THF Solvent Molecule Research Articles

Tetra-aqua-dodekakis-μ2-chlorido-di-iodido-octa-hedro-hexa-niobium(12 Nb-Nb) tetra-hydro-furan octa-solvate.

The title compound, [Nb6Cl12I2(H2O)4]·8THF (THF is tetra-hydro-furan, C4H8O), comprises an uncharged niobium cluster unit surrounded by THF solvent mol-ecules. The edges of the {Nb6} octa-hedron are μ 2-coordinated by twelve chlorido ligands. Four in-plane (equatorial plane) aqua ligands and two iodido ligands coordinating above and below the plane are bound at the corners of the {Nb6} atomic octa-hedron. O-H⋯O hydrogen bonds are formed between the aqua ligands and the THF solvent mol-ecules; one THF molecule is disordered over two positions with the major component having a site occupancy of 0.64 (2).

Crystal structure of bromido-penta-kis-(tetra-hydro-furan-κO)magnesium bis-[1,2-bis-(di-phenyl-phosphan-yl)benzene-κ2 P,P']cobaltate(-1) tetra-hydro-furan disolvate.

Structural characterization of the ionic title complex, [MgBr(THF)5][Co(dpbz)2]·2THF [THF is tetra-hydro-furan, C4H8O; dpbz is 1,2-bis-(di-phenyl-phosphan-yl)benzene, C30H24P2], revealed a well-separated cation and anion co-crystallized with two THF solvent mol-ecules that inter-act with the cation via weak C-H⋯O contacts. The geometry about the cobalt center is pseudo-tetra-hedral, as is expected for a d 10 metal center, only deviating from an ideal tetra-hedral geometry because of the restrictive bite angles of the bidentate phosphane ligands. Three THF ligands of the cation and one co-crystallized THF solvent mol-ecule are each disordered over two orientations. In the extended structure, the cations and THF solvent mol-ecules are arranged in (100) sheets that alternate with layers of anions, the latter of which show various π-inter-actions, which may explain the particular packing arrangement.

Me6TREN-Supported Alkali Metal Hydridotriphenylborates [(L)M][HBPh3] (M = Li, Na, K): Synthesis, Structure, and Reactivity

Triphenylborane (BPh3) abstracted the β-SiH in [(L)M{N(SiHMe2)2}] (L = Me6TREN; M = Li, Na, K) in THF to give the hydridotriphenylborates [(L)M][HBPh3]. Reactions in benzene favored silazide instead of hydride abstraction to give [(L)M][Ph3B–N(SiHMe2)2]. The hydridotriphenylborates [(L)M][HBPh3] catalyzed the chemoselective hydroboration of benzophenone by pinacolborane (HBpin), with the lithium derivative being the most active. The solution structure of [(L)Li][HBPh3] was qualitatively investigated in the context of its superior catalytic activity. Fluxional coordination of L in [(L)Li(THF)]+ in tandem with a THF solvent molecule was revealed by NMR spectroscopy. para-Substituents in [HB(C6H4-p-X)3]− influenced the rate which is apparently determined by the addition of the B–H function to the isolable alkoxy borate intermediate [(L)Li][Ph2CHOBPh3].

Emission Tuning of Luminescent Copper(I) Complexes by Vapor-Induced Ligand Exchange Reactions.

We have synthesized two luminescent mononuclear Cu(I) complexes, [Cu(PPh2Tol)(THF)(4Mepy)2](BF4) (1) and [Cu(PPh2Tol)(4Mepy)3](BF4) (2) (PPh2Tol = diphenyl(o-tolyl)phosphine, 4Mepy = 4-methylpyridine, THF = tetrahydrofuran), and investigated their crystal structures, luminescence properties, and vapor-induced ligand exchange reactions in the solid state. Both coordination complexes are tetrahedral, but one of the three 4Mepy ligands of complex 2 is replaced by a THF solvent molecule in complex 1. In contrast to the very weak blue emission of the THF-bound complex 1 (wavelength of emission maximum (λem) = 457 nm, emission quantum yield (Φem) = 0.02) in the solid state at room temperature, a very bright blue-green emission was observed for 2 (λem = 484 nm, Φem = 0.63), suggesting a contribution of the THF ligand to nonradiative deactivation. Time-dependent density functional theory calculations and emission lifetime measurements suggest that the room-temperature emissions of the complexes are due to thermally activated delayed fluorescence from the metal-to-ligand charge transfer excited state. Interestingly, by exposing the solid sample of THF-bound 1 to 4Mepy vapor, the emission intensity drastically increased and the emission color changed from blue to blue-green. Powder X-ray diffraction measurements revealed that the emission change of 1 is due to the vapor-induced ligand exchange of THF for 4Mepy, forming the strongly emissive complex 2. Further emission tuning was achieved by exposing 1 to pyrimidine or pyrazine vapors, forming green (λem = 510 nm) or orange (λem = 618 nm) emissive complexes, respectively. These results suggest that the vapor-induced ligand exchange is a promising method to control the emission color of luminescent Cu(I) complexes.

Optical Dedoping Mechanism for P3HT:F4TCNQ Mixtures.

Doping-induced solubility control (DISC) is a recently introduced photolithographic technique for semiconducting polymers, which utilizes reversible changes in polymer solubility upon doping to allow the polymer to function as its own photoresist. Central to this process is a wavelength sensitive optical dedoping reaction, which is poorly understood but generates subdiffraction-limited topographic features and provides optical control of the polymer doping level. Here, we examine the mechanism of optical dedoping in the semiconducting polymer poly-3-hexylthiophene (P3HT) doped by 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), via a combination of ultrafast and steady-state spectroscopy, ab initio calculations, and multidimensional NMR. A simple photoinduced back electron transfer mechanism from reduced F4TCNQ to oxidized P3HT does not explain the observed photophysics. Instead, photoexcited F4TCNQ* reacts with THF solvent molecules to form a neutral, nondoping, and highly soluble F4TCNQ-THF complex. Hence, ionized F4TCNQ is removed from the P3HT indirectly by depletion of the neutral F4TCNQ. Because the reaction involves only the dopant and similar photoreactivity would expected for most other dopant molecules, we expect optical DISC patterning should be generalizable to a wide range of polymer:dopant systems.

Supramolecular Assembly of Tris(4-carboxyphenyl)arenes: Relationship between Molecular Structure and Solid-State Catenation Motifs

The crystal structures of seven 1,3,5-tris(4-carboxyphenyl)arenes with functionalized central arene rings are reported. The formation of (6,3) hcb hexagonal sheets as a result of carboxylic acid dimer formation was observed in most of the crystal structures, with the exception of two compounds with functional groups capable of forming hydrogen bonds, namely, 2,4,6-tris(4-carboxyphenyl)-1,3-diaminobenzene and 2,4,6-tris(4-carboxyphenyl)-3-methylaniline. These structures were found to incorporate THF solvent molecules in their hydrogen-bonding motif, giving rise to distorted pseudohexagonal arrays. Functional groups on the central ring were found to influence stacking distances, stacking offsets, inclination angles, degree of catenation, and dimensions of solvent-occupied channels. To better understand and appreciate these complicated crystal structures, they were categorized into four distinct stacking/catenation families: simple stacking, single-layer offset catenation, double-layer offset catenation, and...

A novel 2D porous Cd(II) MOF with a (4,4) connected binodal network: Synthesis and photoluminescence sensing of small molecules

A novel cadmium metal organic framework, {[Cd(L)(H2O)]∙THF}n (1), has been synthesized solvothermally using a newly synthesized ligand (L=4-(((1 H-imidazol-2-yl)methylene)amino)benzoic acid). Complex 1, is a 3D supramolecular framework having 2D hydrogen bonded undulated sheets. The network contains solvent accessible void volume of 34.0% which is occupied by THF solvent molecules. The compound exhibits a (4,4) connected binodal network. Solid state photo luminescent property of 1 in different solvents has also been investigated which demonstrate distinct solvent dependent luminescent spectra.

Synthesis and characterization of some new fluoroquinolone-barbiturate hybrid systems

Abstract New hybrid molecules containing fluoroquinolone-barbiturate moieties were synthesized via simple routes, followed by characterization using various spectroscopic approaches. The THF solvent molecule was incorporated into compounds 2 and 3 through its oxygen atom based on its nucleophilicity. Facile displacement of the chloride ion in 4-oxoquinoline-3-carbonyl chloride by the nucleophilic methylene carbon of 1,3-dialkylbarbiturate/thiobarbiturate afforded the respective hybrids 5 and 6.

Synthesis and structural analysis of formamidinate-supported Mg complexes

Reactions of 2-mesitylmagnesium bromide with N,N′-diarylformamidines afforded five Mg compounds [(DPhF)Mg(THF)2]2(μ-Br)2 (1), [D(3,5-Xyl)F]2Mg(THF)2 (2), [D(2,6-Xyl)F]2Mg(THF) (3), [D(2-iPrPh)F]MgBr(THF)3 (4), and [D(2-tBuPh)F]2Mg(THF) (5). Complexes 1, 2 and 4 displayed monomeric octahedral metal centers supported by formamidinates, bromide counter anions, and coordinating THF solvent molecules, while the metal cores in 3 and 5 were five-coordinated and in distorted square-pyramidal geometries. Detailed structural analysis indicated that only dimagnesium or mononuclear complexes were obtained through the use of formamidinate ligands. Ligands of increased steric demands resulted in the formation of monomeric complexes. Solvent molecules and counter anions that can coordinate to the metal cores further regulated the product conformation. Monoanionic formamidinates in the complexes, mostly featuring two nearly identical N–C bonds on the N–C–N backbone upon complexation, exhibited a symmetric bidentate chelating (η2) coordination mode.

Synthesis, Characterization, and Theoretical Investigation of Two-Coordinate Palladium(0) and Platinum(0) Complexes Utilizing π-Accepting Carbenes.

An elegant general synthesis route for the preparation of two coordinate palladium(0) and platinum(0) complexes was developed by reacting commercially available tetrakis(triphenylphosphine)palladium/platinum with π-accepting cyclic alkyl(amino) carbenes (cAACs). The complexes are characterized by NMR spectroscopy, mass spectrometry, and single-crystal X-ray diffraction. The palladium complexes exhibit sharp color changes (crystallochromism) from dark maroon to bright green if the C-Pd-C bond angle is sharpened by approximately 6°, which is chemically feasible by elimination of one lattice THF solvent molecule. The analogous dark orange-colored platinum complexes are more rigid and thus do not show this phenomenon. Additionally, [(cAAC)2 Pd/Pt] complexes can be quasi-reversibly oxidized to their corresponding [(cAAC)2 Pd/Pt](+) cations, as evidenced by cyclic voltammetry measurements. The bonding and stability are studied by theoretical calculations.

Group 4 Lanthanide and Actinide Organometallic Inclusion Complexes

Reaction of the f-element complexes ThCl4(THF)3, Cp*2Sm(μ-Cl)2MgCl(THF)2, NdCl3, Cp*2UMe2, and Cp*2ZrMe2 with an excess of catecholborane (HBCat) yields macrocyclic complexes where the metal is encapsulated inside a 15-membered, hexaoxo, trianionic macrocycle built from alternating catechol and catecholborate fragments. With ThCl4(THF)3 as the starting material, the reaction produced a macrocyclic complex with one chloride ligand and three solvent molecules in the apical positions; however, for the zirconium and uranium complexes the apical positions are occupied by one C5Me5 ligand and a THF solvent molecule. In the samarium and neodymium complexes, only solvent molecules occupy the apical positions. Transmetalation of the ligand among different complexes in refluxing THF were performed. When the zirconium macrocycle was treated with a slight excess of ThCl4 or NdCl3, the corresponding (η2-catechol-μ-catecholborate)3ThCl(C4H8O)3·C4H8O (2) and (η2-catechol-μ-catecholborate)3Nd(C4H8O)3·C4H8O (4) macrocycles were obtained in 87% and 79% yields, respectively. In addition, the reaction of the samarium macrocycle complex (η2-catechol-μ-catecholborate)3Sm(C4H8O)3·C4H8O (3) with a slight excess of ThCl4 allowed the formation of complex 2 in 76% yield. While some of the pentamethylcyclopentadienyl (Cp*)-containing inclusion complexes were found to be catalytically inactive in the polymerization of ε-caprolactone, the lanthanides and thorium complexes were found to be active, yielding only short chains of polycaprolactone. The X-ray molecular structures for all of the complexes are presented and discussed. Experiments performed with Cp*2ThMe2 and catecholborane allowed us to trap the intermediate Cp*(H)BH2BH2 complex, which was trapped in situ and characterized by 11B NMR, allowing us to propose a possible mechanism for the formation of the macrocycle.

Highly constrained guests in complexes of p-tert-butylcalix[6]arene dianion: Pentane-1,5-diammonium and choline

The structures of the complexes of choline and pentane-1,5-diammonium with p-t-bu-calix[6]arene dianion were determined. Both salts display the calixarene moiety at 1,2,3-alternate conformation, with two concave surfaces formed by three aromatic rings, and the phenolate units are at distal positions, interacting with two phenol units by hydrogen bonds.The salt of pentane-1,5-diammonium shows the diammonium connecting both calixarene dianion units, and one NH3+ is located endo-calix position and the other occupies an exo-calix position. The t-butyl groups and the calix cavity constrains the pentane-1,5-diammonium chain to near syn-eclipsed and gauche conformations. The other semi-calix accomodates a THF solvent molecule. The salt of choline shows the trimethylammonium groups of choline units immersed in these concave surfaces, with several interactions N+–C–H---π interactions with the aromatic semi-cavities.

Catenar bimetallomesogens derived from quinoxaline–salicylaldimine conjugates

The preparation, characterization, and mesomorphic properties of two series of tridentate N-salicylidene-2-hydroxyanilines and their metal complexes were described. The crystal and molecular structure of bis[2-hydroxy-4-propyloxy-N-(2-hydroxy-3,4-dipropyloxybenzylidene) aniline]copper(II) were determined by means of X-ray analysis. It crystallizes in the monoclinic space group P2(1)/n and a Z=4. The geometry at Cu2+ ions is square pyramidal with a THF solvent molecule coordinated. The core structure was nearly flat, and the intramolecular Cu–Cu atoms were separated by ca. 3.0163(6) Å. All compounds 2a formed smectic C phases, and copper complexes 1a–Cu were not mesogenic. In contrast, compound 2e and complexes 1b–Cu, 1d–Cu, 1e–Cu, and 1e–Pd exhibited columnar phases. The lack of mesomorphism in 1e–Zn was attributed to a preferred tetrahedral over square planar geometry. A Ncell equal to 2.44–2.92, calculated from powder XRD data within a 9.0 Å thick indicated that an induced structure correlated by two catenar-shaped molecules was formed in Colh phases.

Deprotonation of a hydrophosphorane and synthesis of the Ni(II) metallophosphorane [NiCl{P(OC6H4N(CH3))2}(P(CH3)3)2

The hydrophosphorane [HP(OC6H4N(CH3))2] has been deprotonated using lithium tetramethylpiperidide to produce Li[P(OC6H4N(CH3))2] (1). Compound 1 reacts further with NiCl2(PMe3)2 to form the Ni(II) phosphoranide complex [NiCl{P(OC6H4N(CH3))2}(P(CH3)3)2] (2). The crystal structures of both 1 and 2 were determined. The structure of 1 is dimeric with bridging lithium cations and also features one THF solvent molecule coordinated to each lithium cation; the geometry about the lithium atom is tetrahedral. The structure of 2 displays tetrahedral distortion from an idealized square-planar geometry. Both 1 and 2 characterized by 1H and 31P NMR, with 13C NMR for 2 also. DFT calculations (B3LYP/6-311++G(2df,2p)) were also done on 2; both the NMR and DFT studies indicate π-donation from the metal to the pentacoordinate phosphorus.

Effects of External Electric Field and Self-Aggregations on Conformational Transition and Optical Properties of Azobenzene-Based D-π-A Type Chromophore in THF Solution

The influence of environments (THF solvents and electric field) and molecular self-aggregations on the structure and optical properties of 4-(4-hydroxyphenylazo)nitrobenzene has been investigated by molecular dynamics (MD) simulations and quantum chemical calculations. Long-range electrostatic effects and the hydrogen bond interactions between the solute and the THF solvent molecules lead to the augments of nonlinear optical (NLO) response by about two times from the gas phase to THF solution, accompanied by considerable red-shift of more than 40 nm in the maximum absorption wavelengths of the ground (S(0)) and low-lying excited states (S(1), S(2), and S(3)). The solvated chromophore reorients quickly (within 300 ps) under external electric field of 1.0 V/nm, even when the direction of the applied electric field is antiparallel to the dipole moment of the solute. Nonequilibrium MD simulations demonstrate that the light-induced cis-trans isomerization in THF solution and external electric field need longer relaxation time (about 1.0 ps) than that in gas phase (about 500 fs). The dipole-dipole interactions and intermolecular hydrogen bonds facilitate the self-aggregations of solute molecules in solution. The V-shaped dimer exhibits higher hyperpolarizability value by about 1.2 times of the monomer, whereas the antiparallel alignment leads to a cancellation of dipole moment and hence dramatic decrease in hyperpolarizability (one-third of the monomer). However, the Boltzmann-weighted contribution to hyperpolarizability from these two aggregations (with 82% V-shaped and 18% antiparallel) is close to that of the monomer. Orientations of D-π-A dipoles in various environments and molecular aggregations are important to modulate the optical properties of materials.

1H NMR study of the solvent THF concerning their structural and dynamical properties in chemically Li-intercalated SWNT

Abstract Structural and dynamical properties of the THF solvent in single-walled carbon nanotubes intercalated with lithium are investigated by NMR. 1 H NMR experiments reveal the existence of two types of inequivalent THF solvent molecules with different chemical environments and dynamical behavior. At low temperatures THF molecules perpendicularly arranged in between adjacent SWNT presumably exhibit a restricted rotation around their dipolar axis. At higher temperatures THF molecules are isotropically rotating and diffusing along the interstitial channels of the SWNT bundles.

Metal−Metal Multiple Bonds in Early/Late Heterobimetallics Support Unusual Trigonal Monopyramidal Geometries at both Zr and Co

Reduction of Zr/Co heterobimetallic complexes ICo(MesNP(i)Pr(2))(3)ZrCl (1) and ICo((i)PrNP(i)Pr(2))(3)ZrCl (2) with excess Na/Hg under N(2), followed by subsequent benzene extraction to remove coordinated Na halide salts, leads to neutral two-electron reduced, dinitrogen-bound complexes (THF)Zr(MesNP(i)Pr(2))(3)Co-N(2) (4) and Zr((i)PrNP(i)Pr(2))(3)Co-N(2) (5). Upon halide loss, a THF solvent molecule coordinates to the axial site of the Zr center in 4, while this axial site remains unoccupied in 5. X-ray crystallography reveals short Co-Zr distances in 4 and 5, indicative of metal-metal multiple bonding, and an unprecedented trigonal monopyramidal geometry about the Zr center in 5. Reduction of 4 under an Ar atmosphere (in the absence of N(2)) results in another unusual structure type: an unoccupied axial Co coordination site and a trigonal monopyramidal Co center in (THF)Zr(MesNP(i)Pr(2))(3)Co (6). X-ray crystallography reveals that, in the absence of coordinated N(2), the Co-Zr bond can attain full triple bond character with a Co-Zr distance of 2.14 A, the shortest M-M distance in an early/late heterobimetallic complex reported to date. To further assess the electronic structure and bonding in 4, 5, and 6, calculations were performed on these molecules using DFT and the results of these theoretical investigations will be discussed.

Dichlorido[tris(1H-benzimidazol-2-ylmethyl)amine-κ4N,N3,N3′,N3′′]iron(III) chloride tetrahydrofuran monosolvate monohydrate

In the title compound, [FeCl2(C24H21N7)]Cl·C4H8O·H2O, the FeIII atom is coordinated by four N atoms of the polybenzimidazole ligand and two Cl atoms in a distorted octa­hedral environment. The cation, anion, the uncoordinated water mol­ecule and the THF solvent molecule are linked by hydrogen bonds into a three-dimensional network structure. The THF molecule is disordered with two sets of sites in a 0.58 (1):0.42 (2) ratio..

A Theoretical Study on nBuLi/Lithium Aminoalkoxide Aggregation in Hexane and THF

Theoretical calculations on aggregation of nBuLi/lithium aminoalkoxide superbases, such as nBuLi/LiDMAE (LiDMAE = Me(2)N(CH(2))(2)OLi) and nBuLi/LiPM (LiPM = Li-N-methyl-2-pyrrolidine methoxide) in gas phase and solution are reported. The combination of equimolar amounts of each component in hexane induced unusual reactivity of the resulting superbase, which remains misunderstood. In order to elucidate the corresponding reaction mechanisms, it is imperative to get a deeper insight into the energetics of aggregation and the effect of the medium on equilibrium constants. In the present study, we compute and compare the stability of (nBuLi)(n), (LiPM)(n), and equimolecular mixed aggregates (nBuLi:LiPM)(n) in gas phase, hexane, and THF. Calculations have been carried out at the density functional theory level (B3LYP/6-31G(d)) using continuum and discrete continuum models of solvation. Higher-level calculations (MP2/aug-ccpVQZ) have been done in some cases for test purposes. Enthalpic and entropic contributions have been discussed and were shown to play an opposite role in hexane (or gas phase) and THF. The characteristics of LiPM and mixed nBuLi/LiPM solutions are found to be significantly different from those of nBuLi solutions. These calculations are in accordance with experimental data in both hexane and THF. Further comparison of theoretical and experimental results for gas-phase Li(+)-THF and Li(+)-DME complexes has enabled a discussion on computational errors for entropic contributions in THF. The value for the release of a THF solvent molecule is proposed to be DeltaS approximately 23 eu. These results provide new insights to the aggregation of organolithium compounds in solution and will be useful for the investigation of other systems.

Crystal Structure of Boryllithium with Two THF Molecules and DFT Analysis of Its Property as a Boryl Anion

Abstract The second crystal structure of boryllithium 2 with two coordinating THF solvent molecules was obtained. The 11B NMR chemical shift of a THF solution, made by dissolving single crystals of 2·(THF)2 in THF-d8, significantly and reversibly changed depending on temperature (from 20 to −100 °C). The calculated 11B chemical shift by GIAO method was close to two experimental values. The character of the sp2 lone pair on the boron center in opt-2·(THF)2 was shown to be similar to those in the calculated free phenyl anion and boryl anion. AIM analyses for opt-2·(THF)2 suggested that the B–Li bond of boryllithium is polarized, similar to the C–Li bond of alkyllithium.