Alkylammonium Complexes Research Articles

Structure of diisopropylammonium dicitratoborate and crystallochemical features of alkylammonium complexes with boric and citric acids

Single crystals of diisopropylammonium dicitratoborate of the formula (C3H7)2NH2[(C6H6O7)2B] (I) were prepared and characterized by X-ray diffraction. The crystals are monoclinic, space group C2/c, a = 15.9978(5) A, b = 11.0805(4) A, c = 13.1872(4) A, α = 90°, β = 103.34(1)°, γ = 90°, Z = 8, V = 2274.5 (1) A 3, Z = 8, ρcalc = 1.440 g/cm3, 2237 reflections with I > 2σ(I); R1 = 0.0408. Structure I is built from complex spiran-type dicitratoborate anions and diisopropylammonium cations. In the crystal packing, the anions and the cations form staggered stacks linked by a system of hydrogen bonds involving three independent contacts O(N)-H...O. X-ray diffraction data for structure I were compared with those for complexes of boric and citric acids with ammonium and alkylammonium cations.

Metal Anion–Alkyl Ammonium Complexes as Direct Write Precursors to Produce Nanopatterns of Metals, Nitrides, Oxides, Sulfides, And Alloys

The study explores the possibility of using metal anions complexed with tetraoctylammonium bromide (ToABr) as single-source direct write precursors in e-beam and soft lithography processes to obtain micro- and nanoscale patterns of various metals, i.e., Au, Pd, Pt, Ag, Pb and Cu, as well as of their alloys (AuCu), oxides (Co(3)O(4), ZnO), nitrides (CoN, InN, GaN), and sulfides (Ag(2)S). The extraction efficiency of ToABr for different metal anions is found to be varied (40-90%), but the obtained precursors are easily processable as they have reasonable solubility in common solvents and are obtainable as smooth films, both being important for high-resolution patterning. The e-resist action of the precursors originates from the extreme e-beam sensitivity of the hydrocarbon chain present in ToABr, while direct micromolding has been possible due to easy flow of the precursor solutions in capillaries. The interaction of the anion and ToABr being mainly electrostatic enables easy removal of the hydrocarbon from patterned regions by thermolysis on a hot plate in the ambient or in controlled atmosphere to form the desired product. This method can be easily generalized.

Hydrogen Bonding in Phosphonate Cavitands: Investigation of Host–Guest Complexes with Ammonium Salts

The H-bonding in alkylammonium complexes of phosphonate cavitands were studied by mass spectrometric methods and theoretical calculations. The alkylammonium ions included primary, secondary, and tertiary methyl- and ethylammonium ions. Their complexation with mono-, tetra-, and two di-phosphonate cavitands, which differ according to the number and position of H-bond acceptor P = O groups, was evaluated by using different competition experiments, energy-resolved CID, gas-phase H/D-exchange, and ligand-exchange reactions, together with ab initio theoretical optimization of the complexes. The phosphonate cavitands with two or more adjacent P = O groups were found to be selective towards secondary alkylammonium ions, due to simultaneous formation of two stable hydrogen bonds. In the ion-molecule reactions (both H/D- and ligand-exchange), the formation of two stable hydrogen bonds was observed either to slow down the reaction or to completely prevent it. This was, however, limited to situations where two hydrogen bonds are formed between the H-bond donor sites of the alkyl ammonium ion and the vicinal H-bond acceptor sites of the cavitand.

Structure of Liquid Crystalline Aerosol-OT and Its Alkylammonium Salts

Aerosol-OT is a widely used anionic surfactant, and its lyotropic properties have been studied extensively. However, neat AOT is itself liquid crystalline. We carried out an X-ray study of neat AOT sodium salt, as well as of AOT-n-decyl-, n-dodecyl-, n-tetradecyl-, and n-hexadecylammonium salts. We confirm an earlier report that pure AOT forms a hexagonal columnar phase but propose a different packing model. This involves a relatively highly ordered structure with each column cross-section containing three tessellated molecules in the plane normal to the column axis. The structure is trigonal locally but hexagonal over the long-range. This mode of assembly is supported by electron density reconstruction and molecular modeling. At subambient temperatures, the AOT-alkylammonium complexes Cn-AOT, with n=10-16, also display a hexagonal columnar phase, but this is more disordered, and each column cross-section contains only two ion pairs. Unusually, molar enthalpy and entropy of the columnar-isotropic transition in Cn-AOT salts decrease with increasing n. This is attributed to a disproportionally high conformational disorder of the radial chains in the columnar phase, which is required for efficient space filling.

Solvo-Hydrothermal Approach for the Shape-Selective Synthesis of Vanadium Oxide Nanocrystals and Their Characterization

A new solvo-hydrothermal method has been developed for the synthesis of uniform vanadium oxide nanocrystals (NCs) with various sizes and shapes in aliphatic amine/toluene/water using V(V) diperoxo alkylammonium complexes. The vanadium complex precursors were prepared from an ion exchange reaction of V(V) diperoxo gels and tetraalkylammonium bromide in the water-toluene mixture using H(2)O(2) solution and commercial bulk V(2)O(5) powders as starting vanadium gel source. The obtained VO(2) NC products were characterized by means of transmission electron microscopy (TEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), powder X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), Fourier transform infrared absorption spectroscopy (FTIR), thermogravimetric differential thermal analysis (TGA-DTA), and nitrogen adsorption/desorption (BET). The size and shape of NCs can be controlled by different synthesis parameters such as water content, steric ligands of complexes, alkyl chain lengths of capping aliphatic amines, as well as nature of solvent. Monodisperse vanadium oxide NCs with various sizes and shapes, nanospheres, nanocubes, nanorices, and nanorods, can be easily achieved. The possible mechanisms for the formation of vanadium complex precursors and vanadium oxide NCs as well as the shape evolution of NCs were also discussed. The as-made vanadium oxide products exhibited the monoclinic rutile VO(2) structure, which was however converted to the orthorhombic V(2)O(4.6) structure after calcination in air. The XPS results also revealed only one V(4+) state for the as-made sample; however, the coexistence of V(5+) and V(4+) states and two components of oxygen associated with OV and O-V for the calcined samples on the vanadium oxide NC surface were observed. The surface chemical composition of both as-made and calcined samples were found to be VO(2) and V(2)O(5-x) (x = 0.4), respectively. Our approach may provide a novel route for the extended synthesis to other inorganic NCs.

DFT Study of p-tert-Butylcalix[5]crown-6-ether Complexed with Alkylammonium Ions

The structures and energies of p-tert-butylcalix[5]crown-6-ether (1) and its alkylammonium complexes have been calculated by DFT B3LYP/6-31G(d,p) method. We have studied the binding sites of these host-guest complexes focusing on the p-tert-butylcalix[5]arene pocket (endo) or the crown-6-ether moiety (exo) of 1. The smaller alkylammonium cations have the better complexation efficiency with p-tert-butylcalix[5]crown-6- ether than the bulkier alkylammonium ions. For the sec- and tert-butylammonium ions, the hydrogen-bond distances of the exo-complexes are shorter, therefore, stronger than the endo-cases. This DFT calculated result is in parallel with the trend of the experimental association constants of the branched butylammonium ions.

A stepped bilayer packing motif for para-sulphonatocalix[4]arene: The solid-state structure of the para-sulphonatocalix[4]arene–triethylamine complex

A new para-sulphonatocalix[4]arene supramolecular packing architecture with triethylammonium ligands has been determined. The structure is based on a “stepped bilayer” formed by para-sulphonatocalixarenes in which triethylammonium cations are complexed in two different manners, with one cation included in the macrocyclic cage and the other situated externally in the hydrophobic interlayer environment. This architecture is quite different from those observed in the case of arginine, lysine or other alkylammonium complexes.

Ab Initio Study of Conformers of p-tert-Butylcalix[4]crown-6-ether Complexed with Alkyl Ammonium Cations

The structures and energies of p-tert-butylcalix[4]crown-6-ether(1) in various conformers and their alkyl ammonium complexes have been calculated by ab initio HF/6-31G quantum mechanics method. We have tried to obtain the relative affinity of partial-cone and 1,3-alternate conformers of 1 for alkyl ammonium guests by comparison with its cone-shaped analogue. We have also calculated the relative complexation efficiency of these host-guest complexes focusing on the binding sites of <TEX>$crown-\sigma-enther$</TEX> moiety or benzene-rings pocket of the host molecule 1. These calculations revealed that the crown moiey has better complexation efficiency than upper rim part of calyx[4]arene that is in similar trend to the cone-shaped complexes.

New Ionophoric Calix[4]diquinones: Coordination Chemistry, Electrochemistry, and X-ray Crystal Structures.

A new library of ionophoric p-tert-butylcalix[4]diquinones containing ester (1), primary, secondary, and tertiary amide (2-4), and crown ether (5) substituents has been synthesized by treatment of the respective 1,3-bis-substituted p-tert-butylcalix[4]arene with Tl(OCOCF(3))(3) in trifluoroacetic acid. The structures of the free ligands 1 and 2, a p-tert-butylcalix[4]diquinone bridged at the lower rim by two linked veratrole groups (7), and a previously synthesized p-tert-butylcalix[4]diquinone bis(methyl ether) species (8) have been elucidated by X-ray crystallography. The X-ray crystal structures of 1-Sr(ClO(4))(2), 1-KClO(4), 2-NaClO(4), 4-n-BuNH(3)BF(4), 5-NaOCOCF(3), and 5-KPF(6) demonstrate that these complexes adopt the cone conformation in the solid state. Interestingly, cation-quinone oxygen atom coordination occurs at both the upper and lower rim of 2-NaClO(4) and 4-n-BuNH(3)BF(4). Solution coordination properties have been studied by both (1)H NMR and UV/vis techniques. The electrochemical properties of the "acyclic" p-tert-butylcalixdiquinones 1, 4, and 8 and their complexes have been studied using cyclic and square wave voltammetric techniques. The reduction potentials of the group 1 or 2 metal, ammonium, and alkylammonium complexes are significantly anodically shifted with respect to that of the free ligand. Addition of cations to electrochemical solutions of a p-tert-butylcalixdiquinone-crown-5 compound (5) caused large anodic shifts (by up to 555 mV in the presence of Ba(2+)) in a manner similar to that of the acyclic species.

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Eu3+ and Tb3+ intercalations were studied on layered titanic acids. H2Ti307, H2Ti409. H20, and their alkylammonium complexes in aqueous chloride solutions. The lanthanoid ions were taken up into the alkylammonium complexes but were not detected in the products obtained directly from H2Ti307 and H2Ti409. H20. The interlayer alkylammonium ions were quantitatively exchanged with hydrated Eu3+ and Tb3+ ions during the reactions. The layered Eu titanate showed red luminescence under excitation at 400 nm and the Tb titanate emitted green luminescence by 380 nm excitation. The luminescence spectra of the Eu titanates are discussed in relation to the crystal structure of titanates.

Determination of the surface energy of clay—organic complexes by contact angle measurements

Surface energies of montmorillonite—alkylammonium complexes were determined from contact angle measurements performed using the two-liquid phase method. An apparent surface energy ⇐ a (with ⇐ a=⇐ a P+⇐ a D) was determined for partially hydrated surfaces. When the length of the organic ion increases, that is to say when the part of the organic surface increases, ⇐ S approaches values characteristic of low surface energy polymers. It was possible to correlate the variation of ⇐ a P and ⇐ a D with the nature of the surface, i.e. organic/mineral, hydrated/dry. At complete coverage of the mineral, the surface properties measured are the organic coating ones.

Formation and properties of n-alkylammonium complexes with layered tri- and tetra-titanates

The formation of n-alkylammonium complexes was studied using Na 2Ti 3O 7 and K 2Ti 4O 9 and the results for both compounds were compared. Alkylammonium complexes could be obtained from H 2Ti 3O 7 and H 2Ti 4O 9·H 2O, which were prepared by HCl treatment of Na 2Ti 3O 7 and K 2Ti 4O 9 respectivel The complexes were formed by exchange of H + with alkylammonium ions. Molecular intercalation of alkylamine was also possible with H 2Ti 4O 9·H 2O. However, alkylammonium complexes were not formed directly from Na 2Ti 3O 7 and from K 2Ti 4O 9. Orientations of alkylammonium ions in the interlayer are also discussed in relation to the structure of the titanate layers.

Cation-complexing properties of synthetic macrocyclic polyether-diester ligands containing the furan, benzene, tetrahydrofuran, and thiophene subcyclic units

The synthesis of 13 new macrocyclic polyether-diester ligands containing the furan, 3,4-dimethoxyfuran, tetrahydrofuran, and thiophene subcyclic by the reaction of a diacid dichloride with the appropriate glycol is described. The complexation properties of these ligands with alkylammonium and metal cations were determined and compared with the crown ethers. The free energies of activation (..delta..G*) for the dissociation of the alkylammonium complexes were determined from their temperature-dependent /sup 1/H NMR spectra. The relative kinetic stability (as measured by the ..delta..G* values) for the complexes between benzylammonium perchlorate and ligands containing an aromatic subcyclic unit increased with increasing ring size in the order 18-<21-<24-membered ring. Formation constants as well as ..delta..H and T..delta..S values were determined in methanol by a calorimetric titration technique for the reaction of Na/sup +/, K/sup +/, Cs/sup +/ and Sr/sup 2 +/ with the tetrahydrofurano ligands. The 21- and 24-membered ring compounds containing a furan subcyclic unit were found to be effective carriers of Cs/sup +/ across a CHC1/sub 3/ ligand membrane separating aqueous phases.

Alkylammonium complexes of copper (II)

Alkylammonium complexes of copper (II)