Iridium(III) Blue Phosphors with Heteroleptic Carbene Cyclometalates: Isomerization, Emission Tuning, and OLED Fabrications.

Ir(III) complexes are particularly noted for their excellent photophysical properties in giving blue OLED phosphors. In this study, two distinctive carbene pro-chelates LAH2+ and LBH2+ (or LCH2+) were employed in preparation of heteroleptic Ir(III) complexes, to which LAH2+ bears a cyano substituted benzoimidazolium along with N-mesityl appendage, while LBH2+ (or LCH2+) carries the symmetrical benzoimidazolium entity. Notably, the reversible equilibration at high temperature was observed for m, f-ct14 and m, f-ct15 with a single LA chelate.

Tetradentate Pt(II) Complexes Based on Xylenylamino Linked Dual Pyrazolate Chelates for Organic Light Emitting Diodes.

In this work, we report the syntheses of three Pt(II) emitters, namely, Pt4N1, Pt4N2, and Pt4N3, to which their tetradentate chelates were assembled by linking two pyrazolate chelates with a single xylenylamino entity. Functionalization of Pt4N1 was achieved upon the addition of electronegative CF substituent on pyridinyl groups and switching to more electron-deficient pyrazinyl groups in giving Pt4N2 and Pt4N3, respectively. The vertically arranged xylenylamino entity has effectively suppressed the inter-molecular π-π stacking and Pt⋅⋅⋅Pt interaction, as shown by the single crystal X-ray structural analyses.

Ir(III) Metal Emitters with Cyano-Modified Imidazo[4,5-b]pyridin-2-ylidene Chelates for Deep-Blue Organic Light-Emitting Diodes.

Ir(III) carbene complexes have been explored as one of the best blue phosphors for their high performance. Herein, the authors designed and synthesized a series of blue-emitting Ir(III) phosphors (f-ct9a-c), featuring fac-coordinated cyano-imidazo[4,5-b]pyridin-2-ylidene cyclometalates. These Ir(III) complexes exhibit true-blue emission with a peak maximum spanning 448-467 nm, with high photoluminescence quantum yields of 81-88% recorded in degassed toluene.

Structural Engineering of Iridium(III) Phosphors with Imidazo[4,5-b]pyrazin-2-ylidene Cyclometalates for Efficient Blue Electroluminescence.

Iridium(III) complexes are particularly noted for their excellent potentials in fabrication of blue organic light-emitting diodes (OLEDs), but the severe efficiency roll-off largely hampered their practical applications. To reveal the underlying characteristics, three Ir(III) complexes, namely f-ct5c, f-ct5d, and f-ct11, bearing imidazo[4,5-b]pyrazin-2-ylidene cyclometalates are prepared and characterized in detail. Both f-ct5c and f-ct5d (also their mixture f-ct5mix) gave intensive blue emissions peaking at ≈465 nm with short radiative lifetimes of 1.

Visible-Light-Driven CO Reduction with Homobimetallic Complexes. Cooperativity between Metals and Activation of Different Pathways.

Visible-light-driven reduction of CO to both CO and formate (HCOO) was achieved in acetonitrile solutions using a homobimetallic Cu bisquaterpyridine complex. In the presence of a weak acid (water) as coreactant, the reaction rate was enhanced, and a total of ca. 766 TON (turnover number) was reached for the CO reduction, with 60% selectivity for formate and 28% selectivity for CO, using Ru(phen) as a sensitizer and amines as sacrificial electron donors.

Blue Electrophosphorescence from Iridium(III) Phosphors Bearing Asymmetric Di-N-aryl 6-(trifluoromethyl)-2H-imidazo[4,5-b]pyridin-2-ylidene Chelates.

Efficient blue phosphors remain a formidable challenge for organic light-emitting diodes (OLEDs). To circumvent this obstacle, a series of Ir(III)-based carbene complexes bearing asymmetric di-N-aryl 6-(trifluoromethyl)-2H-imidazo[4,5-b]pyridin-2-ylidene chelates, namely, f-ct6a‒c, are synthesized, and their structures and photophysical properties are comprehensively investigated. Moreover, these emitters can undergo interconversion in refluxing 1,2,4-trichlorobenzene, catalyzed by a mixture of sodium acetate (NaOAc) and p-toluenesulfonic acid monohydrate (TsOH·HO) without decomposition.

Ferrocene/ferrocenium, cobaltocene/cobaltocenium and nickelocene/nickelocenium: from gas phase ionization energy to one-electron reduction potential in solvated medium.

We propose a theoretical procedure for accurate determination of reduction potentials for three metallocene couples, CpM/CpM, where M = Fe, Co and Ni. This procedure first computes the gas phase ionization energy (IE) using the explicitly correlated CCSD(T)-F12 method and includes the zero-point energy correction, core-valence electronic correlation, and relativistic and spin-orbit coupling effects. By means of Born-Haber thermochemical cycle, the one-electron reduction potential is obtained as the sum of the gas phase IE and the corresponding Gibbs free energies of solvation (Δ) for both the neutral and cationic species.

In situ Electropolymerized 3D Microporous Cobalt-Porphyrin Nanofilm for Highly Effective Molecular Electrocatalytic Reduction of Carbon Dioxide.

Electrocatalytic CO reduction reaction (CO RR) based on molecular catalysts, for example, cobalt porphyrin, is promising to enhance the carbon cycle and mitigate current climate crisis. However, the electrocatalytic performance and accurate evaluations remain problems because of either the low loading amount or the low utilization rate of the electroactive CoN sites. Herein a monomer is synthesized, cobalt(II)-5,10,15,20-tetrakis(3,5-di(thiophen-2-yl)phenyl)porphyrin (CoP), electropolymerized onto carbon nanotubes (CNTs) networks, affording a molecular electrocatalyst of 3D microporous nanofilm (EP-CoP, 2-3 nm thickness) with highly dispersed CoN sites.

Structure and Reactivity of a Seven-Coordinate Ruthenium Iodosylbenzene Complex.

Seven-coordinate (CN7) ruthenium-oxo species have attracted much attention as highly reactive intermediates in both organic and water oxidation. Apart from metal-oxo, other metal-oxidant adducts, such as metal-iodosylarenes, have also recently emerged as active oxidants. We reported herein the first example of a CN7 Ru-iodosylbenzene complex, [Ru(bdpm)(pic)(O)I(Cl)Ph] (Hbdpm = [2,2'-bipyridine]-6,6'-diylbis(diphenylmethanol); pic = 4-picoline).

Visible Light-Induced Oxidation of Alcohols by a Luminescent Osmium(VI) Nitrido Complex: Evidence for the Generation of PhIO as a Highly Active Oxidant in the Presence of PhIO.

Although alcohols are readily oxidized by a variety of oxidants, their oxidation by metal nitrido complexes is yet to be studied. We report herein visible-light-induced oxidation of primary and secondary alcohols to carbonyl compounds by a strongly luminescent osmium(VI) nitrido complex (). The proposed mechanism involves initial rate-limiting hydrogen-atom transfer (HAT) from the α-carbon of the alcohol to .

Synergistic effects of CHCOH and Ca on C-H bond activation by MnO.

The activation of metal-oxo species with Lewis acids is of current interest. In this work, the effects of a weak Brønsted acid such as CHCOH and a weak Lewis acid such as Ca on C-H bond activation by KMnO have been investigated. Although MnO is rather non-basic (p of MnO(OH) = -2.

Selective functionalization of C(sp)-H bonds: catalytic chlorination and bromination by Iron-acacen-halide under ambient condition.

The oxidative catalytic halogenations of the C(sp)-H bond of alkanes promoted by Fe(acacen)Cl (1III-Cl) and Fe(acacen)Br (1III-Br) in the presence of trifluoroacetic acid (TFA) were investigated. Four major steps were involved: (i) formation of [Fe(acacen)(oxo)X] species (X = Cl or Br), (ii) hydrogen-atom transfer, (iii) halogen atom rebound, and (iv) regeneration of 1III-Cl or 1III-Br. TFA played a significant role in (i) forming the high-valent iron-oxo intermediate and (ii) generating the reaction selectivity.

Oxidative C-O bond cleavage of dihydroxybenzenes and conversion of coordinated cyanide to carbon monoxide using a luminescent Os(VI) cyanonitrido complex.

The photoreactions of a luminescent osmium(VI) nitrido complex, [Os(N)(L)(CN)] (OsN, HL = 2-(2-hydroxy-5-nitrophenyl)benzoxazole), with catechol (HCat) and hydroquinone (HQ) lead to the cleavage of strong C-OH bonds ( 120 kcal mol) of the dihydroxybenzenes with concomitant conversion of the coordinated cyanide to carbon monoxide.

Structure and Reactivity of One- and Two-Electron Oxidized Manganese(V) Nitrido Complexes Bearing a Bulky Corrole Ligand.

As a strategy to design stable but highly reactive metal nitrido species, we have synthesized a manganese(V) nitrido complex bearing a bulky corrole ligand, [Mn(N)(TTPPC)] (, TTPPC is the trianion of 5,10,15-Tris(2,4,6-triphenylphenyl)corrole). Complex is readily oxidized by 1 equiv of CpFe to give the neutral complex , which can be further oxidized by 1 equiv of [(-Br-CH)N][B(CF)] to afford the cationic complex . All three complexes are stable in the solid state and in CHCl solution, and their molecular structures have been determined by X-ray crystallography.

Facile C-N bond cleavage of primary aliphatic amines by (salen)ruthenium(VI) nitrido complexes.

We report the first example of oxidative cleavage of the strong C-N bonds of primary amines by a ruthenium(VI) nitrido complex. The driving force for this very fast C-N cleavage reaction comes from the formation of stable NN after the initial coupling of the amine N and the nitrido ligand.

Visible light-induced oxidative -dealkylation of alkylamines by a luminescent osmium(vi) nitrido complex.

-Dealkylation of amines by metal oxo intermediates (M[double bond, length as m-dash]O) is related to drug detoxification and DNA repair in biological systems. In this study, we report the first example of -dealkylation of various alkylamines by a luminescent osmium(vi) nitrido complex induced by visible light.

Waste-to-Energy: Production of Fuel Gases from Plastic Wastes.

A new mechanochemical method was developed to convert polymer wastes, polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC), to fuel gases (H, CH, and CO) under ball-milling with KMnO at room temperature. By using various solid-state characterizations (XPS, SEM, EDS, FTIR, and NMR), and density functional theory calculations, it was found that the activation followed the hydrogen atom transfer (HAT) mechanism. Two metal oxidant molecules were found to abstract two separate hydrogen atoms from the α-CH and β-CH units of substrates, [-CH-CH(R)-], where R = H in PE, R = CH in PP, and R = Cl in PVC, resulting in a di-radical, [-CH-C(R)-].

Structure and Reactivity of a Manganese(VI) Nitrido Complex Bearing a Tetraamido Macrocyclic Ligand.

Manganese complexes in +6 oxidation state are rare. Although a number of Mn(VI) nitrido complexes have been generated in solution via one-electron oxidation of the corresponding Mn(V) nitrido species, they are too unstable to isolate. Herein we report the isolation and the X-ray structure of a Mn(VI) nitrido complex, [Mn(N)(TAML)] (), which was obtained by one-electron oxidation of [Mn(N)(TAML)] ().

Cooperative activating effects of metal ion and Brønsted acid on a metal oxo species.

Metal oxo (M[double bond, length as m-dash]O) complexes are common oxidants in chemical and biological systems. The use of Lewis acids to activate metal oxo species has attracted great interest in recent years, especially after the discovery of the CaMnO cluster in the oxygen-evolving centre of photosystem II. Strong Lewis acids such as Sc and BF, as well as strong Brønsted acids such as HSO and CFSOH, are commonly used to activate metal oxo species.

Isomerization Dynamics in the Symmetric and Asymmetric Fragmentation of Ethane Dications.

Hydrogen- or proton-migration-induced isomerization has recently been of concern for its critical role in the dissociation of organic molecules of astrophysical or biological relevance. Herein we present a combined experimental and theoretical study of the two-body C-C bond breakdown dissociation of ethane dication. For the asymmetric fragmentation channel CH + CH, the kinetic energy release measurements and quantum chemical calculations demonstrate that the reaction pathway involving hydrogen-migration-induced isomerization of [CH-CH] to [CH-CH] can be accessed the lowest triplet state rather than the ground singlet state of ethane dication.

Thermochemical Trends in Carbon Chain Molecules HCH/HCH ( = 1-6) Studied by Explicitly Correlated CCSD(T)-F12b Composite Methods.

We present a composite procedure based on explicitly correlated CCSD(T)-F12 calculations for accurate energetic predictions for carbon chain molecules HCH encompassing both the even (HCH) and odd series (HCH), with the shorter members playing a key role in the evolution of cosmic carbon compounds in both circumstellar envelopes and interstellar medium. This approach considers the contributions of core-valence correlation, scalar relativistic effect, spin-orbit coupling, and zero-point vibrational energy in an additive manner. The computed ionization energies demonstrate outstanding agreement (±0.

High-Level Predictions for the Ionization Energies, Bond Dissociation Energies, and Heats of Formation of Vanadium Methylidene, Vanadium Methyl Species, and Their Cations (VCH/VCH, VCH/VCH).

The ionization energies of VCH and VCH, the various 0 K bond dissociation energies (s) in their neutrals and cations, and their respective heats of formation at 0 and 298 K are computed by the single-reference, wave function-based CCSDTQ/CBS procedure. The core of the composite method is the approximation to the complete basis set (CBS) limit at the coupled cluster (CC) level which includes up to full quadruple excitations. The zero-point vibrational energy, core-valence correlation, spin-orbit coupling, and scalar relativistic effects have their contributions incorporated in an additive manner.

Hydrogen atom transfer in the oxidation of alkylbenzenesulfonates by ferrate(VI) in aqueous solutions.

Ferrate(vi), [FeO4]2-, is a very powerful oxidant that can oxidize a wide variety of inorganic and organic compounds. However, the mechanisms of many of these oxidation reactions have not been studied in detail. In this work, we have investigated the kinetics and mechanism of the oxidation of 4-alkylbenzenesulfonates by ferrate in aqueous solutions at pH 7.