Micowave assisted synthesis of benzo‐substituted macrocyclic diamides and their corresponding macrocyclic dithiodiamides

A synthesis of a series of macrocyclic diamides 3 in good yields by reacting the corresponding bis phenols 4 with the appropriate dihalo alkanes 6 either in solvent or in dry media under microwave irradiation. Thiation of 3 with P₂S₅ or Lawesson's reagent in solvent free conditions under microwave irradiation is also described.     

Uranyl-selective PVC membrane electrodes based on some recently synthesized benzo-substituted macrocyclic diamides

Four different recently synthesized macrocyclic diamides were studied to characterize their abilities as uranyl ion carriers in PVC membrane electrodes. The electrodes based on macrocycle 1,18-diaza-3,4;15,16-dibenzo-5,8,11,14,21,24-hexaoxacyclohexaeicosane-2,17-dione resulted in a Nernstian response for UO(2)(2+) ion over wide concentration ranges. The linear concentration range for the polymeric membrane electrode (PME) is 3.0x10(-6)-8.2x10(-3) M with a detection limit of 2.2x10(-6) and that for the coated graphite electrode (CGE) is 5.0x10(-7)-1.5x10(-3) M with a detection limit of 3.5x10(-7) M. The electrodes manifest advantages of low resistance, very fast response and, most importantly, good selectivities relative to a wide variety of other cations.     

Semi-empirical molecular orbital calculations on some tautomers of cytosine

The stability of a series of cytosine tautomers has been investigated using both all valence electron and -electron SCF methods. The effect of general and selective scaling of the bond lengths was studied in the CNDO/2 calculations. The enol tautomer of cytosine exceeded the keto form in stability in these calculations. -electron SCF CI calculations were performed on the cytosine tautomers using two different parameterization schemes. The calculated transitions obtained for the enol form showed a close proximity to that of the keto and imino structures. Comparison was made with the experimental electronic spectrum in water and acetonitrile. No clear distiction between the keto and enol forms could be made on the basis of these calculations.

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Zusammenfassung Die StabilitÄt einer Reihe von Cytosin-Tautomeren wurde mit einer Allvalenzelektronen- und mit einer -Elektronen-SCF-Methode untersucht. Die Auswirkung einer allgemeinen als auch selektiven Skalierung der BindungslÄngen wurde bei den CNDO2-Berechnungen untersucht. Das Enoltautomere des Cytosins übertrifft nach diesen Rechnungen die Ketoform an StabilitÄt. Bei den -Elektronen-SCF-CI-Rechnungen wurden zwei Methoden der Parametrisierung angewandt. Die für die Enolform berechneten übergÄnge zeigten eine gro\e Ähnlichkeit zu denjenigen der Keto- und Iminostrukturen. Die berechneten Werte wurden mit dem experimentellen Spektrum von Cytosin in Wasser sowie Acetonitril verglichen. Auf Grund der Berechnungen konnte keine klare Unterscheidung zwischen der Keto- und der Enolform getroffen werden.

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Résumé Etude de la stabilité d'une série de tautomères de la cytosine par les méthodes SCF à électrons de valence et à électrons . L'effet d'ajustement global ou selectif des longueurs de liaison a été étudié dans le cadre CNDO/2. Le tautomère énolique de la cytosine s'avère dans ces calculs plus stable que la forme cétonique. Des calculs d'électrons SCF CI ont été effectués sur les tautomères de la cytosine en utilisant deux schémas différents pour la paramétrisation. Les transitions calculées obtenues pour la forme énolique montrent une grande analogie avec celles des structures cétoniques et iminiques. La comparaison a été faite avec le spectre électronique expérimental dans l'eau et l'acétonitrile. Aucune distinction claire entre les formes cétoniques et énoliques n'a pu Être faite à partir de ces calculs.

     

A facile and efficient synthetic approach to novel lariat macrocyclic diamides and bis macrocyclic diamides

The hydroxy macrocycles 8, 19a‐c were prepared in 40–55% yields by reacting the dipotassium salts 2a‐c with each of epichlorohydrin ( 7 ) and bis(chloromethyl) derivative 18 . Acylation of the hydroxyl group of each of 8, 19a‐c with 2‐chloroacetylchloride ( 9 ) in DMF gave the corresponding esters 10, 20a,b . Reaction of the latter with different amines as well as phenoxides furnished exclusively the target lariat macrocycles 13a‐c, 22a‐c and 23a‐c in 60–63% and 50–55% yields, respectively. Amination of two equivalents of the chloroacetyloxy derivative 10 and 2a,b with 1 equiv. of piperazine ( 12c ) afforded the corresponding bismacrocycles 14 and 26a,b respectively, in 60–65% yields. Moreover, the novel bis(macrocycles) 27–29 were prepared in 45–50% yields, respectively, by reacting each of 20a,b with the dipotassium salts 2b, 24 and 25 respectively, in DMF.     

Efficient synthesis and metal cations complexation of some novel dinaphthosulfide-substituted macrocyclic diamides

Some dinaphthosulfide aza macrocycles (3–9) were synthesized based on the conventional route from the reaction of corresponding dinaphthosulfide diester and aliphathic diamines in refluxing methanol in good yields. Dinaphthosulfide diester were synthesized from the reaction of 1,1′-thiobis (2-hydroxy naphthalene) and methyl chloroacetate. The structures of these compounds were confirmed using IR, ¹H NMR, ¹³C NMR, MASS spectroscopy and elemental analysis. Conductometric studies of the complexation of some metal ions with aza derivative 8 (TDN) in methanol as solvent implied the formation of 1:1 complexes. The stability of the 1:1 complexes of TDN decreases in the order Hg²⁺ >> Pb²⁺ > Cu²⁺ > Zn²⁺ > Ca²⁺ > Mg²⁺ > Cd²⁺ > Sr²⁺ > Ag⁺ > Ba²⁺.     

Study on the interaction between dinaphthosulfide-substituted macrocyclic diamides and some metal ions: experimental measurements vs. quantum mechanical calculations

Complexation properties of dinaphthosulfide-substituted macrocyclic diamides 1 and 2 with some metal cations that have been obtained by conductometric method are described with quantum mechanics calculations. To do this, the most stable structures of ligands, Hg²⁺-ligand complexes, ligand-MeOH and ClO₄ ^?–MeOH are optimized at HF/Lanl2dz level of theory and the most important interactions are analyzed by atoms in molecules (AIM) theory. These calculations predict the existence of strong interaction between Hg²⁺ cation and ligands 1 and 2, particularly, S–Hg²⁺ interaction. The different conductometric behaviors of complexation of ligands 1 and 2 with metal ions are interpreted on the basis of the calculated intramolecular hydrogen bonds in ligands and intermolecular hydrogen bonds between ligands and methanol as a solvent and perchlorate as a counter ion. In addition, binding energies between Hg²⁺ and ligands are also calculated by HF/Lanl2dz level of theory. Results show that all theoretical predictions are in line agreement with the experimental data.     

Synthesis, mechanism of formation, and molecular orbital calculations of arylamidoximes

Abstract  

A simple and easy synthesis of ten arylamidoximes from arylnitriles and hydroxylamine is described. The formation of the arylamides has been observed to a much lesser extent in the present work. A new mechanism for the formation of arylamidoximes, as well as arylamides, from arylnitriles and hydroxylamine is suggested. Quantum mechanical calculations have been carried out to support this mechanism. The enthalpy of formation in conjunction with atomic charges of the reactants and intermediates helped to understand more about the generation of the products.     

Ab initio molecular orbital calculations

A series of non-empirical calculations on furan, pyrrole and 1,2,5-oxadiazole are reported in which the effect of polarisation functions added to the minimal 7s 3p basis on each atom is studied. The effect on these planar molecules is largely through the rather than the-system. A comparison with the results of work with scaled functions is reported. Both series are shown to lead to much improved agreement with the electron spectroscopy energy levels. The effect on the dipole moments of these changes in basis is more variable but, with the exception of furan, the agreement with experiment is improved in the present method.

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Zusammenfassung Für die Moleküle Furan, Pyrrol und 1,2,5-Oxadiazol wurde eine Reihe von nichtempirischen Rechnungen durchgeführt, in denen der Einfluß von zusätzlichen Polarisationsfunktionen zur minimalen 7s 3p-Basis an jedem Atom untersucht wird. Die Ergebnisse werden mehr durch die Art der Beschreibung des Systems der-Elektronen als durch diejenige der-Elektronen beeinflußt. Ein Vergleich mit den Ergebnissen bei Verwendung skalierter Funktionen wird durchgeführt. Beide Reihen von Ergebnissen zeigen eine verbesserte Übereinstimmung zu den Energiemeßwerten der Elektronenspektroskopie. Die Änderungen des berechneten Dipolmoments bei derartigen Basisvariationen sind größer als bei früheren Methoden. Die Übereinstimmung mit dem Experiment wird, mit Ausnahme von Furan, jedoch verbessert.

     

Ab Initio molecular orbital calculations

Linear combinations of Gaussian orbitals were contracted to minimal basis sets. The binding energies (B.E.) obtained for the three compounds furan, pyrrole and 1,2,5-oxadiazole are 0.75, 0.84 and 0.26 a.u. respectively. Correlation of these figures and those obtained in related calculations leads to the relationship (B.E.)_exp.=0.7347 (B.E.)_calc.+633 (Kcal/mole). The photoelectron spectra of these compounds are extended and correlated with the orbital energies; the -electron excitations are given by (I.P.)_exp.=1.00 (I.P.)_calc.–2.20 eV. Mulliken population analyses give dipole moments in reasonable agreement with experiment.

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Zusammenfassung Linearkombinationen von Gauß-Orbitalen wurden zu minimalen Basissätzen kontrahiert.Die Bindungsenergien (B.E.) für die drei Komponenten Furan, Pyrrol und 1,2,5-Oxadiazol haben die Werte: 0,75, 0,84 und 0,26 a.u. Setzt man diese Werte zu den berechneten in Beziehung, so erhält man die Gleichung: (B.E.)_exp.=0,7347 (B.E.)_calc.+633 (Kcal/Mol).Die Photoelektronenspektren dieser drei Komponenten werden erweitert und mit den Orbitalenergien korreliert; die -Elektronen-Anregungsenergien werden durch die Beziehung: (I.P.)_exp. =1.00 (I.P.)_calc.–2,20 eV gegeben. Mulliken-Populations-Analysen ergeben die Dipolmomente in bemerkenswerter Übereinstimmung mit experimentellen Werten.

     

Semiempirical molecular orbital calculations on boranes

Traditional Pariser-Parr-Pople and variable electronegativity calculations have been carried out on C₆H₅B(OR)₂ and p-CH₃OC₆H₄B(OR)₂, and the results compared with calculations for C₆H₅BR₂. It is concluded that the VE-SCF method offers a real advantage over the simple PPP method for predicting percent charge transfer and transition intensity in cases where excited states possess substantial C.T. character. The restriction that empirically chosen parameters fit the observed transition energies and intensities of both triarylboranes and ArB(OR)₂ requires the choice of a boron VSIP greater than 2.0 eV in the fixed parameter procedure of the usual PPP-SCF-CI method for these molecules. Observed transitions in C₆H₅B(OR)₂ correlate with ¹ L _b, ¹ L _a, ¹ B _b, whereas the first absorption maximum of (C₆H₅)₃B is assigned to C.T. (¹ A ₁¹ A ₁) local C _2v symmetry.

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Zusammenfassung PPP- und VE SCF-Rechnungen wurden für C₆H₅B(OR)₂ und p-CH₃OC₆H₄(OR)₂ durch- geführt, und die Ergebnisse wurden mit denjenigen für C₆H₅BR₂ verglichen. Es kann der Schluß gezogen werden, daß die VE SCF-Methode einen Vorteil gegenüber der einfachen PPP-Methode bietet, um den prozentualen Charge Transfer und Übergangsintensitäten in Fällen zu bestimmen, in denen die angeregten Zustände einen wesentlichen C.T.-Charakter besitzen. Die Bedingung, daß die empirisch gewählten Parameter den beobachteten Übergangsenergien und -intensitäten von sowohl Triarylboranen als auch ArB(OR)₂ angepaßt sein sollen, erfordert die Wahl eines Bor-VSIP größer als 2,0 eV im Rahmen der üblichen Parametrisierung der PPP-SCF-CI-Methode. Beobachtete Über-gänge in C₆H₅B(OR)₂ korrelieren mit ¹ L _b, ¹ L _a, ¹ B _b, wogegen das erste Absorptionsmaximum des (C₆H₅)₃B einem C.T.-Übergang (¹ A ₁¹ A ₁) lokaler C_2v -Symmetrie zugeordnet wird.

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Résumé Des calculs traditionnels Pariser-Parr-Pople et des calculs d'électronégativité variable ont été effectués sur C₆H₅B(OR)₂ et p-CH₃OC₆H₄B(OR)₂ avec comparison aux résultats obtenus pour C₆H₅BR₂. La conclusion est que la méthode VE-SCF offre un réel avantage sur la méthode PPP simple en ce qui concerne la prédiction du transfert de charge et de l'intensité de transition pour les états excités possédant un net caractère de transfert de charge. La restriction selon laquelle les paramètres empiriques doivent permettre de reproduire les énergies de transition et les intensités des deux triarylboranes et de ArB(OR)₂, nécessite le choix d'un potential d'ionisation de l'état de valence du bore supérieur de 2 eV à celui employé dans les méthodes ordinaires. Les transitions observées dans C₆H₅B(OR)₂ sont reliées à ¹ L _b, ¹ L _a, ¹ B _b, tandis que la première absorption de (C₆H₅)₃B est attribuée à un transfert de charge (¹ A ₁¹ A ₁) de symétrie locale C_2v.

     

Flavin enzymes: molecular orbital calculations

Molecular orbital calculations were obtained for one hundred and forty-four versions of the flavin group contained in oxidase enzymes. Ten different structures were considered and the results indicate that the flavin group changes its identity from a pi electron acceptor to a pi electron donor after reduction occurs, regardless of the inductive effect of the attached protein. Furthermore, the calculations suggest both the site for reduction and the mechanism by which it proceeds.     

Aromatic polyamides. I. Synthesis and characterization of some aromatic polyamides and their model diamides

The synthesis of some wholly aromatic polyamides based on unsubstituted and chloro- and nitro-substituted diamines by low temperature solution polymerization is described. Poly(1,3-phenylene isophthalamide) and poly(chloro-2,4-phenylene isophthalamide) were selected for further investigation. To study the two polyamides on a systematic basis their model diamides were synthesized. These materials were characterized with respect to chemical structure and purity by elemental analysis, infrared (IR), and nuclear magnetic resonance (NMR) spectroscopic techniques. The usefulness of the model compounds in the interpretation of the polymer spectra is also demonstrated.     

Ab initio molecular orbital calculations on some selected boron(I) hydrides

Ab initio LCAO-MO-SCF Hartree-Fock-Roothaan calculations have been carried out for a series of closed-shell boron hydrides (B³⁺, B⁺ BH, BH₂⁻,BH₂⁺, BH₃ and BH₄⁻). Koopmans' theorem vertical ionization potentials for the core and highest occupied molecular orbitals are presented. Proton and hydride affinities of some of these molecules have been calculated along with the energies of reaction between various pairs of these boron hydrides.     

Semi-empirical molecular orbital calculations for pyridinealdoximes and acetamidopyridines

Tautomerism of pyridinealdoximes and acetamidopyridines is discussed with regard to their electronic absorption spectra. The spectra of both neutral and ionic forms of the molecules are interpreted by means of the Pariser—Parr—Pople type of calculation in a satisfactory way.The stability of 2- and 4-pyridinealdoxime tautomers is investigated using the CNDO/2 method. The lactim are more stable than the lactam forms of the molecules. The molecules having the substituent group of the syn-configuration are more stable than the molecules with other configurations of the substituent.     

Self-consistent molecular orbital calculations on organoboron compounds

The Pariser-Parr-Pople method has been used to calculate the electronic structures and spectra of three methylvinylboranes. Two separate calculational models of the methyl group are considered and the agreement between observed and calculated spectral quantities is good. The reorganisation energies of these molecules are also evaluated.

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Zusammenfassung Mit der Methode von Pariser, Pople und Parr werden Struktur und Spektren der -Elektronensysteme von drei Methylvinylboranen berechnet, ebenso ihre Reorganisationsenergien. Für die Methylgruppe werden zwei verschiedene Modelle verwendet. Die übereinstimmung zwischen berechneten und experimentellen Werten ist gut.

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Résumé A l'aide de la méthode Pariser-Parr-Pople nous avons calculé les structures et les spectres -électroniques de trois méthylvinylboranes. Nous considérons deux modèles du groupe méthyl; les spectres observés et calculés s'accordent bien. En plus, les énergies de réorganisation de ces molécules sont évaluées.

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One of us (D.R.A.) wishes to thank the S.R.C. for a maintenance grant.     

Self-consistent molecular orbital calculations on organoboron compounds

The PPP-SCMO-method is used to calculate the energies of the ground and lower excited states of triphenylborane and tri-p-tolylborane for which both planar and propellor models are considered. It is found necessary to include a large measure of configuration interaction in the excited states in order to produce satisfactory agreement with published u.v. spectra. However the calculations are not diagnostic for the detailed geometry of these compounds. The electronic spectra may be interpreted in terms of ring exciton states and interring and phenyl-boron charge-resonance states. The electron density on the central atom and the B-C bond orders are small and so the phenyl rings are but little perturbed by their bonding to boron.

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Zusammenfassung PPP-SCMO-Rechnungen wurden für Triphenyl- und Tri-p-tolylboran durchgeführt. Ohne ausgedehnte Konfigurationenwechselwirkung erhält man keine befriedigende Übereinstimmung mit veröffentlichten UV-Spektren. Die Deutung der Elektronenspektren geschieht mit Hilfe der Begriffe der einzelnen Einganregung sowie des Ring-Ring- und des Ring-Bor-Ladungsaustausches. Ob die Molekeln in einer planaren oder einer Propeller-Konformation vorliegen, kann aufgrund dieser Rechnungen nicht entschieden werden. Bor--Ladung und B-C--Bindungsordnung sind gering; die Phenylringe werden durch ihre Bindung an Bor kaum beeinflußt.

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Résumé La méthode SCMO-PPP a été utilisée pour calculer les énergies de l'état fondamental et des plus bas états excités du triphènylborane et du tri-p-tolylborane pour lequel on a considéré les modèles plan et en hêlice de bâteau. L'inclusion d'une interaction de configurations étendue entre états excités est nécessaire pour obtenir un accord satisfaisant avec les spectres UV publiés. Mais les calculs ne permettent pas de préciser la géométrie détaillée de ces composés. Les spectres électroniques peuvent être interprétés en termes d'états excitoniques du cycle et d'états de résonance de charge entre cycles et entre le phényl et le bore. La densité électronique sur l'atome central et les indices de liaison sur les liaisons B-C sont faibles ce qui montre que les noyaux phényliques sont peu perturbés par leur liaison au bore.

     

Self-consistent molecular orbital calculations on organoboron compounds

The electronic structures of three dihalogenophenylboranes have been investigated by the Pariser-Parr-Pople method. The agreement between the observed and calculated electronic spectra is quite good.

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Zusammenfassung Die -Elektronen-Strukturen von drei Dihalogenphenylboranen wurden mit der PPP-Methode untersucht. Beobachtete und berechnete Elektronenspektren stimmen recht gut überein.

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Résumé On a étudié par la méthode de Pariser-Parr-Pople les structures électroniques de trois dihalogénophenylboranes. L'accord entre les spectres électroniques observés et calculés est assez satisfaisant.