OCF3 Groups Research Articles

Enhancing Van der Waals Interactions of Functionalized UiO-66 with Non-polar Adsorbates: The Unique Effect of para Hydroxyl Groups.

UiO-66 is a highly stable metal-organic framework (MOF) that has garnered interest for many adsorption applications. For small, nonpolar adsorbates, physisorption is dominated by weak Van der Waals interactions limiting the adsorption capacity. A common strategy to enhance the adsorption properties of isoreticular MOFs, such as UiO-66, is to add functional groups to the organic linker. Low and high pressure O2 isotherms were measured on UiO-66 MOFs functionalized with electron donating and withdrawing groups. It was found that the electron donating effects of -NH2 , -OH, and -OCF3 groups enhance the uptake of O2 . Interestingly, a significant enhancement in both the binding energy and adsorption capacity of O2 was observed for UiO-66-(OH)2 -p, which has two -OH groups para from one another. Density functional theory (DFT) simulations were used to calculate the binding energy of oxygen to each MOF, which trended with the adsorption capacity and agreed well with the heats of adsorption calculated from the Toth model fit to multi-temperature isotherms. DFT simulations also determined the highest energy binding site to be on top of the electron π-cloud of the aromatic ring of the ligand, with a direct trend of the binding energy with low pressure adsorption capacity. Uniquely, DFT found that oxygen molecules adsorbed to UiO-66-(OH)2 -p prefer to align parallel to the -OH groups on the aromatic ring. Similar effects for the electron donation of the functional groups were observed for the low pressure adsorption of N2 , CH4 , and CO2 .

Effect of the CF3 Substituents on the Charge-Transfer Kinetics of High-Efficiency Cyclometalated Ruthenium Sensitizers.

Six thiocyanate-free complexes, DUY1-DUY6, were synthesized, and their application in a dye-sensitized solar cell was studied to explore the effect of the CF3 substituent positioned in the ancillary ligand and the structure of the anchoring ligand on the physicochemical properties, charge-transfer kinetics, and photovoltaic properties of ruthenium sensitizers. When the electron-withdrawing groups were installed on the cyclometalating ligands and their π conjugation of the ancillary ligand was extended, the frontier orbital energy levels of the ruthenium complex appeared to be sufficient for effective electron injection and dye regeneration, at the same time having high light-harvesting ability. Two electron-withdrawing CF3 groups meta to the cyclometalated position reduce the electron density at the metal center less seriously than o-CF3 and p-CF3 groups. The sensitizers containing a m-CF3 group also reveal a more favorable distribution of β lowest unoccupied spin orbital for interaction between the oxidized dyes and the iodide ion, which promotes dye regeneration. The absorption profiles of DUY1-DUY4 adsorbed a TiO2 film extended to longer wavelength compared to those in an N,N-dimethylformamide solution, especially DUY1 and DUY2 dyes, which have λmax red shifts of up to 30 nm. The DUY2-dyed cell exhibited the highest efficiency of 9.03%, while the power conversion efficiencies of DUY1-, DUY3-, DUY4-, and N719-based devices were 7.40%, 7.01%, 8.92%, and 8.63%, respectively. DUY5 and DUY6 (the side products of DUY3 and DUY4) without anchoring groups have very weak physical adsorption on a TiO2 anode. The corresponding cells exhibit very low efficiency (<0.1%), although both dyes have high light-harvesting ability and proper frontier orbital energy levels.

ChemInform Abstract: New Entries Toward the Synthesis of OCF3‐Containing Molecules

AbstractReview: 25 refs.

New entries toward the synthesis of OCF3-containing molecules

The OCF3 group is of high interest in the quest for new drugs and agrochemicals, thanks to its atypical features. This Highlight article depicted the recent and impressive advances toward the synthesis of OCF3-containing molecules.

Computer-aided scaffold hopping to identify a novel series of casein kinase 1 delta (CK1d) inhibitors for amyotrophic lateral sclerosis

In this study as the first attempt; comparative molecular field analysis (CoMFA), comparative molecular similarity indices analysis (CoMSIA) and AutoGPA-based 3D-QSAR methods were applied on a set of 47 recently reported Ck1d inhibitors, in order to gain an insight into the structural requirements which providing guidelines for the design of next generation compounds with enhanced bioactivity. The results of 3D-QSAR analyses indicated that hydrophobic and negatively charged groups at 6th position of benzothiazole ring and positively charged and bulky groups at ortho position of phenyl ring are favorable for high activity. Moreover, molecular docking studies with GOLD protocol revealed that this chemical series has two different orientations in CK1d active site: orientation 1, in which the benzothiazole ring of the compounds is the closet to the hydrophobic area created by Ile23 and 37, Ala36 Lys 38, Met80, 82 and Val81, and orientation 2, in which the benzene ring of the compounds is directed toward the hydrophobic center. Molecular docking result of the riluzole, the only drug approved by FDA for amyotrophic lateral sclerosis (ALS), indicated that the orientation 2 is preferred due to the presence of OCF3 group in R1 situation at 6th position of benzothiazole ring, while with replacement of OCF3 group by CF3, the orientation 1 is observed. At the end, to find similar analogs by virtual screening, a two-stage approach: pharmacophore-based screening using generated AutoGPA-based 3D-QSAR model followed by structure-based virtual screening using molecular docking was employed. Visual inspection of the docking results of virtually obtained hits revealed two different binding orientations, in which compounds with high GOLD fitness scores produced binding modes, which were the same as the one observed in compounds with orientation 1, whereas the binding modes of the structures with low GOLD fitness scores were in agreement with orientation 2. Further, the drug-like properties of the obtained seven hits with the highest GOLD scores were investigated as a tool to optimize the selection of the most suitable candidates for drug development.

Aryl-BIAN-ligated silver(I) trifluoromethoxide complex.

A reaction of acetonitrile-solvated AgOCF3 with 1 equiv. of Aryl-BIAN ligand in THF at room-temperature afforded the silver(i) complex (Aryl-BIAN)AgOCF3 (1) in 75% yield. The crystal structure of this silver(i) trifluoromethoxide was determined by single-crystal X-ray crystallography. The molecular structure of 1 shows the metal centre bound to one molecule of BIAN, one trifluoromethoxide and one THF solvate, resulting in a distorted tetrahedral silver. Density functional theory (DFT) calculations and the natural bond orbital (NBO) analysis were conducted to give insights into the electronic structure of 1 and the bonding characters of the OCF3 group. The reactivity of 1 towards trifluoromethoxylation of organic halides was also examined; a reaction with benzyl bromides gave the desired products of benzyl trifluoromethyl ethers in good to excellent yields.

Trifluoromethyl Ethers and –Thioethers as Tools for Medicinal Chemistry and Drug Discovery

The ever-growing number of fluorinated compounds in medicinal and agrochemical applications has led to a remarkable positive emulation in research. The last few years have been the witness of several advances in the search of more effective and user-friendlier methods for the introduction of fluorine as substituent or of fluorinated groups on various structures. In particular, the synthesis of trifluoromethyl ethers and thioethers is receiving increasing attention due to the peculiar properties of the OCF3 and SCF3 groups. This review will cover the different methods for the preparation of trifluoromethyl ethers and thioethers, and will emphasize on the most recent developments, including the use of catalytic methods or of methodologies for trifluoromethylation or trifluoromethanesulfanylation.

Substituent-controlled preference of carbonyl group–metal coordination in d8metal complexes with non-symmetric pentadentate ligands. Structural and stereochemical aspects

Chirally switchable Ni(II) and Pd(II) complexes were synthesized and fully characterized by X-ray crystallography and additionally by spectroscopic means (NMR and MS). The syntheses and characterization of their ligands are also reported. It was found that control of the stereochemical preference between (S*,S*) and (S*,R*) diastereomers by substituent modification of the ligand sidearms was possible in the solid state with the preferred atomic coordinations of the sidearms consistent with expectations based on the electron-withdrawing properties of the substituent -o-CF3 group. The dilemma arising in terms of assigning the absolute configuration descriptors resulting from selecting between strictly following only the covalent bonds of the ligand and disregarding the nature of the bonds altogether and thus bringing the coordinate bonds into consideration to determine the stereochemical priority sequence is hereby resolved by declaring that the latter option is to be preferred. The results obtained here provide a clear indication that sidearm substitution of the Ni(II) and Pd(II) complexes need not disturb macromolecular stereochemical arrangements leading to quasidiastereomeric relationships. This permits the design of molecular systems sensitive to external stimuli with predictable macromolecular structure.

Investigation of the Physical Properties of Poly(ortho‐ and para‐trifluoromethoxy styrenes)

AbstractOrtho and para ‐OCF3 substituted styrenes are prepared by the Grignard cross‐coupling reaction between ‐OCF3 substituted bromobenzene and vinyl bromide and further polymerized in bulk using benzoyl peroxide. The glass‐transition temperatures (Tg) are 80 °C and 73 °C for the ortho and para –OCF3 substituted polystyrenes, respectively, which are much lower compared with polystyrene (100 °C). The size of the ‐OCF3 group is large and the ether bond is flexible; thus, the ‐OCF3 substituted polystyrenes have larger free volumes, which has more effect on the Tg value compared with that of the steric hindrance effect. The refractive indices are 1.4908 and 1.4809 at 650 nm for ortho and para –OCF3 substituted polystyrenes, respectively, which are much lower than that of polystyrene (1.5861) due to the presence of fluorine atoms in the polymer unit. magnified image

Enantioselective hydrogenation of tiglic acid in methanol and in dense carbon dioxide catalyzed by a ruthenium–BINAP complex substituted with OCF3 groups

Abstract A fluorinated analog of the 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (BINAP) ligand was synthesized with OCF 3 -substitution of the aryl groups in BINAP skeleton ( p -OCF 3 –BINAP). Ruthenium complexes of both BINAP (Ru–BINAP) and ( p -OCF 3 )–BINAP (Ru–[( p -OCF 3 )–BINAP]) were also synthesized and investigated as catalysts for hydrogenation of tiglic acid in methanol. Typically, Ru–[( p -OCF 3 )–BINAP] had lower activity but had higher enantioselectivity at high hydrogen pressures than Ru–BINAP at the same condition. The effect of OCF 3 groups on the catalytic properties was discussed on the basis of NMR spectra and kinetic data. Ru–[( p -OCF 3 )–BINAP] was found to have sufficiently high solubility in dense CO 2 for homogeneous catalytic reactions and was investigated for hydrogenation of tiglic acid in CO 2 . The results showed that CO 2 had a great influence on both activity and enantioselectivity. Addition of methanol to CO 2 was found to increase the enantioselectivity.

Acidity of Substituted Benzenes − An Ab Initio Study of the Influence of Methoxy, Trifluoromethyl and Trifluoromethoxy Groups by a Novel Trichotomy Formula

AbstractThe acidities of mono‐ and polysubstituted benzenes incorporating one, two, or three OCH3, OCF3, or CF3 groups were investigated by use of reliable ab initio theoretical models. The calculated deprotonation energies are in very good agreement with available experimental data, although these are unfortunately sparse. A recently developed novel trichotomy formula proved useful for interpretation of predicted variation in acidity in the monosubstituted compounds. In particular, the long‐range final state effect in OCF3 and CF3 derivatives is confirmed. It is reflected in the stabilization of the lone‐pair electrons formed upon deprotonation at the meta and para positions. The theoretically established long‐range influence of OCF3 and CF3 substituents is in accordance with empirical knowledge obtained by experimental chemical reactivity studies. The acidities of multiply substituted benzenes exhibit additivity properties based on the ISA (independent substituent approximation) model established earlier. It is conclusively shown that the combination of the additivity rule and the trichotomy formula offers a powerful tool for interpretation of the acidity of polysubstituted benzenes and of other multiply substituted aromatics, thus shedding new light on this very old and important problem. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2003)

The synthesis and characterisation of some Group 14 compounds containing the 2,4,6-(CF3)3C6H2, 2,6-(CF3)2C6H3 or 2,4-(CF3)2C6H3 ligands

New (aryl)2ECl2 and (aryl)ECl3 compounds [E = Si, Ge or Sn; aryl = 2,4,6-(CF3)3C6H2 (Ar), 2,6-(CF3)2C6H3 (Ar′) and/or 2,4-(CF3)3C6H3 (Ar″)] were prepared by reactions of ECl4 with 2 equivalents of ArLi or of a Ar′Li/Ar″Li mixture. The latter gives predominantly the less sterically hindered product Ar″2ECl2 for E = Si or Ge, but Ar′2SnCl2 for the larger central atom. The products were characterised by elemental analysis, 19F and (where appropriate) 119Sn NMR spectroscopy, and single-crystal X-ray diffraction for Ar″2SiCl2, ArGeCl3, Ar2GeCl2, Ar″2GeCl2, Ar2SnCl2 and Ar′2SnCl2. For E = Si the synthesis is complicated by Cl/F exchange: besides Ar′2SiCl2 and Ar″2SiCl2, 19F NMR spectroscopy identified in solution Ar″2SiF2 and Ar′2SiF2. The latter was isolated and its X-ray structure determined. In all compounds, the E atom has a strongly distorted tetrahedral coordination, supplemented by short intramolecular E⋯F contacts (secondary coordination) with o-CF3 group(s).

Trifluoromethoxy benzene in the gas phase studied by electron diffraction and spectroscopy supplemented with ab initio calculations

Trifluoromethoxybenzene (TFMB) can occur in a conformation with the OCF3 group in the plane of the phenylgroup ([e]-form) and with the OCF3 group perpendicular to the phenyl plane ([o]-form). Ab initio calculations on the MP2/6-31G∗∗ level give the [o]-form as the energy minimum with the [e]-form as the top of the rotation barrier about 1.4kcal/mol above the [o]-minimum. In contrast, DFT calculations on the B3LYP/cc-pvtz level give the [e]- and [o]-forms as energy minima with a small (<0.3kcal/mol) energy difference and a small (<0.5kcal/mol) barrier between them. Extensive vibrational spectroscopic studies (IR and Raman) of the gaseous, the liquid and the solid (glass and crystal) state gave evidence of TFMB occurring in the gas phase, and in the liquid and amorphous solid as a mixture of [o]- and [e]-forms. In the crystal (annealed at 155K) the [o]-form dominates.Electron diffraction intensities of the gas, fitted to a dynamic model, resulted for room temperature in the ratio [o]/[e]=70%/30%, i.e. the [o]-form being 0.4kcal/mol more stable than the [e]-form with a barrier of 2.8kcal/mol between them.

Ruthenium-Catalyzed Addition of Carbon–Hydrogen Bonds in Aromatic Ketones to Olefins. The Effect of Various Substituents at the Aromatic Ring

Abstract To obtain further insight into the new ruthenium-catalyzed reaction of carbon–hydrogen bonds in aromatic ketones with olefins, the effect of various substituents at the aromatic ring is examined. Reaction of o-methylacetophenone with triethoxyvinylsilane (2) in the presence of [Ru(H)2(CO)(PPh3)3] (3)as the catalyst gave the 1 : 1 addition product in quantitative yield. Similarly, the ketone having an o-CF3 group gave the coupling product 9 in 92% yield. However, ortho substituents such as OMe, F, and CN, seem to react with and kill the catalyst so that no efficient reaction was attained. In the cases of the reactions of p-methoxy- and p-fluoroacetophenones with 2, the corresponding 1 : 2 addition products were obtained as the major products. In the cases of m-substituted acetophenones, two different C–H bonds at the ortho positions are available. The C–C bond formation preferentially occurred at the sterically less congested positions. Exceptions are the reactions of m-methoxy- and m-fluoroacetophenones, in which the C–C bond formation took place preferentially at the more congested position. This may be due to the coordination of oxygen or fluorine atom to ruthenium. The factors controlling these selectivities are discussed.

Random fluorinated copolymers of tetrafluoroethylene: a study of the inclusion/exclusion of defects from the crystal by conformational and packing energy calculations

AbstractA conformational analysis has been performed on the isolated chains of copolymers of tetrafluoroethylene with hexafluoropropene, chlorotrifluoroethylene or perfluoromethyl vinyl ether, in comparison with polytetrafluoroethylene. The lowest energy conformations in accordance with the chain repeating distance of polytetrafluoroethylene in the low temperature crystal phase have been used in packing energy calculations. The results of both conformational and packing energy calculations suggest that the Cl group is easily tolerated in the crystal phase. The —CF3 group could also be tolerated in the crystal phase but at the cost of conformational and crystal lattice deformations. On the contrary, it can be concluded that the —OCF3 group is excluded from the crystal phase because its presence should require high energy values and wide deformations in the unit cell parameters.

A study of the infrared spectra of aryl trifluoromethyl ethers

1. The infrared spectra of seven aryl trifluoromethyl ethers have been obtained and the attribution of the trifluoromethoxy group absorption is discussed. The intense 1262±5 cm−1 (υCarom), 1178±10 cm−1 (νC-F), 1222±4 cm−1 (νc-f), and 925 cm−1 bands can be used in analysis for determining the presence of an OCF3 group in the benzene ring. 2. The shifts in the frequencies of theC-F valence vibrations show that transmission of the electron effects of the para substituent on the C-F bond via the ring-heteroatom system diminishes in the order-S->-O->-SO2-.

Investigation of the infrared spectra and polar effects in para-derivatives of benzene containing SCF3, SOCF3, SO2CF3 and OCF3 groups

Investigation of the infrared spectra and polar effects in para-derivatives of benzene containing SCF3, SOCF3, SO2CF3 and OCF3 groups

Fluorine-19 Contact Interaction Shifts: The CF3, OCF3, SCF3, SF5, and SO2CF3 Groups

<b>Fluorine-19 Contact Interaction Shifts: The CF₃, OCF₃, SCF₃, SF₅, and SO₂CF₃ Groups</b>