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Dialkylmagnesium compounds (MgR2, R = C2H5, C4H9 etc.,) have drawn considerable interest in recent years due to their role in commercial polymerization reactions. Herein, we report a thorough account on the reaction intermediates involved in the synthesis of di-n-butylmagnesium from anhydrous magnesium chloride and n-butyllithium. Energy-dispersive X-ray spectroscopy (EDX) and powder X-ray diffraction (PXRD) were used to characterize the products formed in transmetalation reaction and it supports that the Schlenk equilibrium between the nBuMgCl and nBu2Mg may be operating during the synthesis of di-n-butylmagnesium from anhydrous magnesium chloride. 1,4-Dioxane was used to shift the Schlenk equilibrium to form soluble 1,4-dioxane adduct of di-n-butylmagnesium and insoluble MgCl2 based product. PXRD was used to study the transformation of 1,4-dioxane adduct of di-n-butylmagnesium to pure di-n-butylmagnesium.

Mass transfer coefficients of CO2 are anomalously high in water-lean solvents as compared to aqueous amines. Such phenomena are intrinsic to the molecular and nanoscale structure of concentrated organic CO2 capture solvents. To decipher the connections, we performed in situ liquid time-of-flight secondary ionization mass spectroscopy on a representative water-lean solvent, 1-((1,3-Dimethylimidazolidin-2-ylidene)amino)propan-2-ol (IPADM-2-BOL). Two-dimensional (2D) and three-dimensional (3D) chemical mapping of the solvent revealed that IPADM-2-BOL exhibited a heterogeneous molecular structure with regions of CO2-free solvent coexisting with clusters of zwitterionic carbonate ions. Chemical mapping were consistent with molecular dynamic simulation results, indicating CO2 diffusing through pockets and channels of unreacted solvent. The observed mesoscopic structure promotes and enhances the diffusion and reactivity of CO2, likely prevalent in other water-lean solvents. This finding suggests that if the size...

A new efficient and solvent-free method for the synthesis of anhydrous MgCl2 from its hexahydrate is presented. Fluidized dehydration of MgCl2·6H2O feedstock at 200 °C in a porous bed reactor yields MgCl2·nH2O (0 < n < 1), which has a similar diffraction pattern as activated MgCl2. The MgCl2·nH2O is then ammoniated directly using liquefied NH3 in the absence of solvent to form MgCl2·6NH3. Calcination of the hexammoniate complex at 300 °C then yields anhydrous MgCl2. Both dehydration and deammoniation were thoroughly studied using in situ as well as ex situ characterization techniques. Specifically, a detailed understanding of the dehydration process was monitored by in situ PXRD and in situ FTIR techniques where formation of salt with nH2O (n = 4, 2, 1

Addition of high pressures of H2 to five-coordinate [(tBu)4(POCOP)Ir(CO)(H)]OTf [(tBu)4(POCOP) = κ3-C6H3-2,6-(OP(tBu)2)2] complexes results in observation of two new iridium–dihydrogen complexes. If the aryl moiety of the POCOP ligand is substituted with an electron withdrawing protonated dimethylamino group at the para position, hydrogen coordination is enhanced. Five-coordinate Ir–H complexes generated by addition of triflic acid to (tBu)4(POCOP)Ir(CO) species show an Ir–H 1H NMR chemical shift dependence on the number of equivalents of acid present. It is proposed that excess triflic acid in solution facilitates triflate dissociation from iridium, resulting in unsaturated five-coordinate Ir–H complexes. The five-coordinate iridium–hydride complexes were found to catalyze H/D exchange between H2 and CD3OD. The existence of the dihydrogen complexes, as well as isotope exchange reactions, provide evidence for proposed ionic hydrogenation intermediates for glycerol deoxygenation.

This experimental and theoretical study investigates how dynamic solvation environments in switchable ionic liquids regulate the composition of nanoparticulate green rust. A custom microfluidic device enables in situ X-ray absorption spectroscopy to elucidate characterization of the solvent structure and speciation of reaction intermediates of air-sensitive nanoparticles growing in solution.

© 2017 the Owner Societies. Switchable ionic liquids (SWILs) derived from organic bases and alcohols are attractive due to their applications in gas capture, separations, and nanomaterial synthesis. However, their exact solvent structure still remains a mystery. We present the first chemical mapping of a SWIL solvent structure using in situ time-of-flight secondary ion mass spectrometry. In situ chemical mapping discovers two coexisting liquid phases and molecular structures vastly different from conventional ionic liquids. SWIL chemical speciation is found to be more complex than the known stoichiometry. Dimers and ionic clusters have been identified in SIMS spectra; and confirmed to be the chemical species differentiating from non-ionic liquids via spectral principal component analysis. Our unique in situ molecular imaging has advanced the understanding of SWIL chemistry and how this "heterogeneous" liquid structure may impact SWILs' physical and thermodynamic properties and associated applications.

In situ liquid secondary ion mass spectrometry (SIMS) enabled by system for analysis at the liquid vacuum interface (SALVI) has proven to be a promising new tool to provide molecular information at solid-liquid and liquid-vacuum interfaces. However, the initial data showed that useful signals in positive ion spectra are too weak to be meaningful in most cases. In addition, it is difficult to obtain strong negative molecular ion signals when m/z>200. These two drawbacks have been the biggest obstacle towards practical use of this new analytical approach. In this study, we report that strong and reliable positive and negative molecular signals are achievable after optimizing the SIMS experimental conditions. Four model systems, including a 1,8-diazabicycloundec-7-ene (DBU)-base switchable ionic liquid, a live Shewanella oneidensis biofilm, a hydrated mammalian epithelia cell, and an electrolyte popularly used in Li ion batteries were studied. A signal enhancement of about two orders of magnitude was obtained in comparison with non-optimized conditions. Therefore, molecular ion signal intensity has become very acceptable for use of in situ liquid SIMS to study solid-liquid and liquid-vacuum interfaces. Graphical Abstract ᅟ.

Three water adsorption-desorption mechanisms are common in inorganic materials: chemisorption, which can lead to the modification of the first coordination sphere; simple adsorption, which is reversible; and condensation, which is irreversible. Regardless of the sorption mechanism, all known materials exhibit an isotherm in which the quantity of water adsorbed increases with an increase in relative humidity. Here, we show that carbon-based rods can adsorb water at low humidity and spontaneously expel about half of the adsorbed water when the relative humidity exceeds a 50-80% threshold. The water expulsion is reversible, and is attributed to the interfacial forces between the confined rod surfaces. At wide rod spacings, a monolayer of water can form on the surface of the carbon-based rods, which subsequently leads to condensation in the confined space between adjacent rods. As the relative humidity increases, adjacent rods (confining surfaces) in the bundles are drawn closer together via capillary forces. At high relative humidity, and once the size of the confining surfaces has decreased to a critical length, a surface-induced evaporation phenomenon known as solvent cavitation occurs and water that had condensed inside the confined area is released as a vapour.

Switchable ionic liquids (SWIL) play an important role in green chemistry. Due to the nature of SWIL chemistry, such as air sensitivity, pressure, and temperature dependence, it is difficult to characterize SWIL using vacuum-based surface techniques. The fully CO2 loaded 1:1 mixtures of 1,8-diazabicycloundec-7-ene (DBU) and 1-hexanol (a SWIL system) and non-CO2 loaded DBU and 1-hexanol mixture were analyzed by in situ time-of-flight secondary ion mass spectrometry (ToF-SIMS) coupled with the system for analysis at the liquid vacuum interface (SALVI), respectively. The DBU/1-hexanol/CO2 SWIL was injected into the microchannel before liquid secondary ion mass spectrometry analysis. Bi3+ primary ion beam was used. The positive and negative spectra of the SWIL chemical components are presented. The characteristic peaks m/z 153 (protonated DBU) in the positive mode and m/z 101 (deprotonated 1-hexanol) in the negative mode were observed. In addition, ion pair peaks including m/z 253, 319, 305, and 451 in the po...

Mass transfer coefficients of CO

Combining CO2 capture and reduction is an efficient strategy to alleviate the high energy requirements for processing CO2 prior to reduction. Catalytic hydrogenation of CO2 captured as alkylcarbonate has previously been reported, but it's ambiguous whether the alkylcarbonate is reduced, as it is in dynamic equilibrium with neutral CO2 in solution. New studies are presented to elucidate the reduction mechanisms of CO2, and CO2 that is captured in solution using a homogeneous ruthenium hydride complex.

Dimethyl palladium(II) complexes with various bi- and tri-dentate ligands, (L2)PdII(CH3)2, react readily with the one-electron oxidant ferrocenium hexafluorophosphate (Fc+) in acetone-d6. These oxidations typically proceed by one of two pathways. Oxidatively-induced methyl transfer forms trimethyl palladium(IV) intermediates which usually undergo reductive C−C coupling and form ethane. Alternatively, oxidation can cause Pd–C bond homolysis, which yields predominantly methane and methylferrocene, a product of methyl radical trapping. The reaction selectivity is dependent on ligand identity and likely due to the ability of different classes of ligands to stabilize intermediates in the PdIV oxidation state. Complexes containing the bidentate diimine ligands 1,10-phenanthroline (phen) or 2,3-dimethyl-1,4-di-4-tolyl-1,4-diazabuta-1,3-diene (Tol2DAB) adhere to the ethane producing pathway previously reported for (tBu2bpy)Pd(CH3)2 (tBu2bpy = 4,4′-bis(tert-butyl)-2,2′-bipyridine), as does the complex of the potentially tridentate 6-methyl-N,N′-bis-2-pyridinyl-2-pyridinamine ligand. In contrast, Fc+ oxidations of complexes with bis-carbene (1,1′-methylene-3,3′-tert-butyldiimidazole-2,2′-diylidene, tBuCCtBu), bis-phosphine (tert-butyl-bis(diphenylphosphinomethyl)amine (tBuN(CH2PPh2)2, PCNCP), or tris(pyrazolyl)methane ligands resulted in little or no ethane production. These reactions likely involve either methyl radicals or trimethyl PdIV complexes that are stable towards C−C reductive elimination. Oxidation of (TMEDA)Pd(CH3)2 (TMEDA = (N,N,N′,N′-tetramethylethylenediamine) yields both methane and ethane, suggesting that both Pd–C bond homolysis and oxidative methyl transfer are competitive in this case.

Iridium pincer complexes (POCOP)Ir(CO) (POCOP = κ3-C6H3-1,3-[OP(tBu)2]2) and substituted POCOP derivatives catalyze deoxygenation of glycerol to n-propanol and 1,3-propanediol in good yield under moderate conditions (acidic aqueous dioxane, 200 °C, 80 bar H2). Catalyst solubility in the polar reaction mixture is improved by incorporation of a polar moiety in the para position of the POCOP phenyl ring, with the best results obtained with a dimethylamino substituent.

Tuning the aryl substituents of N,N′-diaryl-2,3-dimethyl-1,4-diaza-1,3-butadiene (DAB) ligands promotes the challenging C–C bond-forming reductive elimination from PtIV diimine complexes [(DAB)Pt(CH3)3(solvent)]+ (2) under mild conditions. Experimental results and density functional calculations indicate that 2,6-aryl substitution promotes reductive elimination by facilitating dissociation of the coordinating solvent by close to 10 kcal mol–1, but too much steric bulk inhibits the formation of 2 in the one-electron outersphere oxidation of (DAB)Pt(CH3)2 (1).

Theoretical guidance based on correlated real-time, time-dependent density functional theory (RTTDDFT) quantum mechanical and pseudo-atomistic Monte Carlo molecular dynamical (PAMCMD) statistical mechanical computational methods have led to dramatic (exceeding a Moore’s rate) improvement in molecular and macroscopic optical nonlinearity. New materials permit optical signal processing at terahertz rates using millivolts electrical and milliwatt optical control powers. Theory has also provided insight into the optimization of optical loss, thermal stability, and photochemical stability. The advent of silicon photonics for telecommunication applications has raised the prospect of achieving high density integration of photonic circuitry and even the chipscale integration of photonics and electronics. Such integration promises significant improvement in size, weight, and power (SWAP) together with dramatic improvements in performance, cost, and reliability. We demonstrate the integration of organic nonlinear optical materials into 25–150 × 200 nm slots in silicon photonic ring microresonator and stripline device structures. Slotted waveguides permit nearly lossless transition of light from 450 × 200 nm silicon photonic waveguides into the organic nonlinear optical material filled slots for active control of light. These device structures permit dramatic enhancement of electrical and optical control fields amplifying the already large nonlinearities of organic pi electron materials. Such amplification permits observation of new phenomena such as low optical power optical rectification, difference frequency generation, and all-optical signal processing.

In order to explore the effects of incorporation of an amino-phenyl-thienyl (APT) donor moiety into state-of-the art donor-bridge-acceptor organic NLO chromophores, two new materials were synthesized and characterized. Density functional theory (DFT) quantum-mechanical modeling indicates that this structural modification, producing enhanced ground-state electron density asymmetry and increased conjugation length, should lead to appreciable enhancement in first molecular hyperpolarizability ( β ). Previous empirical data suggests that such an approach to enhancements in nonlinearity may overcome the tradeoffs in nonlinearity with optical absorption and thermal stability, often encountered in organic NLO chromophore design. Material properties were evaluated in terms of poling-induced electro-optic coefficients normalized against applied poling field ( r 33 / E p ), DFT calculated β and gas-phase dipole moment, experimentally determined β HRS , absorption maxima, and thermal stability. These data were then compared against those from benchmark materials. Experimental data were determined to reflect enhancements in nonlinearity with little detriment to thermal stability and optical absorption, making them excellent candidates for use in electro-optic polymer applications. The most active material (C3) demonstrated highly reproducible values of r 33 = 130 pm/V.

Application of bis(propylenedioxythiophene) (bis(ProDOT)) π-conjugated bridges bearing alkyl or aryl substituents in electro-optic (EO) chromophores is presented. A series of three bis(ProDOT)-based chromophores and a bithiophene-based control chromophore were prepared and fully characterized with regard to EO applications. The highly planar bis(ProDOT) bridge results in slightly larger (∼10%) molecular hyperpolarizability (β) values as compared to the bithiophene bridge, as measured by hyper-Rayleigh scattering at a variety of wavelengths. In amorphous polycarbonate guest–host films, however, the bulky substituents on the bis(ProDOT) bridge result in significantly larger (∼70%) poling-induced EO coefficient (r33) values, as measured by simple reflection ellipsometry at 1310 nm. This can be attributed to a roughly 2-fold enhancement in poling efficiency due to reduced intermolecular dipole–dipole interactions. This chromophore architecture also exhibits excellent temporal alignment stability and photochem...

Two series of highly efficient and thermally stable nonlinear optical chromophores based on the (4-diarylamino)phenyl electron donors have been synthesized and systematically investigated. A modular approach has been employed to synthesize these electron donors with tunable size, shape, and electron-donating abilities. Efficient conjugated bridges were extended from these donors and coupled with very strong CF3−TCF electron acceptors to afford chromophores with very high β values (up to 7077 × 10-30 esu at 1.907 μm). These chromophores possess much higher thermal stability (with their onset decomposition temperatures all above 220 °C) than those substituted with (4-dialkylamino)phenyl donors. Most importantly, the high molecular hyperpolarizability of these chromophores can be effectively translated into very large electro-optic (E-O) coefficients (r33) in poled polymers through suitable shape engineering. Exemplified by the chromophore B4, which has a fluorinated aromatic substituent anchored at its dono...

We have synthesized a new class of highly efficient nonlinear optical (NLO) chromophores based on the novel tricyanopyrroline (TCP) electron acceptor. Molecular linear and nonlinear optical properties of the prototypical chromophores were measured and calculated to understand structure−property relationships. One such chromophore showed molecular first hyperpolarizability (β) of (8700 ± 702) × 10-30 esu at excitation wavelengths of 1.9 μm, and another showed macroscopic electro-optic (EO) coefficients (r33) of 51 pm/V at 1.55 μm with 20 wt % chromophore loading when poled with 65 V/μm in amorphous polycarbonate film. Synthetic strategies for extending the utility of the acceptor and chromophores are discussed.

A macrocyclic trichromophore bundle 1 with parallel-aligned dipole moments has been synthesized to study the influence of aggregation and orientation of a nonlinear optical (NLO) chromophore on its optical properties. The linear and nonlinear optical properties of 1 and a single chromophore standard 2 have been studied by UV-vis absorption, fluorescence, solvatochromic spectrometry, and hyper-Rayleigh scattering (HRS). Reduced first-order hyperpolarizability beta, hypsochromic shift, enhanced solvatochromic shifts, and fluorescence quenching for individual chromophores were observed when 1 was compared with 2. Analysis of the data showed that the transition dipole moment changes only slightly when the chromophores are parallel aligned in the bundle architecture. However, the apparent hyperpolarizability of the individual chromophores decreased significantly by about 20%. The reduction in beta for the individual chromophores in 1 is largely due to the hypsochromic shift, i.e., excitation energy increase of the interband (charge-transfer) energy gap and the reduced difference between the ground-state and excited-state dipole moments. The hypsochromic shift and fluorescence quenching are consistent with exciton theory. Possible reasons for the enhanced solvatochromic shift are discussed.

This article describes the high-yielding and selective oxidatively induced formation of ethane from mono-methyl palladium complexes. Mechanistic details of this reaction have been explored via both experiment and computation. On the basis of these studies, a mechanism involving methyl group transmetalation between Pd(II) and Pd(IV) interediates is proposed.

Hyper-Rayleigh scattering (HRS) is used to measure the first-hyperpolarizability (β) of electro-optic (EO) chromophores. One of the inherent concerns in any HRS measurement is the extent to which resonant enhancement contributes to the observed intensity thereby leading to inaccuracies when evaluating chromophore potential for application in electro-optical devices. One way to address this concern is to employ increasingly longer excitation wavelengths far from resonance. However, in charge-transfer-based non-linear optical chromophores, enhanced β generally correlates with a red-shift of the charge transfer absorption band so that even at the longest excitation wavelengths generally employed in HRS studies, resonant enhancement remains an issue. We have adopted an alternative approach in which the wavelength dispersion of the HRS intensity is determined by performing measurements at a variety of excitation wavelengths. This approach allows one to ascertain the role of resonance enhancement thereby allowing for more accurate correlation of improved β with molecular architecture. We report the results of our HRS studies for nine chromophores employing excitation wavelengths ranging from 780 to 1907 nm. Our HRS results demonstrate good agreement with the predictions of density functional theory. This synthesis of experimental and theoretical techniques has resulted in more effective designs for the next generations of electro-optical chromophores.

A family of nonlinear optical chromophores has been synthesized containing novel donor systems based on functionalized guanidines. Chromophores utilizing these donor systems display superior transparency and stability properties. The unusual and highly desirable characteristics of these chromophores make them very promising candidates for electro-optic applications. Systematic study of the molecular hyperpolarizabilities and bulk electro-optic properties of polymers containing these chromophores is being used to guide optimization of these systems.