Evaluation of Anisole‐Substituted Boron Difluoride Formazanate Complexes for Fluorescence Cell Imaging

Evaluation of three subclasses of boron difluoride formazanate complexes bearing o‐, m‐, and p‐anisole N‐aryl substituents (Ar) as readily accessible alternatives to boron dipyrromethene (BODIPY) dyes for cell imaging applications is described. While the wavelengths of maximum absorption (λ_max) and emission (λ_em) observed for each subclass of complexes, which differed by their carbon‐bound substituents (R), were similar, the emission quantum yields for 7 a – c (R=cyano) were enhanced relative to 8 a – c (R=nitro) and 9 a – c (R=phenyl). Complexes 7 a – c and 8 a – c were also significantly easier to reduce electrochemically to their radical anion and dianion forms compared to 9 a – c . Within each subclass, the o‐substituted derivatives were more difficult to reduce, had shorter λ_max and λ_em, and lower emission quantum yields than the p‐substituted analogues as a result of sterically driven twisting of the N‐aryl substituents and a decrease in the degree of π‐conjugation. The m‐substituted complexes were the least difficult to reduce and possessed intermediate λ_max, λ_em, and quantum yields. The complexes studied also exhibited large Stokes shifts (82–152 nm, 2143–5483 cm^?1). Finally, the utility of complex 7 c (Ar=p‐anisole, R=cyano), which can be prepared for just a few dollars per gram, for fluorescence cell imaging was demonstrated. The use of 7 c and 4′,6‐diamino‐2‐phenylindole (DAPI) allowed for simultaneous imaging of the cytoplasm and nucleus of mouse fibroblast cells.     

Comparison of Phosphorescent Pt(II) Complexes with C^N^N vs N^N^N Chelators and Caffeine-Based NHC-co-ligands†

In this work, we explored coordination compounds featuring caffeine-based carbene co-ligands and tridentate dianionic pincer luminophores derived from 2,6-bis(1H-1,2,4-triazol-5-yl)pyridine (N), as well as from 2-phenyl-6-(1H-1,2,4-triazol-5-yl)pyridine (C), bearing either Ad (adamantyl) or tBu (tertiary butyl) substituents. The new 2-phenyl-6-(1H-1,2,4-triazol-5-yl)pyridine-based ligand precursors along with four Pt(II) complexes, namely Pt(C-tBu), Pt(C-Ad), Pt(N-tBu) and Pt(N-Ad) were characterized. Further on, the influence of the different substituents at the chelating luminophores and of the caffeine-based NHC-co-ligand on the photophysical properties (including photoluminescence quantum yields (Φ_L), excited-state lifetimes (τ), radiative (k_r), and non-radiative (k_nr) deactivation rate constants) was assessed in fluid solutions at room temperature (RT) and in frozen glassy matrices at 77 K. All four luminophores perform equivalently well within the experimental uncertainty. In deoxygenated fluid solutions at RT, photoluminescence quantum yields reaching up to 24 ± 2% and excited-state lifetimes of around 12 μs were found. The generally long excited-state lifetimes and only minor blue shift upon cooling to 77 K along with mostly well-resolved vibrational progressions point to metal-perturbed ligand-centered excited states. Notably, the yield of the complexation reaction in case of Pt(C-tBu) and Pt(C-Ad) was almost two times higher compared to Pt(N-tBu) and Pt(N-Ad). Cyclometallation is not an essential feature to achieve high photoluminescence quantum yields, but it can improve the synthetic efficiency. In summary, it can be observed that coordination chemical concepts based on natural products can lead to stable phosphorescent species with interesting excited-state properties.     

Konformative Beweglichkeit Flexibler Ringsysteme—X. Untersuchungen mit Hilfe der Protonenresonanz-Spektroskopie. Substituentenabhängigkeit der Ringinversion bei 1.3-Dioxanen, 1.3-Dithianen und 1.3-Oxathianen

Activation energies E_α and free enthalpies of activation ΔG? were determined by NMR for the ring inversions of nineteen 1.3-dioxanes, 1.3-dithianes and 1.3-oxathianes and their methyl-substituted derivatives. The rate constant k of the chair to chair-inversion of these rings depend on the number and positions of the substituents. In substituted 1.3-dioxanes k is lower than in 1.3-dioxane itself if two geminal CH₃-groups are situated in position 5. However, k becomes higher when the geminal CH₃-groups are in positions 2 or 4. The rate constants are particularly high for 4.4.6.6-tetramethyl-1.3-dioxane. A similar dependence of k on substituents has been observed in the oxathianes, while with 1.3-dithianes only a small influence is noticed. The effect of the methyl substituents in positions 2 or 4 in 1.3-dioxanes can be explained by assuming that the chair conformation is deformed by 1.3-interactions. In 1.3-dithianes such 1.3-interactions are expected to be smaller because of the larger C? S bond length. For 1.3-oxathianes the dependence of k on the substituents is more difficult to understand since these molecules are not symmetrical.     

Facile and Efficient Oxidation of Quinazolines into Quinazolin-4(3H)-ones by Peracetic Acid

A new approach to synthesize quinazoline-4(3H)-ones was achieved by oxidation of quinazolines using peracetic acid, which possesses some advantages of economic reagents, simplified operation, high efficiency, and environmental friendliness. Application of this method allowed us to synthesize a series of quinazolin-4(3H)-ones with different substituents at 6 and 7 positions in good to excellent yields, including the key intermediates of tyrosine kinase inhibitors such as PD153035, Erlotinib, and Gefitinib.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Regioselectivity of methoxydebromination of substituted pentabromobenzenes C6Br5X in pyridine

The kinetics and regioselectivity of methoxydebromination of some substituted pentabromobenzenes C₆Br₅X (X = NO₂, CN, NH₂, MeNH, and MeO) were studied in pyridine at 115°C. The partial rate factors (k _f) were calculated for different positions of the polybrominated ring in these compounds. The effect of substituents X on methoxydebromination at themeta- andpara-positions is satisfactorily described only by the Hammett substituent constants ( = 2.22,r = 0.96). This allows one to conclude that direct polar conjugation of the substituents contributes only slightly to the transition state of the reaction. Theorthobromine atoms have a significant steric effect.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1784–1788, September, 1995.     

Organylarsino-substituierte Schwefeldiimide: Die Kristallstrukturanalysen von 3, 7-Di-t-butyl-3H, 7H,-1λ4, 5λ4, 2, 4, 6, 8, 3, 7-dithiatetrazadiarsocin und Bis(diphenylarsino)schwefeldiimid

Organoarsino-Substituted Sulphur Diimides: Crystal Structure Analyses of 3, 7-Di-t-butyl-3H, 7H-1λ⁴, 5λ⁴, 2, 4, 6, 8, 3, 7-dithiatetrazadiarsocine and Bis (diphenylarsino)sulphur Diimide Reaction of the salt K₂SN₂ with organoarsenic chlorides leads to sulphur diimides containing organoarsino substituents at both ends. Single crystal X-ray structure analyses were carried out for two typical compounds, i.e. the cyclic eight-membered 3, 7-di-t-butyl-3H, 7H-1λ⁴, 5λ⁴, 2, 4, 6, 8, 3, 7-dithiatetrazadiarsocine ( 1a , prepared from K₂SN₂ and (t-Bu)AsCl₂ (1:1)) and the open-chain bis(diphenylarsino)sulphur diimide ( 2a , prepared from K₂SN₂ and Ph₂AsCl (1:2)). In both compounds the sulphur diimide groups are coplanar with their directly bound arsenic atoms. This coplanarity principle leads, in the case of 1a , to about conformation (mm2(C_2v) symmetry) of the eight-membered heterocycle; the t-butyl substituents occupy quasi equatorial positions. Small deviations from mm2 symmetry and torsions around the S?N bonds up to 12° can be explained as a consequence of the transnnular repulsion of the lone pairs at the arsenic atoms (As …As distance 3.683(1) Å). In the case of the open-chain S(N? AsPh₂)₂ ( 2a , 2(C₂) symmetry), a cis, cis configuration was found at the S?N double bonds which indicates As…As interaction. The As…As distance (3.379(1) Å) is shorter than in 1a and parallells a reduced interaction of the lone pairs at the As atoms. The S?N bond lenghts (1.517(5) Å in 1 a and 1.521(3) Å in 2a ) are characteristic of sulphur diimides withoug significant π-interaction with the substituents and correspond to S^IV?N double bonds.     

Solvent Isotope Effect on the Rate Constants of Singlet-Oxygen Quenching by edta and Its Metal Complexes

The reactivity of singlet oxygen (O₂(¹Δ_g)) with edta and its metal complexes with Al³⁺, Cu²⁺, Fe³⁺, and Mn²⁺ was investigated. The emission of singlet oxygen at 1270 nm in D₂O was measured in order to determine the quenching efficiency of edta and edta-metal complexes for different metal/edta ratios. The sum of the rate constant (k_r + k_q) of the chemical reaction between singlet oxygen and the acceptor (k_r) and of the physical quenching of singlet oxygen by the acceptor (k_q) was obtained by a Stern-Volmer analysis. Measurements of the oxygen consumption in H₂O were used to determine quantum yields of the sensitized photooxidation, and the combined results of these experiments allowed the determination of k_r and k_q separately. A strong isotope effect was observed between the deuterated and the hydrogenated solvents. This effect was shown to be independent of the analytical procedure used. The isotope effect, as well as the reactivity of edta and its metal complexes, depend markedly on the complexed metal ion.     

Solvolysis of 2‐chloro‐2(3,4‐disubstituted) phenylpropanes: Validity of Hammett–Brown σ+ constants in assessing additive effects of substituents

The objective of this study is to test the suitability of the extended Hammett–Brown equation, log (k_XX/k_HH) = ρ⁺Σσ⁺, in depicting satisfactorily additive effects of electronegative atom‐bearing substituents, which are known to possess diverse and multicomponent influences on the side chain reactions of polysubstituted benzenes. The equation has been used to correlate, for the first time, the additive effect of substituents in the specific rates of solvolysis of 2‐chloro‐2‐phenylpropanes ( 3b–3f ) having 3‐F,4‐Me, 3‐Br,4‐Me, 3‐I,4‐Me, 3‐Me,4‐Me, or 3‐MeO,4‐Me substituents. The rates were determined titrimetrically at 288, 298, and 308 K using 90% aqueous acetone as solvent. Measured additive effects of these substituents on the solvolysis rate and activation parameters of the parent cumyl chloride (2‐chloro‐2‐phenylpropane) are found to be well correlated using the equation given above. Plots of log (k_XX/k_HH) of 3b–3f together with mainly di‐, but also tri‐ and mono‐substituted cumyl chlorides from previous studies against Σσ⁺ give a linear correlation coefficient of 0.990 as a measure of the validity of the equation to depict such systems. The halogen substituents' extent of conformity with additivity reflected in their relative (k_obsd/k_calcd) rate ratios is found to correlate with the steric size of substituents. Plots of rate ratios against Taft's steric factor of each halogen give a linear correlation coefficient of 0.994 for the 3‐halo substituents. The 3,4‐dimethyl substituents' relative rate ratio of 1.03 shows excellent additivity, whereas the 3‐methoxy‐4‐methyl ratio of 1.43 shows the methoxy group to be far less deactivating than predicted. Similar trends were found for the free energy of activation (ΔG? – ΔG₀?) differences, which correlated linearly with a coefficient of 0.983 with Taft's steric factor of halogen atoms. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 514–523, 2012     

Photophysical Properties and Electronic Structure of Bacteriochlorin–Chalcones with Extended Near‐Infrared Absorption

Synthetic bacteriochlorins enable systematic tailoring of substituents about the bacteriochlorin chromophore and thereby provide insights concerning the native bacteriochlorophylls of bacterial photosynthesis. Nine free‐base bacteriochlorins (eight prepared previously and one prepared here) have been examined that bear diverse substituents at the 13‐ or 3,13‐positions. The substituents include chalcone (3‐phenylprop‐2‐en‐1‐onyl) derivatives with groups attached to the phenyl moiety, a “reverse chalcone” (3‐phenyl‐3‐oxo‐1‐enyl), and extended chalcones (5‐phenylpenta‐2,4‐dien‐1‐onyl, retinylidenonyl). The spectral and photophysical properties (τ_s, Φ_f, Φ_ic, Φ_isc, τ_T, k_f, k_ic, k_isc) of the bacteriochlorins have been characterized. The bacteriochlorins absorb strongly in the 780–800 nm region and have fluorescence quantum yields (Φ_f) in the range 0.05–0.11 in toluene and dimethylsulfoxide. Light‐induced electron promotions between orbitals with predominantly substituent or macrocycle character or both may give rise to some net macrocycle ? substituent charge‐transfer character in the lowest and higher singlet excited states as indicated by density functional theory (DFT) and time‐dependent DFT calculations. Such calculations indicated significant participation of molecular orbitals beyond those (HOMO ? 1 to LUMO + 1) in the Gouterman four‐orbital model. Taken together, the studies provide insight into the fundamental properties of bacteriochlorins and illustrate designs for tuning the spectral and photophysical features of these near‐infrared‐absorbing tetrapyrrole chromophores.     

Kinetics of the reactions of OH radicals with some oxygenated volatile organic compounds under simulated atmospheric conditions

Some relative rate experiments have been carried out at room temperature and at atmospheric pressure. This concerns the OH-oxidation of some oxygenated volatile organic compounds including methanol (k₁), ethanol (k₂), MTBE (k₃), ethyl acetate (k₄), n-propyl acetate (k₅), isopropyl acetate (k₆), n-butyl acetate (k₇), isobutyl acetate (k₈), and t-butyl acetate (k₉). The experiments were performed in a Teflon-film bag smog chamber. The rate constants obtained are (in cm³ molecule⁻¹ s⁻¹): k₁=(0.90±0.08)×10⁻¹²; k₂=(3.88±0.11)×10⁻¹²; k₃=(2.98±0.06)×10⁻¹²; k₄=(1.73±0.20)×10⁻¹²; k₅=(3.56±0.15)×10⁻¹²; k₆=(3.97±0.18)×10⁻¹²; k₇=(5.78±0.15)×10⁻¹²; k₈=(6.77±0.30)×10⁻¹²; and k₉=(0.56±0.11)×10⁻¹². The agreement between the obtained rate constants and some previously published data has allowed for most of the studied compounds to point out a coherent group of values and to suggest recommended values. Atmospheric implications are also discussed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 839–847, 1998     

Pyrrolo[3,2‐b]pyrroles—From Unprecedented Solvatofluorochromism to Two‐Photon Absorption

A combined experimental and theoretical study of the two‐photon absorption (2PA) properties of a series of quadrupolar molecules possessing a highly electron‐rich heterocyclic core, pyrrolo[3,2‐b]pyrrole, is presented. In agreement with quantum‐chemical calculations, large 2PA cross‐section values, σ_2PA≈10²–10³ GM (1 GM=10⁵⁰ cm⁴ s photon^?1), are observed at wavelengths of 650–700 nm, which correspond to the two‐photon allowed but one‐photon forbidden transitions. The calculations also predict that increased planarity of this molecule through removal of two N‐substituents leads to further increase in the σ_2PA values. Surprisingly, the most quadrupolar pyrrolo[3,2‐b]pyrrole derivative, containing two 4‐nitrophenyl substituents at positions 2 and 5, demonstrates a very strong solvatofluorochromic effect, with a fluorescence quantum yield as high as 0.96 in cyclohexane, whereas the fluorescence vanishes in DMSO.     

The synthesis and photophysicochemical properties of low-symmetry zinc phthalocyanine analogues

The synthesis of a low-symmetry derivative, zinc mono-carboxy substituted phthalocyanine, ZnPc-COOH (4) has been reported. The photochemical and photophysical properties of ZnPc-COOH (4), ZnTMPyPc (5), ZnttbPc (6) and a previously synthesized low-symmetry derivative, ZnttbIPc (7), in various organic solvents are reported. The red-shifting of the spectra of 4 and 5 (relative to that of unsubstituted zinc phthalocyanine, ZnPc) is a function of the electron-donating sulfur-containing substituents attached to the periphery of the molecule. High triplet quantum yields (Ф_T) generally occur in response to substitution on the zinc phthalocyanine ring periphery. The highest Ф_T values and triplet lifetimes (τ_T) occur in DMSO for all derivatives as a result of the solvent's high viscosity. The strongly electron-withdrawing imido fused ring of ZnttbIPc (7) stabilizes it against photo-oxidative degradation relative to the other derivatives.     

Testing the capability of a polynomial‐modified gaussian model in the description and simulation of chromatographic peaks of amlodipine and its impurity in ion‐interaction chromatography

In this paper, the capability of a polynomial‐modified Gaussian model to relate the peak shape of basic analytes, amlodipine, and its impurity A, with the change of chromatographic conditions was tested. For the accurate simulation of real chromatographic peaks the authors proposed the three‐step procedure based on indirect modeling of peak width at 10% of peak height (W_0.1), individual values of left‐half width (A) and right‐half width (B), number of theoretical plates (N), and tailing factor (Tf). The values of retention factors corresponding to the peak beginning (k_B), peak apex (k_A), peak ending (k_E), and peak heights (H₀) of the analytes were directly modeled. Then, the investigated experimental domain was divided to acquire a grid of appropriate density, which allowed the subsequent calculation of W_0.1, A, B, N, and Tf. On the basis of the predicted results for Tf and N, as well as the defined criteria for the simulation the following conditions were selected: 33% acetonitrile/67% aqueous phase (55 mM perchloric acid, pH 2.2) at 40°C column temperature. Perfect agreement between predicted and experimental values was obtained confirming the ability of polynomial modified Gaussian model and three‐step procedure to successfully simulate the real chromatograms in ion‐interaction chromatography.     

Synthese von Fluoro-λ5-monophosphazenen und Fluoro-1, 3-diaza-2λ5, 4λ5-diphosphetidinen mittels der Staudinger-Reaktion

Synthesis of Fluoro-λ⁵-monophosphazenes and Fluoro-1,3-diaza-2λ⁵,4λ⁵-diphosphetidines by Means of the Staudinger Reaction 35 Tetrafluoro- and 2 difluorodiaza-diphosphetidines as well as 4 difluoro- and 30 monofluoro-λ⁵-monophosphazenes were prepared by the Staudinger reaction between tervalent phosphorus fluorides, R_nPF_3?n (n = 1, 2; R = R₂N, (CH₂)₅N, O(CH₂)₄N, RO, (CH₂O)₂, alkyl, aryl) and phenylazides, X? C₆H₄N₃ (X = H, 4-CH₃, 4-Cl, 4-Br, 4-NO₂, 3-NO₂). PF₃ does not react with phenylazide The influence of substituents on the structure of the reaction products is discussed. Kinetic measurements allowed to determine the constants λ^P_I of the substituents (CH₂)₅N, O(CH₂)₄N and R(C₆H₅)N (R = CH₃, C₂H₅, n-C₄H₉).     

The production of organic nitrates from atmospheric oxidation of ethers and glycol ethers

The production of organic nitrates from OH reaction (in the presence of NO) with methoxy propane, 1‐methoxy‐2‐propanol, ethoxy butane, and 2‐butoxyethanol was studied. The measured total organic nitrate yields were 1.8 (±0.4)%, 0.98 (±0.2)%, 7.7 (±2)%, and 9.6 (±1)%, respectively. The total organic nitrate yield for methoxypropane is 26% of that (7.0%) for n‐butane. The organic nitrate yield for ethoxy butane is 55% of that (14%) for n‐hexane. The peroxy radicals produced from OH reaction with the methylene groups α to the ether linkage have an organic nitrate branching ratio (k_3b/k₃) value ∼50% of those in analogous n‐alkanes. On the other hand, k_3b/k₃ values for peroxy radical functional groups not adjacent to the ether linkage (in γ and δ positions) are on average 1.7 times greater than for the analogous n‐alkyl peroxy radicals. The organic nitrate formation yield for 1‐methoxy‐2‐propanol is almost half that of methoxy propane, while for 2‐butoxyethanol it is 21% greater than that of butoxyethane. Our data lead us to the conclusion that the ether linkage imparts an inductive effect that decreases the value of k_3b/k₃ for peroxy radicals adjacent to it, yet has a stabilizing effect, from the additional vibrational modes for those peroxy radicals not adjacent to it, increasing their k_3b/k₃ values. The effect of both the  O and OH groups in these molecules and the importance of their position relative to the peroxy group are discussed in this paper. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 686–699, 2005     

Ab initio investigation of 2,2′‐bis(4‐trifluoromethylphenyl)‐5,5′‐bithiazole for the design of efficient organic field‐effect transistors

The initial molecular structure of 2,2′‐bis(4‐trifluoromethylphenyl)‐ 5,5′‐bithiazole has been optimized in the ground state using density functional theory (DFT). The distribution patterns of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) have also been evaluated. To shed light on the charge transfer properties, we have calculated the reorganization energy of electron λ_e, the reorganization energy of hole λ_h, adiabatic electron affinity (EA_a), vertical electron affinity (EA_v), adiabatic ionization potential (IP_a), and vertical ionization potential (IP_v) using DFT. Based on the evaluation of hole reorganization energy, λ_h, and electron reorganization energy, λ_e, it has been predicted that 2,2′‐bis(4‐trifluoromethylphenyl)‐5,5′‐bithiazole would be a better electron transport material. Finally, the effect of electric field on the HOMO, LUMO, and HOMO–LUMO gap were observed to check its suitability for the use as a conducting channel in organic field‐effect transistors. © 2015 Wiley Periodicals, Inc.     

The effect of CH<Subscript>3</Subscript>, F and NO<Subscript>2</Subscript> substituents on the individual hydrogen bond energies in the adenine–thymine and guanine–cytosine base pairs

The substituent effects on the geometrical parameters and the individual hydrogen bond (HB) energies of base pairs such as X–adenine–thymine (X–A–T), X–thymine–adenine (X–T–A), X–guanine–cytosine (X–G–C), and X–cytosine–guanine (X–C–G) have been studied by the quantum mechanical calculations at the B3LYP and MP2 levels with the 6–311++G(d,p) basis set. The electron withdrawing (EW) substituents (F and NO₂) increase the total binding energy (ΔE) of X–G–C derivatives and the electron donating (ED) substituent (CH₃) decreases it when they are introduced in the 8 and 9 positions of G. The effects of substituents are reversed when they are located in the 1, 5, and 6 positions of C, with exception of CH₃ in the 1 position and F in the 5 position, which in both cases the ΔE value decreases negligibly small. With minor exceptions (X=8–CH₃, 8–F, and 9–NO₂), both ED and EW substituents increase slightly the ΔE values of X–A–T derivatives. The individual HB energies (∆E _HBs) have been estimated using electron densities that calculated at the hydrogen bond critical points (HBCPs) by the atoms in molecules (AIM) method. Most of changes of individual HBs are in consistent with the ED/EW nature of substituents and the role of atoms entered H-bonding. The remarkable change is observed for NO₂ substituted derivative in each case.     

Optoelectronic,Aggregation, and Redox Properties of Double-Rotor Boron Difluoride Hydrazone Dyes

We develop the chemistry of boron difluoride hydrazone dyes (BODIHYs) bearing two aryl substituents and explore their properties. The low-energy absorption bands (λ_max=427–464 nm) of these dyes depend on the nature of the N-aryl groups appended to the BODIHY framework. Electron-donating and extended π-conjugated groups cause a redshift, whereas electron-withdrawing groups result in a blueshift. The title compounds were weakly photoluminescent in solution and strongly photoluminescent as thin films (λ_PL=525–578 nm) with quantum yields of up to 18 % and lifetimes of 1.1–1.7 ns, consistent with the dominant radiative decay through fluorescence. Addition of water to THF solutions of the BODIHYs studied causes molecular aggregation which restricts intramolecular motion and thereby enhances photoluminescence. The observed photoluminescence of BODIHY thin films is likely facilitated by a similar molecular packing effect. Finally, cyclic voltammetry studies confirmed that BODIHY derivatives bearing para-substituted N-aryl groups could be reversibly oxidized (E_ox1=0.62–1.02 V vs. Fc/Fc⁺) to their radical cation forms. Chemical oxidation studies confirmed that para-substituents at the N-aryl groups are required to circumvent radical decomposition pathways. Our findings provide new opportunities and guiding principles for the design of sought-after multifunctional boron difluoride complexes that are photoluminescent in the solid state.     

Untersuchungen über Chinone, 9. Mitt. Über Acetylderivate vonp-Indazolchinonen

Summary Acetylation of the indazolquinones1a (6-anilino-),b (6-p-toluidino-),c (6-N-methylanilino-),g (6- or 5-methylthio-), andk (benz[f]-) by heating with acetic anhydride yields the 2-acetylindazolquinones4a, b, c, g, andk. Reductive acetylation of the quinones1c, g, h/h ₁(6/5-methyl),k and — for structure elucidation — their 1-N- (2c) and 2-N- (3c, 3e)-methyl derivatives with acetic anhydride, zink powder, and sodium acetate gives the 1-acetyl-(7c, g, h/h ₁,k), resp. 1-methyl- (8c), and 2-methyl- (9c, e) diacetoxyindazoles. In case of1k, two diacetyl derivatives were isolated in addition to the already known triacetyl derivative7k, regardless of the conditions chosen. Acetylation of the intermediate product of the reaction from phenylthio-benzoquinone with diazomethane also yields a triacetyl-hydroquinone (7f). UV/Vis, IR, and¹H NMR spectroscopy were used for structure determination. Comparison of the UV/Vis spectra of the acetyl derivatives4 with those of1, 2, 3, and of compounds7 with those of analog substituted indazols shows that the acetyl group is located in position 2 with compounds4 and in position 1 with compounds7. By means of¹H NMR spectra the position of the acetyl group can be determined by the effect of the carbonyl group on the proton in position3.

     

Computational studies on optoelectronic and charge transfer properties of some perylene‐based donor‐π‐acceptor systems for dye sensitized solar cell applications

We report DFT studies on some perylene‐based dyes for their electron transfer properties in solar cell applications. The study involves modeling of different donor‐π‐acceptor type sensitizers, with perylene as the donor, furan/pyrrole/thiophene as the π‐bridge and cyanoacrylic group as the acceptor. The effect of different π‐bridges and various substituents on the perylene donor was evaluated in terms of opto‐electronic and photovoltaic parameters such as HOMO‐LUMO energy gap, λ_max, light harvesting efficiency(LHE), electron injection efficiency (Ø_inject), excited state dye potential (E^dye*), reorganization energy(λ), and free energy of dye regeneration (). The effect of various substituents on the dye–I₂ interaction and hence recombination process was also evaluated. We found that the furan‐based dimethylamine derivative exhibits a better balance of the various optical and photovoltaic properties. Finally, we evaluated the overall opto‐electronic and transport parameters of the TiO₂‐dye assembly after anchoring the dyes on the model TiO₂ cluster assembly.