Five solvates of a multicomponent pharmaceutical salt formed by berberine and diclofenac

A multicomponent pharmaceutical salt formed by the isoquinoline alkaloid berberine (5,6‐dihydro‐9,10‐dimethoxybenzo[g]‐1,3‐benzodioxolo[5,6‐a]quinolizinium, BBR) and the nonsteroidal anti‐inflammatory drug diclofenac {2‐[2‐(2,6‐dichloroanilino)phenyl]acetic acid, DIC} was discovered. Five solvates of the pharmaceutical salt form were obtained by solid‐form screening. These five multicomponent solvates are the dihydrate (BBR–DIC·2H₂O or C₂₀H₁₈NO₄⁺·C₁₄H₁₀Cl₂NO₂^?·2H₂O), the dichloromethane hemisolvate dihydrate (BBR–DIC·0.5CH₂Cl₂·2H₂O or C₂₀H₁₈NO₄⁺·C₁₄H₁₀Cl₂NO₂^?·0.5CH₂Cl₂·2H₂O), the ethanol monosolvate (BBR–DIC·C₂H₅OH or C₂₀H₁₈NO₄⁺·C₁₄H₁₀Cl₂NO₂^?·C₂H₅OH), the methanol monosolvate (BBR–DIC·CH₃OH or C₂₀H₁₈NO₄⁺·C₁₄H₁₀Cl₂NO₂^?·CH₃OH) and the methanol disolvate (BBR–DIC·2CH₃OH or C₂₀H₁₈NO₄⁺·C₁₄H₁₀Cl₂NO₂^?·2CH₃OH), and their crystal structures were determined. All five solvates of BBR–DIC (1:1 molar ratio) were crystallized from different organic solvents. Solvent molecules in a pharmaceutical salt are essential components for the formation of crystalline structures and stabilization of the crystal lattices. These solvates have strong intermolecular O…H hydrogen bonds between the DIC anions and solvent molecules. The intermolecular hydrogen‐bond interactions were visualized by two‐dimensional fingerprint plots. All the multicomponent solvates contained intramolecular N—H…O hydrogen bonds. Various π–π interactions dominate the packing structures of the solvates.     

Interaction of the Benzenium Ion with Inert Ligands: IR Spectra of C6H7+?Ln Cluster Cations (L=Ar,N2, CH4, H2O)

IR photodissociation spectra of mass‐selected clusters composed of protonated benzene (C₆H₇⁺) and several ligands L are analyzed in the range of the C? H stretch fundamentals. The investigated systems include C₆H₇⁺? Ar, C₆H₇⁺? (N₂)_n (n=1–4), C₆H₇⁺? (CH₄)_n (n=1–4), and C₆H₇⁺? H₂O. The complexes are produced in a supersonic plasma expansion using chemical ionization. The IR spectra display absorptions near 2800 and 3100 cm^?1, which are attributed to the aliphatic and aromatic C? H stretch vibrations, respectively, of the benzenium ion, that is, the σ complex of C₆H₇⁺. The C₆H₇⁺? (CH₄)_n clusters show additional C? H stretch bands of the CH₄ ligands. Both the frequencies and the relative intensities of the C₆H₇⁺ absorptions are nearly independent of the choice and number of ligands, suggesting that the benzenium ion in the detected C₆H₇⁺? L_n clusters is only weakly perturbed by the microsolvation process. Analysis of photofragmentation branching ratios yield estimated ligand binding energies of the order of 800 and 950 cm^?1 (≈9.5 and 11.5 kJ mol^?1) for N₂ and CH₄, respectively. The interpretation of the experimental data is supported by ab initio calculations for C₆H₇⁺? Ar and C₆H₇⁺? N₂ at the MP 2/6‐311 G(2df,2pd) level. Both the calculations and the spectra are consistent with weak intermolecular π bonds of Ar and N₂ to the C₆H₇⁺ ring. The astrophysical implications of the deduced IR spectrum of C₆H₇⁺ are briefly discussed.     

Thermal Stability of n‐Acyl Peroxynitrates

Peroxynitrates (RO₂NO₂), in particular acyl peroxynitrates (R = R′C(O) with R′ = alkyl), are prominent constituents of polluted air. In this work, a systematic study on the thermal decomposition rate constants of the first five members of the series of homologous R′C(O)O₂NO₂ with R′ = CH₃ ( =PAN), C₂H₅, n‐C₃H₇, n‐C₄H₉, and n‐C₅H₁₁ is undertaken to verify the conclusions from previous laboratory data (Grosjean et al., Environ. Sci. Technol. 1994, 28, 1099–1105; Grosjean et al., Environ. Sci. Technol. 1996, 30, 1038–1047; Bossmeyer et al., Geophys. Res. Lett. 2006, 33, L18810) that the longer chain peroxynitrates may be considerably more stable than PAN. Experiments are performed in a temperature‐controlled, evacuable 200 L‐photoreactor made from quartz. n‐Acyl peroxynitrates are generated by stationary photolysis of mixtures of molecular bromine, O₂, NO₂, and the corresponding parent aldehydes, highly diluted in N₂. Thermal decomposition of R′C(O)O₂NO₂ is initiated by the addition of an excess of NO. First‐order decomposition rate constants k₁ of the reactions R′C(O)O₂NO₂ (+M) → R′C(O)O₂ + NO₂ (+M) are derived at 298 K and a total pressure of 1 bar from the measured loss rates of R′C(O)O₂NO₂, correcting for wall loss of R′C(O)O₂NO₂ and several percentages of reformation of R′C(O)O₂NO₂ by the reaction of R′C(O)O₂ radicals with NO₂. With increasing chain length of R′, k₁(298 K) slightly decreases from 4.4 × 10^?4 s^?1 (R′ = CH₃) to 3.7 × 10^?4 s^?1 (R′ = C₂H₅), leveling off at (3.4 ± 0.1) × 10^?4 s^?1 for R′ = n‐C₃H₇, n‐C₄H₉, and n‐C₅H₁₁. Temperature dependencies of k₁ were measured for CH₃C(O)O₂NO₂ and n‐C₅H₁₁C(O)O₂NO₂ in the temperature range 289–308 K, resulting in the same activation energy within the statistical error limits (2σ) of 0.9 and 1.5 kJ mol^?1, respectively. A few experiments on n‐C₆H₁₃C(O)O₂NO₂, n‐C₇H₁₅C(O)O₂NO₂, and n‐C₈H₁₇C(O)O₂NO₂ were also performed, but the results were considered to be unreliable due to strong wall loss of the peroxynitrate and possible complications caused by radical‐sinitiated side reactions.     

N‐phosphinyl ureas: Synthesis,characterization, X‐ray structure,and in vitro evaluation of antitumor activity

A new series of N‐phosphinylureas 5b, 6a–7c was synthesized and characterized by ¹H, ¹³C, ³¹P NMR, IR, and elemental analysis. The three‐dimensional structure of 5b has been determined by X‐ray crystallography. The crystal structure revealed the existence of four independent molecules. All structures form two chains with different arrangements and connect to each other via hydrogen bonds to produce two‐dimensional polymeric chains. The cytotoxicity of cyclophosphamide (a standard antitumor compound) and its nine analogues with formula R¹C₆H₄ NHC(O)NHP(O)XCH₂C(R²)₂ CH₂Y(X = Y = NH, R² = CH₃, R¹ = H ( 5a ), CH₃ ( 5b ), NO₂ ( 5c ), X = O, Y = NH, R² = H, R¹ = H ( 6a , CH₃ ( 6b ), NO₂ ( 6c ), and X = Y = O, R² = CH₃, R¹ = H ( 7a ), CH₃ ( 7b ), NO₂ ( 7c )) as well as phenyl urea were evaluated in vitro against three human tumor cell lines K562, MDA‐MB‐231, and HepG2. The results showed that most of the compounds have significant activity against the selected cell lines. Also, HepG2 cells were more sensitive to all the tested compounds than other cell lines. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 23:74–83, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20754     

Synthesis,structural characterization and molecular modelling of bidentate azo dye metal complexes: DNA interaction to antimicrobial and anticancer activities

A novel azo dye ligand, namely 1‐[(5‐mercapto‐1H‐1,2,4‐triazole‐3‐yl)diazenyl]naphthalen‐2‐ol (HL), was synthesized. Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ and UO₂²⁺ complexes were also prepared by the treatment of HL with Mn(CH₃COO)₂?4H₂O, Co(CH₃COO)₂?4H₂O, Ni(CH₃COO)₂?4H₂O, Cu(CH₃COO)₂?H₂O, CuCl₂?2H₂O, Cu(NO₃)₂?6H₂O and UO₂(NO₃)₂?6H₂O. The structures of these metal chelates were confirmed using elemental, spectral, magnetic moment, molar conductance and thermal analyses. The analytical data confirmed the formation of the chelates in 1:1 (metal‐to‐ligand) ratio having the formula [ML(H₂O)X]Y?H₂O, where M is Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ or UO₂²⁺; X is Cl^?, NO₃^? or CH₃COO^?; and Y is H₂O. The azo compound acts in a monobasic bidentate manner via the nitrogen and oxygen atoms of azo and hydroxyl groups, respectively. All complexes were found to have tetrahedral structures, except the UO₂²⁺ complex that showed octahedral geometry. The mode of interaction between the synthesized complexes and calf thymus DNA was explored by the aid of absorption spectroscopy and viscosity measurements. The azo dye and its chelates were evaluated against the growth of various bacterial and fungal strains (Escherichia coli, Staphylococcus aureus, Aspergillus flavus and Candida albicans) with insight gained into the effect of type of metal centre, type of coordinated anion and position of the metal in the periodic table on the activity of the complexes. The geometric structure of the complexes was optimized using molecular modelling. The in vitro cytotoxicity of the synthesized compounds was tested against HEPG2 cell line.     

High temperature pyrolysis of methane in shock waves. Rates for dissociative recombination reactions of methyl radicals and for propyne formation reaction

The pyrolysis of 2% CH₄ and 5% CH₄ diluted with Ar was studied using both a single–pulse and time–resolved spectroscopic methods over the temperature range 1400–2200 K and pressure range 2.3–3.7 atm. The rate constant expressions for dissociative recombination reactions of methyl radicals, CH₃ + CH₃ → C₂H₅ + H and CH₃ + CH₃ → C₂H₄ + H₂, and for C₃H₄ formation reaction were investigated. The simulation results required considerably lower value than that reported for CH₃ + CH₃ → C₂H₄ + H₂. Propyne formation was interpreted well by reaction C₂H₂ + CH₃ → P-C₃H₄ + H with ?? = 6.2 × ¹⁰12 exp(?17 kcal/RT) ^cm3 mol^?1 s^?1.     

Synthesis and single crystal X‐ray determination of the Schiff base 1‐[(2‐isopropyl‐5‐methylphenoxy)hydrazono] ethyl ferrocene

The reaction of acetylferrocene [Fe(η‐C₅H₅)(η‐C₅H₄COCH₃)] (1) with (2‐isopropyl‐5‐methylphenoxy) acetic acid hydrazide [CH₃C₆H₃CH(CH₃)₂OCH₂CONHNH₂] (2) in refluxing ethanol gives the stable light‐orange–brown Schiff base 1‐[(2‐isopropyl‐5‐methylphenoxy)hydrazono] ethyl ferrocene, [CH₃C₆H₃CH(CH₃)₂OCH₂CONHN?C(CH₃)Fe(η‐C₅H₅)(η‐C₅H₄)] (3). Complex 3 has been characterized by elemental analysis, IR, ¹H NMR and single crystal X‐ray diffraction study. It crystallizes in the monoclinic space group P2₁/n, with a = 9.6965(15), b = 7.4991(12), c = 29.698(7) Å, β = 99.010(13) °, V = 2132.8(7) ų, D_calc = 1.346 Mg m^?3; absorption coefficient, 0.729 mm^?1. The crystal structure clearly shows the characteristic [N? H···O] hydrogen bonding between the two adjacent molecules of 3. This acts as a bidentale ligand, which, on treatment with [Ru(CO)₂Cl₂] _n, gives a stable bimetallic yellow–orange complex (4). Copyright © 2002 John Wiley & Sons, Ltd.     

Morpholine‐2,5‐dione

In the title compound, C₄H₅NO₃, the morpholine ring adopts a boat conformation that is distorted towards twist–boat, the boat ends being the two Csp³ atoms of the ring. The mol­ecular packing is stabilized by the establishment of strong inter­molecular NH⋯OC hydrogen bonds, which give rise to centrosymmetric dimers, and a network of weak CH₂⋯OC hydrogen bonds, where each dimer inter­acts with eight neighbouring morpholine­dione rings.     

Unimolecular reactions of the isolated immonium ions CH3CH = NH+C4H9, CH3CH2Ch = NH+C4H9 and (CH3)2C = NH+C4H9

The reactions of ten metastable immonium ions of general structure R¹R²C?NH⁺C₄H₉ (R¹ = H, R² = CH₃, C₂H₅; R¹ = R² = CH₃) are reported and discussed. Elimination of C₄H₈ is usually the dominant fragmentation pathway. This process gives rise to a Gaussian metastable peak; it is interpreted in terms of a mechanism involving ion-neutral complexes containing incipient butyl) cations. Metastable immonium ions ontaining an isobutyl group are unique in undergoing a minor amount of imine (R¹R²C?NH) loss. This decomposition route, which also produces a Gaussian metastable peak, decreases in importance as the basicity of the imine increases. The correlation between imine loss and the presence of an isobutyl group is rationalized by the rearrangement of the appropriate ion-neutral complexes in which there are isobutyl cations to the isomeric complexes containing the thermodynamically more stable tert-butyl cations. A sizeable amount of a third reaction, expulsion of C₃H₆, is observed for metastable n-C₄H₉ ⁺NH?CR¹R² ions; in contrast to C₄H₈ and R¹R²C?NH loss, C₃H₆ elimination occurs with a large kinetic energy release (40–48 kJ mol^?1) and is evidenced by a dish-topped metastable peak. This process is explained using a two-step mechanism involving a 1,5-hydride shift, followed by cleavage of the resultant secondary open-chain cations, CH₃CH⁺ CH₂CH₂NHCHR¹R².     

The role of ion–neutral complexes in the reactions of onium ions and related species

An account is given of the development of the proposal that ion–neutral complexes are involved in the unimolecular reactions of onium ions (R¹R²C?Z⁺R³; Z = O, S, NR⁴; R¹, R², R³, R⁴ = H, C_nH_{2n + 1}), with particular emphasis on the informative C₄H₉O⁺ oxonium ion system (Z = O; R¹, R² = H; R³ = C₃H₇). Current ideas on the role of ion-neutral complexes in cation rearrangements, hydrogen transfer processes and more complex isomerizations are illustrated by considering the behaviour of isomeric CH₃CH₂CH₂X⁺ and (CH₃)₂CHX⁺ species [X = CH₂O, CH₃CHO, H₂O, CH₃OH, NH₃, NH₂CH₃, NH(CH₃)₂, CH₂?NH, CH₂?NCH₃, CO, CH₃˙, Br˙ and I˙]. Attention is focused on the importance of four energetic factors (the stabilization energy of the ion–neutral complex, the energy released by rearrangement of the cationic component, the enthalpy change for proton transfer between the partners of the ion neutral complex and the ergicity of recombination of the components) which influence the reactivity of the complexes. The nature and extent of the chemistry involving ion-neutral complexes depend on the relative magnitudes of these parameters. Thus, when the magnitude of the stabilization energy exceeds the energy released by cation rearrangement, the ergicity of proton transfer is small, and recombination of the components in a new way is energetically favourable, extensive complex-mediated isomerizations tend to occur. Loss of H₂O from metastable CH₂?O⁺C₃H₇ ions is an example of such a reaction. Conversely, if the stabilization energy is small compared with the magnitude of the energy released by eation rearrangement, the opportunities for complex-mediated processes to become manifest are decreased, especially if proton transfer is endoergic. Thus, CH₃CH₂CH₂CO⁺ expels CO, with an increased kinetic energy release, after rate-limiting isomerization of CH₃CH₂CH₂⁺? CO to (CH₃)₂CH⁺? CO has taken place. When proton transfer between the components of the complex is strongly exoergic, fragmentation corresponding to single hydrogen transfer occurs readily. The proton-transfer step is often preceded by cation rearrangement for CH₃CH₂CH₂X⁺ species. In such circumstances, the involvement of ion–neutral complexes can be detected by the observation of unusual site selectivity in the hydrogen-transfer step. Thus, C₃H₆ loss from CH₂?N⁺(R¹)CH₂CH₂CH₃ (R¹ = H, CH₃, C₃H₇) immonium ions is found by ²H-labelling experiments to proceed via preferential α-and γ-hydrogen transfer; this finding is explained if the incipient ⁺CH₂CH₂CH₃ ion isomerizes to CH₃CH⁺CH₃ prior to proton abstraction. In contrast, the isomeric CH₂?N⁺(R¹)CH(CH₃)₂ species undergo specific β-hydrogen transfer because the developing CH₃CH⁺CH₃ cation is stable with respect to rearrangements involving a 1,2-H shift.     

Relaxation of DF(v = 1) by various polyatomic molecules

By means of the technique of laser-induced fluorescence, the room-temperature vibrational relaxation of DF(v = 1) has been studied in the presence of several polyatomic chaperones. The rate coefficients obtained [in units of (μ;sec·torr)^?1] are CH₄, 0.22; C₂H₆, 0.61; C₄H₁₀, 1.26; C₂H₂, 4.0 × 10^?2; C₂H₂F₂, 1.86 × 10^?2; C₂H₄, 0.175; CH₃F, 0.36; CF₃H, 1.95 × 10^?2; CF₄, 1.0 × 10^?3; CBrF₃, 5.6 × 10^?4; NF₃, 5.1 × 10^?4; SO₂, 1.27 × 10^?2; and BF₃, 7.1 × 10^?3. Results are also reported for vibrational relaxation rate coefficients for HF(v = 1) in the presence of the following chaperones: CH₄, 2.6 × 10^?2; C₂H₆, 5.9 × 10^?2; C₃H₈, 8.4 × 10^?2; and C₄H₁₀, 0.128. A comparison of DF and HF results indicates that for deactivation by C_nH_n+2, rate coefficients for DF are approximately an order of magnitude larger than for HF. The deactivation rate coefficient of DF(v = 1) by CH₄ was found to decrease with increasing temperature between 300 and 740°K.     

2‐Chloro‐4‐nitrobenzoic acid as a coformer with pharmaceutical cocrystals and molecular salts

A series of five binary complexes, i.e. three cocrystals and two molecular salts, using 2‐chloro‐4‐nitrobenzoic acid as a coformer have been produced with five commonly available compounds, some of pharmaceutical relevance, namely, 2‐chloro‐4‐nitrobenzoic acid–isonicotinamide (1/1), C₇H₄ClNO₄·C₆H₆N₂O, 2‐chloro‐4‐nitrobenzoic acid–3,3‐diethylpyridine‐2,4(1H,3H)‐dione (2/1), 2C₇H₄ClNO₄·C₉H₁₃NO₂, 2‐chloro‐4‐nitrobenzoic acid–pyrrolidin‐2‐one (1/1), C₇H₄ClNO₄·C₄H₇NO, 2‐carboxypiperidinium 2‐chloro‐4‐nitrobenzoate, C₆H₁₂NO₂^?·C₇H₃ClNO₄^?, and (2‐hydroxyethyl)ammonium 2‐chloro‐4‐nitrobenzoate, C₂H₈NO⁺·C₇H₃ClNO₄^?. The coformer falls under the classification of a `generally regarded as safe' compound. All five complexes make use of a number of different heteromeric hydrogen‐bonded interactions. Intermolecular potentials were evaluated using the CSD‐Materials module.     

Structure and formation of gaseous [C4H6O]+˙ ions: 1—The enolic ions [CH2C(OH)?CHCH2]+˙ and [CH2CH?CHCH(OH)]+˙ and their relationship with their keto counterparts

The [C₄H₆O]^+˙ ion of structure [CH₂?CHCH?CHOH]^+˙ (a) is generated by loss of C₄H₈ from ionized 6,6-dimethyl-2-cyclohexen-1-ol. The heat of formation ΔH_f of [CH₂?CHCH?CHOH]^+˙ was estimated to be 736 kJ mol^?1. The isomeric ion [CH₂?C(OH)CH?CH₂]^+˙ (b) was shown to have ΔH_f, ? 761 kJ mol^?1, 54 kJ mol^?1 less than that of its keto analogue [CH₃COCH?CH₂]^+˙. Ion [CH₂?C(OH)CH?CH₂]^+˙ may be generated by loss of C₂H₄ from ionized hex-1-en-3-one or by loss of C₄H₈ from ionized 4,4-dimethyl-2-cyclohexen-1-ol. The [C₄H₆O]^+˙ ion generated by loss of C₂H₄ from ionized 2-cyclohexen-1-ol was shown to consist of a mixture of the above enol ions by comparing the metastable ion and collisional activation mass spectra of [CH₂?CHCH?CHOH]^+˙ and [CH₂?C(OH)CH?CH₂]^+˙ ions with that of the above daughter ion. It is further concluded that prior to their major fragmentations by loss of CH₃˙ and CO, [CH₂?CHCH?CHOH]⁺˙ and [CH₂?C(OH)CH?CH₂]^+˙ do not rearrange to their keto counterparts. The metastable ion and collisional activation characteristics of the isomeric allenic [C₄H₆O]^+˙ ion [CH₂?C?CHCH₂OH]^+˙ are also reported.     

The use of transition-state theory to extrapolate rate coefficients for reactions of O atoms with alkanes

Conventional transition-state theory is used for extrapolating rate coefficients for reactions of O atoms with alkanes to temperatures above the range of experimental data. Expressions are developed for estimating structural properties of the activated complex necessary for calculating enthalpies and entropies of activation. Particular attention is given to the problem of the effect of the O atom adduct on the internal rotations in the activated complex. Differences between primary, secondary, and tertiary attack are discussed, and the validity of representing the activated complexes of all O + alkane reactions by a fixed set of vibrational frequencies and other internal modes is evaluated. Experimental data for reactions of O atoms with 15 different alkanes (CH₄, C₂H₆, C₃H₈, C₄H₁₀, C₅H₁₂, C₆H₁₄, C₇H₁₆, C₈H₁₈, i–C₄H₁₀, (CH₃)₄C, (CH₃)₂CHCH(CH₃)₂, (CH₃)₃CC(CH₃)₃, c–C₅H₁₀, c–C₆H₁₂, c–C₇H₁₄) are reviewed. The following approximate expressions for ΔS^?(298) and E(298), the entropy and energy of activation, respectively, are consistent with the experimental data and with the calculations: where n_C = number of carbon atoms in the alkane and n_H = the number of “equivalent” H atoms. Using the conventional transition state theory expression, k(298) = 10^15.06 exp(ΔS^?/R) exp(–E(298)/298R) L mol^?1s^?1, one then obtains: These expressions agree with experimental values within a factor approximately 2 for alkanes larger than C₃H₈.     

Thermal decomposition of 1-butyne in shock waves

1-Butyne diluted with Ar was heated behind reflected shock waves over the temperature range of 1100–1600 K and the total density range of 1.36 × 10^?5?1.75 × 10^?5 mol/cm³. Reaction products were analyzed by gas-chromatography. The progress of the reaction was followed by IR laser kinetic absorption spectroscopy. The products were CH₄, C₂H₂, C₂H₄, C₂H₆, allene, propyne, C₄H₂, vinylacetyiene, 1,2- butadiene, 1,3-butadiene, and benzene. The present data were successfully modeled with a 80 reaction mechanism. 1-Butyne was found to isomerize to 1,2-butadiene. The initial decomposition was dominated by 1-butyne → C₃H₃ + CH₃ under these conditions. Rate constant expressions were derived for the decomposition to be k₇ = 3.0 × 10¹⁵ exp(?75800 cal/RT) s^?1 and for the isomerization to be k₄ = 2.5 × 10¹³ exp(?65000 cal/RT) s^?1. The activation energy 75.8 kcal/mol was cited from literature value and the activation energy 65 kcal/mol was assumed. These rate constant expressions are applicable under the present experimental conditions, 1100–1600 K and 1.23–2.30 atm. © 1995 John Wiley & Sons, Inc.     

Luminescent Amphiphilic 2,6‐Bis(1,2,3‐triazol‐4‐yl)pyridine?Platinum(II) Complexes: Synthesis,Characterization, Electrochemical,Photophysical, and Langmuir–Blodgett Film‐Formation Studies

A new series of platinum(II) complexes with tridentate ligands 2,6‐bis(1‐alkyl‐1,2,3‐triazol‐4‐yl)pyridine and 2,6‐bis(1‐aryl‐1,2,3‐triazol‐4‐yl)pyridine (N7R), [Pt(N7R)Cl]X ( 1 – 7 ) and [Pt(N7R)(C?CR′)]X ( 8 – 17 ; R=n‐C₄H₉, n‐C₈H₁₇, n‐C₁₂H₂₅, n‐C₁₄H₂₉, n‐C₁₈H₃₇, C₆H₅, and CH₂‐C₆H₅; R′=C₆H₅, C₆H₄‐CH₃‐p_, C₆H₄‐CF₃‐p, C₆H₄‐N(CH₃)₂‐p, and cholesteryl 2‐propyn‐1‐yl carbonate; X=OTf^?, PF₆^?, and Cl^?), has been synthesized and characterized. Their electrochemical and photophysical properties have also been studied. Two amphiphilic platinum(II)? 2,6‐bis(1‐dodecyl‐1,2,3‐triazol‐4‐yl)pyridine complexes ( 3‐Cl and 8 ) were found to form stable and reproducible Langmuir–Blodgett (LB) films at the air/water interface. These LB films were characterized by the study of their surface‐pressure–molecular‐area (π–A) isotherms, XRD, and IR and polarized‐IR spectroscopy.     

A [Fe(CB6)] platform for binding of small molecules: Insights from DFT calculations

The viability of making [Fe(CB₆)L] (L = H₂, N₂, O₂, nitric oxide [NO^?, NO, and NO⁺], CO₂, and hydrocarbons [CH₄, C₂H₆, C₂H₄, and C₆H₆]) has been investigated by density functional theory (DFT) calculations. The complexes 2 – 18 are thermodynamically stable and may be synthesized. The small molecules are activated to some extent after complexation. Molecular orbital and ΔG calculation revealed that the molecular hydrogen and hydrocarbons can be chemically adsorbed and desorbed on [Fe(CB₆)] without any significant chemical modification and therefore [Fe(CB₆)] may serve as a storage material. The N₂, O₂, and nitric oxide (NO^?, NO, and NO⁺) can be activated using [Fe(CB₆)]. Proton, carbon, boron, and nitrogen NMR chemical shift calculation predicts drastic chemical shift difference before and after the complexation of [Fe(CB₆)] with small molecules. This new findings suggest that the CB₆^2? ligand‐based complex may provide several applications in the future. © 2012 Wiley Periodicals, Inc.     

Two‐component molecular crystals from N‐heteroaromatics and nitro­benzoic acids

Five two‐component molecular crystals, benzimidazolium 3‐nitro­benzoate, C₇H₇N₂⁺·C₇H₄NO₄^?, (I), benzimidazolium 4‐nitro­benzoate, C₇H₇N₂⁺·C₇H₄NO₄^?, (II), 1H‐benzotriazole–3‐nitro­benzoic acid (1/1), C₆H₅N₃·C₇H₅NO₄, (III), imidazol­ium 3‐nitro­benzoate, C₃H₅N₂⁺·C₇H₄NO₄^?, (IV), and imid­azolium 4‐nitro­benzoate, C₃H₅N₂⁺·C₇H₄NO₄^?, (V), were prepared with the aim of making chiral crystals. Only (I) crystallizes in a chiral space group. The mol­ecules of (I) and (II) are linked by hydrogen bonds to form 2₁ spiral chains. In (III), (IV) and (V), macrocyclic structures are formed from two acid and two base components, by an alternate arrangement of the acid and base moieties.     

Reactions of nucleophilic addition of primary amines to the nitrilium derivative of the <Emphasis Type="Italic">closo</Emphasis>-decaborate anion [2-B<Subscript>10</Subscript>H<Subscript>9</Subscript>(N≡CCH<Subscript>3</Subscript>)]<Superscript>−</Superscript>

Compounds (Bu₄N)[2-B₁₀H₉{NH=C(NHR)CH₃}]⁻ are obtained by reactions of the tetrabutylammonium salt of the [2-B₁₀H₉(N≡CCH₃)]⁻ anion with aliphatic and aromatic primary amines RNH₂ (R = n-C₃H₇, n-C₄H₉, cyclo-C₅H₉, C₆H₅, cyclo-C₆H₁₁, n-C₆H₁₃, C₇H₇, C₈H₈NH₂, C₆H₄NO₂, and C₁₈H₃₇) and identified by IR, ESI/MS, and NMR (¹H, ¹¹B, and ¹³C) spectroscopy. The structures of the amidine-type derivatives [2-B₁₀H₉{Z-NH=C(NH-cyclo-C₅H₉)CH₃}]⁻ and [2-B₁₀H₉{Z-NH=C(NH-C₇H₇)CH₃}]⁻ are determined by X-ray diffraction.     

Theoretical study of the structure and unimolecular decomposition pathways of ethyloxonium, [CH3CH2OH2]+

Ab initio molecular orbital calculations with split-valence plus polarization basis sets and incorporating valence-electron correlation have been performed to determine the equilibrium structure of ethyloxonium ([CH₃CH₂OH₂]⁺) and examine its modes of unimolecular dissociation. An asymmetric structure (1) is predicted to be the most stable form of ethyloxonium, but a second conformational isomer of C_s symmetry lies only 1.4 kJ mol^?1 higher in energy than 1. Four unimolecular decomposition pathways for 1 have been examined involving loss of H₂, CH₄, H₂O or C₂H₄. The most stable fragmentation products, lying 65 kJ mol^?1 above 1, are associated with the H₂ elimination reaction. However, large barriers of 257 and 223 kJ mol^?1 have to be surmounted for H₂ and CH₄ loss, respectively. On the other hand, elimination of either C₂H₄ or H₂O from ethyloxonium can proceed without a barrier to the reverse associations and, with total endothermicities of 130 and 160 kJ mol^?1, respectively, these reactions are expected to dominate at lower energies. A second important equilibrium structure on the surface is a hydrogen-bridged complex, lying 53 kJ mol^?1 above 1. This complex is involved in the C₂H₄ elimination reaction, acts as an intermediate in the proton-transfer reaction connecting [C₂H₅]⁺ +H₂O and C₂H₄ + [H₃O]⁺ and plays an important role in the isotopic scrambling that has been observed experimentally in the elimination of either H₂O or C₂H₄ from ethyloxonium. The proton affinity of ethanol was calculated as 799 kJ mol^?1, in close agreement with the experimental value of 794 kJ mol^?1.