPHEN)BuMgLi, where (rac)‐BIPHEN is (rac)‐5,5′,6,6′‐tetramethyl‐3,3′‐di‐t‐butyl‐1,1′‐biphenyl‐2,2′‐diol, followed by addition of a ketone which lead to an intramolecular cyclisation, and the formation of a series of diverse 3,3‐disubstituted isobenzofuranones in good yield. Among the several MHE agents investigated, (rac)‐(BIPHEN)BuMgLi was the only one to make such a process possible with full tolerance of various reactive functional substituents useful for subsequent transformations. The synthetic pathway to access the magnesiate has been found to play a prominent role in its reactivity. Therefore, the bimetallic magnesiate complex has been characterized by solution‐state 1H, 7Li and 1H DOSY NMR experiments. [ABSTRACT FROM AUTHOR]

A series of homo- and heteroleptic Ru(II) complexes [Ru(phen)3−n(phen-X)n](PF6)2 (n = 0–3, X = CN, epoxy, H, NH2) were prepared and characterized. The influence of electron-withdrawing or electron-releasing substituents of the 1,10-phenanthroline ligands on the photo-physical properties was evaluated. It reveals fundamental interests in the fine tuning of redox potentials and photo-physical characteristics, depending both on the nature of the substitution of the ligand, and on the symmetry of the related homo- or heteroleptic complex. These complexes exhibit linear absorption and two-photon absorption (2PA) cross-sections over a broad range of wavelength (700–900 nm) due to absorption in the intra-ligand charge transfer (ILCT) and the metal-to-ligand charge transfer (MLCT) bands. These 2PA properties were more particularly investigated in the 700–1000 spectral range for a family of complexes bearing electro-donating ligands (phen-NH2). [ABSTRACT FROM AUTHOR]

The regioselective functionalization of aza‐ullazines has been successfully realized for the first time by either metalation using BuLi‐containing aggregates (BuLi‐LiDMAE) or electrophilic substitution. Mono and di‐bromo‐derivatives were obtained in good to excellent yields and further successfully converted into aryl and alkynyl azaullazine derivatives by Suzuki and Sonogashira cross‐coupling reactions. [ABSTRACT FROM AUTHOR]

A novel family of IrIII complexes bearing a pyridoannelated N‐heterocyclic carbene is herein described. The target compounds 1–5 are straightforwardly prepared and fully characterized. Comprehensive investigation of their optical properties reveals a rare case of dual emission ascribed to two excited states localized onto different portions of the molecule, as confirmed by both optical spectroscopy and time‐dependent density functional calculations including spin‐orbit coupling. The cytotoxicity against cancer cell lines is investigated as well. Remarkably, 2–5 show up to 50‐fold higher anticancer activity in vitro compared to oxaliplatin market drug with concentration values required to reduce by 50 % the cell viability (IC50) in the low μM range. Finally, in‐depth biological investigation on the most cytotoxic compound 4 reveals its powerful mitochondrial dysfunctioning activity and efficient reactive oxygen species production, associated with apoptosis as the mechanism of cell death. [ABSTRACT FROM AUTHOR]

Three Fe(II) pyridylNHC-carboxylic heteroleptic complexes with (ARM7 and ARM11) or without spacers (ARM13) between the pyridine and the COOH anchoring group have been designed and characterized with the aim to increase the metal to surface charge separation and avoid undesired recombination processes in iron-sensitized DSCCs. The ARM13-sensitized DSSC scored the highest efficiency ever reported for an iron-sensitized solar cell (1.44%) providing that Mg2+ cations and NBu4I were present in the electrolyte, thus substantially boosting the photocurrent. The gain in efficiency derived from the use of MgI2-based electrolytes was rationalized by employing DFT calculations for the isolated dye sensitizers and dye/TiO2 interface models. [ABSTRACT FROM AUTHOR]

In this perspective, we discuss iron-complexes as drug candidates that are promising alternatives to conventional platinum-based chemotherapies owing to their broad range of reactivities and to the targeting of different biological systems. Breakthroughs in the comprehension of iron complexes' structure–activity relationship contributed to the clarification of their metabolization pathways, sub-cellular localization and influence on iron homeostasis, while enlightening the primary molecular targets of theses likely multi-target metallodrugs. Both the antiproliferative activity and elevated safety index observed among the family of iron complexes showed encouraging results as per their therapeutic potential and selectivity also with the aim of reducing chemotherapy side-effects, and facilitated more pre-clinical investigations. The purpose of this perspective is to summarize the recent advances that contributed in unveiling the intricate relationships between the structural modifications on iron-complexes and their reactivity, cellular trafficking and global mechanisms of action to broaden their use as anticancer drugs and advance to clinical evaluation. [ABSTRACT FROM AUTHOR]

Bimetallic sodium magnesiates have been employed in metal–halogen exchange for the first time. Utilising the racemic phenoxide ligand 5,5′,6,6′-tetramethyl-3,3′-di-tert-butyl-1,1′-biphenyl-2,2′-diol [(rac)-BIPHEN-H2], the dialkyl sodium magnesiates [(rac)-BIPHEN]Na2MgBu2(TMEDA)23 and [(rac)-BIPHEN]Na2MgBu2(PMDETA)24 have been synthesised. Both 3 and 4 can be easily prepared through co-complexation of di-n-butylmagnesium with the sodiated (rac)-BIPHEN precursor which can be prepared in situ in hydrocarbon solvent. Prior to the main investigation, synthesis of the sodiated precursor [BIPHEN]2Na4(THF)41 was explored in order to better understand the formation of sodium magnesiates utilising the dianionic (rac)-BIPHEN ligand as the parent ligand. In addition, a BIPHEN-rich sodium magnesiate [BIPHEN]2Na2Mg(THF)42 was prepared and characterised, and its formation was rationalised. Complex 1 and 4 have also been fully characterised in both solid and solution state. In terms of onward reactivity, 3 and 4 have been tested as potential exchange reagents with aryl and heteroaryl iodides to produce aryl and heteroaryl magnesium phenoxides utilising toluene as a non-polar hydrocarbon solvent. Complex 3 reacted smoothly to give a range of aryl and heteroaryl magnesium phenoxides, whilst 4′s reactivity is more sluggish. [ABSTRACT FROM AUTHOR]

Two novel rhenium(I) tricarbonyl complexes of general formula fac-[Re(N^C:)(CO)3X] are herein presented, where N^C: is the pyridoannelated N-heterocyclic carbene (NHC) arising from 2-(2-pyridinyl)imidazo[1,5-a]pyridinium hexafluorophosphate proligand, namely [pyipy]PF6, and X being Cl and Br. The synthetic pathway is a one-pot reaction that starts from the azolium salt as the NHC source and [Re(CO)5X] to yield the desired charge-neutral fac-[Re(pyipy)(CO)3X] complexes (1–2). Both complexes were thoroughly characterized by spectroscopic, electrochemical, theoretical investigation as well as X-ray diffraction analysis. They display a rather similar electronic absorption spectrum in dilute CH2Cl2 solution, which is characterized by a broad profile extending into the blue region. This lowest-lying absorption band is attributed to a transition with admixed metal-to-ligand charge transfer and intraligand charge transfer (1MLCT/1ILCT) character. Degassed samples of the complexes display moderate (Φ ≈ 1.5%) and long-lived (τ = 12.8–13.4 μs) red photoluminescence with highly structured profile independent of the nature of the ancillary halogen ligand and little sensitivity to the solvent polarity, highlighting the markedly different nature of the emitting excited state in comparison with the lowest-lying absorption. Indeed, photoluminescence is ascribed to a long-lived excited state with metal-perturbed triplet ligand-centred (3LC) character as supported by both experimental and density functional theory (DFT) investigations. [ABSTRACT FROM AUTHOR]

Recombination and regeneration dynamics in Fe-NHC-sensitized DSSCs revealed incomplete injection and the detrimental effect of photoinjected electron recapture by the I3-form of the redox electrolyte on performance. Importantly, the use of additives in the electrolyte allowed the best efficiency ever recorded for an iron-based DSSC to be reached. [ABSTRACT FROM AUTHOR]

This article, titled "The Mechanism of Lithium Zincate-Mediated I/Zn Exchange Revisited: A Computational Microsolvation Approach in THF," explores the mechanism of the I/Zn exchange reaction using a computational microsolvation approach. The front cover of the journal showcases the most favorable calculated transition state for this reaction. The authors found that the reaction proceeds through a two-step mechanism, with the ArI substrate first converting into an ArLi intermediate, which then reacts with the remaining Et2Zn entity. This research provides valuable insights into the mechanism of this reaction. [Extracted from the article]

N,N-Diisopropylferrocenecarboxamide can be enantioselectively deprotometalated by combining butyllithium with (−)-sparteine in diethyl ether at low temperature. It is of interest to identify conditions that could allow substrates bearing more reactive functional groups (such as esters and ketones) to be similarly converted. We here report our efforts to use different chiral lithium–zinc bases, made from a simple chiral lithium amide, (R,R)- or (S,S)-lithium bis(1-phenylethyl)amide (PEALi), for the enantioselective deprotonation of N,N-diisopropylferrocenecarboxamide. First, different zinc-based in situ traps were employed to intercept the formed ferrocenyllithium; optimization using enantiopure lithium bis[1-(S)-phenylethyl]amide ((S)-PEALi) led to the 2-iodo derivative in 96% yield and 69% ee in favor of the RP enantiomer. The method was extended to N,N-dimethylferrocenecarboxamide, morpholinoferrocenecarboxamide and N,N-diethylferrocenecarboxamide; for the latter, similar yield and enantioselectivity were recorded. DFT calculations on a model reaction showed very small differences between the activation energies leading to (RP)- and (SP)-2-lithioferrocenecarboxamides. Next, the behavior of various mixed amino-alkyl lithium zincates of the types R2[(S)-PEA]ZnLi and R2[(S)-PEA]2ZnLi2 (R = alkyl) was studied, notably by varying the reaction temperature and time, and the amount of base. The best results were obtained with Me2[(S)-PEA]2ZnLi2, affording the 2-iodo derivative in 97% yield and 86% ee in favor of the SP enantiomer. [ABSTRACT FROM AUTHOR]

Due to its high societal impact, the replacement of precious metals used in technological devices by more abundant and eco‐friendly metals, such as iron, has stimulated significant scientific efforts in the last years. In the present review, we focus on different computational strategies and techniques used to characterize the potential energy surfaces (PESs) that govern the photophysical pathways of a wide variety of FeII complexes. The different procedures are discussed in terms of accuracy, computational cost and availability of the implementations, and illustrated with specific examples taken from the literature. The determination of minimum energy paths (MEPs) and the optimization of minimum energy crossing points (MECPs) are particularly emphasized since they can be combined to provide connected and optimized PESs independent from any a priori selected coordinate. The use of such computational techniques is exemplified in detail through a recent study on the influence of the facial and meridional isomerism in the triplet PESs of a pyridylcarbene Fe(II) complex, and its implications in the decay mechanism of each isomer. [ABSTRACT FROM AUTHOR]

Ligand field enhancing N-heterocyclic carbene (NHC) ligands were recently shown to prevent photo-induced spin crossover in Fe(ii) complexes due to their intricate effects on the electronic excited state structure. Due to their pico- to nanosecond lifetimes, these complexes are now good candidates for photo-sensitizing applications. Herein we report the synthesis and photophysical characterization of a new family of homoleptic Fe(ii) complexes with C^N^C ligands involving diazines as the central N-heteroaromatic ligand. For these four carbene bond complexes, ultrafast transient absorption spectroscopy revealed a significant improvement of the excited-state lifetime. A record 32 ps lifetime was measured for a complex bearing a ligand combining a π-deficient pyrazine nucleus and a benzimidazolylidene as NHC. When compared to other azine-based ligands investigated, we argue that the lifetimes are modulated by a small excited state barrier expressing the ability of the ligand to reach the Fe–N distance needed for internal conversion to the ground state. [ABSTRACT FROM AUTHOR]

We report the synthetic routes to mono‐ and di‐TCBD adducts onto N‐(het)arylpyrrole derivatives. We present herein two series of panchromatic chromophores bearing different combinations of donor–acceptor moieties. Additionally, we observe an impact of the nature of the central core. Cyclic voltammograms show very different behaviors at negative potentials between the two series. Particularly, four waves are observed for symmetrical di‐TCDB adducts, thus indicating a communication through the central unit despite the non‐planarity of these molecules. [ABSTRACT FROM AUTHOR]

Bioinorganic chemistry, Iron, Optical properties, Photoacoustic imaging, Photothermal therapy Front Cover: Water-Soluble Fe(II) Complexes for Theranostic Application: Synthesis, Photoacoustic Imaging, and Photothermal Conversion (Eur. J. Inorg. Keywords: Bioinorganic chemistry; Iron; Optical properties; Photoacoustic imaging; Photothermal therapy EN Bioinorganic chemistry Iron Optical properties Photoacoustic imaging Photothermal therapy 1 1 1 09/27/23 20230925 NES 230925 B The Front Cover b highlights the "light-in, sound-out" principle exploited in photoacoustic imaging with a representative iron(II)-terpyridine complex. [Extracted from the article]

Zincate, Green solvent, Remote functionalisation, metallotropy, metal-shift Keywords: Zincate; Green solvent; Remote functionalisation; metallotropy; metal-shift EN Zincate Green solvent Remote functionalisation metallotropy metal-shift 3755 3755 1 11/24/22 20221122 NES 221122 The front cover picture illustrates the 1,5-rearrangement of lithium benzyl(dibutyl)zincate derived from I p i -iodobenzyl mesylate. Front Cover Picture: Zincate-Mediated Remote Functionalisation of p-Iodobenzyl Derivatives Through Metallotropy in 2-Methyltetrahydrofuran as Key Solvent (Adv. [Extracted from the article]

The first combined theoretical and photovoltaic characterization of both homoleptic and heteroleptic Fe(ii)–carbene sensitized photoanodes in working dye sensitized solar cells (DSSCs) has been performed. Three new heteroleptic Fe(ii)–NHC dye sensitizers have been synthesized, characterized and tested. Despite an improved interfacial charge separation in comparison to the homoleptic compounds, the heteroleptic complexes did not show boosted photovoltaic performances. The ab initio quantitative analysis of the interfacial electron and hole transfers and the measured photovoltaic data clearly evidenced fast recombination reactions for heteroleptics, even associated with un unfavorable directional electron flow, and hence slower injection rates, in the case of homoleptics. Notably, quantum mechanics calculations revealed that deprotonation of the not anchored carboxylic function in the homoleptic complex can effectively accelerate the electron injection rate and completely suppress the electron recombination to the oxidized dye. This result suggests that introduction of strong electron-donating substituents on the not-anchored carbene ligand in heteroleptic complexes, in such a way of mimicking the electronic effects of the carboxylate functionality, should yield markedly improved interfacial charge generation properties. The present results, providing for the first time a detailed understanding of the interfacial electron transfers and photovoltaic characterization in Fe(ii)–carbene sensitized solar cells, open the way to a rational molecular engineering of efficient iron-based dyes for photoelectrochemical applications. [ABSTRACT FROM AUTHOR]

Herein we report the synthesis and time-resolved spectroscopic characterization of a homoleptic Fe(ii) complex exhibiting a record 3MLCT lifetime of 26 ps promoted by benzimidazolylidene-based ligands. Time dependent density functional molecular modeling of the triplet excited state manifold clearly reveals that, at equilibrium geometries, the lowest 3MC state lies higher in energy than the lowest 3MLCT one. This unprecedented energetic reversal in a series of iron complexes, with the stabilization of the charge-transfer state, opens up new perspectives towards iron-made excitonic and photonic devices, hampering the deactivation of the excitation via metal centered channels. [ABSTRACT FROM AUTHOR]

Three ruthenium complexes bearing glycol chains of varied length and number have been prepared and evaluated as hydrophilic sensitizers in aqueous dye-sensitized solar cell (DSSC) devices. The new complexes performed better than N719 in a 100 % aqueous electrolyte. The use of co-adsorbents and particularly bis(4-methoxyphenyl)phosphinic acid (BMPP) improved the efficiency and short-circuit photocurrent. [ABSTRACT FROM AUTHOR]

Herein, we report a homoleptic iron complex bearing tridentate bis-carbene (CNC) ligands designed for sensitization of TiO2 photoanodes. Its excited state has been characterized by ultra-fast transient spectroscopy and time-dependent density functional theory (TD-DFT) computations, which reveal a record triplet metal-to-ligand charge-transfer (3MLCT) excited-state lifetime (16 ps). The new dye was efficiently chemisorbed on TiO2 and promoted electron injection and photocurrent generation in a dye-sensitized solar cell upon solar irradiation. [ABSTRACT FROM AUTHOR]

New heteroleptic iron complexes mixing a terpyridine bearing a protonable pyridyl substituent (pytpy) and a pyridyl carbene ligand (carb) have been prepared and characterised by UV/Vis spectroscopy, cyclic voltammetry and TD-DFT computations. The absorption spectrum of [Fe(carb)(pytpy)]2+ showed a notable redshift compared with the homoleptic [Fe(carb)2]2+ complex. The MLCT transition occurred at even lower energy when the pendant pyridine was protonated, leading to a wide absorption domain in the 450-650 nm range. Calculations revealed the strong propensity of excited electrons to move from the metal to the pytpy ligand in the complex. This new family of complexes is a promising addition to the arsenal of iron-based chromophores with tuneable electronic properties. [ABSTRACT FROM AUTHOR]

With the aim of synthesizing biaryl compounds, several aromatic iodides were prepared by the deprotonative metalation of methoxybenzenes, 3-substituted naphthalenes, isoquinoline, and methoxypyridines by using a mixed lithium/zinc-TMP (TMP=2,2,6,6-tetramethylpiperidino) base and subsequent iodolysis. The halides thus obtained, as well as commercial compounds, were cross-coupled under palladium catalysis (e.g., Suzuki coupling with 2,4-dimethoxy-5-pyrimidylboronic acid) to afford various representative biaryl compounds. Deprotometalation of the latter compounds was performed by using the lithium/zinc-TMP base and evaluated by subsequent iodolysis. The outcome of these reactions has been discussed in light of the CH acidities of these substrates, as determined in THF solution by using the DFT B3LYP method. Except for in the presence of decidedly lower p Ka values, the regioselectivities of the deprotometalation reactions tend to be governed by nearby coordinating atoms rather than by site acidities. In particular, azine and diazine nitrogen atoms have been shown to be efficient in inducing the reactions with the lithium/zinc-TMP base at adjacent sites (e.g., by using 1-(2-methoxyphenyl)isoquinoline, 4-(2,5-dimethoxyphenyl)-3-methoxypyridine, or 5-(2,5-dimethoxyphenyl)-2,4-dimethoxypyrimidine as the substrate), a behavior that has already been observed upon treatment with lithium amides under kinetic conditions. Finally, the iodinated biaryl derivatives were involved in palladium-catalyzed reactions. [ABSTRACT FROM AUTHOR]

Enantioselective deprotonative metalations of substituted ferrocenes using mixed lithium-metal bases are described. Using N, N-diisopropylferrocenecarboxamide as substrate, magnesium, iron, cobalt, zinc, and cadmium were tested as metals in bis[( S)-1-phenylethyl]amido-based combinations; after interception of the metalated species with iodine, very high enantiomeric excess (96 %) but low yield was obtained with cobalt, whereas zinc and cadmium only gave 27 and 30 % ee, respectively, but in excellent yields. The small alkyl groups methyl and ethyl were identified as particularly suitable in the reaction using the putative dialkyl bis[( S)-1-phenylethyl]amido-based lithium and dilithium zincates. The dimethyl dilithium zincate was selected for a study of dependency on the temperature, reaction time, and amount of base. Increased enantioselectivities with temperature, reaction time, and amount of base were noted ( ee = 86 % at 0 °C after 2 h, 2 equiv. of base). The best result using methyl ferrocenecarboxylate as substrate was observed without alkyl ligand. [ABSTRACT FROM AUTHOR]

The article discusses the compound structure of 2,2'-(Ethane-1,2-diyl) bis [2-(5-bromothiopen-2-yl)-1,3-dioxolane]. This compound is a precursor in synthesizing oligothiophenes and their substituted homologues which are classes of organic semiconductor materials used in the production of organic field-effect transistors and organic solar cells. This compound lies about an inversion center at a C-C bond mid-point and the crystal molecules are linked by various types of weak interactions.

Molecular dynamics simulations of organolithium aggregates in solution are reported for the first time. We use a combined quantum/classical force field (the so-called QM/MM approach) and study ethyl-lithium aggregates in dimethyl ether (DME) solvent. The solutes are described at the Density Functional Theory level while solvent molecules are described using molecular mechanics. NVT Molecular Dynamics simulations at 200 K are carried out in the Born–Oppenheimer approximation. After equilibration, the production phase was run for 80 ps (monomer), 40 ps (dimer) and 26 ps (tetramer). The analysis of the results focuses on Li coordination as a function of aggregate size and we show that the total Li coordination number is always 4. No decoordination has been observed along the simulations. Fluctuations of the structures are predicted to be large in some cases and possible implications on reactivity are discussed. [ABSTRACT FROM AUTHOR]

The control of ligand-field splitting in iron (II) complexes is critical to slow down the metal-to-ligand charge transfer (MLCT)-excited states deactivation pathways. The gap between the metal-centered states is maximal when the coordination sphere of the complex approaches an ideal octahedral geometry. Two new iron(II) complexes (C1 and C2), prepared from pyridylNHC and pyridylquinoline type ligands, respectively, have a near-perfect octahedral coordination of the metal. The photophysics of the complexes have been further investigated by means of ultrafast spectroscopy and TD-DFT modeling. For C1, it is shown that—despite the geometrical improvement—the excited state deactivation is faster than for the parent pseudo-octahedral C0 complex. This unexpected result is due to the increased ligand flexibility in C1 that lowers the energetic barrier for the relaxation of 3MLCT into the 3MC state. For C2, the effect of the increased ligand field is not strong enough to close the prominent deactivation channel into the metal-centered quintet state, as for other Fe-polypyridine complexes. [ABSTRACT FROM AUTHOR]