O,O'-Disubstituted N,N'-dihydroxynaphthalenediimides (DHNDI): first principles designed organic building blocks for materials science

N,N'-Disubstituted naphthalenediimides (NDIs), planar, electron-deficient building blocks, play an important role in materials and biological sciences. Naphthalene core substituents control the HOMO and LUMO energies, whereas the N-alkyl or aryl substituents affect the solubility, aggregation, and packing propensity in condensed phases. N,N'-Dihydroxynaphthalenediimide (DHNDI) allows expanding the chemical diversity by O-alkylation, acylation, or sulfonylation; these derivatives also allow fine-tuning of the HOMO/LUMO levels. The synthesis, UV-vis, electrochemical, solid state, and computational prediction of the properties of such derivatives are presented.     

Microwave-assisted synthesis of N,N'-diaryl cyanoguanidines

[reaction: see text] A mild, efficient, and high-yielding method for the synthesis of N,N'-diaryl cyanoguanidines from their corresponding thioureas under microwave-assisted conditions is described. A series of cyanoguanidines were synthesized containing both electron-donating and electron-withdrawing substituents. The reactions were facilitated by the use of polar solvents along with moderate temperatures.     

Use of 13C NMR Spectroscopy to Establish the Structure of 6(7)-R-Quinoxaline N,N′-Dioxides

The effect of substituents in position 6 on the positions of the signals of the carbon atoms in the ¹³C NMR spectra of substituted 1,2,3,4-tetrahydro-5,10-phenazine N,N′-dioxides has been analyzed, increments of substituents have been found, and a scheme has been proposed for the calculation of the chemical shifts of carbon atoms in the ¹³C NMR spectra of 6(7)-R-quinoxaline N,N′-dioxides. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, 1076–1080, July, 2005.     

Complete assignment of the 1H, 13C, 15N and 19F NMR spectra of nine DL-phenylalcoholamide anticonvulsants

The 1H, 13C, 15N and 19F NMR spectra of nine DL-phenylalcoholamides bearing fluorine and chlorine as substituents of the phenyl ring are reported. All of them are active as anticonvulsants in pentylenetetrazole-induced seizures.     

1H, 13C,and 14N NMR study of 3-methylfurazans with nitrogen-containing substituents at position 4

3-Methylfurazans with nitrogen-containing substituents at position 4 were studied by ¹H, ¹³C, and ¹⁴N NMR spectroscopy. A correlation between the chemical shifts in ¹³C NMR spectra of these furazans and monosubstituted benzenes with the same substituents was found. The increments for a number of furazan-containing substituents were determined for the first time.     

Synthesis and color of 2-(N,N-diethyl-p-quinonediimine)-indazolones

A number of substituted 2-(N, N-diethyl-p-quinonediimine)indazolones have been synthesized, and their optical properties investigated. It has been shown that introduction of electrophilic substituents into the benzene ring of an indazolone gives rise to a bathochromic shift in the absorption spectra of 2-(N, N-diethyl-p-quinonediimine)indazolones in alcohol and benzene solution.     

15N chemical shifts in aziridines

For a number of 1-substituted aziridines and also some 1,2-disubstituted aziridines it has been shown that electron-donating substituents on the nitrogen atom produce a downfield shift of the ¹⁵N resonance. The ¹⁵N chemical shifts of aziridines correlate with the ¹⁵N shifts in N,N-dimethylamines and primary amines as well as with the ¹⁷O shifts in oxiranes. A correlation is also observed between the ¹⁵N chemical shifts and the electronegativity of the substituents on the nitrogen atom.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, 1336–1339, October, 1988.     

Benzimidazolin-2-stannylenes with N,N'-alkyl (Me and Et) and Lewis base functional groups

Symmetrically and unsymmetrically N,N'-substituted benzimidazolin-2-stannylenes with sterically nondemanding alkyl (Me and Et) and Lewis base functional groups (-(CH2)nOMe, -(CH2)nNMe2; n=2, 3) have been synthesized by the transamination reaction between suitably substituted o-phenylenediamines and Sn[N(SiMe3)2]2. The N,N'-dimethyl-substituted stannylene 3 exists in the solid state as a bimolecular aggregate which is held together by strong intermolecular Sn...N interactions leading to three-coordinated tin atoms. The benzimidazolin-2-stannylenes with N,N'-(CH2)nOMe substituents (5, n=2; 6, n=3) exhibit weak intramolecular Sn...O interactions in solution. Benzannulated stannylenes with N,N'-(CH2)nNMe2 substituents (7, n=2; 8, n=3) are again dimers which exhibit both intramolecular Sn...NMe2 and intermolecular Sn...N interactions, which leads to tri- or tetracoordinated tin atoms. Some unsymmetrically N,N'-substituted benzimidazolin-2-stannylenes have also been synthesized. The molecular structures of 3, 5, and 8 and the relation between the chemical shift recorded for the tin atoms and the solvent (C6D6 or THF-d8) used for recording 119Sn NMR spectra will be discussed.     

Etude par RMN du carbone des systèmes CN: imines,phénylhydrazones,semicarbazones, amidines,iminoéthers

A carbon-13 NMR study of compounds containing C?N or conjugated C? N bonds (iminoethers, saturated and unsaturated aliphatic imines, amidines, oximes, phenylhydrazones, semicarbazones) is presented. The influence of the Z/E isomerism, the substituents and the steric effects on the chemical shifts are discussed.     

Conformational equilibrium of N,N-disubstituted 5-phenyl-1,3,5-diazaphosphorinanes and their derivatives

Conclusions In the conformational equilibrium of N,N-disubstituted 5-phenyl-1,3,5-diazaphosphorinanes and their oxides and sulfides forms can exist with an axial substituent on one of the heteroatoms, as well as a form with all equatorial substituents at the P and N atoms.Translated from Izvestiya Akademii Nauk SSSR, Seriyra Khimicheskaya, No. 7, pp. 1539–1544, July, 1981.     

Saturated amine oxides: Part 8. Hydroacridines: Part 27. Effects of N-oxidation and of N-quaternization on the 15N NMR chemical shifts of N-methylpiperidine-derived mono-, bi-, and tricycloaliphatic tertiary amines

The (15)N chemical shifts of 13 N-methylpiperidine-derived mono-, bi- and tricycloaliphatic tertiary amines, their methiodides and their N-epimeric pairs of N-oxides were measured, and the contributions of specific structural parameters to the chemical shifts were determined by multilinear regression analysis. Within the examined compounds, the effects of N-oxidation upon the (15)N chemical shifts of the amines vary from +56 ppm to +90 ppm (deshielding), of which approx. +67.7 ppm is due to the inductive effect of the incoming N(+)--O(-) oxygen atom, whereas the rest is due to the additive shift effects of the various C-alkyl substituents of the piperidine ring. The effects of quaternization vary from -3.1 ppm to +29.3 ppm, of which approx. +8.9 ppm is due to the inductive effect of the incoming N(+)--CH(3) methyl group, and the rest is due to the additive shift effects of the various C-alkyl substituents of the piperidine ring. The shift effects of the C-alkyl substituents in the amines, the N-oxides and the methiodides are discussed.     

Substituent cross-interaction effects on the electronic character of the C=N bridging group in substituted benzylidene anilines--models for molecular cores of mesogenic compounds. A 13C NMR study and comparison with theoretical results

13C NMR chemical shifts delta(C)(C=N) were measured in CDCl3 for a wide set of mesogenic molecule model compounds, viz. the substituted benzylidene anilines p-X-C6H4CH=NC6H4-p-Y (X = NO2, CN, CF3, F, Cl, H, Me, MeO, or NMe2; Y = NO2, CN, F, Cl, H, Me, MeO, or NMe2). The substituent dependence of delta(C)(C=N) was used as a tool to study electronic substituent effects on the azomethine unit. The benzylidene substituents X have a reverse effect on delta(C)(C=N): electron-withdrawing substituents cause shielding, while electron-donating ones behave oppositely, the inductive effects clearly predominating over the resonance effects. In contrast, the aniline substituents Y exert normal effects: electron-withdrawing substituents cause deshielding, while electron-donating ones cause shielding of the C=N carbon, the strengths of the inductive and resonance effects being closely similar. Additionally, the presence of a specific cross-interaction between X and Y could be verified. The electronic effects of the neighboring aromatic ring substituents systematically modify the sensitivity of the C=N group to the electronic effects of the benzylidene or aniline ring substituents. Electron-withdrawing substituents on the aniline ring decrease the sensitivity of delta(C)(C=N) to the substitution on the benzylidine ring, while electron-donating substituents have the opposite effect. In contrast, electron-withdrawing substituents on the benzylidene ring increase the sensitivity of delta(C)(C=N) to the substituent on the aniline ring, while electron-donating substituents act in the opposite way. These results can be rationalized in terms of the substituent-sensitive balance of the electron delocalization (mesomeric effects). The present NMR characteristics are discussed as regards the computational literature data. Valuable information has been obtained on the effects of the substituents on the molecular core of the mesogenic model compounds.     

N, P, and As ylides and aza- and arsa-Wittig reactions from topological analyses of electron density

The nature of bonding between N, P, and As constituent atoms in ylide systems with the R(3)XYR' formula (X = N, P, As; Y = N, P, As; R = F, H; R' = H, CH(3)) has been characterized by ab initio (MP2/6-311++G**) and density functional theory (B3LYP/6-311++G**) calculations. Its electronic structure has been analyzed through electron density with the quantum theory of atoms in molecules and the electron localization function (ELF). The characteristics of the central bond are inspected with the calculated rotational barriers. The results show that N has a behavior different from that of the remaining pnicogen atoms (P, As), where the bond is much stronger. Fluorine substituents strengthen the X-Y bond, reduce the bond distance, and increase the electron density in the central bond so that the substituent pulls charge from the bond in the pnicogen X atom. For the N-pnicogen ylides, the results showed different bonding characters between F and X atoms; depending on the position of the F atom, the difference of the bond character is sensed by the basin synaptic order, as it is deduced from the analysis of the ELF basins. The energy profiles of the rotational barriers have been calculated at the MP2/6-311++G** level, indicating that the electronegativity of the substituents is a relevant factor that has consequences in the characteristics of the X-Y bond.     

Base-assisted one-pot synthesis of N,N',N"-triaryltriazatriangulenium dyes: enhanced fluorescence efficiency by steric constraints

In this paper we report the first synthesis of cationic N,N',N"-triaryltriazatriangulenium dyes (Ar(3)-TATA(+)). Previously, only alkyl-substituted triazatriangulenium derivatives (R(3)-TATA(+)) were known, a consequence of the low reactivity of anilines in the aromatic nucleophilic substitution reaction leading to the formation of the TATA(+) core. The synthesis of Ar(3)-TATA(+) was achieved by heating the tris(2,6-dimethoxyphenyl)methylium ion (DMP(3)C(+)) in various anilines in the presence of NaH. In the solvent-free reaction all three aryl substituents could be introduced despite the low reactivity of the anilines. The symmetric Ar(3)-TATA(+) derivatives with Ar = phenyl (2), 4-methoxyphenyl (3), and 4-bromophenyl (4) were synthesized. Single crystal structures of 2 and 4 were obtained as BF(4)(-) salts, where torsional angles larger than 80° were observed between the TATA(+) chromophore and the aryl substituents. The photophysical properties were studied in solution and in thin films. The results show that the Ar(3)-TATA(+) dyes have a surprising 3-fold increase in fluorescence quantum yields when compared to the parent alkyl-substituted R(3)-TATA(+) salts. With a high quantum yield (>50%) and emission in the red (λ(fl) = 560 nm) the Ar(3)-TATA(+) dyes represent a promising new addition to the family of superstable cationic triangulenium dyes. Additionally, the synthesized tribromo derivative 4 is shown to be a potential triagonal synthon for polymers and other macromolecules.     

Mechanistic Insights into the Photoisomerization of N,N′-Disubstituted Indigos

N,N′-disubstituted indigos are photoswitchable molecules that have recently caught the attention due to their addressability by red-light. When alkyl and aryl groups are utilized as the N-substituents, the thermal half-lives of Z isomers can be tuned independently while maintaining the advantageous red-shifted absorption spectra. To utilize these molecules in real-world applications, it is of immense importance to understand how their molecular structures as well as the environment influence their switching properties. To this end, we probed their photoisomerization mechanism by carrying out photophysical and computational studies in solvents of different polarities. The fluorescence and transient absorption experiments suggest for more polar excited and transition states, which explains the bathochromic shifts of absorption spectra and shorter thermal half-lives. On the other hand, the quantum chemical calculations reveal that in contrast to N-carbonyl groups, N-alkyl and N-aryl substituents are not strongly conjugated with the indigo chromophore and can thus serve as a tool for tuning the thermal stability of Z isomers. Both approaches are combined to provide in-depth understandings of how indigos undergo photoswitching as well as how they are influenced by N-substituent and the chemical surroundings. These mechanistic insights will serve as guiding principles for designing molecules eyeing broader applications.     

15N NMR substituent effects in pyridines and pyrimidines

¹⁵N chemical shifts of 32 substituted pyridines and 19 substituted pyrimidines, together with additional data from the literature, are used to evalute substituent increments, A_i and A_ik, in the respective series. Differential chemical shifts, Δδ(N), correlate with corresponding Δδ(C) values whereby, on the ppm scale, nitrogen shifts are approximately three times more sensitive towards substituents than carbon shifts. The ¹⁵N increments have proven additive and useful for assignment purposes.     

A study of the 15N NMR chemical shifts in substituted anilines and phenylhydrazines, and their derivatives

The analysis of (15)N chemical shift data from over a hundred anilines, N-methyl anilines, N,N-dimethyl anilines and phenylhydrazines with substituents in the phenyl ring leads to an empirical equation, delta(cal) = deltaon + Deltao + Deltam + Deltap, for calculating (15)N NMR chemical shifts of the amino group. This equation is based on a linear regression analysis using eighteen substituent parameters and leads to good conformity with the expected data.     

Reaction of ketenes with N,N-Disubstituted 2-Aminomethylenecycloalkanones III. Synthesis of N,N-Disubstituted 3,3-Diehloro-4-amino-5,6-polymethylene-3,4-dihydro-α-pyrones

The reaction of dichloroketene with N,N-Disubstituted 2-aminomethylenecyclopentanones, cyclohexanones, cycloheptanones and cyclooctanones gave the 1,4-cycloadducts, namely N,N-Disubstituted 3,3-dichloro-4-amino-5,6-polymethylene-3,4-dihydro-α-pyrones. The structures of these products were determined by uv, ir and nmr spectral data, as well as by dehydrochlorination of the adduct, 3,3-dichloro-4-diphenylamino-5,6-tetramethylene-3,4-dihydro-α-pyrone, which led to 3-chloro-4-diphenylamino-5,6-tetramethylene-α-pyrone. The by-product of the cycloaddition reaction was the N,N-Disubstituted dichloroacetamide, the formation of which varies according to the substituents on the nitrogen atom.     

Different Coordinative (N,N) and (N,O) Bidentate Behaviour of N‐2‐Pyridyl‐Sulfonamides. Electrochemical Synthesis and Characterization of Cadmium(II) Complexes

Electrochemical oxidation of cadmium in an acetonitrile solution of N‐2‐pyridyl‐sulfonamides (HL) afforded cadmium coordination compounds of composition [CdL₂]. Heteroleptic complexes of composition [CdL₂L′] (L′ = 2, 2′‐bipyridine or 1, 10‐phenanthroline) were obtained when the coligand L′ was added to the electrolytic phase. The crystal structures of several compounds have been determined by X‐ray diffraction. In all cases the cadmium atom is hexacoordinated, but the coordinative behaviour of the N‐2‐pyridyl‐sulfonamide ligand depends on the location of the substituents in the pyridyl ring. When the substituent is in position 3, the ligands act as N, O‐donors. In all other cases, the ligands act as N, N′‐bidentate systems.     

15N nuclear magnetic resonance spectroscopy. Natural-abundance 15N spectra of aliphatic oximes

¹⁵N chemical shifts of the Z and E isomers of twenty-two ketoximes and fourteen aldoximes have been determined at the natural-abundance level of ¹⁵N, using Fourier transform methods. The influences of π delocalization, methyl substituents and solute concentration on the oxime nitrogen shielding have been determined. The ¹⁵N shifts for oximes of several cycloalkanones have been measured and the influence of ring size on the chemical shifts is discussed.