The synthesis of [15]annulenone 4,7:10,13-dioxides and aromatic 4,7:10,13-dioxido[15]annulenium cations : Novel 14]gp ‘odd’ annulene systems

2,15 - Dimethoxycarbonyl - [15]annulenone 4,7:10,13 - dioxide (14) has been prepared by the condensation of cis -α,β -bis(5 - formyl - 2 - furyl)ethy]ene (13) with dimethyl acetonedicarboxylate. Treatment of 14 with conc H₂SO₄ led to 4,7:10,13-dioxido[15]annulenone 2,15-dicarboxylic acid anhydride (17), which was subsequently converted to the corresponding dicarboxylic acid (18) by dilute KOH. Decarboxylation of 18 gave rise to two isomeric [15]annulenone 4,7:10,13 - dioxides, i.e., the tri-cis isomer (7) and the mono - trans - di - cis isomer (8).Regarding to the ring current effects, the proton chemical shifts of these [15]annulenones were compared with those of a reference model, 4,7:10,13 - dioxido - cyclopentadecaheptaene (2.4.6.8.10.12.14) (3). Both of the parent [15]annulenones (7 and 8) have been interpreted as nondiatropic, while the anhydride (17) has been shown to be diatropic, sustaining an induced diamagnetic ring current. The enforced planarity and symmetrical geometry of the anhydride have been discussed. As expected, when 7, 8, 14, 17 and 18 were dissolved in CF₃COOH or conc H₂SO₄, completely delocalized [15]annulenium cations were produced, all of which proved to be diatropic. Three possible geometrical isomers of these 14π cations were established experimentally.     

Synhtesis of 2-ethoxy-6,11-dimethyl-7,9-bisdehydroaza[16]annulene and 2-ethoxy-8,13-dimethyl-9,11-bisdehydroaza[18]annulene

Title azaannulenes, the paratropic and diatropic vinylogues of pyridine, were synthesized starting from the annulenones.     

The synthesis of diphenyltrideca-, -pentadeca-, -heptadeca-, and -nonadecafulvene derivatives

Title fulvenes were synthesized through the reaction of the large-membered annulenones with diphenylketene, and examination of ¹H-NMR spectra suggests that the fulvenes are atropic.     

The synthesis of 2-ethoxy-6,11-dimethyl-7,9-bisdehydroaza[14]annulene and its benzannelated derivatives

Title azaannulenes were synthesized starting from annulenones, and the ¹H-NMR spectra are discussed in connection with tropicity of these annulenes.     

On the aromaticity of annulenones

Application of our method of predicting aromaticity¹ shows that the behavior of the annulenones is intermediate between that of the fulvenes (a nonaromatic series) and the annulenes (a series with strong alternation between aromatic and antiaromatic).     

Thermal electrocyclization reactions II: benzooctatetraenes and benzodecapentaenes

Thermal electrocyclization reactions of benzooctatetraenes and benzodecapentaenes substituted with R=H, Cl, and methyl were studied experimentally and computationally. Methyl and unsubstituted benzooctatetraenes and benzodecapentaenes give the [4.2.0]bicyclooctadiene products by 8π,6π-electrocyclization. Chlorine substitution led to thermal rearrangement of the initially formed 8π,6π-electrocyclization intermediates to give unprecedented products.     

Trimethylbisdehydro[23]- and -[25]annulenones

Syntheses of trimethylbisdehydro [23]- and -[25]annulenones have been described, and the examination of their ¹H NMR spectra suggests the diatropicity and the paratropicity of the 25-membered and 25-membered rings, respectively.     

Cycloaddition reactions of 2H-benzo[b]thiete and conjugated cyclic dienes

2H-Benzo[b]thiete 1 reacts with cyclopentadiene 3 in consecutive [8π + 2π]cycloadditions yielding the condensed heterocycles 6–8 . Tetracyclone 9 on the other hand gives only the monoadduct 10 . An [8π + 8π]cycloaddition can be observed for 1 and diphenylisobenzofuran 11 . The related π system 13 shows again consecutive [477π + 27π]processes ( 1 + 13 ← 14, 15 ).     

Spezifisch π→π*-induzierte Reaktionen von γ-Dimethoxymethylcyclohexen-2-onen: 1,3-Umlagerung und Wasserstoffabstraktion durch das α-Kohlenstoffatom

When α,β-unsaturated γ-dimethoxymethyl cyclohexenones are excited to the S₂(π,π*) state, certain unimolecular reactions can be observed to compete with S₂ → S₁ internal conversion. These reactions do not occur from the S₁(n,π*) or the lowest T(π,π* and n,π*) states. They comprise the radical elimination of the formylacetal substituent (cf. 8 , 9 → 32 + 33 ), γ → α formylacetal migration (cf. 6 → 27 , 8 → 30 , 9 → 34 , 12 → 37 ), and a cyclization process involving the transfer of a methoxyl hydrogen to the α carbon and ring closure at the β position (cf. 6 → 28 , 8 → 31 , 12 → 38 , 20 → 40 + 41 ). The quantum yield of the ring closure 20a → 40a + 41a is 0.016 at ≤ 0.05M concentration. It is independent of the excitation wavelength within the π→π* absorption band (238–254 nm), but Φ ( 40a + 41a ) decreases at higher concentrations. According to the experimental data the reactive species of these specifically π→π*-induced transformations is placed energetically higher than the S₁(n,π*) state, and it is either identical with the thermally equilibrated S₂(n,π*) state, or reached via this latter state. The linear dienone 14 undergoes a similar π→π*-induced cyclization (→ 42 ) whereas the benzohomologue 26 proved unreactive, and the dienone 22 at both n → π and π→π* excitation only gives rise to rearrangements generally characteristic of cross-conjugated cyclohexadienones.     

Near-infrared-emitting phthalocyanines. A combined experimental and density functional theory study of the structural, optical, and photophysical properties of Pd(II) and Pt(II) α-butoxyphthalocyanines

The structural, optical, and photophysical properties of 1,4,8,11,15,18,22,25-octabutoxyphthalocyaninato-palladium(II), PdPc(OBu)(8), and the newly synthesized platinum analogue PtPc(OBu)(8) are investigated combining X-ray crystallography, static and transient absorption spectroscopy, and relativistic zeroth-order regular approximation (ZORA) Density Functional Theory (DFT)/Time Dependent DFT (TDDFT) calculations where spin-orbit coupling (SOC) effects are explicitly considered. The results are compared to those previously reported for NiPc(OBu)(8) (J. Phys. Chem. A 2005, 109, 2078) in an effort to highlight the effect of the central metal on the structural and photophysical properties of the group 10 transition metal octabutoxyphthalocyanines. Different from the nickel analogue, PdPc(OBu)(8) and PtPc(OBu)(8) show a modest and irregular saddling distortion of the macrocycle, but share with the first member of the group similar UV-vis spectra, with the deep red and intense Q-band absorption experiencing a blue shift down the group, as observed in virtually all tetrapyrrolic complexes of this triad. The blue shift of the Q-band along the MPc(OBu)(8) (M = Ni, Pd, Pt) series is interpreted on the basis of the metal-induced electronic structure changes. Besides the intense deep red absorption, the title complexes exhibit a distinct near-infrared (NIR) absorption due to a transition to the double-group 1E (π,π*) state, which is dominated by the lowest single-group (3)E (π,π*) state. Unlike NiPc(OBu)(8), which is nonluminescent, PdPc(OBu)(8) and PtPc(OBu)(8) show both deep red fluorescence emission and NIR phosphorescence emission. Transient absorption experiments and relativistic spin-orbit TDDFT calculations consistently indicate that fluorescence and phosphorescence emissions occur from the S(1)(π,π*) and T(1)(π,π*) states, respectively, the latter being directly populated from the former, and the triplet state decays directly to the S(0) surface (the triplet lifetime in deaerated benzene solution was 3.04 μs for Pd and 0.55 μs for Pt). Owing to their triplet properties, PdPc(OBu)(8) and PtPc(OBu)(8) have potential for use in photodynamic therapy (PDT) and are potential candidates for NIR light emitting diodes or NIR emitting probes.     

Photochemische Reaktionen. 109. Mitteilung [1]. Zur Photochemie konjugierter δ-Keto-enone und β,γ,δ,ϵ-ungesättigter Ketone

Photochemistry of Conjugated δ-Keto-enones and β,γ,δ,?-Unsaturated Ketones On ¹π,π*-excitation the δ-keto-enones 5–8 are isomerized to compounds B ( 18 , 22 , 26 , 28 ) via 1,3-acyl shift and to compounds C ( 19 , 23 , 27 , 29 ) via 1,2-acyl shift, whereas the β,γ,δ,?-unsaturated ketone 9 gives the isomers 32 and 33 by 1,2-and 1,5-acyl shift, respectively. Furthermore, isomerization of 6 to 24 , dimerization of 8 to 30 and addition of methanol to 8 ( 8 → 31 ) is observed. Unlike 7 and 8 the acyclic ketones 5 , 6 and 9 undergo photodecarbonylation on ¹π,π*-excitation ( 5 → 20 , 21 ; 6 → 20 , 25 ; (E)- 9 → 35–38 ). Evidence is given, that the conversion to B as well as the photodecarbonylation of 5,6 and 9 arise from an excited singulet state, but the conversion to C as well as the dimerization of 8 from the T₁-state.     

Benzohydrazide Derivatives: Gelation and Application in Oil Spill Recovery

The synthesis and gelation properties of a series of organogelators containing a benzohydrazide unit and two alkoxy chains(oBn) were reported herein. oBn(n=8, 10, 12) could form stable gels in commercial fuels(e.g., diesel), which were characterized by low critical gelation concentrations(CGCs) and good mechanical properties (G'>10⁵ Pa). The gelation process was further studied by field-emission scanning electron microscopy(FE-SEM), Fourier transform infrared spectroscopy(FTIR) and X-ray diffraction(XRD), etc. It was demonstrated that in these organogels, molecules self-assembled into fibrils 3D-network, where hydrogen bonding, van der Waals force and π-π interaction were confirmed as the driving forces. As compounds oBn(n=8, 10, 12) show very good gelation properties in diesel, their applications in oil spill treatment have also been tested. It was found that oBn could achieve rapid (<30 s) and effective oil removal at room temperature, being good candidates for oil spill treatment in the future. Also, the removal efficiency could be as high as 95%.     

Microwave-assisted generation and reactivity of aza- and diazafulvenium methides: heterocycles via pericyclic reactions

Azafulvenium methides and diazafulvenium methides have been generated under microwave irradiation from 2,2-dioxo-1H,3H-pyrrolo[1,2-c]thiazoles and 2,2-dioxo-1H,3H-pyrazolo[1,5-c]thiazoles, respectively. Pericyclic reactions of these 1,7-dipole intermediates, namely, sigmatropic [1,8]H shifts, 1,7-electrocyclization or [8π+2π] cycloaddition led to the synthesis of a range of pyrrole and pyrazole derivatives. The first evidence for the azafulvenium methides by intermolecular trapping via [8π+2π] cycloaddition is reported.     

Cycloaddition of trifluoromethyl azafulvenium methides: synthesis of new trifluoromethylpyrrole-annulated derivatives

The chemistry of trifluoromethyl azafulvenium methides was explored leading to a new route to trifluoromethylpyrrole-annulated systems. The first evidence of azafulvenium methides acting as 1,3-dipoles is reported. These azafulvenium methides showed site selectivity in the reaction with strong electron-deficient dipolarophiles leading exclusively to 1,3-cycloadducts. In the cycloaddition with less-activated dipolarophiles 1,7-cycloadducts resulting from [8π+2π] cycloaddition are also formed. FMO analysis of the cycloaddition reactions allowed the rationalization of the observed selectivity.     

The preparation and properties of metallofluorene complexes of transition metals.

Metalluorene complexes (π-C₅H₅)M(CO)(C₁₂H₈) (IVa)-(IVc) and (π-C₅H₅) (CO)(C₁₂F₈) (IVd)-(IVf) (M = Co, Rh and Ir) have been prepared from reactions of the appropriate (π-cyclopentadienyl) carbonylmetal diiodides with 2,2′-dilithhiolbiphenyl (IIa) and 2,2′-dilithiooctafluorobiphenyl (IIb), respectively The triphenylphoshine substitution reactions of cobalt compounds (IVa) and (IVd) have also been studied. Reaction of (IIa) and (IIb) with norbornadieneplatinum dichloride result in the preparation of metallocyclic platinum compounds (π-C₇H₈) and (π-C₇H₈)Pt(C₁₂H₈). A reaction of (IIb) with zirconocene dichloride produces (π-C₅H₅)₂Zr(C₁₂F₈), the first example of a ziconium-containing metalofluorene.     

Suppression of HOMO-LUMO transition in a twist form of oligo(phenyleneethynylene) clamped by a right-handed helical peptide

A donor-π-acceptor (D-π-A) system of oligo(phenyleneethynylene) (OPE) was twisted by clamping both ends of the OPE with a right-handed helical peptide (SSA8=OPE). The induced twist in OPE was in a right-handed way. SSA8=OPE showed a weaker HOMO-LUMO band in the absorption spectrum than that of a reference compound AcOPE without the helix bridge. The fluorescence quantum yield of SSA8=OPE was extremely low (0.0045-0.0165), which was in contrast to AcOPE with a moderate quantum yield of 0.355. The fluorescence life times of SSA8=OPE and AcOPE were nearly the same. Time-dependent density functional theory calculations (b3lyp/6-31G(d,p) level) on a twisted conformation of the D-π-A system qualitatively reproduced CD spectra and UV spectra of a weak oscillator strength of the HOMO-LUMO transition. Upon twisting the D-π-A system, the oscillator strength of the HOMO-LUMO transition is thus reduced.     

Thermal reaction of [3,4]-benzo-8-substituted-3Z,5Z,7E-octatetraenes and quantum-chemical study of the (8π,6π)-electrocyclisation

The first example of thermal (8π,6π)-electrocyclisation of 1,3,5,7-octatetraene with one double bond embedded in an aromatic moiety is described. By this process, [3,4]-benzo-8-substituted octatetraene derivatives, the cis,trans-1-(o-vinylphenyl)-4-(R = Me, Ph, 2-furyl)buta-1,3-dienes were transformed to a new endo-7-(R = Me, Ph, 2-furyl) and exo-7-(R = Me)-2,3-benzobicyclo[4.2.0]octa-2,4-dienes. Mechanism of reaction was also studied by DFT quantum-chemical calculations. The M06/6-311+G(d,p)//M06/6-31+G(d,p) calculations indicate that formation of the single endo-isomer in the case of phenyl and 2-furyl substituents is determined by higher activation barriers for exo-6π-electrocyclisation than for 8π-cycloreversion.     

Nature of the intense near-IR absorption and unusual broad UV-visible-NIR spectra of azulenocyanines: density functional theory studies

The nature of the broad and intense near-IR (NIR) absorptions of azulenocyanine (H(2)Azc) in the range of 720-1300 nm due to the π→π* transitions is clearly revealed on the basis of density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. The electron moving between peripheral conjugated systems and the eighteen electron-π-conjugated core due to different types of electron transitions has also been clarified. Because of the small gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of all four H(2)Azc isomers, their Q absorption bands in the region of 850-1300 nm are significantly red-shifted relative to its isoelectronic analogue naphthalocyanine H(2)Nc. Observation of the new absorption bands between Q and Soret bands from 720 to 1050 nm for H(2)Azc is considered to be the result of electron transitions from the fused azulene rings to the 18 electron-π-conjugated core. In addition, the introduction of electron-withdrawing or electron-donating substituents onto the periphery of the azulenocyanine ring is revealed to further reduce the LUMO-HOMO gap, leading to a further red-shifted broad and intense NIR absorption band from 900 to 1700 nm for H(2)(F(8)Azc) and H(2)[(NH(2))(8)Azc].     

Visual sensing of picric acid in 100% aqueous media based on supramolecular polythiophene assemblies with colorimetric and fluorescent dual response

A colorimetric and fluorometric dual probe based on a water-soluble polythiophene derivative (PMTPBA) was designed and synthesized. It can be applied to determination of picric acid (PA) in 100% aqueous solution. The approach relies on the formation of supramolecular polythiophene assemblies in the presence of PA through electrostatic, charge transfer and π-π stacking interactions. This probe could be utilized for the rapid and visual detection of PA both in aqueous solution and solid support with high specificity and sensitivity. The detection limit of this sensor is as low as 5.0 × 10^-8 mol/L.     

Aromatic Amides: A Smart Backbone toward Isolated Ultralong Bright Blue-Phosphorescence in Confined Polymeric Films

We describe an aromatic amide skeleton for manipulation of triplet excited states toward bright long-lived blue phosphorescence. Spectroscopic studies and theoretical calculations demonstrated that the aromatic amides can promote strong spin-orbit coupling between (π,π*) and the bridged (n,π*) states, and enable multiple channels to populate the emissive ³(π,π*), as well as facilitate robust hydrogen bonding with polyvinyl alcohol to suppress non-radiative relaxations. Isolated inherent deep-blue (0.155, 0.056) to sky-blue (0.175, 0.232) phosphorescence with high quantum yields (up to 34.7 %) in confined films are achieved. The blue afterglow of the films can last for several seconds and are showcased in information display, anti-counterfeiting, and white light afterglow. Owing to the high population of ³(π,π*) states, the smart aromatic amide skeleton provides an important molecular design prototype to manipulate triplet excited states for ultralong phosphorescence with various colors.