DABCO as a dynamic hinge between cofacial porphyrin panels and its tumbling inside a supramolecular cavity

The heteroleptic supramolecular double-decker porphyrin 1 was synthesized with DABCO as a guest between two cofacial porphyrin units as characterized by (1)H NMR and ESI-MS. While DABCO is not seen to tumble inside the cavity, even at higher temperatures (80 °C), such motion was triggered upon addition of various coordinating ligands (quinuclidine, 4-bromopyridine, or excess of DABCO). Different stoichiometric amounts were needed depending on the n donor quality of the added ligands to initiate tumbling of the "inside" DABCO. As demonstrated in an example with excess DABCO, the tumbling was stopped by lowering the temperature to -50 °C.     

Computational assisted electrochemical studies for 1,4-diazabicyclo[2,2,2]octane determination at multiwalled carbon nanotube paste electrode

A multiwalled carbon nanotube-modified carbon paste electrode (MWCNT-PE) was used for determination of 1,4-diazabicyclo[2,2,2]octane (DABCO or TEDA) in 0.1 M phosphate buffer solutions (pH 10.25). Cyclic voltammetry(CV) and differential pulse voltammetry (DPV) techniques were used to investigate the electrocatalytic oxidation of DABCO at the surface of modified electrode. The results shown that the oxidation peak current of DABCO at the surface of MWCNT-PE was 2.40 times larger than that at the bare electrode. The experimental formal redox potential (E°') of DABCO was obtained 986 mV versus SHE (Standard Hydrogen Electrode). Density functional theory (DFT) method at B3LYP/6-311++G** level of theory and a conductor-like Polarizable Continuum Model (CPCM) was used to calculate the E°' values. The highest occupied molecular orbital (E _HOMO), lowest unoccupied molecular orbital (E _LUMO) and some thermodynamic parameters such as Gibbs free energy of DABCO and its oxidation forms were calculated. Both direct and indirect methods were used to calculate the theoretical standard electrode potential for DABCO and the results were found to be in good agreement with the experimental values.     

Katalytische Effekte bei der Reaktion von 2,4-Dinitrofluorbenzol mit Morpholin in Benzol. 7. Mitteilung über nucleophile aromatische Substitutionsreaktionen

• (1) The rates of reaction of 2, 4-dinitrofluorobenzene with morpholine have been measured in benzene solution, with and without the addition of pyridine or 1, 4-diaza-bicyclo[2.2.2]octane (DABCO) as catalysts.
• (2) The reaction is catalyzed by morpholine, pyridine and DABCO; the rate laws as functions of these bases are expressed by equations (2)–(4).
• (3) The reaction is considerably more sensitive to pyridine and DABCO catalysis than that of 2, 4-dinitrofluorobenzene with the sterically identical, but more basic piperidine. These findings confirm a previously found trend of greater sensitivity to base catalysis with decreasing base strength of the reacting amine.

     

Dimethyl carbonate synthesis via transesterification of ethylene carbonate and methanol using ionic liquid catalysts immobilized on mesoporous cellular foams

Dimethyl carbonate (DMC) was synthesized via transesterification of ethylene carbonate and methanol with ionic liquid catalysts. For this reaction, 1,4-diazobicyclo[2.2.2]octane (DABCO), [Choline]OH, and [BMIM]Cl were used as a homogeneous catalyst, and hydrotalcite, [DABCO]OH@MCF, [DABCO]Cl@MCF, and DABCO/MCF were used as a heterogeneous catalyst. To support the ionic liquids, mesoporous cellular foam (MCF) was prepared and characterized by SEM, TEM and BET surface area analyzer. The average cell and window sizes of the prepared MCF were 34.4 and 21.3 nm, respectively. The prepared MCF had a well structured three-dimensional structure. Among the homogeneous catalysts used, DABCO showed the highest DMC yield about 84 %, and among the heterogeneous catalysts, [DABCO]OH@MCF showed the highest DMC yield about 77 %. In the reusability test of the used catalysts, there was only 8 % point decrease in DMC yield with [DABCO]OH@MCF, whereas 58 percent point decrease in DMC yield with DABCO/MCF after four times recycling tests. The effects of an anion on the catalytic activity were investigated. The optimum reaction condition for DMC synthesis was also investigated with [DABCO]OH@MCF catalyst.     

pH-Dependent Syntheses,Crystal Structures and Properties of Three Low-Dimensional Iodoargentate Hybrids

By simply changing pH value of reaction solution, three low-dimensional iodoargentate hybrids, [HDABCO]₂[(DABCO)₂(Ag₂I₄)] (1), [HDABCO]_0.5[(HDABCO)_0.5(AgI₂)] (2) and [(Me₂NH₂)(H₂DABCO)][AgI₄] (3) (DABCO = 1,4-diazabicyclo-[2.2.2]octane), have been synthesized. Noteworthy, variation in protonated degree and aggregating forms of DABCO at different pH value, the structure of inorganic moieties vary regularly from 0D [(DABCO)₂(Ag₂I₄)]^2? anion for 1 to 1D [(HDABCO)_0.5(AgI₂)]^0.5? chain for 2 and 0D [AgI₄]^3? anion for 3, exhibiting unique structural directing effects. In addition, three compounds display structure-dependent semiconductor natures and thermal stabilities.     

Sulfonylation of 1,4-Diazabicyclo[2.2.2]octane: Charge-Transfer Complex Triggered C−N Bond Cleavage

A novel charge-transfer complex triggered sulfonylation of 1,4-diazabicyclo[2.2.2]octane (DABCO) with mild reaction conditions has been developed. The formation of a charge-transfer complex between electron-withdrawing (hetero)aryl sulfonyl chloride and DABCO allows the synthesis of N-ethylated piperazine sulfonamide in good yields. The reaction has a high functional group tolerance. Spectroscopic studies confirmed the charge-transfer complex formation between sulfonyl chlorides and DABCO, which facilitates the C−N bond cleavage of DABCO.     

Reaction of 2-Formyl Imidazole with Intermediates From the Baylis-Hillman Reaction

The reaction of formyl imidazole (in the presence and absence of DABCO, and with either THF or methanol as solvent) with α-hydroxylaryl derivatives of methyl acrylate affords novel synthetic intermediates. By controlling the reaction conditions, either allylic substitution products (THF, DABCO) or rearrangement (MeOH, no DABCO) products result.     

Chemical Stimulus‐responsive Folding and Unfolding of a Dendrimeric Assembly

A dendrimeric trimer undergoes folding and unfolding in response to a chemical stimulus. The trimer of interest contains a central dendrimer with a butadiyne‐linked zinc porphyrin dimer ((ZnP)₂) core, in addition to two terminal dendrimers with zinc porphyrin (ZnP) cores. The obtained absorption spectra indicate that the unfolded form is the exclusive conformer in chloroform, while the addition of 1,4‐diazabicyclo[2.2.2]octane (DABCO) in chloroform leads to transformation from the unfolded to the folded structure containing two DABCO units per trimer; the folded structure originates from the cross‐linking of (ZnP)₂ and ZnP with DABCO. Moreover, the addition of excess DABCO promotes the generation of the unfolded structure containing four DABCO units.     

Hetero Face‐to‐Face Porphyrin Array with Cooperative Effects of Coordination and Host–Guest Complexation

We successfully synthesized a hetero face‐to‐face porphyrin array composed of ZnTPP and RuTPP(DABCO)₂ (TPP: 5, 10, 15, 20‐tetraphenylporphyrin, DABCO: 1,4‐diazabi‐cyclo[2.2.2]octane) in 2:1 molar ratio. A cyclic Zn porphyrin dimer (ZnCP) was also used as the host molecule for the Ru porphyrin. In the latter, the Ru‐DABCO bonding in RuTPP(DABCO)₂ was stabilized by the host‐guest complexation. Reaction progress kinetic analysis of the ligand substitution reaction of RuTPP(DABCO)₂ and that in ZnCP revealed the stabilization mechanism of the Ru‐DABCO bonding. Photoinduced electron transfer (PET) from the Zn porphyrin to the Ru porphyrin was observed in the porphyrin array. The host‐guest stabilization of unstable complex for construction of a donor—acceptor–donor structure is expected to be a new method for an artificial photosynthesis.     

Organic/Bismuth Iodides Hybrids: Structural Perturbation of Substitutes and Their Photocurrent Response Properties

Two new organic/bismuth halides hybrids, (Et₂DABCO)₂(Bi₂I₁₀) (1) and (Pr₂DABCO)₂(Bi₂I₁₀) (2) (Et₂DABCO²⁺ = N, N’-diethyl-1,4-diazabicyclo[2.2.2] octane, Pr₂DABCO²⁺ = N, N’-diproyl-1,4- diazabicyclo[2.2.2] octane) have been synthesized. Both hybrids contain (Bi₂I₁₀)^4? halobismuthate dimers and (Et₂DABCO)²⁺/(Pr₂DABCO)²⁺ cations, and C–H···I hydrogen bonds contribute to the structural extending from 0-d clusters to 2-d layer (for 1) and 3-d network (for 2). Theoretical calculations were conducted to reveal the perturbation effects of 1,4-diazabicyclo[2.2.2] octane substitutes on their structures. Their absorption spectra were investigated, and energy band gaps of 2.10/2.16 eV indicate their narrow-gap semiconductor natures. Their photocurrent response properties were also discussed.     

Poly(ethyleneglycol) (PEG): a rapid and recyclable reaction medium for the DABCO-catalyzed Baylis-Hillman reaction

PEG (400) has been used as a rapid and recyclable reaction medium for the Baylis-Hillman reaction with the conventional basic catalyst DABCO (20 mol %) with very good yields of products. Recyclability is achieved with no further addition of DABCO to the reaction medium for over four runs without substantial loss in yields. Incidentally, DABCO is recycled for the first time in this transformation.     

DABCO-triggered mild cascade reaction of electron-deficient cyclopentadienone: facile and efficient synthesis of condensed carbocycles

2,5-Bis(methoxycarbonyl)-3,4-diphenylcyclopentadienone (1) reacts with 4-phenylbut-3-yn-2-one (2b) in the presence of DABCO to give the bicyclic carbocycles (6b) and the tetracyclic carbocycle (7b) under extremely mild reaction conditions.     

Synthesis, characterization, and photochromic properties of hybrid organic-inorganic materials based on molybdate, DABCO, and piperazine

Prompted by our interest in new photochromic organic-inorganic hybrid materials, the reactivity of [Mo7O24]6- toward a structure-directing reagent diamine such as 1,4-diazabicyclo[2.2.2]octane (DABCO) and piperazine (pipz) has been investigated, and three new molybdenum(VI)-containing compounds, namely, (H2DABCO)3[Mo7O24].4H2O (1), (H2DABCO)[Mo3O10].H2O (2), and (H2DABCO)2(NH4)2[Mo8O27].4H2O (3), have been synthesized and characterized. New synthetic routes to achieve the known compounds (H2DABCO)2(H2pipz)[Mo8O27] (4), (H2pipz)3[Mo8O27] (5), and (H2DABCO)2[Mo8O26].4H2O (6) are also reported. All of these compounds contain different poly(oxomolybdate) clusters, i.e., discrete [Mo7O24]6- blocks in 1, infinite polymeric chains 1/infinity[Mo3O10]2- in 2, 1/infinity[Mo8O27]6- in 3-5, and 1/infinity[Mo8O26]4- in 6, associated in a tridimensional assembly by hydrogen bonds with H2DABCO2+ and/or H2pipz2+ cations. Interconversion pathways and chemical factors affecting the stabilization of the different species are highlighted and discussed. At the opposite of 6, compounds 1-5 show photochromic behavior under UV excitation. Namely, compounds 1-5 shift from white or pale yellow to pale pink, reddish brown, or purple under UV illumination depending on the chemical nature of the mineral framework, with the kinetics of the color change being dictated by the nature of the organic component and by the organic-inorganic interface.     

Lewis base-catalyzed divergent isomerizations of 5-hydroxyl-2,3-dienoate

A divergent isomerization of 5-hydroxyl-2,3-dienoate 1 catalyzed by Lewis base has been developed, the phosphine catalyst leads to 5-oxohex-2(3)-enoates 2 while DABCO catalyst affords 3-ethoxy α,β-unsaturated lactone 3.     

Recyclable and reusable Pd(OAc)2/DABCO/PEG-400 system for Suzuki-Miyaura cross-coupling reaction

[reaction: see text] A stable and efficient Pd(OAc)2/DABCO (triethylenediamine) catalytic system for Suzuki-Miyaura cross-coupling reaction has been developed. In the presence of Pd(OAc)2 and DABCO, coupling of aryl halides with arylboronic acids was carried out smoothly to afford good to excellent yields and high turnover numbers (TONs) (the maximal TONs were up to 960,000 for the reaction of 1-iodo-4-nitrobenzene with phenylboronic acid) using PEG-400 as the solvent. Moreover, the Pd(OAc)2/DABCO/PEG-400 system could be recycled and reused five times without any loss of catalytic activity for aryl iodides and bromides.     

On the effect of 1,4-diazabicyclo[2.2.2]octane on the singlet-oxygen dimol emission: photosensitized generation of (1O2)2

Time-resolved singlet-oxygen dimol luminescence has been recorded upon laser-pulsed photosensitization of singlet oxygen by 2-acetonaphthone or 1-H-phenalen-1-one in perfluorobenzene, perdeuterobenzene, and perdeuteroacetonitrile. It is shown that 1,4-diazabicyclo[2.2.2]octane (DABCO) does not enhance radiative properties of the dimol species generated by the photosensitization. Instead, DABCO strongly reduces the singlet-oxygen dimol luminescence. Rate constants for the quenching of the dimol luminescence by DABCO have been determined for the three solvents used.     

DABCO作为高效配体促进钯催化末端炔烃自偶联反应研究

发展了一种以DABCO(1,4-diaza-bicyclo[2.2.2]octane)为配体高效钯催化末端炔烃自偶联反应方法.在醋酸钯(2 mol%)、碘化亚铜(2 mol%)、DABCO(4 mol%)、醋酸钠(3 mmol)、乙腈(5 mL)和空气氛等条件下,1 mmol的末端炔烃可以顺利发生自偶联反应生成相应的二炔化合物,产率为中等到良好.     

Molecular acrobatics: self-assembly of calixarene-porphyrin cages

Calix[4]arenes equipped with two and four zinc porphyrins have been prepared, and they show remarkable flexibility in their self-assembly properties with the bidentate ligand DABCO. The calix-bisporphyrin forms a 2:2 complex with DABCO, generating a large cavity that has the potential to act as a supramolecular host. The calix-tetraporphyrin, on the other hand, forms four different complexes with DABCO depending on the stoichiometry and concentration. During the course of a titration, all four complexes are populated, leading to large conformational changes and the formation of both intramolecular and intermolecular calix-tetraporphyrin-DABCO sandwich complexes. The system was fully characterized using a combination of UV-visible and (1)H NMR spectroscopy to identify the complexes. At a calix-tetraporphyrin:DABCO ratio of 2:4, the major species is dimeric cage assembly that features a large internal cavity for guest complexation.     

[Cu4OCl6(DABCO)2]·0.5DABCO·4CH3OH (“MFU-5”): Modular synthesis of a zeolite-like metal-organic framework constructed from tetrahedral {Cu4OCl6} secondary building units and linear organic linkers

A novel metal-organic framework (MOF) based on a tetranuclear copper cluster and a linear organic ligand formulated as [Cu₄OCl₆(DABCO)₂]·0.5DABCO·4CH₃OH (denoted as MFU-5, MFU=Metal-Organic Framework, Ulm University; DABCO=1,4-diazabicyclo[2.2.2]octane), was prepared via solvothermal synthesis. In contrast with common MOF synthesis strategies, MFU-5 is assembled from pre-defined molecular secondary building units, i.e. {Cu₄OCl₆} moieties, which become the nodes of the coordination framework. The title compound was characterized by single crystal X-ray diffraction, variable temperature powder diffraction (VT-XRPD), thermal analysis, as well as IR- and UV/Vis spectroscopy. Crystal data for MFU-5: hexagonal, P6/mcc (no. 192), a=25.645(9), c=17.105(11) Å, V=9742(8) Å³, Z=12, 1690 structure factors, R[F²>2σ(F²)]=0.049. MFU-5 is a 3D metal-organic framework with 1D channels running along the c-axis hosting DABCO and methanol solvent molecules. The framework displays a zeolite-like structure constructed from mso cages, which represents the composite building units in the zeolites SSF, MSO and SZR. Two-fold interpenetration is observed between these building units. TG/DTA-MS and VT-XRPD characterization reveal a stepwise release of methanol and DABCO molecules upon heating, eventually resulting in a structural change into a non-porous material.     

双核Salen锌配合物对含氮小分子的分子识别研究

合成并表征了由一定长度烷氧链桥连的新型双核SalenZn配合物[简记为C₁₀-(SalenZn)₂],用紫外-可见光谱滴定方法测定了主体C₁₀-(SalenZn)₂与单齿客体咪唑(Im)、吡啶(Py)、双齿客体DABCO(1,4-重氮双环[2.2.2]辛烷)及吡嗪(Pyrazine)等4种含氮客体间的轴向配位反应的配位数及缔合常数.结果表明,双核主体与咪唑、吡啶和吡嗪的配位数均为2,与DABCO的配位数为1;各主客体体系的缔合常数按K0(Im)>K0(DABCO)>K0(Pyrazine)>K0(Py)顺序递减.各主客体缔合反应的热力学参数Δ_rH0_m,Δ_rS0_m和Δ_rG0_m结果表明,此类识别过程均为放热和熵减少的过程.采用¹HNMR方法和分子动力学构象搜索方法对主体C₁₀-(SalenZn)₂与双齿客体DABCO间的分子识别行为及产物构型作了合理解释.通过量子化学计算进一步解释了主客体识别过程中光谱性质的变化.