Synthesis and characterization of trifluoromethylcarboxonium salts.

The low-temperature protonation of trifluoroacetic acid with the superacids HF/SbF and HF/AsF resulted in the syntheses of the first examples of trifluoromethylcarboxonium salts. The less acidic trifluoromethylacetamide was also protonated in the same fashion, resulting in exclusive protonation of the carbonyl function. Their [SbF] and [AsF] salts were characterized by crystal structures, vibrational and multinuclear NMR spectra, and by electronic structure calculations.

Polarizable Anionic Sublattices Can Screen Molecular Dipoles in Noncentrosymmetric Inorganic-Organic Hybrids.

We report the growth and photophysical characterization of two polar hybrid lead halide phases, methylenedianiline lead iodide and bromide, (MDA)PbI and (MDA)PbBr, respectively. The phases crystallize in noncentrosymmetric space group 2, which produces a highly oriented molecular dipole moment that gives rise to second harmonic generation (SHG) upon excitation at 1064 nm. While both compositions are isostructural, the size dependence of the SHG signal suggests that the bromide exhibits a stronger phase-matching response whereas the iodide exhibits a significantly weaker non-phase-matching signal.

Pushing steric limits in osmium(IV) tetraaryl complexes.

Investigations into the reactivity, properties, and applications of osmium(IV) tetraaryl complexes have been hampered by their low yielding syntheses from volatile and toxic OsO (typically ≤34%). Here we show that known air-stable M(aryl) compounds (M = Os, Ru; aryl = 2-tolyl, 2,5-xylyl) can be prepared in ≤73% yields using new, less hazardous (OctN)[MX] precursors (M = Os, Ru; X = Cl, Br). This approach also facilitates the preparation of Os(mesityl) (Os3) for the first time, a complex comprising bulky 2,6-dimethyl substituted aryl ligands, albeit in low yield (5%).

Electronically-coupled redox centers in trimetallic cobalt complexes.

Synthesis and isolation of molecular building blocks of metal-organic frameworks (MOFs) can provide unique opportunities for characterization that would otherwise be inaccessible due to the heterogeneous nature of MOFs. Herein, we report a series of trinuclear cobalt complexes incorporating dithiolene ligands, triphenylene-2,3,6,7,10,11-hexathiolate (THT) (13+), and benzene hexathiolate (BHT) (23+), with 1,1,1,-tris(diphenylphosphinomethyl)ethane (triphos) employed as the capping ligand. Single crystal X-ray analyses of 13+ and 23+ display three five-coordinate cobalt centers bound to the triphos and dithiolene ligands in a distorted square pyramidal geometry.

Switching Catalyst Selectivity via the Introduction of a Pendant Nitrophenyl Group.

The conversion of abundant small molecules to value-added products serves as an attractive method to store renewable energy in chemical bonds. A family of macrocyclic cobalt aminopyridine complexes was previously reported to reduce CO to CO with 98% faradaic efficiency through the formation of hydrogen-bonding networks and with the number of secondary amines affecting catalyst performance. One of these aminopyridine macrocycles, (NH)(NMe)-bridged calix[4]pyridine (), was modified with a nitrophenyl group to form and metalated with a cobalt(II) precursor to generate , which would allow for probing the positioning and steric effects on catalysis.

Fluoro-nitrogen Cations.

The crystal structures of [NH F] [CF SO ] , [NH F ] [SbF ] , and [N F ] [Sb F ] have been determined, representing the first structural characterizations of these simple fluoro-nitrogen cations. The influences of the hybridization of the central nitrogen atom and of the number of fluorine substituents on the N-F bond lengths are evaluated for the series N F , N F , NF O , NH F , NH F , and NF . It is shown that the N-F bond length decreases from 1.

High frequency atomic tunneling yields ultralow and glass-like thermal conductivity in chalcogenide single crystals.

Crystalline solids exhibiting glass-like thermal conductivity have attracted substantial attention both for fundamental interest and applications such as thermoelectrics. In most crystals, the competition of phonon scattering by anharmonic interactions and crystalline imperfections leads to a non-monotonic trend of thermal conductivity with temperature. Defect-free crystals that exhibit the glassy trend of low thermal conductivity with a monotonic increase with temperature are desirable because they are intrinsically thermally insulating while retaining useful properties of perfect crystals.

Electronically Modified Cobalt Aminopyridine Complexes Reveal an Orthogonal Axis for Catalytic Optimization for CO Reduction.

The design of effective electrocatalysts for carbon dioxide reduction requires understanding the mechanistic underpinnings governing the binding, reduction, and protonation of CO. A critical aspect to understanding and tuning these factors for optimal catalysis revolves around controlling the electronic environments of the primary and secondary coordination sphere. Herein we report a series of -substituted cobalt aminopyridine macrocyclic catalysts - capable of carrying out the electrochemical reduction of CO to CO.

Highly Efficient Deep Blue Luminescence of 2-Coordinate Coinage Metal Complexes Bearing Bulky NHC Benzimidazolyl Carbene.

The structural, photophysical and electrochemical properties of three luminescent 2-coordinate coinage metal (i.e., M = Cu, Ag, Au) complexes bearing a sterically bulky benzimidazolyl carbene, 1,3-bis(2,6-diisopropylphenyl)-1-H-benzo[d]imidazol-2-ylidene (), and carbazolide (Cz) as the anionic ligand were investigated.

Protonation of CH N and CF N in Superacids: Isolation and Structural Characterization of Long-Lived Methyl- and Trifluoromethylamino Diazonium Ions.

The methylamino diazonium cations [CH N(H)N ] and [CF N(H)N ] were prepared as their low-temperature stable [AsF ] salts by protonation of azidomethane and azidotrifluoromethane in superacidic systems. They were characterized by NMR and Raman spectroscopy. Unequivocal proof of the protonation site was obtained by the crystal structures of both salts, confirming the formation of alkylamino diazonium ions.

Enhancement of the Luminescent Efficiency in Carbene-Au-Aryl Complexes by the Restriction of Renner-Teller Distortion and Bond Rotation.

A series of (carbene)Au(aryl) complexes are reported. The nature of the lowest excited state in these complexes changes character from metal-to-ligand charge transfer (MLCT) to interligand charge transfer (ICT) with increasing electron-donating strength of the aryl ligand. Complexes that have the MLCT lowest excited state undergo a Renner-Teller bending distortion upon excitation.

Photochemistry of 2-Nitroarenes: 2-Nitrophenyl-α-trifluoromethyl Carbinols as Synthons for Fluoroorganics.

Facile synthesis of a new series of 2,2'-bis(trifluoroacetyl) azoxybenzene derivatives and trifluoromethylated benzo[]isoxazoline systems, along with trifluoroacetyl nitrosobenzene derivatives was achieved by solvent controlled photolysis of appropriate 2-nitrobenzyl alcohols. Corresponding photoactive 2-nitrobenzyl chromophore plays a distinct role in this photosynthetic process, while, quite unprecedented, pertinent fluoromethyl substitution leads to high value fluoromethylated products, whose direct access is not feasible by common synthetic protocols. The significance of fluorine and fluoroalkyl substitution and its prominent biological effects makes this new photochemical approach an important discovery in synthetic methodology.

Rhenium bipyridine catalysts with hydrogen bonding pendant amines for CO reduction.

Rhenium tricarbonyl bipyridine complexes modified with pendant secondary and tertiary amines in the 6- and 6'-positions were synthesized and characterized. Electrocatalytic studies performed under CO with 2,2,2-trifluoroethanol display large current densities, corresponding to the reduction of CO to CO with moderate faradaic efficiencies (51-73%).

Studies on Long-Lived (Pentafluorosulfanyl)phenyl-Substituted Carbocations.

A variety of long-lived carbocations containing the -(pentafluorosulfanyl)phenyl and -(pentafluorosulfanyl)phenyl groups have been characterized by low-temperature NMR spectroscopy. In the case of potential nonclassical carbocations substituted with the -(pentafluorosulfanyl)phenyl substituent, deviations from linearity when the Hammett parameter (σ) is plotted versus C NMR shifts of the carbocationic center were observed. Plotting the experimentally derived C NMR shifts versus σ or σ of classical 4-phenyl-X substituted carbocations also provides a means to accurately back-calculate the σ and σ parameters of the -SF substituent.

"Quick-Silver" from a Systematic Study of Highly Luminescent, Two-Coordinate, d Coinage Metal Complexes.

A systematic study is presented on the physical and photophysical properties of isoelectronic and isostructural Cu, Ag, and Au complexes with a common amide (N-carbazolyl) and two different carbene ligands (i.e., CAAC = (5 R,6 S)-2-(2,6-diisopropylphenyl)-6-isopropyl-3,3,9-trimethyl-2-azaspiro[4.

Mechanistic Insights into Ruthenium-Pincer-Catalyzed Amine-Assisted Homogeneous Hydrogenation of CO to Methanol.

Amine-assisted homogeneous hydrogenation of CO to methanol is one of the most effective approaches to integrate CO capture with its subsequent conversion to CHOH. The hydrogenation typically proceeds in two steps. In the first step the amine is formylated via an in situ formed alkylammonium formate salt (with consumption of 1 equiv of H).

Eliminating nonradiative decay in Cu(I) emitters: >99% quantum efficiency and microsecond lifetime.

Luminescent complexes of heavy metals such as iridium, platinum, and ruthenium play an important role in photocatalysis and energy conversion applications as well as organic light-emitting diodes (OLEDs). Achieving comparable performance from more-earth-abundant copper requires overcoming the weak spin-orbit coupling of the light metal as well as limiting the high reorganization energies typical in copper(I) [Cu(I)] complexes. Here we report that two-coordinate Cu(I) complexes with redox active ligands in coplanar conformation manifest suppressed nonradiative decay, reduced structural reorganization, and sufficient orbital overlap for efficient charge transfer.

Recent developments in the chemistry of metal oxopolyazides.

The recent acomplished syntheses of novel metal oxopolyazides VO(N3)3, NbO(N3)3, NbO(N3)3·2CH3CN, MoO(N3)3, MoO(N3)3·2CH3CN, WO(N3)4, WO(N3)4·CH3CN, MoO2(N3)2, MoO2(N3)2·2CH3CN, WO2(N3)2, WO2(N3)2·2CH3CN and UO2(N3)2·CH3CN by the author is reviewed. The conversion of the compounds into 2,2'-bipyridine donor adducts and oxaazido metallates is discribed. The properties and X-ray crystal structures of the metal oxopolyazides are compared and discussed.

A 2,2'-bipyridine-containing covalent organic framework bearing rhenium(i) tricarbonyl moieties for CO reduction.

The reduction of CO2 into higher energy products such as carbon-based fuels and feedstocks is an attractive strategy for mitigating the continuous rise in CO2 emissions associated with the growing global energy demand. Rhenium tricarbonyl complexes bearing 2,2'-bipyridine (2,2'-bpy) ligands are well-established molecular electrocatalysts for the selective reduction of CO2 to CO. Construction of efficient devices for this electrochemical process requires the immobilization of electrocatalysts to electrode surfaces.

Tetra-Aza-Pentacenes by means of a One-Pot Friedländer Synthesis.

Tetra-aza-pentacenes are attractive n-type small molecules for optoelectronic device applications, yet their syntheses are often laborious. Disclosed here is a one-pot Friedländer synthesis of 1,7,8,14-tetraazapentacece (tAP) derivatives (linear and/or bent), fully aromatized in situ despite the absence of an exogenous oxidant. The photophysics of linear tAPs resembles that of regular pentacene though their crystal structures differ.