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In this paper, we develop the first equation of state for alcohol containing mixtures which includes the effect of steric hindrance between the two electron lone pair hydrogen bond acceptor sites on the alcohol&'s hydroxyl oxygen. The theory is derived for multi-component mixtures within Wertheim&'s multi-density statistical mechanics in a second order perturbation theory. The accuracy of the new approach is demonstrated by application to pure methanol and ethanol and binary ethanol/water mixtures. It is demonstrated that the new approach gives a substantial improvement in the prediction of the hydrogen bonding structure of both pure alcohol and alcohol/water mixtures, as compared to conventional approaches which do not include steric effects between the alcohol association sites. Finally, it is demonstrated that the inclusion of steric effects allows for more accurate binary phase equilibria and heats of mixing prediction with water. [ABSTRACT FROM AUTHOR]

The phase behaviors of homopolymer-monotethered nanoparticles (HMNs) in melt are investigated via a theoretical method combining self-consistent field theory for polymers and density functional theory for hard spheres. An extremely asymmetric phase diagram is observed: (i) microphases are only possible for the volume fraction of the tethered polymer fA > 0.35; (ii) in addition to lamellar phase, the system can only self-assemble into variousmorphologies with a polymer-richmatrix, including gyroid phase, cylindrical phase, and spherical phase. In the frame of this theory, the critical point for HMNs' microphase separation is significantly lower than that of linear diblock copolymers. Furthermore, the characteristic length of microphase-separated structures of HMNs is much smaller than that of linear diblock copolymers with the same molecular weight. Our calculation results on morphologies and characteristic length agree well with recent simulations and experimental observations. Published by AIP Publishing [ABSTRACT FROM AUTHOR]

Time dependence of the rate coefficients of sterically specific reactions is analyzed theoretically. Generally, such reactions exhibit a non-trivial dependence of their rate constant on the steric factor, ƒ < 1, which is defined as the fraction of reactive surface area. Notably, the rate constant of a diffusion-controlled reaction is proportional not to ƒ but, counter-intuitively, to√ƒ due to partial averaging of the reaction anisotropy by translational diffusion. Here we demonstrate that the effective steric factor of a diffusion-influenced reaction is strongly time-dependent, increasing from f to √ƒ. When reactants have several active sites, these sites "interfere" each other in the sense that the rate constant depends on their relative positions. We demonstrate that such an interference effect is strongly time-dependent as well: it is absent at t = 0 but builds up with time. We argue that the outlined effects are also of importance for calculating the fluorescence quenching rate constants. [ABSTRACT FROM AUTHOR]

Regioselective functionalization of arenes remains a challenging problem in organic synthesis. Steric interactions are often used to block sites adjacent to a given substituent, but they do not distinguish the remaining remote sites. We report a strategy based on remote steric control, whereby a roof-like ligand protects the distant para site in addition to the ortho sites, and thereby enables selective activation of meta carbon-hydrogen (C–H) bonds in the absence of ortho or para substituents. We demonstrate this concept for iridium-catalyzed meta-selective borylation of various monosubstituted arenes, including complex drug molecules. This strategy has the potential to expand the toolbox of C–H bond functionalization to previously nondifferentiable reaction sites. [ABSTRACT FROM AUTHOR]

The interaction between polymer brush and colloidal particles has been intensively studied in the last two decades. Here, we consider a flat chain-grafted substrate immersed in a bath of active particles. Simulations show that an increase in the self-propelling force causes an increase in the number of particles that penetrate into the brush. Anomalously, the particle density inside the main body of the brush eventually becomes higher than that outside the brush at very large self-propelling force. The grafted chains are further stretched due to the steric repulsion from the intruded particles. Upon the increase of the self-propelling force, distinct stretching behaviors of the chains were observed for low and high grafting densities. Surprisingly, we find a weak descent of the average end-to-end distance of chains at high grafting density and very large force which is reminiscent of the compression effect of a chain in the active bath. [ABSTRACT FROM AUTHOR]

The vector correlation between the alignment of reactant N2 (A ³Σu+) and the alignment of product NO (A ²Σ+) rotation has been studied in the energy transfer reaction of aligned N2 (A ³Σu+) + NO (X ²Σ) . NO (A 2Σ+) + N2 (X 1Σg+) under the crossed beam condition at a collision energy of ~0.07 eV. NO (A ²Σ+) emission in the two linear polarization directions (i.e., parallel and perpendicular with respect to the relative velocity vector vR) has been measured as a function of the alignment of N2 (A ³Σu+) along its molecular axis in the collision frame. The degree of polarization of NO (A ²Σ+) emission is found to depend on the alignment angle (.vR) of N2 (A ³Σu+) in the collision frame. The shape of the steric opacity function at the two polarization conditions turns out to be extremely different from each other: The steric opacity function at the parallel polarization condition is more favorable for the oblique configuration of N2 (A 3Σu+) at an alignment angle of πvR ~ 45. as compared with that at the perpendicular polarization condition. The alignment of N2 (A ³Σu+) is found to give a significant effect on the alignment of NO (A ²Σ+) rotation in the collision frame: The N2 (A ³Σu+) configuration at an oblique alignment angle πvR ~ 45. leads to a parallel alignment of NO (A ²Σ+) rotation (J-vector) with respect to vR, while the axial and sideways configurations of N2 (A ³Σu+) lead to a perpendicular alignment of NO (A ²Σ+) rotation with respect to vR. These stereocorrelated alignments of the product rotation have a good correlation with the stereocorrelated reactivity observed in the multi-dimensional steric opacity function [H. Ohoyama and S. Maruyama, J. Chem. Phys. 137, 064311 (2012)]. [ABSTRACT FROM AUTHOR]

In this work the system formed by charged (ionic) microgels in the presence of monovalent salt is investigated by solving numerically the Ornstein-Zernike integral equations within the Hypernetted-Chain approximation. The ionic density profiles, effective interaction between microgel particles, and the effective charge of the particles are calculated. In addition to the electrostatic interaction, the excluded-volume repulsion between the microgel particle and the ions is also explicitly taken into account. Although this steric interaction is irrelevant in the swollen state (when the packing fraction of the polymer network is low), it becomes a very important contribution close to the de-swollen state, hindering the counterion penetration inside the microgel mesh. The theoretical predictions indicate that the ionic density profiles are strongly affected by the degree of swelling, going from a volumetric distribution of counterions in the swollen state to a surface accumulation outside the particle that becomes more important as the particle shrinks. The electrostatic effective interaction between pairs of microgel particles is shown to be the result of a complex interplay between electrostatic and depletion effects that strongly depend on the bare charge density of the particle. For sufficiently charged microgel particles, the steric exclusion leads to a less efficient screening of the microgel charge near the de-swollen configuration, and so to a significant increase of the effective charge of the microgel particle. [ABSTRACT FROM AUTHOR]

Isosurfaces appearing in three‐dimensional Non‐Covalent Interactions (NCI) representations of molecules are attributed to bonding interactions (sign(λ2)*ρ < 0) or to non‐bonding interactions, often referred to as "steric clashes" and typical of ring systems (sign(λ2)*ρ > 0). Since the second eigenvalue of the Hessian of the electron density, λ2, is positive for a ring or a cage critical point and negative for a bond critical point, in many cases NCI isosurfaces simply surround QTAIM critical points, which means that the attribution of positive‐λ2 isosurfaces to steric clashes in rings or cages is not justified. Examples are given for sterically congested hydrocarbons, where isosurfaces associated with C–H...H–C interactions enclose bond and ring critical points. In the same way, their appearance in the absence of critical points can be attributed to a variation of λ2. It is shown that for small, very strained rings, positive‐λ2 isosurfaces are not found when the recommended plot parameters are used. [ABSTRACT FROM AUTHOR]

Abstract The intramolecular evolutionary pathways of three phenylhydrazine derivatives are investigated via Density Functional calculations, as a possible convenient synthetic route towards the preparation of 1H-Indazole derivatives. All reaction steps occur via concerted four membered transition states; stabilized by intramolecular sigma-pi interactions when more than one aromatic rings are present. Steric and polarization effects are critical where activation and forward reaction free energies are concerned. The calculated values for these parameters are achievable under laboratory conditions, however, the first step of this process might require a high boiling solvent but for the remaining steps, the forward reactions potentials are increasingly modest. Graphical abstract Intramolecular evolution of 3-pyridil(2-hydrozinylphenyl) ketone. Image 1 Highlights • 1H-Indazole can be prepared from the intramolecular evolution of phenylhydrazines. • Intramolecular evolution of phenylhydrazines is controlled by electronic and steric effects. • Density function calculations provides a fast and accurate road map for the preparation of 1H-Indazoles via this method. • The evolution of phenylhydrazines to 1H-indazoles is feasible under regular laboratory conditions. [ABSTRACT FROM AUTHOR]

Abstract Fluid phase behaviour of three isomeric 1,3,6-trisubstituted benzo[ e ][1,2,4]triazin-4-yl derivatives with the half-disc molecular architecture was examined in the pure form and in binary mixtures. Results indicate that the position of substitution with two wedge-shaped 3,4,5-tridodecyloxyphenyl groups and one Ph group has dramatic impact on the Col h phase stability, which ranges from 73 °C to presumably below −60 °C. Analysis of electronic and steric factors suggests that the intermolecular interactions of the wedge-shaped substituents are dominant and through their conformational behaviour they affect packing of the column's core and hence phase stability. Graphical abstract Unlabelled Image Highlights • Isomeric disc-like derivatives of a stable radical with diverse mesophase behavior • Columnar phase binary mixture investigation • Correlation of DFT-derived structural parameters with mesophase behavior. [ABSTRACT FROM AUTHOR]

Abstract The steric effect of the α-diimine nickel catalyst on allylcyclohexane (ACH) and vinylcyclohexane (VCH) polymerizations has been studied with the aim of improving the monomer conversion and living fashion. We herein proposed a promising approach to enhancement on α-diimine nickel-catalyzed alkenylcyclohexane polymerization by moving steric bulk from the ortho -aryl to the ligand backbone to overcome the steric repulsion between them. A camphyl derived α-diimine nickel catalyst with 2,6-dimethylphenyl was successfully used to catalyze living isomerization polymerizations of ACH and VCH. Microstructure analysis of the obtained polymers revealed that ACH and VCH were preferentially inserted into secondary Ni–alkyl species (Ni–CH) in 2,1-insertion fashion followed by precise chain walking to form 1,ω-unit on the main chain. The isolated 1,2-insertion of the alkenylcyclohexane monomers infrequently took place, thus leading to the presence of 2,ω-unit by chain walking and 1,2-unit by direct insertion on the main chain. Graphical abstract Image 1 Highlights • Novel hydrocarbon polymers with cyclic units from alkenylcyclohexane monomers. • Enhancement on alkenylcyclohexanes polymerization by bulky ligand backbone. • Living polymerization and high regioselectivity. [ABSTRACT FROM AUTHOR]

A three-step synthesis of ß-alkoxy-substituted alicyclic sulfonyl chlorides from cyclic alkenes and alcohols is reported. The scope of the method was studied for a range of the substrates with various steric and electronic properties. The title compounds were obtained on a hundred-gram scale in up to 52% overall yield scale as single cis-diastereomers. [ABSTRACT FROM AUTHOR]

Graphical abstract Reactions of chloro-bridged dimeric C,N -cyclopalladated complexes with secondary phosphines are sensitive to the molar ratio of the reagents, base presence, solvent, time and temperature and provide either aminophosphines (or other N,P ligands), mononuclear HPR 2 adducts or mono-chloro, monophosphido-bridged dimeric C,N -cyclopalladated complexes as major products. Abstract Reactions of secondary phosphines HPR1R2 [R1 = R2 = p -MeOC 6 H 4 (b), p -CF 3 C 6 H 4 (c), mesityl (Mes, d) or 1-adamantyl (Ad, e); R1 = t -Bu, R2 = Ph (f)] with cyclopalladated complexes (CPCs) derived from N,N -dimethylbenzylamine (1), l -fenchone methyloxime (3), (S)- N,N -dimethylbenzylamine (9), and (S)-di-2,4- tert -butyloxazoline (11) were studied. Phosphination of the cyclopalladated ligands in complexes 1 and 3 was observed using either 4.5:1 or 9:1 molar ratios of HPAr 2 (b , c) to CPC in the presence of 9 equiv. Cs 2 CO 3. The corresponding N,P ligands 2b,c and 4b,c were isolated in 44–59% yields. Reactions of the sterically hindered HPMes 2 with CPCs 1 and 3 provided the phosphination product, 4d′ , only for the latter complex (32% yield). Attempts to synthesize N,P ligands with HPAd 2 were unsuccessful with either palladacycle. Major products of the reactions of complexes 1 and 3 with bulky HPMes 2 and HPAd 2 were either rare mononuclear complexes 5d,e (up to 90%) and 7d,e (81 and 86%) with an ancillary secondary phosphine ligand or dinuclear monophosphido, monochloro-bridged complexes 6d (98%) and 8d,e (69% and 66%) depending on the HPR 2 :CPC molar ratio used. Enantiopure CPC 3 reacted with racemic HP t -BuPh to give a single diastereomer of the phosphination product 4f in 12% yield. Attempts to use the racemic phosphine in transformations with two other enantiopure CPCs, 9 and 11 , to form a C P t -BuPh bond were unsuccessful. Instead, reactions of these two complexes with racemic HP t -BuPh provided monophosphido, monochloro-bridged CPCs 11f and 13f in 32 and 76% yield, respectively. Analysis of 1H, 13C{1H} and 31P{1H} NMR data of all new Pd(II) complexes and N,P ligands is provided. An X-ray crystallographic study of complex 7d proved its trans- N,P geometry. [ABSTRACT FROM AUTHOR]

The synthesis and coordination chemistry of a saturated analogue of a "bulky‐yet‐flexible" N‐heterocyclic carbene (NHC) ligand are described. "SIPaul" is a 4,5‐dihydroimidazol‐2‐ylidene ligand with unsymmetrical aryl N‐substituents, and is one of the growing class of "bulky‐yet‐flexible" NHCs that are sufficiently bulky to stabilize catalytic intermediates, but sufficiently flexible that they do not inhibit productive chemistry at the central metal atom. Here, the synthesis of SIPaul.HCl and its complexes with copper, silver, iridium, palladium, and nickel, and its selenourea, are reported. The steric impact of the ligand is quantified using percent buried volume (% Vbur), whereas the electronic properties are probed and quantified using the Tolman Electronic Parameter (TEP) and δSe of the corresponding selenourea. This work shows that despite the often very different performance of saturated versus unsaturated carbenes in catalysis, the effect of backbone saturation on measurable properties is very small. [ABSTRACT FROM AUTHOR]

The synthesis of persistent, neutral organic radicals is challenging because of their inherent reactivities. Herein, we report the synthesis and characterization of a highly congested mesityl‐substituted tri(9‐anthryl)methyl (TAntM) radical (1). The scaffold was successfully synthesized by circumventing the steric hindrance imposed by the bulky groups surrounding the central methyl carbon atom. The radical has a threefold propeller structure, and the unpaired electron is mainly localized on the central carbon atom. Owing to its congested structure, 1 is remarkably stable, which facilitated handling under ambient conditions. Evaluation of the dynamic behavior of the TAntM scaffold indicated that the stability is due to the bulky anthryl units and the mesityl substituents. Because of its high persistence, wide‐range absorption, and good reversible redox properties, 1 has promising applications in organic devices. A highly congested tri(9‐anthryl)methyl radical was successfully synthesized by circumventing the steric hindrance imposed by the bulky groups surrounding the central methyl carbon atom. Owing to its congested structure, the mesityl‐substituted tri(9‐anthryl)methyl radical is remarkably stable, which facilitates its handling under ambient conditions. [ABSTRACT FROM AUTHOR]

Abstract Phosphatidylcholine-coated emulsions are unstable and prone to phase separation under certain environmental stresses, such as low pH and moderate ionic strength (>100 mmol/L NaCl). This study investigated the formation and stability of octenyl succinic anhydride-modified starch (OSAS)-stabilized nanoemulsions enhanced with phosphatidylcholine for the encapsulation of soybean oil. The effect of variables (OSAS/phosphatidylcholine weight ratio, oil composition, emulsifier concentration, etc.) and environmental stresses (pH, temperature, ionic strength, etc.) on the stability of phosphatidylcholine-enhanced nanoemulsions stabilized by OSAS was examined. Adequate addition of OSAS (OSAS/phosphatidylcholine weight ratio = 3:7) led to the formation of a more stable nanoemulsion. An emulsion at pH 2 was unstable against creaming, and no phase separation occurred after 130 h; presumably, OSAS has a certain degree of steric repulsion that protects the nanoemulsion from oiling-off. The phosphatidylcholine-enhanced nanoemulsions stabilized by OSAS were stable at high NaCl concentrations (≤800 mmol/L) and temperatures from 30 to 90 °C, which was attributed to steric and electrostatic repulsions. Transmission electron microscopy images showed that OSAS and phosphatidylcholine were both adsorbed around the surface of the emulsion. These results showed that adding OSAS could improve the formation and stability of phosphatidylcholine-stabilized emulsions. [ABSTRACT FROM AUTHOR]

The insertion of fragments of sterically hindered phenols into the structure of phosphorylacetic acids hydrazides in their reactions with 3,5-di-tert-butyl-4-hydroxybenzylacetates and sterically hindered 2- and 4-hydroxybenzaldehydes has been carried out. The synthesis of 3,5-di-tert-butyl-4-benzyl derivatives of 5-[(diphenylphosphoryl) methyl]-2,4-dihydro-3H-1,2,4-triazol-3-thiones was also carried out. [ABSTRACT FROM AUTHOR]

Highlights • Effect of field programming in Flow FFF on steric transition was studied. • Steric transition was investigated with frit inlet asymmetrical Flow FFF channels. • Steric inversion diameter (d i) in Flow FFF can be increased to >1 μm. • Field programming with increased channel thickness was effective to increase d i. Abstract Steric transition in flow field-flow fractionation (FlFFF) was investigated under field programming by varying the channel thickness of a frit inlet asymmetrical FlFFF (FI-AF4). Steric transition is a typical inversion in sample elution mode from the increasing order of diameter (normal mode) to the opposite order (steric mode). Owing to the co-elution of two different-sized particles in the steric transition region where particles elute by the combination of the two elution modes, a loss of information in determining the accurate size of sample components in field-flow fractionation occurs. In this study, the effect of field programming on the steric transition in FI-AF4 was examined with the increase in channel thickness in order to increase the diffusional contribution of particle retention with the simultaneous reduction of steric contribution. This study demonstrated that the steric inversion diameter can be increased to >1 μm by programming the crossflow rate and by increasing the channel thickness to 350 and 490 μm. The present study also investigated the effects of outflow rate and initial field strength on the particle separation in field-programmed FI-AF4. [ABSTRACT FROM AUTHOR]

Transition-metal-catalyzed nitrene transfer is a convenient method to introduce nitrogen into simple substrates through either alkene aziridination or C-H bond amination. Silver complexes have an unusual capability to accommodate a broad range of N-donor ligands and coordination geometries in catalysts competent for nitrene transfer. This behavior has resulted in the ability to achieve tunable chemoselectivity between aziridination and C-H bond amidation, as well as tunable site-selective functionalization between two different C-H bonds. In this paper, efforts to engage the diversity of silver and rhodium catalysts to accomplish selective and tunable aziridination of mixtures of alkenes are discussed. It was found that the selectivity of dinuclear Rh catalysts is dictated largely by steric effects, while the identity of the ligand on silver can be tuned to influence whether the steric or electronic features in the competing alkenes is the primary factor controlling which precursor is preferentially aziridinated. [ABSTRACT FROM AUTHOR]

The synthesis and the study of the molecular structure of a series of heteroleptic copper(I) compounds with triphenylphosphine and α-diimines presenting a varying degree of bulk at their chelating cite is reported. The most sterically crowded diimine acts as a monodentate ligand towards copper(I) promoting bridging of the halogen atom present in the metal coordination sphere and formation of a dimer. Evidence for this behavior is obtained from the electronic spectra and semiempirical quantum chemical calculations with MOPAC. Steric demands in all the studied compounds preclude coordination of silver(I) under similar reaction conditions. [ABSTRACT FROM AUTHOR]

To understand the substitution effects of 2-hydroxymethyl pyridine on the reaction equilibrium, the interactions between a series of 2-hydroxymethyl pyridine derivatives and diperoxovanadium(V) complex [OV(O2)2(D2O)]−/[OV(O2)2(HOD)]− in solution were explored by the combined use of multinuclear (1H, 13C, and 51V) magnetic resonance together with HSQC in 0.15 mol L−1 NaCl ionic medium for mimicking the physiological conditions. Some direct NMR data are given for the first time. The relative reactivity among the 2-hydroxymethyl pyridine ligands is 2-hydroxymethyl pyridine (1) > 2-methoxymethyl pyridine (2) > 2-ethoxymethyl pyridine (3) > 2-propoxymethyl pyridine (4). The competitive coordination results in the formation of a series of new seven-coordinate diperoxovanadium species [OV(O2)2L]- (L = 1, 2, 3, and 4). The results of density functional calculations indicated that steric effects play an important role in these reactions, providing a reasonable explanation on the relative reactivity of the 2-hydroxymethyl pyridine derivative. [ABSTRACT FROM AUTHOR]

Redox transformations of sulfides 1-8 combining a fragment of sterically hindered pyrocatechol with alkyl, cycloalkyl, and aromatic substituents were studied. The first step of electrooxidation of thioethers affords o-benzoquinones. The introduction of the redox-active thioether group extends the range of redox properties of pyrocatechols. In the second step, the thioether fragment is involved in the quasi-reversible anodic process, and the number of electrons participating in the electrode reaction depends on the structure of the hydrocarbon group bonded to the sulfur atom. The reactivity of compounds 1-8 toward O2•- was evaluated on the basis of the electrochemical data. Cyclopentyl, phenyl, or benzyl substituents in the thioether group exert a greater effect on the antiradical activity than the alkyl moieties. The formation of an o-semiquinolate radical anion in the reaction of pyrocatechol thioethers with KO2 was detected by the ESR method. It was shown using the reaction with the stable 2,2-diphenyl-1-picrylhydrazyl radical as an example that RS-functionalized pyrocatechols show a higher antiradical activity compared to 3,5-di-tert-butylpyrocatechol. [ABSTRACT FROM AUTHOR]

Abstract: A family of six homoleptic [CuI(Ln)]2(ClO4)2 and six heteroleptic [CuI(Ln)(PPh3)2]2(ClO4)2 bimetallic complexes, in which Ln are bis‐Schiff base ligands with alkyl spacers of variable length (n=2–7 −CH2−), were prepared to evaluate the role of the spacer on the formation of helicates or mesocates. In the homoleptic series, spectroscopic and theoretical studies indicate that preferences for a conformation are based on energetic parameters, mainly, the establishment of noncovalent interactions. The odd–even nature of the spacers preconditions the superposition of the aromatic rings to allow the juxtaposition necessary for noncovalent interactions, whereas the increase of the length reduces the strength of such interactions. Consequently, complexes with even‐spacers of short length were identified as helicates in solution, [CuI(Ln)]22+ (n=2, 4). Complexes [CuI(Ln)]22+ (n=3–7) dissociate in solution to produce the monometallic complexes in equilibrium, [CuI(Ln)]+. The stability of the bimetallic species is discussed in terms of their conformations. The set of heteroleptic complexes was prepared to evaluate the reach of the “odd–even rule” in the solid, which is based on the “zig–zag” arrangements of the spacers. Based on crystallographic information, “S‐” and “C”‐type conformations of Ln are related to even and odd spacers, respectively. This trend is considered in addition to other factors to explain preferences for either a mesocate or helicate conformation in the homoleptic series. [ABSTRACT FROM AUTHOR]

In this study, we have optimised the sterically directed attachment of biomolecules on the surface of coaxial membranes prepared by co-electrospinning which have been proved to be a material with very high performance for the development of biosensors with optical oxygen transduction. Uricase has been used as model enzyme. Two sterically directed strategies: a) covalent attachment via maleimide, and b) affinity bonding via biotin-streptavidin interaction, have been tested in order to preserve the enzymatic activity of uricase and to improve the analytical figures of merits on the determination of uric acid. The best results were obtained with biotin-streptavidin affinity interaction and using a biotinylation reagent containing a polyethylene glycol chain. The developed biosensor showed high sensitivity towards uric acid with a detection limit of 0.5 µM, a quantification limit of 1.8 µM and linear range from 1.8 to 250 µM. The applicability of the membrane as biosensor with optical oxygen transduction was proved by determining uric acid in serum samples. The obtained results showed a good correlation (0.999) with those obtained by an external reference laboratory. [ABSTRACT FROM AUTHOR]

Dopamine D 3 receptor has become an attractive target in the treatment of abused drugs. 3D-QSAR studies were performed on a novel series of D 3 receptor antagonists, 1,2,4-triazolyl 5-azaspiro [2.4]-heptanes, using CoMFA and CoMSIA methods. Two predictive 3D-QSAR models have been generated for the modified design of D 3 R antagonists. Based on the steric, electrostatic, hydrophobic and hydrogen-bond acceptor information of contour maps, key structural factors affecting the bioactivity were explored. This work gives helpful suggestions on the design of novel D 3 R antagonists with increased activities. [ABSTRACT FROM AUTHOR]

Two new copper(I) complexes supported by pyrazolylmethylpyridine (PMP) ligands are synthesized and investigated regarding their ability to catalyze the oxygenation of several monophenolic substrates. The PMP ligands containing a pyridine and a pyrazole donor group represent hybrids between dipyridylmethane (DPM) and bis(pyrazolyl)methane (BPM) ligands. The catalytic activity of the two new [Cu(MeCN)2PMP]PF6 complexes is found to be intermediate between that of catalytically inactive [Cu(MeCN)2DPM]PF6 and highly active [Cu(MeCN)2BPM]PF6, suggesting that the electronic properties of a multidentate ligand can be designed in a modular fashion. DFT calculations are used to explore the differences in reactivity between the two systems. Regarding the behavior of these complexes in solution, evidence for an equilibrium between homoleptic and heteroleptic forms is presented. The crystal structure of a dinuclear complex exhibiting two homoleptic CuII units bridged by a fluorido ligand is obtained, which might represent one of the decay products of PMP‐type catalysts after prolonged reaction times. [ABSTRACT FROM AUTHOR]

Ion mobility spectrometry (IMS) is an analytical technique used for fast and sensitive detection of illegal substances in customs and airports, diagnosis of diseases through detection of metabolites in breath, fundamental studies in physics and chemistry, space exploration, and many more applications. Ion mobility spectrometry separates ions in the gas-phase drifting under an electric field according to their size to charge ratio. Ion mobility spectrometry disadvantages are false positives that delay transportation, compromise patient's health and other negative issues when IMS is used for detection. To prevent false positives, IMS measures the ion mobilities in 2 different conditions, in pure buffer gas or when shift reagents (SRs) are introduced in this gas, providing 2 different characteristic properties of the ion and increasing the chances of right identification. Mobility shifts with the introduction of SRs in the buffer gas are due to clustering of analyte ions with SRs. Effective SRs are polar volatile compounds with free electron pairs with a tendency to form clusters with the analyte ion. Formation of clusters is favored by formation of stable analyte ion-SR hydrogen bonds, high analytes' proton affinity, and low steric hindrance in the ion charge while stabilization of ion charge by resonance may disfavor it. Inductive effects and the number of adduction sites also affect cluster formation. The prediction of IMS separations of overlapping peaks is important because it simplifies a trial and error procedure. Doping experiments to simplify IMS spectra by changing the ion-analyte reactions forming the so-called alternative reactant ions are not considered in this review and techniques other than drift tube IMS are marginally covered. [ABSTRACT FROM AUTHOR]

Abstract: The similarities and differences between carbon and silicon have attracted the curiosity of chemists for centuries. Similarities and analogies can be found in their saturated compounds, but carbon exhibits a cornucopia of unsaturated compounds that silicon (and most other elements) cannot replicate. While this qualitative difference is empirically well known, quantum chemistry has previously only described quantitative differences related to orbital overlap, steric effects, or orbital energies. We study C2 and Si2 and their hydrides X2H2n (X=C, Si; n=1, 2, 3) by first‐principles quantum chemical calculation, and find a qualitative difference in the topologies of the core electrons: carbon has the propensity to alter its core electron topology when forming unsaturated compounds, and silicon has not. We draw a connection between the core electron topologies and ionization energies, and identify other elements we expect to have similarly flexible core topologies as carbon. [ABSTRACT FROM AUTHOR]

Imino- and amino-pyridine ligands are versatile scaffolds to probe how ligand sterics influence polymerization outcomes for nickel(II) ethylene polymerization catalysts. Six imino- and one amino-pyridine nickel(II) complexes with varied imino/amino-carbon substitution (R 1  = methyl, ethyl, isopropyl or tert -butyl) were synthesized ( 1 - 7 ). Five of these complexes were analyzed crystallographically: dimeric {[2-[(2,6-Me 2 -C 6 H 3 )N=C(R 1 )]C 5 H 4 N]NiBr 2 } 2 (R 1  = Et 2 ; R 1  =  t -Bu 4 ), monomeric [2-[(2,6-Me 2 -C 6 H 3 )N=C(R 1 )]C 5 H 4 N]NiBr 2 NCCH 3 (R 1  = Me 5 ; R 1  =  t -Bu 6 ), and monomeric [2-[(2,6-Me 2 -C 6 H 3 )NHCH( t -Bu)]C 5 H 4 N]NiBr 2 ( 7 ). Complexes 1 - 7 are competent ethylene polymerization precatalysts at 0 ° C, and tert -butyl substituted imino-pyridine precatalysts 4 and 6 and amino-pyridine precatalyst 7 display the best activity, highest polyethylene molecular weight, and narrowest dispersity values of series. 13 C-NMR analyses of polyethylene samples reveal a lightly branched morphology with a modest amount of methyl branching; polymer T m values are consistent with this assessment. Ongoing work includes further exploration of precatalysts 4 , 6 , and 7 in attempt to maximize polyethylene molecular weight and achieve living polymerization. [ABSTRACT FROM AUTHOR]

Two new trinuclear copper(II) complexes, [(CuL 1 ) 3 (μ 3 -OH)](ClO 4 ) 2 ( 1 ) and [(CuL 2 ) 3 (μ 3 -OH)](ClO 4 ) 2 ·5H 2 O ( 2 ), and one new dinuclear Cu(II) complex, [(CuL 3 ) 2 (μ 2 -OH)(CH 3 OH)]ClO 4 ( 3 ), have been synthesized using three tridentate NNO donor Schiff bases, HL 1 , HL 2 and HL 3 (HL 1  = 1-((2-aminoethylimino)methyl)naphthalen-2-ol, HL 2  = 1-((2-(methylamino)ethylimino)methyl)naphthalen-2-ol and HL 3  = 1-((2-(dimethylamino)ethylimino)methyl)naphthalen-2-ol), respectively and structurally characterized by single-crystal X-ray diffraction. Complexes 1 and 2 consist of trinuclear [(CuL) 3 (μ 3 -OH)] 2+ units, whereas 3 contains dinuclear [(CuL) 2 (μ 2 -OH)] + unit along, with perchlorate anions which are needed to balance the charge. In each of the complexes, all the copper atoms are five-coordinated with a distorted square-pyramidal geometry, except for complex 1 in which one of the Cu(II) ions of the trinuclear unit is six-coordinate, being weakly coordinated to one of the perchlorate anions to form an elongated distorted octahedron. The equatorial plane consists of the bridging oxygen of the central OH − group together with three atoms (NNO) from the Schiff base. The phenoxido oxygen atom of the Schiff base coordinates to the axial position of the Cu(II) ion of another subunit to form the cyclic trimer in 1 and 2 and dimer in 3 . Magnetic measurements of complexes 1 – 3 in the 2–300 K temperature range indicate antiferromagnetic coupling in the complexes with J  = −8.85, −4.86 and −50.60 cm −1 for 1 – 3 respectively. Density Functional Theory has also been performed in order to estimate the exchange coupling constants in these three complexes. The theoretically calculated J values are in good agreement with the experimental values. [ABSTRACT FROM AUTHOR]

A Pd-catalyzed site-selective C(sp2)–H activation/cycloimidoylation of 2-isocyano-2,3-diarylpropanoates to construct diverse cyclic imine products has been developed. Six-membered 3,4-dihydroisoquinolines containing a C3 quaternary carbon center were generated dominantly by using bulky Ad2Pn-Bu as a ligand, while five-membered 1,1-disubstituted 1H-isoindoles were formed preferentially in the presence of bidentate phosphine ligand DPPB. The selectivity for 1H-isoindole formation was enhanced by using steric hindered aryl iodides. DFT calculations suggested that the experimentally observed ligand-controlled selectivity was a result of trans effect. [ABSTRACT FROM AUTHOR]

Abstract: The effect of molecular interactions between the components on the self‐assembly process of Pd2L4 structures was investigated by a 1H NMR‐based quantitative approach (QASAP: quantitative analysis of self‐assembly process). Although the self‐assembly of the Pd2L4 cage without interactions between the bent ligands took place, mainly producing small intermediates, the self‐assembly of the Pd2L4 capsule composed of bent ligands with anthracene panels tends to produce large intermediates containing more components than the capsule. This is ascribed to steric interactions between the panels. [ABSTRACT FROM AUTHOR]

In this study, a series of 42 molecules, based on substituted 2,5-dibutyl-2, 4-dihydro derivatives, was studied by three-dimensional quantitative structureactivity relationship (QSAR) studies. The best 3D-QSAR model using genetic algorithm method, showing good correlative and predictive capabilities in terms of q2 = 0.6581 and pred_r2 = 0.7165. The strong correlation between experimental and predicted activity values was observed, indicating the validation and good quality of the derived QSAR model. [ABSTRACT FROM AUTHOR]

The coordination ability of tris(pyridyl)aluminates can be modified by the steric and electronic character of substituents at the 6-positions of their pyridyl rings. Whereas [EtAl(6-Me-2-py)3]− (1) coordinates strongly to lanthanide(ii) ions [Eu(ii) and Yb(ii)], [EtAl(6-Br-2-py)3]− (2) forms much weaker complexes, and [EtAl(6-CF3-2-py)3]− does not coordinate at all. The modification of the donor ability of these ligands is investigated by solid-state studies of the Ln(ii) sandwich compounds and by competitive coordination studies in solution. [ABSTRACT FROM AUTHOR]

A novel series of Zn(II) complexes [LnZnCl2] (Ln = LA − LF) based on N,N′,N-bis((1H-pyrazol-1-yl)methyl)amine bidentate ligands, N,N-bis((1H-pyrazol-1-yl)methyl)-3,5-dimethylaniline [LA], N,N-bis((1H-pyrazol-1-yl)methyl)-2,6-dimethylaniline [LB], N,N-bis((1H-pyrazol-1-yl)methyl)-2,6-diethylaniline [LC], N,N-bis((1H-pyrazol-1-yl)methyl)-2,6-diisopropylaniline [LD], N,N-bis((1H-pyrazol-1-yl)methyl)-4-bromoaniline [LE] and N,N-bis((1H-pyrazol-1-yl)methyl)benzhydrylamine [LF], has been synthesized and characterized. X-ray structures of these Zn(II) complexes showed a distorted tetrahedral geometry. No interaction exists between the Namine and the Zn(II) center in the [LnZnCl2] (Ln = LA − LF) complexes, resulting in formation of an eight-membered chelate ring. [LFZnCl2] exhibited the highest catalytic activity (3.95 × 104 g PMMA/mol·Zn·h) for the polymerization of methyl methacrylate (MMA) in the presence of modified methylaluminoxane (MMAO) at 60 °C and yielded high molecular weight (Mw) (11.0 × 105 g/mol) of poly(methylmethacrylate) (PMMA). All the complexes resulted in syndiotactic enriched PMMA with high Tg (125-131 °C). The steric bulk of ligand architecture plays an influential role in controlling the catalytic activity and stereoregularity of the resultant PMMA. Further, alkyl derivatives [LnZnMe2] (Ln = LA − LF) of synthesized Zn(II) complexes, generated in situ, showed moderate to high activities toward ring opening polymerization (ROP) of rac-lactide (rac-LA) and yielded heterotactic polylactide (PLA) with Pr up to 0.95 at −50 °C. The activity and stereoselectivity toward ROP of rac-LA by these dimethyl Zn(II) complexes should be considered as a combined effect of steric hindrance and electronic density around the metal center. [ABSTRACT FROM AUTHOR]

A systematic study of reactions between Cp*2Yb(THF) (Cp* = η5-C5Me5, 1) and iminopyridine ligands (IPy = 2,6-iPr2C6H3N=CH(C5H3N-R), R = H (2a), 6-C4H3O (2b), 6-C4H3S (2c), 6-C6H5 (2d)) featuring similar electron accepting properties but variable denticity and steric demand, has provided a new example of steric control on the redox chemistry of ytterbocenes. The reaction of the unsubstituted IPy 2a with 1, either in THF or toluene, gives rise to the paramagnetic species Cp*2YbIII(IPy)Ṗ− (3a) as a result of a formal one-electron oxidation of the YbII ion along with IPy reduction to a radical-anionic state. The reactions of 1 with substituted iminopyridines 2b–d, bearing aryl or hetero-aryl dangling arms on the 6 position of the pyridine ring occur in a non-coordinating solvent (toluene) only and afford coordination compounds of a formally divalent ytterbium ion, coordinated by neutral IPy ligands Cp*2YbII(IPy)0 (3b–d). The X-ray diffraction studies revealed that 2a–c act as bidentate ligands; while the radical-anionic IPy in 3a chelates the YbIII ion with both nitrogens, neutral IPy ligands in 3b and 3c participate in the metal coordination sphere through the pyridine nitrogen and O or S atoms from the furan or thiophene moieties, respectively. Finally, in complex 3d the neutral IPy ligand formally adopts a monodentate coordination mode. However, an agostic interaction between the YbII ion and an ortho C–H bond of the phenyl ring has been detected. Imino-nitrogens in 3b–d are not involved in the metal coordination. Variable temperature magnetic measurements on 3a are consistent with a multiconfigurational ground state of the Yb ion and suggest that the largest contribution arises from the 4f13-radical configuration. For complexes 3b and 3c the data of magnetic measurements are indicative of a YbII-closed shell ligand electronic distribution. Complex 3d is characterized by a complex magnetic behavior which does not allow for an unambiguous estimation of its electronic structure. The results are rationalized using DFT and CSSCF calculations. Unlike diazabutadiene analogues, 3a does not undergo a solvent mediated metal–ligand electron transfer and remains paramagnetic in THF solution. On the other hand, complexes 3b–d readily react with THF to afford 1 and free IPy 2b–d. [ABSTRACT FROM AUTHOR]

A series of binuclear tetracarboxylate-linked Mn(II), Fe(II), Co(II), Ni(II), and Cu(II) complexes with 1,2-substituted pyridine, viz., 2,3-cyclododecenopyridine (L), were prepared. Study of the crystal structures of isolated compounds (CIF file CCDC nos. 1575855-1575859) revealed a distortion of the {Ni2(O2CR)4L2} binuclear moiety, manifested as a change in the NiNiN angle (151.67°), in the bridging function of two out of the four carboxylate groups (from μ2- to (κ²,μ2-)), and in the coordination environment of the metal ion (NiO5N). The results were analyzed in comparison with known data. The magnetic properties of copper(II) and nickel(II) complexes were studied. The copper(II) complex is diamagnetic as a result of strong exchange interactions between the unpaired electrons; in the nickel(II) complex antiferromagnetic exchange interactions were detected (JNi-Ni = -25 cm-1). [ABSTRACT FROM AUTHOR]

A series of binuclear tetracarboxylate-linked Mn(II), Fe(II), Co(II), Ni(II), and Cu(II) complexes with 1,2-substituted pyridine, viz., 2,3-cyclododecenopyridine (L), were prepared. Study of the crystal structures of isolated compounds (CIF file CCDC nos. 1575855-1575859) revealed a distortion of the {Ni2(O2CR)4L2} binuclear moiety, manifested as a change in the NiNiN angle (151.67°), in the bridging function of two out of the four carboxylate groups (from μ2- to (κ²,μ2-)), and in the coordination environment of the metal ion (NiO5N). The results were analyzed in comparison with known data. The magnetic properties of copper(II) and nickel(II) complexes were studied. The copper(II) complex is diamagnetic as a result of strong exchange interactions between the unpaired electrons; in the nickel(II) complex antiferromagnetic exchange interactions were detected (JNi-Ni = -25 cm-1). [ABSTRACT FROM AUTHOR]

This tutorial review describes how recent quantum chemical calculations and non-adiabatic molecular dynamics simulations have provided valuable guidelines and insights for the design of more powerful synthetic rotary molecular motors. Following a brief overview of the various types of rotary motors synthesized to date, we present computationally identified steric and electronic approaches to significantly reduce the free-energy barriers of the critical thermal isomerization steps of chiral overcrowded alkenes, a main class of motors whose potential for many different kinds of applications is well documented. Furthermore, we describe how computational research in this field has provided new motor designs that differ from overcrowded alkenes by either (1) completing a full 360° rotation through fewer steps, (2) exhibiting more efficient photochemical steps, or (3) requiring fewer chiral features for their function, including a design that even in the absence of a stereocenter achieves unidirectional rotary motion from two Z/ E photoisomerizations alone. [ABSTRACT FROM AUTHOR]

The benzene ring of low-molecular-weight gelators provides strong intermolecular forces but increases molecular spacing during self-assembly. To explore both of the above influences on the gel properties, we synthesize two gelators (Glu-CBZ and Glu-DPA) consisting of the same terminal long side chain but different aliphatic functional groups. The aliphatic functional groups are carbobenzoxy group and diphenyl phosphate group. The self-assembly driving forces, self-organization patterns, network morphologies, rheological properties, and the influences of solvents are researched through 1H NMR spectra, Fourier transform infrared spectra, field-emission scanning electron microscopy images, rheological characterizations curves, tube-inversion experiment, and calculation of van't Hoff plots. The results show that the carbobenzoxy group of Glu-CBZ makes molecules pack more tightly such that it improves the gel properties during static equilibrium. Whereas the diphenyl phosphate group of Glu-DPA provides stronger intermolecular forces, performing outstandingly during dynamic equilibrium. It is advantageous to further investigate the competitive relationship in gel system between the increased number of functional groups and the consequent steric effect. [ABSTRACT FROM AUTHOR]

A Molecular Electron Density Theory study of the zw-type 32CA reactions of acetonitrile oxide (NO) with two 7-oxanorborn-5-en-2-ones (ONBs) has been performed at the DFT B3LYP/6-31G(d) computational level. These cycloadditions proceed through one-step mechanisms with high activation energies and present low para regio and complete syn diastereofacial selectivities. While the non-polar character of these zw-type 32CA reactions, which is the consequence of the insufficient electrophilic activation of ONBs, according to the analysis of the conceptual DFT reactivity indices, accounts for the high activation energies, and low para regioselectivity, NCI topological analyses at the anti/syn pairs of para TSs reveal that the steric hindrance encountered between the NO framework and the ONB side containing the carbonyl group along the anti approach mode is responsible for the complete syn diastereofacial selectivity. [ABSTRACT FROM AUTHOR]

The asymmetric transfer hydrogenation (ATH) of ketones is an efficient method for producing enantio-enriched alcohols which are used as intermediates in a variety of industrial processes. Here we report the synthesis of new iron ATH precatalysts ( S,S)-[FeBr(CO)(Ph2PCH2CH2NHCHPhCHPhNC=CHCH2PR′2)][BPh4] (R′=Et, and ortho-tolyl (o-Tol)) where one of the phosphine groups is modified with small alkyl and large aryl substituents to probe the effect of this change on the activity and selectivity of the catalytic system. A simple reversible equilibrium kinetic model is used to obtain the initial TOF and the inherent enantioselectivity S=kR/kS of these catalysts along with those for the previously reported catalysts with R′=Ph and Cy for the ATH of acetophenone. With an increase in the size of the PR′2 group, the TOF goes through a maximum at PPh2 while the S value goes through a maximum of 510 at R′=Cy. The complex with R′=o-Tol starts with a high S value of 200 but is rapidly changed to a second catalyst with an S value of 28. For the reduction of acetophenone to ( R)-1-phenylethanol, turnover numbers of up to 5200 and ee up to 98 % were achieved. The chemotherapeutic pharmaceutical precursor ( R)-(3′,5′-bis(trifluoromethyl))-1-phenylethanol is synthesized in up to 95 % ee. Several other alcohols can be prepared in greater than 90 % ee by choosing the precatalyst with the correctly matched steric properties. A hydride complex derived from the catalyst with R′=Cy is characterized by NMR spectroscopy. It is proposed that low concentration trans-hydride carbonyl complexes with the FeH parallel to the NH of the ligand are the active catalysts in all of these systems. [ABSTRACT FROM AUTHOR]

Rate constants are reported for the reactions of 1-phenoxy-dinitrobenzenes, 3, 1-phenoxy-dinitrotrifluoromethylbenzenes, 4, with n-propylamine, and 1-methylheptylamine in acetonitrile as solvent. The results are compared with results reported previously for n-butylamine, pyrrolidine, and piperidine. Decreasing ring activation leads to lower values of k1 for nucleophilic attack although this may be mediated by reduced steric congestion around the reaction centre. Specific steric effects, leading to rate retardation, are noted for the ortho-CF3 group. In general, reactant-bearing ortho-CF3 group were subject to base catalysis irrespective of the amine nucleophile and values of kAm/k−1 are reduced as the size of the amine get bulkier. This is likely to reflect increases in values of k−1 coupled with decreases in values of kAm as the proton transfer from zwitterionic intermediates to catalysing amine becomes less thermodynamically favourable. [ABSTRACT FROM AUTHOR]

The effect of a series of hydrotris(pyrazolyl)borate ligands (Tpx) in the regioselectivity of the catalytic functionalization of the secondary carbon-hydrogen bonds of hexane with ethyl diazoacetate and TpxCuL as the catalysts has led to the definition of the relative steric parameter SPR. The validity of the parameter has been assessed upon its correlation with the regioselectivity observed in several transformations (olefin cyclopropanation, C−H functionalization, C−H amidation), in all cases a good degree of fitting being observed. [ABSTRACT FROM AUTHOR]

Density functional theory calculations have been performed to investigate the binaphthol-catalyzed allylboration of skatoles. The high stereoselectivity observed for the reaction is reproduced well by the calculations and was found to be mainly a result of steric repulsions in the corresponding Zimmerman-Traxler transition states. The role of the additive MeOH in enhancing the stereoselectivity was also investigated and is suggested to promote the formation of less reactive allylboronic ester intermediates, thereby suppressing the formation of allylboroxine species, which undergo the facile racemic background reaction. [ABSTRACT FROM AUTHOR]

The reaction between (Dipp)2PH and one equivalent of n-BuLi, PhCH2Na or PhCH2K in THF gives the complexes [(Dipp)2P]Li(THF)3 (2a), {[(Dipp)2P]Na(THF)2}2 (3a) and [(Dipp)2P]K(THF)4 (4a), respectively [Dipp = 2,6-iPr2C6H3]. Exposure of these compounds to vacuum yields the alternative solvates [(Dipp)2P]Li(THF)2 (2b), [(Dipp)2P]Na(THF)1.5 (3b), and [(Dipp)2P]K (4b), respectively; the alternative adduct [(Dipp)2P]Na(PMDETA) (3c) was prepared by treatment of 3a with PMDETA. Treatment of (Dipp)(Mes)PH or (Mes)2PH with one equivalent of n-BuLi in THF gives the complexes [(Dipp)(Mes)P]Li(THF)3 (7a) and [(Mes)2P]2Li2(THF)2(OEt2) (8a) after crystallisation from diethyl ether [Mes = 2,4,6-Me3C6H2]; crystallisation of 8a from hexane gives the alternative adduct [(Mes)2P]Li(THF)3 (8b). Exposure of 7a, 8a and 8b to vacuum leads to loss of coordinated solvent, yielding the solvates [(Dipp)(Mes)P]Li(THF)2 (7b) and [(Mes)2P]Li(THF) (8c). The solid-state structures of complexes 2a, 3a, 3c, 4a, 7a, 8a, and 8b have been determined by X-ray crystallography. Variable-temperature 31P{1H} and 7Li NMR spectroscopy indicates that 2b, 3b and 7b are subject to a monomer–dimer equilibrium in solution, where the monomeric forms are favoured at low temperature. In contrast, variable-temperature 31P{1H} and 7Li NMR spectroscopy suggests that 8c is subject to a dynamic equilibrium between a dimer and a cyclic trimer in solution, where the trimer is favoured at low temperatures. [ABSTRACT FROM AUTHOR]

The application of the intramolecular Pauson-Khand reaction of 1,n-enynes provides a convenient method for the construction of polycyclic frameworks but this process has largely been limited to the formation of 5,5- and 5,6-fused ring systems. In this report, we describe the application of the Pauson-Khand cyclization to 1,8-enynes embedded in an aromatic ring system wherein it is determined that the presence of steric buttresses in the form of t -butyl groups facilitates the cycloaddition. These reactions proceed in good yields with either thermal or oxidative activation and in the former case, the diastereoselectivities are high. An investigation of the tolerance of this cycloaddition to substitution around the 1,8-enyne demonstrates that only 2,2-disubstitution does not result in productive cyclization. Cycloadditions with hydroxyl groups at the propargylic position while leading to fused rings are compromised by side reactions leading to reduction and in some cases tautomerization. However, these byproducts are easily minimized through conversion of the hydroxyl group to the corresponding silyl ether. [ABSTRACT FROM AUTHOR]

Various spiroindenyl-2-oxindoles have been synthesized in a one-pot reaction from isatin-derived propargylic alcohols with sterically hindered and electron-rich arenes such as 2-phenylindole and 1,3,5-trimethoxybenzene. The reaction involved montmorillonite K-10-catalyzed tandem Friedel-Crafts alkenylation and a following hydroarylation of an allene intermediate. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of hitherto hypothetical AuIII π-alkyne complexes is reported. Bonding and stability depend strongly on the trans effect and steric factors. Bonding characteristics shed light on the reasons for the very different stabilities between the classical alkyne complexes of PtII and their drastically more reactive AuIII congeners. Lack of back-bonding facilitates alkyne slippage, which is energetically less costly for gold than for platinum and explains the propensity of gold to facilitate C−C bond formation. Cycloaddition followed by aryl migration and reductive deprotonation is presented as a new reaction sequence in gold chemistry. [ABSTRACT FROM AUTHOR]

To release the steric-strain in largely fused molecular backbone and achieve the much planar molecules for efficient organic solar cells, a facile method was proposed by dividing the rigidly fused dibenzosexithiophene (DBST) units in FT3 with large molecular skeletons to two smaller building blocks to construct the electron donor-acceptor type compound FT4. As observed, much improved molecular co-planarity was achieved for FT4 in contrast to that of FT3, then leading to the higher charge carrier mobilities up to 6.7 × 10 −4 cm 2 V −1 s −1 by SCLC method. Meanwhile, FT4-based BHJ solar cells also exhibited much enhanced photovoltaic performance with the maximum PCE value of 3.07% and higher J sc value of 8.23 mA/cm 2 , which is only 2.13% and 5.67 mA/cm 2 for FT3-based solar cells. The results here indicated that the strain-released method, especially in the highly fused molecules, is beneficial to further improve their co-planarity, then leading to the high charge carrier mobilities and much enhanced photovoltaic performance in solar cells. [ABSTRACT FROM AUTHOR]