Synthesis and spectroscopic studies of methoxy-substituted phenylthienylnicotinamidines

Abstract

Five thienylnicotinamidine derivatives 5a–e were prepared from their corresponding nicotinonitriles 3a–e on treatment with lithium trimethylsilylamide [LiN(TMS)₂] followed by hydrolysis using ethanolic/HCl (gas). The nicotinonitriles 3a–e were prepared via Suzuki coupling reaction of bromothienyl derivative 1 with the appropriate phenylboronic acids 2a–e. The DFT calculation was used to optimize the geometric structure of the newly synthesized nicotinamidines. The comparison of DFT/B3LYP calculated spectral data (¹H-NMR and ¹³C-NMR) with the experimental data showed acceptable agreement. Mass fragmentation patterns of 3,4-dimethoxyphenyl, 3,5-dimethoxyphenyl, and 3,4,5-trimethoxyphenyl thienylnicotinamidine derivatives were investigated.     

Synthesis and cytotoxicity of methyl-and methoxy-substituted metal 8-quinolinethiolates

It has been found that the nature of the substituent, its position in the quinoline ring, and the nature of the metal significantly affect the antitumor activity and toxicity of metal 8-quinolinethiolates. The most cytotoxic towards human fibrosarcoma HT-1080 and mouse hepatoma MG-22A tumor cells are the 6-methoxy-8-quinolinethiolates of rhodium, osmium, iridium, indium, antimony, and bismuth, however these are highly toxic towards normal mouse embryonic NIH 3T3 fibroblasts. The iridium 5-methyl-8-quinolinethiolate is somewhat less active to MG-22A cells but shows quite good selectivity of action because of its markedly lower toxicity. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 711–717, May, 2008.     

Improving convergence of experimental and computed vertical ionization energies using the ionization potential equation-of-motion coupled-cluster with singles and doubles method

Comparison of statistically evaluated experimental vertical ionization energies (IEs) for 53 medium-sized molecules (6-34 atoms) with ionization potential equation-of-motion coupled-cluster with singles and doubles (IP-EOMCCSD) computations shows that discrepancies between computed and experimental results can be accounted for with a combination of experimental and theoretical contributions. Discrepancies can be minimized by extrapolating computations to the complete basis set limit and correcting for vibrational zero-point energy (ZPE) while comparing with experimental IEs calculated as the intensity-weighted mean band position to account for band asymmetries. This procedure reduced the average discrepancy for ethylene, (E)-2-butene, 2,5-dihydrofuran, and pyrrole from 0.25 to 0.05 eV. Agreement between reported vertical IEs and computations without either making adjustments as described in this paper or using complete simulation of the ionization spectrum should be considered fortuitous. The comparisons made in this work show that estimates of vertical and adiabatic IE made using IP-EOMCCSD extrapolated to the complete basis set limit and corrected for vibrational ZPE can be used with reasonable confidence when experimental values are not available.     

Synthesis of para-substituted styrenes

Using double Stille cross-coupling reaction bromo (or chloro)benzylbromide is easily transformed into substituted styrene monomers bearing a wide range of substituents in para position     

Synthesis of styrenes using ruthenium-catalyzed ring-closing enyne metathesis

The synthesis of substituted styrenes was achieved by ring-closing enyne metathesis (RCEM)/elimination of enyne substrates 12. The synthetic approach was also effective for a different type of enyne substrate 14, yielding corresponding styrene 15.     

Density functional study of double ionization energies

In this paper, double ionization energies (DIEs) of gas-phase atoms and molecules are calculated by energy difference method with density functional theory. To determine the best functional for double ionization energies, we first study 24 main group atoms in the second, third, and fourth periods. An approximation is used in which the electron density is first obtained from a density functional computation with the exchange-correlation potential V xc known as statistical average of orbital potentials, after which the energy is computed from that density with 59 different exchange-correlation energy functionals E xc. For the 24 atoms, the two best E xc functional providing DIEs with average absolute deviation (AAD) of only 0.25 eV are the Perdew-Burke-Ernzerhof functional modified by Hammer et al. [Phys. Rev. B 59, 6413 (1999)] and one known as the Krieger-Chen-Iafrate-Savin functional modified by Krieger et al. (unpublished). Surprisingly, none of the 20 available hybrid functionals is among the top 15 functionals for the DIEs of the 24 atoms. A similar procedure is then applied to molecules, with opposite results: Only hybrid functionals are among the top 15 functionals for a selection of 29 molecules. The best E xc functional for the 29 molecules is found to be the Becke 1997 functional modified by Wilson et al. [J. Chem. Phys. 115, 9233 (2001)]. With that functional, the AAD from experiment for DIEs of 29 molecules is just under 0.5 eV. If the two suspected values for C2H2 and Fe(CO)5 are excluded, the AAD improves to 0.3(2) eV. Many other hybrid functionals perform almost as well.     

Synthesis,polymerization, and copolymerization of lactam-substituted styrenes

Four new substituted styrene derivatives carrying lactam rings (2-pyrrolidone or 2-piperidone) in para position have been synthesized, namely 4-(2-oxo-3-methylene-pyrrolidinyl)styrene, 4-(2-oxo-3-methylene-piperidinyl)styrene, 4-(p-styryl)-2-pyrrolidone, and 4-(p-styryl)-2-piperidone. Their homopolymerization and copolymerization with styrene, methyl methacrylate, and acrylic acid have been considered. By ring opening of the side lactam groups, the homopolymers are transformed into the corresponding poly aminocarboxylic acids.     

Valence-shell momentum distributions and ionization energies of carbon disulfide

Valence-shell binding energy spectra and momentum distributions of CS₂ have been measured using non-coplanar symmetric binary (e,2e) spectroscopy. The present measurements are compared with previously published binding energy spectra calculated using the many body 2ph-TDA Green's function (GF) method and the symmetry-adapted cluster configuration-interaction (SAC CI) method. The measured and the calculated binding energy spectra both show extensive population splittings particularly above 20 eV, confirming a significant breakdown of independent particle ionization picture. A relatively strong-outer valence many-body state at 17.0 eV is shown to be satellite of the (2π₀)^?1 state, in accord with earlier conclusions of photoelectron studies. Momentum distributions measured at several carefully chosen binding energies are compared with the corresponding molecular orbital momentum distributions calculated using small and extended gaussian basis sets. The good qualitative agreement between momentum distributions measured in the inner-valence region wth theoretical 4σ_m and 5σ_g orbital momentum distributions confirms the qualitative predictions of satellite parentages by GF and SAC CI calculations. Momentum and position density contour maps of individual orbitals are used to interpret the shapes and atomic characters of the experimental momentum distributions. Momentum densities of the valence orbitals of CS₂ are compared with those of the respective valence isoelectronic species CO₂     

On the structure and valence ionization energies of o-benzyne

The valence ionization energies of o-benzyne, computed using a Green function method and by CI calculations at a molecular geometry optimized with the 6-31G^* basis using a two-term GVB wavefunction, suggest an assignment of the photoelectron spectrum of this molecule which differs from that given by a previous MNDO calculation. The first three ionization energies are found to be nearly degenerate.     

Single and double core-hole ionization energies in molecules

The recently demonstrated ability to measure double-hole core-ionization energies in first-row elements has led to a renewed interest in the use of such energies to investigate the effects of initial-state charge distribution and final-state charge rearrangement on the energies of chemical processes that involve addition of charge to a molecule. With theoretical calculations for the molecules CH(4-n)X(n), X = F, Cl, and for C(CH(3))(4) as a basis, the relationships between one-hole and two-hole ionization energies, on one hand, and initial-state and final-state effects, on the other, are reviewed. It is shown that higher-order corrections to the traditionally used relationships are quantitatively significant but do not lead to qualitatively different conclusions. The role of the Wagner plot as a way to display the relationships among the various quantities of interest is discussed, and a generalized Wagner plot for displaying two-site double-hole ionization energies is presented. Some possible applications of measurements of double-hole ionization energies to the investigation of molecular conformation and molecular fragmentation are discussed.     

Correlation of free-electron molecular orbital energies with π ionization energies of aromatic hydrocarbons

With the introduction of an effective mass m^* into the simple free-electron model, the π-orbital energies of aromatic hydrocarbons containing up to 10 condensed benzene rings correlate closely with the π-band positions of the corresponding photoelectron spectra. For a sample of 70 π-orbitals the linear regression yields a standard error SE = 0.129 eV. Compared to HMO results, the number of accidental degeneracies is drastically reduced and the correlation is significantly improved. The free-electron results also compare favorably to those obtained by the PPP, EH and MINDO/2 methods which were scaled by two additional parameters.     

Copper-catalyzed efficient dithiocyanation of styrenes: Synthesis of dithiocyanates

A novel Cu-catalyzed intermolecular chemoselectivity dithiocyanation of styrenes with ammonium thiocyanate has been developed under mild conditions. This reaction exhibits a wide range of functional-group tolerance in styrenes to afford various dithiocyanates. The reaction mechanism was primarily investigated and a radical process was proposed.     

Synthesis of methoxy-substituted phenols by peracid oxidation of the aromatic ring

[reaction: see text] A novel benign protocol for the preparation of hydroxy-methoxybenzene derivatives is disclosed. By utilizing this protocol, activated aromatic compounds such as 1,3-dimethoxy-2-methyl-benzene and 1-(2,6-dimethoxyphenyl)ethanone are smoothly converted to the corresponding monohydroxylated compound. The reaction can be considered to be a normal aromatic electrophilic substitution reaction, and the regioselectivity for the reaction thus follows the similar rules as for electrophilic substitutions. The protocol is composed by benign reagents, namely, hydogenperoxide, acetic acid, and p-toluene sulfonic acid, which lead to the production of ethaneperoxoic acid in situ. The ethaneperoxoic acid operates as the hydroxylating reagent. The hydroxylation reaction is completed within a short period and requires moreover only mild experimental conditions, which make this novel protocol a green, cheap, and rapid process leading to hydroxy-methoxybenzene derivatives. The proposed reaction mechanism is supported by density functional theory and NMR spectroscopy experiments. The mechanism is constituted by two discrete steps: (a) addition of OH+ to the most nucleophilic carbon atom of the aromatic ring, which is the rate-determining step, and (b) the loss of the proton from the aromatic ring.     

Vertical ionization energies of halogen anions in solution

Based on the constrained equilibrium state theory, the nonequilibrium solvation energy is derived in the framework of the continuum model. The formula for spectral shift and vertical ionization energy are deduced for a single sphere cavity with the point charge assumption. The new model is adopted to investigate the vertical ionization for halogen atomic and molecular anions X^? (X = Cl, Br, I, Cl₂, Br₂, I₂) in aqueous solution. According to the calculation using the CCSD-t/aug-cc-pVQZ method in vacuum, our final estimated vertical ionization energies in solution are very close to the experimental observations, while the traditional nonequilibrium solvation theory overestimates these vertical ionization energies.     

Effects of molecular conformation on inner-shell ionization energies

Experimental evidence for an effect of molecular conformation on inner-shell ionization energies has been observed for the first time. Examples are seen in the carbon 1s spectra of butyronitrile, 1-fluoropropane, and propanal, and other similar molecules. At room temperature these exist in two different conformations, with different distances and, hence, different Coulombic interactions between the negatively charged electronegative group and the methyl carbon. The experimental results are in accord with theoretical predictions with respect to both ionization energies and populations of the different conformers.     

Lower bound problems and bounds to atomic ionization energies

A simple extension of a method by Calogero and Marchioro for constructing lower bound problems for ground states of systems of indistinguishable particles is applied to atomic systems. Their method is extended to yield an improved lower bound problem, which raises the ground‐state estimate and yields nontrivial lower bounds to excited states that were previously inaccessible by their method. Rigorous upper bounds to atomic ionization energies are also derived. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 77: 779–784, 2000     

A combined experimental and computational study on the ionization energies of the cyclic and linear C3H isomers.

For the first time, two hydrogen-deficient hydrocarbon radicals are generated in situ via laser ablation of graphite and seeding the ablated species in acetylene gas, which acts as a carrier and reactant simultaneously. By recording photoionization efficiency curves (PIE) and simulating the experimental spectrum with computed Franck-Condon (FC) factors, we can reproduce the general pattern of the PIE curve of m/z=37. We recover ionization energies of 9.15 eV and 9.76 eV for the linear and cyclic isomers, respectively. Our combined experimental and theoretical studies provide an unprecedented, versatile pathway to investigate the ionization energies of even more complex hydrocarbon radicals in situ, which are difficult to prepare by classical synthesis, in future experiments.