Synthesis and fluorescent properties of N(9)-alkylated 2-amino-6-triazolylpurines and 7-deazapurines

• Andrejs Šišuļins,
• Jonas Bucevičius,
• Yu-Ting Tseng,
• Irina Novosjolova,
• Kaspars Traskovskis,
• Ērika Bizdēna,
• Huan-Tsung Chang,
• Sigitas Tumkevičius and
• Māris Turks

Beilstein J. Org. Chem. 2019, 15, 474–489, doi:10.3762/bjoc.15.41

• showed pronounced changes with solvent polarity in terms of emission maxima and quantum yields, though the absorption spectra showed minor or no changes with increasing solvent polarity indicating small dipole moment in the ground state. A good linear correlation between the fluorescence QY and the

Adhesion, forces and the stability of interfaces

• Robin Guttmann,
• Johannes Hoja,
• Christoph Lechner,
• Reinhard J. Maurer and
• Alexander F. Sax

Beilstein J. Org. Chem. 2019, 15, 106–129, doi:10.3762/bjoc.15.12

• ., polyaromatic hydrocarbons) induces a dipole moment; likewise, when a spherical charge distribution is deformed to an ellipsoid, a quadrupole is induced. Discussion of WMI, as found in the chemical literature, often suffers from a profound confusion of tongues due to the preference of a folkloristic [12

The phenyl vinyl ether–methanol complex: a model system for quantum chemistry benchmarking

• Dominic Bernhard,
• Fabian Dietrich,
• Mariyam Fatima,
• Cristóbal Pérez,
• Hannes C. Gottschalk,
• Axel Wuttke,
• Ricardo A. Mata,
• Martin A. Suhm,
• Melanie Schnell and
• Markus Gerhards

Beilstein J. Org. Chem. 2018, 14, 1642–1654, doi:10.3762/bjoc.14.140

• complex, however, we find that the B3LYP-D3(BJ)/def2-TZVP level of theory provides a better prediction of the magnitudes of the dipole-moment components. Experimentally, we only observe a-type transitions for this complex, which points to rather low values for μb and μc. SCS-CC2 calculations predict all

• three dipole-moment components to be of comparable magnitude. At the B3LYP-D3(BJ) level, μa is predicted to be significantly stronger than μb and μc. This change in magnitude for the dipole-moment components for different levels of calculation is more often observed for weakly bound complexes because

• the exact arrangement of the two monomers with respect to each other can have a major influence on the dipole-moment components. Also note that in none of the spectroscopic experiments, we observe the OH–E isomer that is also predicted to be of relatively low energy (cf. Table 1). The rotational

Recent advances in phosphorescent platinum complexes for organic light-emitting diodes

• Cristina Cebrián and
• Matteo Mauro

Beilstein J. Org. Chem. 2018, 14, 1459–1481, doi:10.3762/bjoc.14.124

• without and with outcoupling elements, respectively, via engineering of transition dipole moment orientation in the device active matrix. Owing to the enormous interest they are currently attracting, the scope of the present review article is to highlight the current trends and achievements in the field

Are dispersion corrections accurate outside equilibrium? A case study on benzene

• Tim Gould,
• Erin R. Johnson and
• Sherif Abdulkader Tawfik

Beilstein J. Org. Chem. 2018, 14, 1181–1191, doi:10.3762/bjoc.14.99

• -energy curves of the benzene dimer to determine if they are capable of describing forces and energies outside equilibrium. We find the exchange-hole dipole moment (XDM) model describes most cases with the highest overall agreement with reference data for energies and forces, with many-body dispersion

• by guaranteed success outside it. In the worst cases, some methods have errors in the predicted forces as large as the force itself. The exchange-hole dipole moment (XDM) model, which we tested with several DFAs, performs very well in general. PBE-MBD and PBE-FI (which incorporates an improved

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

Correlation effects and many-body interactions in water clusters

• Andreas Heßelmann

Beilstein J. Org. Chem. 2018, 14, 979–991, doi:10.3762/bjoc.14.83

• moment of the water molecule reduces the dipole moment from the Hartree–Fock method by about 0.13 Debye [33], it can be assessed that a fraction of this repulsive correlation contribution originates from the reduction of the electrostatic interaction energy [34]. Empirical models for water that are based

• interaction energy is, however, only about half the size of the sum of the two-, three- and four-body dispersion interactions, i.e., the large dispersion interaction contribution is strongly quenched by further repulsive correlation contributions. Noting that the correlation effect to the molecular dipole

D–A–D-type orange-light emitting thermally activated delayed fluorescence (TADF) materials based on a fluorenone unit: simulation, photoluminescence and electroluminescence studies

• Lin Gan,
• Xianglong Li,
• Xinyi Cai,
• Kunkun Liu,
• Wei Li and
• Shi-Jian Su

Beilstein J. Org. Chem. 2018, 14, 672–681, doi:10.3762/bjoc.14.55

• solution. However, the PL spectrum of 2 is slightly blue-shifted from its PL spectrum in toluene, while 1:CBP shows alike spectra with 1 in toluene. It could be considered as the solid-state solvation effect [21], as 2 and 1 have different dipole moment of 1.814 D and 3.501 D, respectively from DFT

• simulated EQE by employing the TTA model. Molecular structures of isomers 1 and 2. Thermal and electrochemical properties of the investigated compounds 1 and 2. The calculated HOMO, LUMO, twisting angles (θ, θ’), bond lengths (l, l’), ΔEST and dipole moment in gas phase for S0 and in solution for S1, from

Recent advances on organic blue thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs)

• Thanh-Tuân Bui,
• Fabrice Goubard,
• Malika Ibrahim-Ouali,
• Didier Gigmes and
• Frédéric Dumur

Beilstein J. Org. Chem. 2018, 14, 282–308, doi:10.3762/bjoc.14.18

Fluorescent nucleobase analogues for base–base FRET in nucleic acids: synthesis, photophysics and applications

• Mattias Bood,
• Sangamesh Sarangamath,
• Moa S. Wranne,
• Morten Grøtli and
• L. Marcus Wilhelmsson

Beilstein J. Org. Chem. 2018, 14, 114–129, doi:10.3762/bjoc.14.7

• an isotropic orientation factor, κ2 = 2/3 [14]. Finally, for a high precision in orientation factor, i.e., to enable detailed structure investigations, we determined the direction of the lowest energy transition dipole moment of tCnitro to be 25° in the opposite direction compared to tC and tCO (i.e

Polarization spectroscopy methods in the determination of interactions of small molecules with nucleic acids – tutorial

• Tamara Šmidlehner,
• Ivo Piantanida and
• Gennaro Pescitelli

Beilstein J. Org. Chem. 2018, 14, 84–105, doi:10.3762/bjoc.14.5

• intensity of the LD signal depends on several other factors such as: a) the orientation parameter of the DNA (S in Figure 9); b) the orientation of the bound molecule with respect to the macromolecule (Figure 7); c) the local direction of the transition dipole moment allied with the observed absorption band

• -polarized light parallel to the orientation axis, and A is the absorption for plane-polarized light perpendicular to the orientation axis. For a given ligand, according to induced LD (ILD), its orientation with respect to the DNA can be determined by flow LD as long as the direction of the transition dipole

• moment within the ligand is known or can be established, and the orientation parameter S (Figure 9b) of the DNA is also known. 4.1. Practical information A direct comparison of the experimental conditions and materials applicable in ECD and LD reveals that the LD method is more limited. Here are some

Conformational preferences of α-fluoroketones may influence their reactivity

• Graham Pattison

Beilstein J. Org. Chem. 2017, 13, 2915–2921, doi:10.3762/bjoc.13.284

• , fluorine is often involved in introducing unusual properties to organic molecules, whether by its strong inductive effect, interactions of its tightly-held lone pairs or through the strong dipole moment it can induce in molecules [7]. To begin to quantify the effects of α-halogenation on carbonyl

• reactive conformations more accessible to the fluorinated acetophenone. Potential reasons for the different conformational preferences of the α-halogenated acetophenones were then examined. One possibility is that the increased electronegativity of fluorine induces a high dipole moment at small O=C–C–X

• dihedral angles and that therefore larger dihedral angles are favoured as this minimizes the molecule’s overall dipole moment. However, computational analysis of the angular variation of the dipole moment of each α-haloacetophenone did not show a significant variation between the different halogens (Figure

Recent progress in the racemic and enantioselective synthesis of monofluoroalkene-based dipeptide isosteres

• Myriam Drouin and
• Jean-François Paquin

Beilstein J. Org. Chem. 2017, 13, 2637–2658, doi:10.3762/bjoc.13.262

• located on the oxygen atom and the dipole moment of the amide bond is 3.6 D [7]. The amide bond can also perform hydrogen bonds, with the oxygen atom as the hydrogen bond acceptor and N–H as hydrogen bond donor. This characteristic is important for the formation of secondary structures and folding into

• negative charge, with a dipole moment of 1.4 D. Finally, the monofluoroalkene has the ability to accept a hydrogen bond through the fluorine atom [9]. Geometrically, the monofluoroalkene is quite similar to the amide bond. The C=O bond of the amide is 1.228 Å, compared to 1.376 Å for the C–F bond, and the

Synthesis, effect of substituents on the regiochemistry and equilibrium studies of tetrazolo[1,5-a]pyrimidine/2-azidopyrimidines

• Elisandra Scapin,
• Paulo R. S. Salbego,
• Caroline R. Bender,
• Alexandre R. Meyer,
• Anderson B. Pagliari,
• Tainára Orlando,
• Geórgia C. Zimmer,
• Clarissa P. Frizzo,
• Helio G. Bonacorso,
• Nilo Zanatta and
• Marcos A. P. Martins

Beilstein J. Org. Chem. 2017, 13, 2396–2407, doi:10.3762/bjoc.13.237

• ]. To corroborate with the data, the dipole moment (µ) of two forms (3a and 4a) were estimated using the Gaussian 09 software package [35]. The dipole moment found for 3a and 4a was 7.47 D and 3.83 D, respectively. These results reveal why the tetrazole form is favored in DMSO-d6 when compared to CDCl3

• , since the dipole moment of the DMSO-d6 is greater than the dipole moment of CDCl3, in addition to being able to stabilize the tetrazole form more effectively. Moreover, the results from quantum mechanical calculation confirmed that the tetrazole 3a form is 2.98 kcal mol−1 more stable in DMSO-d6 when

Solvent-free copper-catalyzed click chemistry for the synthesis of N-heterocyclic hybrids based on quinoline and 1,2,3-triazole

• Martina Tireli,
• Silvija Maračić,
• Stipe Lukin,
• Marina Juribašić Kulcsár,
• Dijana Žilić,
• Mario Cetina,
• Ivan Halasz,
• Silvana Raić-Malić and
• Krunoslav Užarević

Beilstein J. Org. Chem. 2017, 13, 2352–2363, doi:10.3762/bjoc.13.232

• time, the 1,2,3-triazoles became the heterocycle of choice in drug discovery, due to their favourable pharmacokinetic and safety profiles, hydrogen-bonding capability, moderate dipole moment, rigidity and stability under in vivo conditions [5][6]. Also, the ability of 1,2,3-triazoles to act as amide

Synthesis and application of trifluoroethoxy-substituted phthalocyanines and subphthalocyanines

• Satoru Mori and
• Norio Shibata

Beilstein J. Org. Chem. 2017, 13, 2273–2296, doi:10.3762/bjoc.13.224

• approximately 23% larger than hydrogen and has the highest electronegativity (4.0) among all the elements [19][20]. Therefore, substituting fluorine for a single hydrogen atom in the structure of an organic compound may cause noticeable changes in the dipole moment although the change in the chemical structure

Conformational impact of structural modifications in 2-fluorocyclohexanone

• Francisco A. Martins,
• Josué M. Silla and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2017, 13, 1781–1787, doi:10.3762/bjoc.13.172

• % in DMSO solution [18], which is in agreement with our theoretical findings (Table 1). This behavior is comprehensive, because the equatorial conformer has the C=O and C–F bonds in the same plane and similarly orientated. This should increase the molecular dipole moment, and favor the axial isomer

Theoretical simulation of the infrared signature of mechanically stressed polymer solids

• Matthew S. Sammon,
• Milan Ončák and
• Martin K. Beyer

Beilstein J. Org. Chem. 2017, 13, 1710–1716, doi:10.3762/bjoc.13.165

• followed by recording infrared spectra [16][17][18][19][20][21][22][23][24][25][26][27][28][29]. External force modifies the force constants of vibrational modes [30]. Since structural deformation changes the charge distribution in the molecule, the transition dipole moment and thus the infrared intensity

• vibration, IR bands mainly attributed to modes including backbone vibrations show a considerable change in intensities. The intensity of the C–N stretching vibration in the range of 1000–1220 cm−1 continuously increases with increasing force due to a stronger dipole moment change resulting from interatomic

New electroactive asymmetrical chalcones and therefrom derived 2-amino- / 2-(1H-pyrrol-1-yl)pyrimidines, containing an N-[ω-(4-methoxyphenoxy)alkyl]carbazole fragment: synthesis, optical and electrochemical properties

• Daria G. Selivanova,
• Alexei A. Gorbunov,
• Olga A. Mayorova,
• Alexander N. Vasyanin,
• Igor V. Lunegov,
• Elena V. Shklyaeva and
• Georgii G. Abashev

Beilstein J. Org. Chem. 2017, 13, 1583–1595, doi:10.3762/bjoc.13.158

• dipole moments in the first excited singlet state were performed on the TD-B3LYP/6-31G* level. The results, which are presented in Table 2, show that the increase of the solvents polarity has brought about the increase of a molecule dipole moment both in the ground and excited states, and the redshift of

Correlation of surface pressure and hue of planarizable push–pull chromophores at the air/water interface

• Frederik Neuhaus,
• Fabio Zobi,
• Gerald Brezesinski,
• Marta Dal Molin,
• Stefan Matile and
• Andreas Zumbuehl

Beilstein J. Org. Chem. 2017, 13, 1099–1105, doi:10.3762/bjoc.13.109

• interesting to note that the ratio of the reflection absorbance (RA) of the νs(SO2) measured with s- and p-polarized light does not change during compression indicating no change in the orientation of this transition dipole moment (see Figure S6, Supporting Information File 1). Effect of flipper on DPPC There

• model of Kuzmin and Michailov [31][32]. The intensity and shape of a reflection absorption band depend on the absorption coefficient k, the full-width of half-height (fwhh), the orientation of the transition dipole moment (TDM) within the molecule α, the molecular tilt angle θ, the polarization and the

Fluorinated cyclohexanes: Synthesis of amine building blocks of the all-cis 2,3,5,6-tetrafluorocyclohexylamine motif

• Tetiana Bykova,
• Nawaf Al-Maharik,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2017, 13, 728–733, doi:10.3762/bjoc.13.72

• (Figure 1) [1][2][3]. The cyclohexane ring has four C–F bonds on one face, two of which are aligned 1,3-diaxial. Due to the particularly polar nature of the C–F bond, the alignment of those two bonds results in a large molecular dipole moment [4][5][6]. For the parent cyclohexane ring 1 the magnitude of

Spectral and DFT studies of anion bound organic receptors: Time dependent studies and logic gate applications

• Srikala Pangannaya,
• Neethu Padinchare Purayil,
• Shweta Dabhi,
• Venu Mankad,
• Prafulla K. Jha,
• Satyam Shinde and
• Darshak R. Trivedi

Beilstein J. Org. Chem. 2017, 13, 222–238, doi:10.3762/bjoc.13.25

• 571 nm fully supports the anion-binding process. A substantial increase in the dipole moment of the fluoride complex indicates an efficient charge separation allowing the formation of the hydrogen bond between OH and F−. While the corresponding acetate complex exhibited a two-fold increase in the

• dipole moment implying the bifurcated nature of the hydrogen bond involving one OH proton with two electronegative oxygen atoms of the acetate ion. Binding mechanism Based on the 1H NMR titration studies the following binding mechanism is proposed. The receptors R1 and R2 undergo an anion-induced

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

• Pavel Nagorny and
• Zhankui Sun

Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283

• substantial dipole moment (≈4.5 D) almost aligned with the C5–H bond and the relatively high acidity of this position (pKa(DMSO) = 27–28, for the 1H-tautomer). These heterocycles, which are easily available from 1,3-cycloaddition of alkynes and azides, can both form strong C–H bonds with hydrogen bond

Organofluorine chemistry: Difluoromethylene motifs spaced 1,3 to each other imparts facial polarity to a cyclohexane ring

• Mathew J. Jones,
• Ricardo Callejo,
• Alexandra M. Z. Slawin,
• Michael Bühl and
• David O'Hagan

Beilstein J. Org. Chem. 2016, 12, 2823–2827, doi:10.3762/bjoc.12.281

• incorporation of fluorine atoms is a powerful strategy for modulating the properties of organic compounds [1][2][3]. For instance, the replacement of hydrogen by fluorine is commonly practised in medicinal [4][5] and agrochemical [6][7] research programmes. The dipole moment associated with the C–F bond has

• bonds (Figure 4). A molecular dipole moment for compound 4c was calculated at 3.1 D and can be compared for example to 1,2,4,5-tetrafluorocyclohexane (2, 5.2 D) [18]. Conclusion In this study we have prepared a novel polar aliphatic structure 4c based on the 1,1,3,3-tetrafluorocyclohexyl motif. The

Benzothiadiazole oligoene fatty acids: fluorescent dyes with large Stokes shifts

• Lukas J. Patalag and
• Daniel B. Werz

Beilstein J. Org. Chem. 2016, 12, 2739–2747, doi:10.3762/bjoc.12.270

• transition. Thus, the low overlap between both wavefunctions results in a small transition dipole moment and subsequently a quite weak absorption. The situation is even aggravated by the specific small angle (≈64°) between the oligoene and the longitudinal axis of the BTD moiety, which diminishes the dipole

• moment of the electronic shift additionally. However, the large displacement of electron density from one part of the π-system to another enforces a geometrical equilibration of the nuclei which triggers the emission event to take place from a considerably relaxed excited state. As a consequence, the