Sorption of benzene vapors to flexible metal–organic framework [Zn2(bdc)2(dabco)]

The isotherms of benzene sorption by the metal–organic coordination polymer [Zn₂(bdc)₂(dabco)] were studied within the temperature range 25–90 °C at pressures up to 75 torr. The maximal benzene content in [Zn₂(bdc)₂(dabco)] at room temperature was demonstrated to correspond to the composition [Zn₂(bdc)₂(dabco)]·3.8C₆H₆. It was established that the process of benzene desorption from the substance under investigation occurs in three stages. (1) Evaporation of benzene from the phase of variable composition (phase C) with compression and distortion of the unit cell (the composition of the phase C varies from [Zn₂(bdc)₂(dabco)]·3.8C₆H₆ to [Zn₂(bdc)₂(dabco)]·3.2C₆H₆). (2) The transformation of the phase C into phase P. The phase P has the same unit cell geometry as that for the empty framework. The maximal benzene content is [Zn₂(bdc)₂(dabco)]·1.0C₆H₆. (3) Benzene evaporation from the phase P of variable composition. We studied the temperature dependences of the equilibrium vapor pressure of benzene for the samples with compositions [Zn₂(bdc)₂(dabco)]·3.0(3)C₆H₆ and [Zn₂(bdc)₂(dabco)]·2.0(3)C₆H₆ within the temperature range 290–370 K. The thermodynamic parameters of benzene vaporization were determined for the latter compound ( $ \Updelta {\text{H}}_{{{\text{av}} .}}^{o} = 49\left( 1 \right) \,{\text{kJ }}\left( {{\text{moleC}}_{6} {\text{H}}_{6} } \right)^{ - 1} $ ; $ \Updelta {\text{S}}_{{{\text{av}} .}}^{^\circ } = 100\left( 3 \right)\, {\text{J}}\left( {{\text{moleC}}_{6} {\text{H}}_{6} {\text{K}}} \right)^{ - 1} $ ; $ \Updelta {\text{G}}_{298}^{^\circ } = 19.0\left( 2 \right)\, {\text{kJ}}\left( {{\text{moleC}}_{6} {\text{H}}_{6} } \right)^{ - 1} $ ).     

Synthesis,Structure, and Theoretical Study of Trifluoromethyl Derivatives of C84(23) Fullerene

Trifluoromethylation of a higher fullerene mixture with CF₃I was performed in ampoules at 550 °C. HPLC separation followed by crystal growth and X‐ray diffraction study resulted in the structure elucidation of nine CF₃ derivatives of D_2d‐C₈₄ (isomer 23). The molecular structures of C₈₄(23)(CF₃)₄, C₈₄(23)(CF₃)₈, C₈₄(23)(CF₃)₁₀, C₈₄(23)(CF₃)₁₂, two isomers of C₈₄(23)(CF₃)₁₄, two isomers of C₈₄(23)(CF₃)₁₆, and C₈₄(23)(CF₃)₁₈ were discussed in terms of their addition patterns and the relative formation energies. Extensive theoretical DFT calculations were performed to identify the most stable molecular structures. It was found that the addition of CF₃ groups to the C₈₄(23) fullerene is governed by two main rules: no additions in positions of triple hexagon junctions and predominantly para additions in C₆(CF₃)₂ hexagons on the fullerene cage. The only exception with an isolated CF₃ group in C₈₄(23)(CF₃)₁₂ is discussed in more detail.     

[6,6]‐Open and [6,6]‐Closed Isomers of C70(CF2): Synthesis,Electrochemical and Quantum Chemical Investigation

Novel difluoromethylenated [70]fullerene derivatives, C₇₀(CF₂)_n (n=1–3), were obtained by the reaction of C₇₀ with sodium difluorochloroacetate. Two major products, isomeric C₇₀(CF₂) mono‐adducts with [6,6]‐open and [6,6]‐closed configurations, were isolated and their homofullerene and methanofullerene structures were reliably determined by a variety of methods that included X‐ray analysis and high‐level spectroscopic techniques. The [6,6]‐open isomer of C₇₀(CF₂) constitutes the first homofullerene example of a non‐hetero [70]fullerene derivative in which functionalisation involves the most reactive bond in the polar region of the cage. Voltammetric estimation of the electron affinity of the C₇₀(CF₂) isomers showed that it is substantially higher for the [6,6]‐open isomer (the 70‐electron π‐conjugated system is retained) than the [6,6]‐closed form, the latter being similar to the electron affinity of pristine C₇₀. In situ ESR spectroelectrochemical investigation of the C₇₀(CF₂) radical anions and DFT calculations of the hyperfine coupling constants provide evidence for the first example of an inter‐conversion between the [6,6]‐closed and [6,6]‐open forms of a cage‐modified fullerene driven by an electrochemical one‐electron transfer. Thus, [6,6]‐closed C₇₀(CF₂) constitutes an interesting example of a redox‐switchable fullerene derivative.     

Synthesis of highly substituted quinolines via heterocyclization of fluorinated acetylenephosphonates with ortho-aminoaryl ketones

A synthetic route to a series of 4-alkyl- or arylquinolines, bearing in 2- and 3-position fluorinated and phosphonate functions at the same time, is reported for the first time. These compounds are synthesized via regioselective heterocyclization of XCF₂-alkynylphosphonates (X=F, Cl, Br, H, CF₃) with ortho-aminoaryl ketones (R=CH₃, CF₃, Ph) in the presence of K₂CO₃ or Li₂CO₃/TMEDA as mediators. 2-Fluoro- and 3-phosphorus-containing 4-Me, 4-CF₃ or 4-Ph quinolines are obtained in good to excellent yields. The influence of substituents in the aromatic ketone, the XCF₂-group in the alkyne as well as mediators and the reaction medium on the reactivity and specificity of the reaction is also investigated.     

Synthesis of tris(β,β,γ-oximinoalkyl)amines from aliphatic nitro compounds and methyl vinyl ketone

A general strategy for the assembly of previously unknown tris(β,β,γ-oximinoalkyl)amines from aliphatic nitro compounds and methyl vinyl ketone is described. The strategy involves N,N-bis(siloxy)enamines as key intermediates. The latter are accessible by double silylation of alkylnitro compounds. Nickel(II) and copper(II) complexes of tris(β,β,γ-oximinoalkyl)amines are prepared and structurally characterized.     

Determination of rhenium and osmium complexes by surface-assisted laser desorption/ionization coupled to Orbitrap mass analyzer

A surface-assisted laser desorption/ionization (SALDI) source is coupled to the Orbitrap mass analyzer; the instrumental approach is tested for the analysis of rhenium (Re) and osmium (Os) complexes with 8-mercaptoquinoline. Silicon (Si) material obtained by laser treatment of monocrystalline Si is used as SALDI substrate. All studied complexes are detected as radical cations, with no protonated molecules. The comparison of SALDI, matrix-assisted laser desorption/ionization (MALDI), and direct laser desorption/ionization (LDI) on metal plates in the same instrumental setup demonstrated that the detection of the studied complexes using SALDI provides the highest sensitivity. The ability to analyze samples rapidly, high purity of spectra, and good analytical parameters make SALDI coupled to the Orbitrap mass analyzer a potentially powerful tool for the detection of Re and Os complexes and related organic, UV-absorbing compounds.

Structures of Chlorinated Fullerenes,IPR C96Cl20 and Non‐classical C94Cl28 and C92Cl32: Evidence of the Existence of Three New Isomers of C96

Chlorination of various HPLC fractions of C₉₆ with a mixture of VCl₄ and SbCl₅ at 340–360 °C and single‐crystal X‐ray diffraction study of the products led to the identification of three new IPR isomers of C₉₆. The C₉₆(175) isomer forms a stable chloride, C₉₆(175)Cl₂₀, while chlorides of two other new isomers, C₉₆(114) and C₉₆(80), undergo cage shrinkage yielding C₉₄(NC1)Cl₂₈ and C₉₆(NC2)Cl₃₂ with non‐classical (NC) cages. These two NC chlorides contain, respectively, one and two heptagons flanked by pairs of fused pentagons and are stabilized by chlorine attachment to the emerging pentagon–pentagon junctions. Thus, the number of the experimentally confirmed C₉₆ isomers has reached nine, which corroborates the empirical rule that the C_6n fullerenes exhibit particularly rich isomerism.     

Cinnamic acid hydrogen bonds to isoniazid and N′‐(propan‐2‐ylidene)isonicotinohydrazide,an in situ reaction product of isoniazid and acetone

A new polymorph of the cinnamic acid–isoniazid cocrystal has been prepared by slow evaporation, namely cinnamic acid–pyridine‐4‐carbohydrazide (1/1), C₉H₈O₂·C₆H₇N₃O. The crystal structure is characterized by a hydrogen‐bonded tetrameric arrangement of two molecules of isoniazid and two of cinnamic acid. Possible modification of the hydrogen bonding was investigated by changing the hydrazide group of isoniazid via an in situ reaction with acetone and cocrystallization with cinnamic acid. In the structure of cinnamic acid–N′‐(propan‐2‐ylidene)isonicotinohydrazide (1/1), C₉H₈O₂·C₉H₁₁N₃O, carboxylic acid–pyridine O—H...N and hydrazide–hydrazide N—H...O hydrogen bonds are formed.