The electronic structure and conformation of dimethylaminobenzonitrile

Ab initio molecular orbital (MO) computations on the closed shell singlet ground state ofN, N-dimethylaminobenzonitrile (DMABN) are reported. Fully optimized structures of several conformers of DMABN were calculated at the HF/6-31G level of theory. Our results indicate that for each of these conformations the minimum energy structure has a trigonal (sp² hybridized] amino nitrogen. The most stable DMABN conformer was found to be planar with its methyl groups eclipsed. The Koopmans ionization potentials and dipole moments of the various ground state conformers are compared. The implications for dynamical models of twisted-intramolecular charge transfer (TICT) are discussed. Moreover, the use of qualitative MO theory arguments provides an interpretation of the computational results in a simple orbital interaction framework.A. Mellon Foundation Fellow (1989–1992).Operated for the U.S. Department of Energy by Battelle Memorial Institute under Contract DE-AC06-76RLO 1830.     

Direct nitration of aldehyde arylhydrazones and the use of the products in the synthesis of some heterocyclic compounds

Direct nitration of substituted benzaldehyde p-nitrophenylhydrazones 1 gave α-nitroarylidene-p-nitrophenylhydrazines 2 . Reactions of 2 with nucleophiles result in displacement of the nitrite. Treatment of 2 with potassium thiocyanate gave 5-imino-1,3,4-Δ²-thiadiazolines 10 . Reactions of 2 with carbanions of active methylene compounds yielded the pyrazole derivatives 15–20 . 1,3-Dipolar cycloadditions of 2 onto acrylonitrile and benzalacetophenone afforded the expected cycloadducts 21 and 22 , respectively.     

On global and local properties of clar Pi-Electron sextets

The individual rings in benzenoid systems are studied via a new structural index, called Clar's ring character. The new index, which is based onselected Kekulé valence structures, differs significantly in a number of cases from similar ring characterizations based onall Kekulé valence structures. It is related to previously introduced quantities based on MO functions, but it can be obtained simply (i.e. without the need of a computer). We have illustrated the new ring index for several families of compounds, and report a number of regularities for a homologous series of molecules.Operated by Iowa State University for the U.S. Department of Energy under Contract No. W-7405-Eng 82. This work was supported by the Office of the Director.     

Synthesis, crystal structure, and thermal properties of {[Cd2(L1)3(sac)4]⋅2CH2Cl2}∞: A coordination polymer with non-interpenetrating ladders containing cadmium in a rare, trigonal bipyramidal coordination environment (L1 = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, sac = saccharinate)

The new coordination polymer, {[Cd₂(L1)₃(sac)₄]?2CH₂Cl₂}_∞:, has been prepared from the reaction of 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene (L1) with [Cd(sac)₂(H₂O)₄].2H₂O(sac = saccharinate) in a methylene chloride/ethanol solvent mixture. The compound features a non-interpenetrating ladder motif constructed from Cd(L1)3 T-shaped units. The Cd atoms are coordinated to three nitrogen donor atoms from three L1 ligands and two nitrogen donor atoms from two saccharinate ligands in a rare, trigonal bipyramidal coordination environment. The compoundwas further characterized by IR spectroscopy and DTA/TGA. {[Cd₂(L1)₃(sac)₄]?2CH₂Cl₂}_∞: crystallizes in the triclinic space group P-1 with a = 10.8747(19)Å, b = 12.626(2)Å, c = 15.749(3)Å, α = 111.839(3)^°, β = 97.442(3)., and γ = 106.239(3)^°     

Facile synthesis and characterization of novel pyrido[3′,2′:4,5]thieno[3,2-d]pyrimidin-4(3H)-one and pyrido[2′,3′:3,4]pyrazolo[1,5-a]pyrimidine incorporating 1,3-diarylpyrazole moiety

4-(3-(4-Hydroxyphenyl)-1-phenyl-1H-pyrazol-4-yl)-6-phenyl-2-thioxo-1,2-di hydro-pyridine-3-carbonitrile (1) reacted with ethyl chloroacetate (2) in ethanolic sodium acetate solution to yield the corresponding ethyl (3-cyanopyridin-2-ylsulphanyl)acetate derivative 3. Intramolecular cyclization of compound 3 was achieved by its heating in DMF containing potassium carbonate to afford the corresponding ethyl 3-aminothieno[2,3-b]pyridine-2-carboxylate derivative 4 which reacted with hydrazine hydrate in refluxing pyridine to yield the starting material 3-aminothieno[2,3-b]pyridine-2-carbohydrazide derivative 7. Compound 7 reacted with different reagents such as triethylorthoformate, formic acid, acetic acid and acetic anhydride to afford the target molecules pyrido[3′,2′:4,5]thieno[3,2-d]pyrimidin-4(3H)-one derivatives 8–10, 12 and 13 in good to excellent yields. On the other hand, pyridine-2(1H)-thione derivative 1 reacted with hydrazine hydrate in refluxing pyridine to give the other starting material 3-amino-1H-pyrazolo[3,4-b]pyridine derivative 20 which reacted with acetylacetone under reflux to afford the target molecule pyrido[2′,3′:3,4]pyrazolo[1,5-a]-pyrimidine derivative 21 in a good yield. The structures of target molecules were elucidated using elemental analyses and spectral data.     

Host-Guest Complexation of Oxaliplatin and Para-Sulfonatocalix[n]Arenes for Potential Use in Cancer Therapy

P-sulfonatocalix[n]arenes have demonstrated a great potential for encapsulation of therapeutic drugs via host-guest complexation to improve solubility, stability, and bioavailability of encapsulated drugs. In this work, guest-host complexes of a third-generation anticancer drug (oxaliplatin) and p-4-sulfocalix[n]arenes (n = 4 and 6; p-SC4 and p-SC6, respectively) were prepared and investigated, using ¹H NMR, UV, Job’s plot analysis, and DFT calculations, for use as cancer therapeutics. The peak amplitude of the prepared host-guest complexes was linearly proportional to the concentration of oxaliplatin in the range of 1.0 × 10⁻⁵ M⁻¹ to 2.1 × 10⁻⁴ M⁻¹. The reaction stoichiometry between either p-SC4 or p-SC6 and oxaliplatin in the formed complexes was 1:1. The stability constants for the complexes were 5.07 × 10⁴ M⁻¹ and 6.3 × 10⁴ M⁻¹. These correspond to complexation free energy of −6.39 and −6.52 kcal/mol for p-SC4 and p-SC6, respectively. Complexation between oxaliplatin and p-SC4 or p-SC6 was found to involve hydrogen bonds. Both complexes exhibited enhanced biological and high cytotoxic activities against HT-29 colorectal cells and MCF-7 breast adenocarcinoma compared to free oxaliplatin, which warrants further investigation for cancer therapy.