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Controlling self-assembled nanostructures on bulk insulators at room temperature is crucial towards the fabrication of future molecular devices, e.g., in the field of nanoelectronics, catalysis and sensor applications. However, at temperatures realistic for operation anchoring individual molecules on electrically insulating support surfaces remains a big challenge. Here, we present the formation of an ordered array of single anchored molecules, dimolybdenum tetraacetate, on the (10.4) plane of calcite (CaCO3). Based on our combined study of atomic force microscopy measurements and density functional theory calculations, we show that the molecules neither diffuse nor rotate at room temperature. The strong anchoring is explained by electrostatic interaction of an ideally size-matched molecule. Especially at high coverage, a hard-sphere repulsion of the molecules and the confinement at the calcite surface drives the molecules to form locally ordered arrays, which is conceptually different from attractive linkers as used in metal-organic frameworks. Our work demonstrates that tailoring the molecule-surface interaction opens up the possibility for anchoring individual metal complexing molecules into ordered arrays.

The new tribasic N2S2 ligand H3ttfasbz has been synthesized by condensation of 4-thenoyl 2,2,2-trifluoroacetone and S-benzyl dithiocarbazate. On complexation with copper(II) acetate, spontaneous oxidation to the CuIII oxidation state is observed, and the complex Cu(ttfasbz) has been isolated and characterized structurally. Reduction to the EPR active CuII analogue has been achieved chemically and also electrochemically, and in both cases, the process is totally reversible. The CuIII/II redox potential of the complex is remarkably low and similar to that of the ferrocenium/ferrocene couple. Further reduction to the formally monovalent (d10) dianion CuI(ttfasbz)2- may be achieved electrochemically. Computational chemistry demonstrates that the three redox states Cu(ttfasbz), Cu(ttfasbz)-, and Cu(ttfasbz)2- are truly CuIII, CuII, and CuI complexes, respectively, and the potentially noninnocent ligand does not undergo any redox reactions.

The molecular and electronic structures of the 2,2′-bipyridine containing series of group 14 compounds (a) [MF4(bpy)]0; (b) [MCl2(bpy)2]2+/0 (c) [MCl2(bpy)]0; (d) [M(bpy)2]2+/0; (e) [Si(bpy)3]1+,0,1–,2–; and (f) [M(bpy)3]0 (M = C, Si, Ge, Sn, Pb) have been calculated using density functional theory (DFT). Where possible, geometry optimized structures are compared with their experimentally determined structures. In general, good to excellent agreement is observed. It is shown that the three successive one-electron reductions within the experimentally known series [Si(bpy)3]1+,0,1–,2– are ligand-based and the Si center has a +IV oxidation state throughout. Hence, these species have the electronic structures [SiIV(bpy•)3]+ (S = 1/2), [SiIV(bpy•)2(bpy2–)]0 (S = 0), [SiIV(bpy•)(bpy2–)2]− (S = 1/2), and [SiIV(bpy2–)3]2– (S = 0). Similarly, it is shown that the crystallographically characterized compound [Si(bpy)2]0 (S = 0) possesses the electronic structure [SiIV(bpy2–)2]0, which contains a tetravalent Si ion and two (bpy2–)2– dianions. It should not be described as [Si0(bpy0)2]0. For the heavier Ge, Sn, and Pb congeners the divalent state, characterized by a stereochemically active electron pair, becomes increasingly significant and dominates in 4-coordinate Sn and Pb species.

Dissecting the barrier: The nuclear resonance vibrational spectrum of the S=2 [(TMG3tren)FeIV=O] complex revealed features indicative of an axial “steric wall” that contributes to the overall reaction barrier. DFT calculations show that both S=2 (axial attack) and S=1 (equatorial attack) surfaces possess steric contributions to their barriers, and estimates of these steric effects result in comparable intrinsic barriers for both spin surfaces (see picture).

Treatment of [FeII(L)](OTf)2 (4), (where L = 1,4,8-Me3cyclam-11-CH2C(O)NMe2) with iodosylbenzene yielded the corresponding S = 1 oxoiron(IV) complex [FeIV(O)(L)](OTf)2 (5) in nearly quantitative yield. The remarkably high stability of 5 (t1/2 ≈ 5 days at 25 °C) facilitated its characterization by X-ray crystallography and a raft of spectroscopic techniques. Treatment of 5 with strong base was found to generate a distinct, significantly less stable S = 1 oxoiron(IV) complex, 6 (t1/2 ∼ 1.5 h at 0 °C), which could be converted back to 5 by addition of a strong acid; these observations indicate that 5 and 6 represent a conjugate acid–base pair. That 6 can be formulated as [FeIV(O)(L–H)](OTf) was further supported by ESI mass spectrometry, spectroscopic and electrochemical studies, and DFT calculations. The close structural similarity of 5 and 6 provided a unique opportunity to probe the influence of the donor trans to the FeIV=O unit upon its reactivity in H-atom transfer (HAT) and O-atom transfer (OAT), and 5 was found to display greater reactivity than 6 in both OAT and HAT. While the greater OAT reactivity of 5 is expected on the basis of its higher redox potential, its higher HAT reactivity does not follow the anti-electrophilic trend reported for a series of [FeIV(O)(TMC)(X)] complexes (TMC = tetramethylcyclam) and thus appears to be inconsistent with the two-state reactivity rationale that is the prevailing explanation for the relative facility of oxoiron(IV) complexes to undergo HAT.

High versus low: The high-yield generation of a synthetic high-spin oxoiron(IV) complex, [FeIV(O)(TMG3tren)]2+ (see picture, TMG3tren = 1,1,1-tris{2-[N2-(1,1,3,3-tetramethylguanidino)]ethyl}amine), has been achieved by using the very bulky tetradentate TMG3tren ligand, in order to both sterically protect the oxoiron(IV) moiety and enforce a trigonal bipyramidal geometry at the iron center, for which an S=2 ground state is favored.

The trigonal-bipyramidal high-spin (S = 2) oxoiron(IV) complex [FeIV(O)(TMG2dien)(CH3CN)]2+ (7) was synthesized and spectroscopically characterized. Substitution of the CH3CN ligand by anions, demonstrated here for X = N3– and Cl–, yielded additional S = 2 oxoiron(IV) complexes of general formulation [FeIV(O)(TMG2dien)(X)]+ (7-X). The reduced steric bulk of 7 relative to the published S = 2 complex [FeIV(O)(TMG3tren)]2+ (2) was reflected by enhanced rates of intermolecular substrate oxidation.

Redox-active ligands: Structural, spectroscopic, and theoretical studies of ruthenium(II) complexes bearing 2-(2-nitrosoaryl)pyridine ligands and their reduced analogues reveals the redox noninnocence of 2-(2-nitrosoaryl)pyridine (see scheme).

The conjugate acids of 1,2,3-triazolylidene mesoionic carbenes can be prepared in a straightforward fashion by alkylation of 1-substituted 1,2,3-triazoles. However, this becomes a much more challenging proposition when other nucleophilic centers are present, which has curtailed the development of ligands containing multiple 1,2,3-triazolylidene donors. Herein, methylation of a series of tris[(1-aryl-1,2,3-triazol-4-yl)methyl]amines possessing both electron-rich and electron-deficient aromatic substituents, using Me3OBF4, is shown to proceed with much higher chemoselectivity under mechanochemical conditions than when conducted in solution. This provides a means to reliably access a series of tricationic tris[4-(1,2,3-triazolium)methyl]amines in good yields. DFT calculations suggest that a potential reason for this change in regioselectivity is the difference between the background dielectric of the DCM solution versus the solid state, which is predicted to have a large effect on the relative thermodynamic driving force for alkylation of the tertiary amine center versus the triazole rings. Homoleptic silver complexes of the triazolylidene ligands derived therefrom, of formulas [Ag3(1a-d)2](X)3 (X- = BF4-, TfO-), have been isolated and fully characterized. In the case of the ligand bearing the smallest aryl substituents, 1b, argentophilic interactions yield a triangular Ag3 core. The [Ag3(1a-d)2](X)3 silver salts are viable agents for transmetalation to other transition metals, demonstrated here for cobalt. In the case of 1a, the complex [CoII(1a)(NCMe)](OTf)2 was obtained. Therein, the bulky mesityl substituents enforce a tetrahedral geometry, in which only the triazolylidene donors of 1a coordinate (i.e., it acts as a tridentate ligand). Transmetalation of the less sterically encumbered ligand 1b yields six-coordinate cobalt(III) complexes, [CoIII(1b)(Cl)(NCMe)](OTf)2 and [CoIII(1b)(NCMe)2](OTf)3, in which the ligand coordinates in a tetradentate fashion. These are t

Combining the unique properties of hybrid halide perovskites and in-plane anisotropic potential of two-dimensional materials, corrugated layered perovskites are excellent candidates for novel optoelectronic devices. Here, we report strong in-plane anisotropy in a two-dimensional hybrid halide perovskite with corrugated inorganic sheets. We assigned the angle-dependent Raman spectra to particular orientations of the crystals where the method applied is suitable for fast determination of the in-plane crystallographic axes. We demonstrated strong in-plane anisotropy of the optoelectronic properties: electrical measurements showed that changes of photoconductivity and angle-resolved reflectance spectroscopy exhibited variation of the band structure. Employing first-principles calculations, we confirmed the observed anisotropy of the dielectric response. Photoluminescence spectroscopy revealed an anomalous energy shift of ∼20 meV dependent on the relative orientation of the crystals and polarization of the excitation light. Using temperature-dependent analysis of the photoluminescence spectra, we obtained the anisotropic exciton-phonon coupling strength as well as the angle-dependent average phonon energy involved, which contributes to the shift of the photoluminescence peak maximum. This discovery of the in-plane anisotropic behavior in layered 2D perovskites could be expected to spur new functionalities in optical and optoelectronic device applications.

Major strides have been made in the development of materials and devices based around low-dimensional hybrid group 14 metal halide perovskites. Thus far, this work has mostly focused upon compounds containing highly toxic Pb, with the analogous less toxic Sn materials being comparatively poorly evolved. In response, the study herein aims to (i) provide insight into the impact of templating cation upon the structure of n = 1 2D tin iodide perovskites (where n refers to the number of contiguous two-dimensional (2D) inorganic layers, i.e., not separated by organic cations), and (ii) examine their potential as light absorbers for photovoltaic (PV) cells. It was discovered through systematic tuning of organic dications, that imidazolium rings are able to induce formation of (110)-oriented materials, including the examples of “3 × 3” corrugated Sn-I perovskites. This structural outcome is a consequence of a combination of supramolecular interactions of the two endocyclic N-atoms in the imidazolium functionalities with the Sn-I framework and the higher tendency of Sn2+ ions to stereochemically express their 5s2 lone pairs relative to the 6s2 electrons of Pb2+. More importantly, the resulting materials feature very short separations between their 2D inorganic layers with iodide–iodide (I···I) contacts as small as 4.174 Å, which is amongst the shortest ever recorded for 2D tin iodide perovskites. The proximate inorganic distances, combined with the polarizable nature of the imidazolium moiety, eases the separation of photogenerated charge within the materials. This is evident from the excitonic activation energies as low as 83(10) meV, measured for ImEA[SnI4]. When combined with superior light absorption capabilities relative to their lead congeners, this allowed fabrication of lead-free solar cells with incident photon-to-current and power conversion efficiencies of up to 70 % and 2.26 %, respectively, which are amongst the highest values reported for pure n = 1 2D group 14

The reaction of a benzofuroxan with [Ru([9]aneS3)(dmso)Cl2] ([9]aneS3 = 1,4,7-trithiacyclononane) and [Ru(bpy)2(CH3CN)2]2+ yields the ruthenium complexes [Ru([9]aneS3)(ON^NO)(Cl)]+ (1a–c) and [Ru(bpy)2(ON^NO)]n+ (n = 2: 2a and 2b; n = 1: 2a- and 2b-), respectively, containing neutral or monoanionic N,N'-coordinated 1,2-dinitrosoarenes (ON^NO). The oxidation states of the ON^NO ligands (0 for 1a–c, 2a and 2b; -1 for 2a- and 2b-) have been deduced through detailed structural, spectroscopic, and theoretical studies. In other words, not only does this work demonstrate the trapping of the putative 1,2-dinitrosoarene intermediate of benzofuroxan tautomerization by coordination to ruthenium, it also provides access to a new family of redox-active bidentate ligands.

Two-dimensional (2D) phenylethyl ammonium (PEA+)-methyl ammonium (MA+) lead iodide ((PEA)2(MA)[Pb2I7]) hybrid perovskite exists as temperature-dependent dimorphs exhibiting an ill-defined phase transition occurring over the 150-200 K range. Raman scattering, photoluminescence, optical absorbance and solid state MAS NMR spectroscopic methods are employed to investigate the structural complexity, disorder and structure/function of this system. The Raman and 1H MAS NMR data indicate that the lower bounds of the phase transition at ∼150 K are characterised by attenuated rotational modes and slower motional dynamics throughout the disordered MA+ organic sublattice, inducing a strengthening of the MA+⋯I hydrogen bonds and a 5 meV increase in the excitonic and photoluminescence energies. It is evident that different recombination mechanisms are dominant for the room temperature and low temperature phases reflecting the importance of MA+ dynamics in the optical properties of the material. Single crystal X-ray studies are unable to position the organic cations within the Pb2I7 framework; however, 1H/13C MAS NMR measurements describe elements of local structural disorder based on conformational isomerism within the PEA+ sublattice. Concomitant I- and Pb2+ migration and [Pb2I7]3- framework defects create stacking disorder, dislocations and dispersed octahedral tilting leading to additional disorder and distributed MA+ and PEA+ cation dynamics.

In addition to oxometal Mn+O and imidometal Mn+NR units, transient metal-iodosylarene M(n-2)+-OIPh and metal-iminoiodane M(n-2)+-N(R)IPh adducts are often invoked as a possible "second oxidant" responsible for the oxo and imido group transfer reactivity. Although a few metal-iodosylarene adducts have been recently isolated and/or spectroscopically characterized, metal-iminoiodane adducts have remained elusive. Herein, we provide UV-Vis, EPR, NMR, XAS and DFT evidence supporting the formation of a metal-iminoiodane complex 2 and its scandium adduct 2-Sc. 2 and 2-Sc are reactive toward substrates in the hydrogen-atom and nitrene transfer reactions, which confirm their potential as active oxidants in metal-catalyzed oxidative transformations. Oxidation of para-substituted 2,6-di-tert-butylphenols by 2 and 2-Sc can occur by both coupled and uncoupled proton and electron transfer mechanisms; the exact mechanism depends on the nature of the para substituent. © 2016 The Royal Society of Chemistry.

The members of the electron transfer series [Mn(bpy)3]n (n = 2+, 1+, 0, 1-) and [Mn(tpy)2]m (m = 2+, 1+, 0) have been investigated using a combination of magnetochemistry, electrochemistry, and UV-vis-NIR spectroscopy; and X-ray crystal structures of [MnII(Mebpy•)2(Mebpy0)]0, [Li(THF)4][MnII(bpy•)3], and [MnII(tpy•)2]0 have been obtained (bpy = 2,2′-bipyridine; Mebpy = 4,4′-dimethyl-2,2′-bipyridine;tpy = 2,2′:6,2″-terpyridine; THF = tetrahydrofuran). It is the first time that the latter complex has been isolated and characterized. Through these studies, the electronic structures of each member of both series of complexes have been elucidated, and their molecular and electronic structures further corroborated by broken symmetry (BS) density functional theoretical (DFT) calculations. It is shown that all one-electron reductions that comprise the aforementioned redox series are ligand-based. Hence, all species contain a central high-spin MnII ion (SMn = 5/2). In contrast, the analogous series of TcII and ReII complexes possess low-spin electron configurations.

The synthesis and characterization of a trinuclear copper complex 1 involving an amine based ligand system, tateb, are reported. Complex 1 acts as a catalyst for a four-electron four-proton reduction of dioxygen to water. 1 represents the first example of a biomimetic model of the trinuclear copper center in the multicopper oxidases. The mechanism of the O2-reduction reaction has been clarified based on kinetic studies on the overall catalytic reaction and by low-temperature detection of reactive intermediates.

A series of non-heme iron(II) bis(triflate) complexes containing linear and tripodal tetradentate ligands has been prepared. Electron withdrawing and electron donating substituents in the para position of the pyridine ligands as well as the effect of pyrazine versus pyridine and sulfur or oxygen donors instead of nitrogen donors have been investigated. The electronic effects induced by these substituents influence the strength of the ligand field. UV-vis spectroscopy and magnetic susceptibility studies have been used to quantify these effects and VT 1H and 19F NMR spectroscopy as well as X-ray diffraction have been used to elucidate structural and geometrical aspects of these complexes. The catalytic properties of the iron(II) complexes as catalysts for the oxidation of cyclohexane with hydrogen peroxide have been evaluated. In the strongly oxidising environment required to oxidise alkanes, catalyst stability determines the overall catalytic efficiency of a given catalyst, which can be related to the ligand field strength and the basicity of the ligand and its propensity to undergo oxidation.

Of a series of new 2D lead-bromide perovskites, templated by closely related dications 1–5, a corrugated (110)-oriented structure was attained only in one, 1[PbBr4]. The others display (100) structures. Upon excitation by UV-light, 1[PbBr4] exhibits intrinsic white-light emission that is ‘‘colder’’ than previously reported for this class of compounds.

The electronic structures of the complexes [M(tbpy)3]0,1- (M = Nb, Ta; tbpy = 4,4′-di-tert-butyl-2,2′-bipyridine) have been investigated using a combination of UV–vis spectroscopy, EPR spectroscopy, and XAS. Furthermore, the crystal structure of [Na(THF)5][Ta(tbpy)3] has been determined. These studies were supplemented by density functional theory (DFT) and the calculations extended to include the series [Y(bpy)3]m (m = 0, 1–, 2–, 3−), [Ti(bpy)3]n (n = 1+, 0, 1–, 2–, 3−), [Zr(bpy)3]p, and [Hf(bpy)3]p (p = 0, 1–, 2−). This has allowed us to define the correct electronic structures of these early transition metal tris(2,2′-bipyridine) complexes. It is shown that in the [Y(bpy)3]m series the central ion possesses an invariant +III oxidation state and that the three successive one-electron redox processes that comprise the series are solely ligand-based, yielding three (bpy•)1- radical anions in the neutral complex through to three diamagnetic dianions (bpy2-)2- in the trianion. The same is true for the [Ti(bpy)3]n series where the neutral complex contains 3(bpy•)1- and the trianion 3(bpy2-)2- anions. Hence, the central ion always possesses a central TiIII (d1) ion that intramolecularly antiferromagnetically couples to any (bpy•)1- ligands present. In contrast, the central metal ions in the series [Zr(bpy)3]p and [Hf(bpy)3]p always possess a +IV oxidation state; hence, the dianions contain three (bpy2-)2- ligands and yield an S = 0 ground state. The electronic structures of the neutral Nb and Ta analogues possessing S = 1/2 ground states are best described as [NbIV(bpy2-)2(bpy)0)]0 and [TaV(bpy•)(bpy2-)2]0, and their S = 0 monoanions as [NbIV(bpy•)(bpy2-)2]1- and [TaV(bpy2-)3]1-. The central metal ion in the Nb series maintains a +IV oxidation state, while in the Ta series the central metal ion displays a +V oxidation state throughout.

[Fe(Me2EBC)(OTf)2], the iron(II) complex of the tetraazamacrocyclic Me2EBC ligand (Me2EBC = 4,11-dimethyl-1,4,8,11-tetraazabicyclo [6.6.2]hexadecane), has been investigated as a catalyst for olefin oxidation by H2O2 and compared to the closely related [Fe(TMC)(OTf)](OTf) complex (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane). Both complexes have tetraazamacrocyclic ligands based on cyclam that differ in how they coordinate to the iron center. This difference results in different orientations of their remaining coordination sites. Whereas the two sites on [Fe(Me2EBC)(OTf)2] are cis to each other, those of [Fe(TMC)(OTf)](OTf) are trans. Previous work on olefin oxidation by several nonheme iron catalysts has emphasized the importance of having two cis-labile sites to activate the H2O2 oxidant, particularly in effecting olefin cis-dihydroxylation, but there were differences in the ligand donor properties in the complexes studied. The fact that TMC and Me2EBC provide essentially identical tertiary amine donors, but in different orientations, provides an excellent opportunity to assess the impact of ligand topology upon reactivity in the absence of other complicating factors. Indeed [Fe(Me2EBC)(OTf)2] was found to be an active catalyst with reactivity properties similar to those of the most thoroughly investigated iron catalyst [Fe(TPA)(OTf)2] (TPA = tris(pyridin-2-ylmethyl)amine). In contrast, [Fe(TMC)(OTf)](OTf) only showed a limited ability for epoxidation and no facility for cis-dihydroxylation. This stark difference irrefutably demonstrates that cis-oriented labile sites are a fundamental requirement for successful nonheme iron catalyzed olefin oxidation. Additionally, mechanistic studies of [Fe(Me2EBC)(OTf)2] lead us to forward a similar FeIII/FeV redox cycle as proposed for [Fe(TPA)(OTf)2].

Octahedral, tetrahedral, and square planar geometries are the most often encountered coordination geometries for transition metal complexes. In certain cases, coordination equilibria can exist between different geometries, such as between six- and four-coordinate geometries in nickel(II) complexes, which were discovered half a century ago. Here, we present the first examples of a seven-five coordination equilibrium. Extensive spectroscopic studies in solution have provided evidence for a dynamic equilibrium between two iron(II) complexes, one with a seven-coordinate pentagonal bipyramidal geometry and one with a five-coordinate trigonal bipyramidal geometry.

The electronic structures of a series of so-called “low-valent” transition metal complexes [M(Mebpy)3]0 and [M(tpy)2]0 (Mebpy = 4,4′-dimethyl-2,2′-bipyridine and tpy = 2,2′,6′,2″-terpyridine) have been determined using a combination of X-ray crystallography, magnetochemistry, and UV–vis–NIR spectroscopy. More specifically, the crystal structures of the long-known complexes [TiIV(tpy2–)2]0 (S = 0, 6), [VIV(tpy2–)2] (S = 1/2, 7), [TiIII(Mebpy•)3]0 (S = 0, 1), [VII(Mebpy•)2(Mebpy0)]0 (S = 1/2, 2), and [MoIII(Mebpy•)3]0 (S = 0, 4) have been determined for the first time. In all cases, the experimental results confirm the electronic structure assignments that we ourselves have recently proposed. Additionally, the six-coordinate complex [MoIII(bpy0)2Cl2]Cl·2.5CH3OH (S = 3/2, 13), and seven-coordinate species [MoIVF(Mebpy•)2(Mebpy0)](PF6) (S = 0, 5), [MoIVCl(tpy•)2](PF6)·CH2Cl2 (S = 0, 11), and [WVF(tpy•)(tpy2–)](PF6)·CH2Cl2 (S = 0, 12) have been synthesized and, for the first time, crystallographically characterized. Using the resulting data, plus that from previously published high-resolution X-ray structures of analogous compounds, it is shown that there is a linear correlation between the average Cpy–C′py bond distances in these complexes and the total charge (n) of the ligands, {(bpy)3}n and {(tpy)2}n. Hence, an assignment of the total charge of coordinated bpy or tpy ligands and, by extension, the oxidation state of the central metal ion can reliably be made on the basis of X-ray crystallography alone. In this study, the oxidation states of the metal ions range from +II to +V and in no case has an oxidation state of zero been validated. It is, therefore, highly misleading to use the term “low-valent” to describe any of the aforementioned neutral complexes.

Currently, there are only a handful of synthetic S = 2 oxoiron(IV) complexes. These serve as models for the high-spin (S = 2) oxoiron(IV) species that have been postulated, and confirmed in several cases, as key intermediates in the catalytic cycles of a variety of nonheme oxygen activating enzymes. The trigonal bipyramidal complex [FeIV(O)(TMG3tren)]2+ (1) was both the first S = 2 oxoiron(IV) model complex to be generated in high yield and the first to be crystallographically characterized. In this study, we demonstrate that the TMG3tren ligand is also capable of supporting a tricationic cyanoiron(IV) unit, [FeIV(CN)(TMG3tren)]3+ (4). This complex was generated by electrolytic oxidation of the high-spin (S = 2) iron(II) complex [FeII(CN)(TMG3tren)]+ (2), via the S = 5/2 complex [FeIII(CN)(TMG3tren)]2+ (3), the progress of which was conveniently monitored by using UV−vis spectroscopy to follow the growth of bathochromically shifting ligand-to-metal charge transfer (LMCT) bands. A combination of X-ray absorption spectroscopy (XAS), Mössbauer and NMR spectroscopies was used to establish that 4 has a S = 0 iron(IV) center. Consistent with its diamagnetic iron(IV) ground state, extended X-ray absorption fine structure (EXAFS) analysis of 4 indicated a significant contraction of the iron-donor atom bond lengths, relative to those of the crystallographically characterized complexes 2 and 3. Notably, 4 has an FeIV/III reduction potential of ∼1.4 V vs Fc+/o, the highest value yet observed for a monoiron complex. The relatively high stability of 4 (t1/2 in CD3CN solution containing 0.1 M KPF6 at 25 °C ≈ 15 min), as reflected by its high-yield accumulation via slow bulk electrolysis and amenability to 13C NMR at −40 °C, highlights the ability of the sterically protecting, highly basic peralkylguanidyl donors of the TMG3tren ligand to support highly charged high-valent complexes.

Oxoferryl gymnastics: The oxo and CH3CN ligands in 1-NCCH3 can swap positions in the presence of iodosobenzene and tetrafluoroborate anion leading to the generation of a more reactive isomer 2. This conversion is proposed to take place via an activated FeIV unit (1 a) or a transient dioxoiron(VI) species (1 b).

Lead-free halide perovskite semiconductors are necessary due to the atmospheric instability and lead toxicity associated with the 3D lead halide perovskites. However, a stable lead-free perovskite with an ideal band gap (1.2-1.4 eV) for photovoltaics is still missing. In this work, we synthesized organic-inorganic gold halide double perovskites ((CH3NH3)2[Au2X6], X = Br, I) through a solution-processed route that offers an ideal direct band gap for photovoltaic applications. Density functional theory calculations confirm the direct nature of the band gap with reasonable absorption coefficients in the visible range and excellent charge transport properties. In addition, the Au-halide perovskites show high chemical stability and photoresponse. These combined properties demonstrate that Au-based halide perovskites can be a promising group of compounds for optoelectronic applications.

A two-dimensional hybrid coordination polymer Pb(CH3NH2)I2n featuring a well-defined layered structure is reported for scalable perovskite ink and deposition. This coordination polymer exhibits structural, spectroscopic, and physicochemical properties distinct from common PbI2 perovskite precursors. Notably, it serves as a methylamine "gas carrier"capable of liberating methylamine (CH3NH2) into the precursor solution, thus improving the solubility of perovskite in unconventional, greener processing solvents, such as acetonitrile. The purity of Pb(CH3NH2)I2n single crystals and the ability of the precursor to reduce sources of defects such as polyiodide species in solution allow the formation of high-quality perovskite films. This eventually results in efficient and stable devices, fabricated via a single-step antisolvent-free deposition method, transferable to large-area slot die coating. Gram scale synthesis of this unique lead precursor is demonstrated, essential for the scale-up of perovskite photovoltaic technology. Copyright © 2020 American Chemical Society.

To probe the possibility that carbodicarbenes (CDCs) are redox active ligands, all four members of the redox series [Fe(1)2]n+ (n = 2 - 5) were synthesized, where 1 is a neutral tridentate CDC. Through a combination of spectroscopy and DFT calculations, the electronic structure of the pentacation is shown to be [FeIII(1.+)2]5+ (S = (Formula presented.)). That of [Fe(1)2]4+ is more ambiguous, but it has significant contributions from the open-shell singlet [FeIII(1)(1.+)]4+ (S=0). The observed spin states derive from antiferromagnetic coupling of their constituent low-spin iron(III) centres and cation radical ligands. This marks the first time redox activity has been observed for carbones and expands the diverse chemical behaviour known for these ligands. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Published studies of layered (2D) (100)-oriented hybrid lead-bromide perovskites evidence a correlation between increased inter-octahedral (Pb-Br-Pb) distortions and the appearance of broadband white light emission. However, the impact of distortions within their constituent [PbBr6]4- octahedra has yet to be assessed. Herein, we report two new (100)-oriented 2D Pb-Br perovskites, whose structures display unusually high intra-octahedral distortions, whilst retaining minimal inter-octahedral distortions. Using a combination of temperature-dependent, power-dependent and time-resolved photoluminescence spectroscopic measurements, we show that increased intra-octahedral distortion induces exciton localization processes and leads to formation of multiple photoinduced emissive colour centres. Ultimately, this leads to highly Stokes-shifted, ultrabroad white light emission at room temperature.