Structures and stability of N9, N9 − and N9 + clusters

 Ab initio molecular orbital calculations for N₉, N⁻ ₉ and N⁺ ₉ isomers were carried out at the HF/ 6-31G*, B3PW91/6-31G*, B3LYP/6-31G* and MP2/ 6-31G* levels of theory. Stable equilibrium geometric structures were determined by harmonic vibrational frequency analyses at the HF/6-31G*, B3PW91/6-31G* and B3LYP/6-31G* levels of theory. The most stable free-radical N₉ cluster is structure 1 with C _{2 v} symmetry and that of anion N⁻ ₉ is structure 3 with C _s symmetry. Only one stable structure of the N⁺ ₉ cation with C _{2 v} symmetry was predicted. Their potential application as high-energy-density materials has been examined. Received: 15 June 1999 / Accepted: 11 October 1999 / Published online: 14 March 2000     

N,N′-Diacylated imidazolidines and hexahydropyrimidines

A method for the preparation ofN-monoacyl imidazolidines and hexahydropyrimidines (as hydrochlorides) by interaction of monoacylated derivatives of ethylenediamine and trimethylenediamine with chloromethyl methyl ether was developed. Also a method for the preparation ofN,N-diacylimidazolidines and hexahydropyrimidines either by acylation of their monoacyl derivatives or by reaction of the correspondingN,N-diacyl alkylenediamine derivatives with dimethoxymethane, diacetoxymethane, 1,3,5-trioxane or chloromethyl methyl ether was designed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1452–1456, August, 1994.     

Improved Syntheses of N‐Desmethylcitalopram and N,N‐Didesmethylcitalopram

An improved and efficient synthesis of N‐desmethylcitalopram (2) and N,N‐didesmethylcitalopram (3) is presented. The method involved N‐demethylation of citalopram (1) using 1‐chloroethyl chloroformate to give 2 in 87% yield. Synthesis of 3 was accomplished by alkylation of 8 with 1‐(3‐bromopropyl)‐2,2,5,5‐tetramethyl‐1‐aza‐2,5‐disilacyclopentane (9).     

Preparation and Characterization of N,N′-Dialkyl-1,3-propanedialdiminium Chlorides,N,N′-Dialkyl-1,3-propanedialdimines,and Lithium N,N′-Dialkyl-1,3-propanedialdiminates

We describe convenient preparations of N,N′-dialkyl-1,3-propanedialdiminium chlorides, N,N′-dialkyl-1,3-propanedialdimines, and lithium N,N′-dialkyl-1,3-propanedialdiminates in which the alkyl groups are methyl, ethyl, isopropyl, or tert-butyl. For the dialdiminium salts, the N₂C₃ backbone is always in the trans-s-trans configuration. Three isomers are present in solution except for the tert-butyl compound, for which only two isomers are present; increasing the steric bulk of the N-alkyl substituents shifts the equilibrium away from the (Z,Z) isomer in favor of the (E,Z), and (E,E) isomers. For the neutral dialdimines, crystal structures show that the methyl and isopropyl compounds adopt the (E,Z) form, whereas the tert-butyl compound is in the (E,E) form. In aprotic solvents all four dialdimines (as well as the lithium dialdiminate salts) adopt cis-s-cis conformations in which there presumably is either an intramolecular hydrogen bond (or a lithium cation) between the two nitrogen atoms.     

Thermal and FTIR spectral studies of N,N′-diphenylguanidine

Thermal decomposition of N,N??-diphenylguanidine (DPG) was investigated by simultaneous TG/DSC-FTIR techniques under nonisothermal conditions. Online FTIR measurements illustrate that aniline is a major product of DPG decomposition. The observation that the activation energy depends on the extent of conversion indicates that the DPG decomposition kinetics features multiple processes. The initial elimination of aniline from DPG involves two pathways because of the isomerization of DPG. Mass spectrometry and thin film chromatography suggest that there are two major intermediate products with the major one of C₂₁N₃H₁₇. The most probable kinetic model deduced through multivariate nonlinear regression method agrees well with the experimental data with a correlation coefficient of 0.9998. The temperature-independent function of conversion f(??), activation energy E and the pre-exponential factor A of DPG decomposition was also established through model-fitting method in this research.     

Phosphate and arsenate electro-insertion processes into a N,N,N′,N′-tetraoctylphenylenediamine redox liquid

The electro-insertion of ions is a well-known phenomenon, which allows the transfer of anions or cations across phase boundaries to be monitored and driven electro-chemically. Extremely hydrophilic anions, such as phosphate and arsenate, are not usually observed to undergo electro-insertion. It is shown here that at organic redox liquid|water|electrode triple interfaces these anions can be forced electro-chemically to transfer into organic media.The transfer process of phosphate anions from aqueous buffer solutions into organic microdroplets of the redox liquid N,N,N^′,N^′-tetraoctylphenylenediamine (TOPD) is pH and concentration sensitive. It is shown that phosphate is transferred in the form of PO₄HK⁻ in the presence of phosphate buffer. Two distinct potential regions are identified and attributed to (i) interfacial redox processes at the liquid|liquid interface associated with deprotonation and (ii) bulk redox processes associated with anion transfer from the aqueous to the organic phase.The comparison of phosphate and arsenate electro-insertion processes suggests that arsenate is less hydrophilic and transferred into the organic phase preferentially.     

Syntheses and Characterization of Metal Complexes of L－Lysine－N，N，N＇，N＇－tetraacetic Acid and L－Lysine－N，N，N＇，N＇－tetramethylenepho sphonic Acid

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Synthesis and Structural Elucidation of N,N ’-Ditosyl-1,11-diaza-4,8,14,18-tetraselena-cycloicosane and its Copper and Platinum Complexes

The reaction of 1,2-diselenacyclopentane with N,O,O-tri-(toluene-p-sulphonate)-diethanolamine afforded a new seleno-azacrown ether, i.e. N,N′-ditosyl-1,11-diaza-4,8,14,18-tetraselena cycloicosane (1), in 19% yield, which was comprehensively characterized by elemental analysis, UV–Vis, ¹H NMR and mass spectroscopy. The reaction of 1 with copper(II) perchlorate (Cu(ClO₄)₂) and platinum(IV) tetrachloride (PtCl₄) gave its corresponding copper (2) and platinum complexes (3), respectively. The crystallographic investigations showed that the disparity of metal ion led not only to the distinct crystal system and space group, i.e. monoclinic system (C2/c) for 2 and triclinic system (P-1) for 3, but also the different coordination modes of copper and platinum ions with 1, i.e. normal coordination mode for 2 and ring-contracted coordination mode for 3. Moreover, the metal ions in the crystals 2 and 3 were found in Cu(I) and Pt(II) forms, respectively, although Cu(II) and Pt(IV) were used at the initial stage of coordination reaction.     

N-Lithio-N,N′,N″,N″-tetramethyldiethylenetriamine and N′-Lithio-N,N,N″,N″-tetramethyldiethylenetriamine; Oxidative Coupling of Aminomethyllithium Derivatives

N-lithio-N,N′,N″,N″-tetramethyldiethylenetriamine (I-Li) is formed from 2,5,8,11-tetramethyl-2,5,8,11-tetraazadodecane (III) or from 2,5,8,11,14,17-hexamethyl-2,5,8,11,14,17-hexaazaoctadecane (IV) with n-BuLi or sec-BuLi, respectively, its isomer N′ -lithio-N,N,N″,N″,-tetramethyldiethylene-triamine (II-Li) from tris(2-dimethylaminoethyl)amine (V) with n-BuLi. IV results from treatment of N-lithiomethyl-N,N′,N″,N″-tetramethyldiethylenetriamine (PMDTA-Li) with 1,2-dibromoethane.     

N,N′ and N,O chelated phosphenium cations containing aminotroponiminate or aminotroponate units

New phosphenium cations stabilized by bidentate monoanionic N-isopropyl-2-(isopropylamino)troponiminate or 2-(isopropylamino)troponate units have been synthesized. These complexes were characterized by ³¹P, ¹H and ¹³C NMR spectroscopies, and the molecular structures were determined by X-ray crystallography. These data indicate the formation of N,N′- and N,O-chelate derivatives having three-coordinate phosphorous atoms included in planar heterobicycles. Moreover, computational studies support the presence of high delocalization of the positive charge into the π-conjugated carbon backbone and of the high-lying phosphorus lone-pair orbital.     

Syntheses of 6N(N′-formyl-D-phenylalanyl)-deoxyamino-β-cyclodextrin and 6N(N′-formyl-L-phenylalanyl)deoxyamino-β-cyclodextrin and their inclusion behavior

6N(N-formyl-D-phenylalanyl)-deoxyamino--cyclodextrin and 6N(N-formyl-L-phenylal-anyl)-deoxyamino--cyclodextrin (I andII) were prepared. These new hosts formed intramolecular host-guest complexes and included naphthyl derivatives preferentially with a stoichiometry of 1:1. The inclusion behavior was different between I and II because the cavity shape formed with the CD cavity and the phenylalanine moiety of I was different from that of II.     

Reactions of N-Allyl- and N-Propargyltriflimides with N,N′-Disubstituted Carbodiimides

The alkylating activity of N-allyl- and N-propargyltriflimides toward N,N′-dicyclohexyl- and N,N′-diphenylcarbodiimides has been studied. Activation of the nitrogen atom by two electron-withdrawing trifluoromethanesulfonyl groups favors cleavage of the C–N bond in the absence of a catalyst with the formation of N-substituted unsaturated ureas.

     

Poly(N,N′-dibromo-N-ethyl-benzene-1,3-disulfonamide) and N,N,N′,N′- tetrabromobenzene-1,3-disulfonamide as effective catalysts for conversion of aldehydes to 1,1-diacetates and acetals

Poly(N,N′-dibromo-N-ethyl-benzene-1,3-disulfonamide) [PBBS] and N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide [TBBDA] are effective catalysts for easy preparation of 1,1-diacetates from aldehydes and acetic anhydride, and for easy preparation of acetals using diols under microwave irradiation in the presence of SiO₂.     

Poly(N,N′-dichloro-N-ethyl-benzene-1,3-disulfonamide, N,N,N′,N′-tetrachlorobenzene-1,3-disulfonamide, poly(N,N′-dibromo-N-ethyl-benzene-1,3-disulfonamide, and N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide catalyzed formylation of amines and alcohols using ethyl formate under microwave irradiation

A simple, rapid, and efficient procedure for formylation of primary and secondary amines and alcohols using ethyl formate catalyzed with poly(N,N′-dichloro-N-ethyl-benzene-1,3-disulfonamide (PCBS), N,N,N′,N′-tetrachlorobenzene-1,3-disulfonamide (TCBDA), poly(N,N′-dibromo-N-ethyl-benzene-1,3-disulfonamide (PBBS) and also N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide (TBBDA) was adopted. The reactions were performed under microwave irradiation with high yields.     

The structure effect of N,N,N′,N′-alkylamide in the extraction of uranium and thorium

In this paper, nine N,N,N,N-tetraalkyldiamides have been synthesized and the extracting ability for uranium and thorium under different conditions has been studied. All results were compared with those obtained by using tributyl phosphate (TBP) under exactly the same conditions. The extracting ability of thorium and uranium for different N,N,N,N-tetraalkyldiamides is discussed.     

Substituent and solvent effects on electronic structure and spectral property of ReCl(CO)3(N∧N) (N∧N = glyoxime): DFT and TDDFT theoretical studies

The ground- and excited-state structures of five Re(I) halide glyoxime complexes ReCl(CO)(3)(N(∧)N) (N(∧)N = glyoxime (DHG 1), dimethylglyoxime (DMG 2), cyclohexane dione glyoxime (CHDG 3), dibromoglyoxime (DBG 4), and dimethylformylgloxime (DMFG 5)) have been studied with density functional theory (DFT) and configuration interaction with single excitations (CIS) methods. Time-dependent density functional theory/polarized continuum model (TDDFT/PCM) was carried out to predict the absorption and emission spectra in different media. The effect of substituent and solvent has been researched. It is found that electron-donating groups increase the lowest unoccupied molecular orbital (LUMO) energy resulting in the increased highest occupied molecular orbital (HOMO)-LUMO energy gap. The change leads to their absorption spectra blue shifts in the order 1 > 2 > 3, which arises from the HOMO-1 → LUMO. Just the opposite, electron-withdrawing groups lead to the spectra red shifts (5 > 4 > 1) because of the decreased HOMO-LUMO energy gap. The reorganization energy (λ) calculations show that the relatively balanceable charges transfer abilities of 2 will result in the higher efficiency of organic light emitting devices (OLEDs). In addition, both the absorption and the emission spectra display red shifts in different extents with the decrease of solvent polarity.     

Vibrational Predissociation Spectra of C2N− and C3N−: Bending and Stretching Vibrations

We present infrared predissociation spectra of C₂N⁻(H₂) and C ₃N⁻(H₂) in the 300–1850 cm⁻¹ range. Measurements were performed using the FELion cryogenic ion trap end user station at the Free Electron Lasers for Infrared eXperiments (FELIX) laboratory. For C₂N⁻(H₂), we detected the CCN bending and CC−N stretching vibrations. For the C₃N⁻(H₂) system, we detected the CCN bending, the CC−CN stretching, and multiple overtones and/or combination bands. The assignment and interpretation of the presented experimental spectra is validated by calculations of anharmonic spectra within the vibrational configuration interaction (VCI) approach, based on potential energy surfaces calculated at explicitly correlated coupled cluster theory (CCSD(T)-F12/cc-pVTZ−F12). The H₂ tag acts as an innocent spectator, not significantly affecting the C_2,3N⁻ bending and stretching mode positions. The recorded infrared predissociation spectra can thus be used as a proxy for the vibrational spectra of the bare anions.