Facile preparation of N-tert-butyl amides under heat-, metal- and acid-free conditions by using tert-butyl nitrite (TBN) as a practical carbon source.

tert-Butyl nitrite (TBN) is a nontoxic substance that has frequently been used as a source of nitrogen, oxygen, or nitric oxide (NO), but not as a carbon source in chemical transformations. Here, for the first time to the best of our knowledge, we introduced TBN as a source of carbon (tert-butyl group) for the synthesis of highly valuable N-tert-butyl amides from nitriles and water under very mild conditions.

A facile tert-butyl nitrite-assisted preparation of deamino graphitic carbon nitride (DA-gCN) as a photocatalyst for the C-H arylation of heteroarenes using anilines as radical source.

In pristine graphitic carbon nitride (g-CN), amino groups often function as structural defects that trap photogenerated charges, resulting in low photocatalytic activity as well as reaction with nitrite, aldehyde, etc., ensuing in poor product yield. Without significantly altering the optical characteristics, the removal of amino groups is necessary to increase the photocatalytic activity and structural stability of pristine g-CN. The deamino graphitic carbon nitride (DA-gCN-5) was prepared by tert-butyl nitrite (TBN)-treatment, characterized and used as a photocatalyst for the radical C-H arylation of heteroarenes using anilines as radical source. Indeed, the photophysical characteristics of DA-gCN-5 and those of pristine g-CN are very comparable, except that DA-gCN-5 has a fewer residual amino groups, higher crystallinity, and compressed structure with a different morphology. Moreover, DA-gCN-5-catalyzed C-H arylation reaction offers greater product yield in a shorter reaction time compared to that of pristine g-CN in the coupling between heteroarenes and the in situ generated aryl diazonium salts from anilines under visible light irradiation. The amino groups in pristine g-CN absorbed the TBN that was added to convert aniline into the appropriate diazonium ions during the reaction. As a result, deamino graphitic carbon nitride produced by chemical treatment has better photophysical properties and catalytic activity than pristine g-CN. Additionally, this is the first method that uses diazotization reaction for the preparation of deamino graphitic carbon nitride, as far as we are aware.

Persulfate-nitrogen doped graphene mixture as an oxidant for the synthesis of 3-nitro-4-aryl-2H-chromen-2-ones from aryl alkynoate esters and nitrite.

A series of 3-nitro-4-aryl-2H-chromen-2-ones in good yields have directly been obtained from aryl alkynoate esters and nitrite by employing a mixture of K2S2O8-nitrogen doped graphene as an oxidant in a watery medium at room temperature. A plausible mechanism for the reaction is also reported. It reveals that the product is formed through a cascade of nitro radical addition, spirocyclization, and ester migration. When compared to known methods for the synthesis of 3-nitro-4-aryl-2H-chromen-2-ones from aryl alkynoate esters, this protocol is environmentally friendly, sustainable, practical and energy efficient and does not use a harmful nitro source. Furthermore, nitrogen doped graphene used in this approach can be easily recovered and reused at least four times without losing its activity.

Persulfate-activated charcoal mixture: an efficient oxidant for the synthesis of sulfonated benzo[d][1,3]oxazines from N-(2-vinylphenyl)amides and thiols in aqueous solution.

A series of 2,4-aryl-4-((arylsulfonyl)methyl)-4H-benzo[d][1,3]oxazines in good to excellent yields have directly been obtained from N-(2-vinylphenyl)amides and thiols by employing a mixture of K2S2O8-activated charcoal in aqueous acetonitrile solution at 50 °C. A plausible mechanism for the reaction is reported. It reveals that the reaction follows a radical pathway and the persulfate has been the oxygen source for formation of the sulfone group in the products. It is worth mentioning that this protocol utilizes an easily accessible K2S2O8-activated charcoal mixture and thiols, respectively, as an oxidant and sulfonylating precursors for the first time.

Nonlinear Dependence on Na+ Ions for the Binding Dynamics of Cucurbit[6]uril with the trans-1-Methyl-4-(4-hydroxystyryl)pyridinium Cation.

The binding dynamics of the trans-1-methyl-4-(4-hydroxystyryl)pyridinium cation (HSP+) to cucurbit[6]uril (CB[6]) in the presence of Na+ cations were studied to establish the effect of the relative concentrations of the system's components (HSP+, CB[6], and Na+) on these dynamics. The formation of the HSP+@CB[6] complex was temporally uncoupled from the photoisomerization of trans-HSP+, while a nonlinear effect of the Na+ cation concentration on the HSP+@CB[6] dynamics was observed. This nonlinearity is a consequence of Na+ having the opposite effect on the association and dissociation rate constants for the HSP+@CB[6] complex, creating a conceptual framework for using such nonlinearities to control multistep reactions in cucurbit[n]uril chemistry.

Teaching Old Compounds New Tricks: DDQ-Photocatalyzed C-H Amination of Arenes with Carbamates, Urea, and N-Heterocycles.

The C-H amination of benzene derivatives was achieved using DDQ as photocatalyst and BocNH2 as the amine source under aerobic conditions and visible light irradiation. Electron-deficient and electron-rich benzenes react as substrates with moderate to good product yields. The amine scope of the reaction comprises Boc-amine, carbamates, pyrazoles, sulfonimides and urea. Preliminary mechanistic investigations indicate arene oxidation by the triplet of DDQ to radical cations with different electrophilicity and a charge transfer complex between the amine and DDQ as intermediate of the reaction.

Correction: Cucurbit[7]uril inclusion complexation as a supramolecular strategy for color stabilization of anthocyanin model compounds.

Correction for 'Cucurbit[7]uril inclusion complexation as a supramolecular strategy for color stabilization of anthocyanin model compounds' by Barbara Held, et al., Photochem. Photobiol. Sci., 2016, DOI: 10.1039/c6pp00060f.

Cucurbit[7]uril inclusion complexation as a supramolecular strategy for color stabilization of anthocyanin model compounds.

Host-guest complexation with cucurbit[7]uril of anthocyanin model compounds in which acid-base equilibria are blocked resulted in essentially complete stabilization of their color. The color protection is a thermodynamic effect and establishes a strategy to stabilize these colored compounds at pH values of interest for practical applications.

Silver(I)-Promoted ipso-Nitration of Carboxylic Acids by Nitronium Tetrafluoroborate.

A novel and efficient method for the regioselective nitration of a series of aliphatic and aromatic carboxylic acids to their corresponding nitro compounds using nitronium tetrafluoroborate and silver carbonate in dimethylacetamide has been described. This transformation is believed to proceed via the alkyl-silver or aryl-silver intermediate, which subsequently reacts with the nitronium ion to form nitro substances. Mild reaction conditions, tolerant of a broad range of functional groups, and formation of only the ipso-nitrated products are the key features of this methodology when compared to known methods for syntheses of nitroalkyls and nitroarenes.

Triboluminescence and vapor-induced phase transitions in the solids of methyltriphenylphosphonium tetrahalomanganate(II) complexes.

Triboluminescence (TL) of the methyltriphenylphosphonium tetrahalomanganate(II) complexes such as bis(methyltriphenylphosphonium) tetrabromomanganate (PMBB) and bis(methyltriphenylphosphonium) dibromodichloromanganate (PMBC) was switched ON and OFF reversibly by vapors of aprotic and protic solvents, respectively, for the first time. Detailed analyses indicate that solids of the PMBB and the PMBC undergo phase transitions depending on the environment, which regulate the TL activity of these compounds. The combined results of luminescence, powder X-ray diffraction, differential scanning calorimetry, and electron paramagnetic resonance were used to demonstrate crystal dynamism as well as the TL emission of PMBB and PMBC.

Photoluminescence, redox properties, and electrogenerated chemiluminescence of twisted 9,9'-bianthryls.

To study the dual emission (from locally excited and charge transfer states) of sterically crowded 9,9'-bianthryl (BAHO) and its 10,10'-disubstituted derivatives, namely, 10,10'-dibromo-9,9'-bianthryl (BABR), 10,10'-bis(p-tolylethynyl)-9,9'-bianthryl (BAET), and 10,10'-bis(N,N-diphenyl-4-anilino)-9,9'-bianthryl (BATA) in detail, we probed their photophysical, redox, and electrogenerated chemiluminescence (ECL) responses. Dual emission for all of the molecules was noticed in PL, whereas in ECL only charge transfer emission was observed over a variety of experimental conditions. The PL in nonpolar solvents is significantly influenced by added supporting electrolyte, yielding exclusively charge transfer emission as in ECL. The stability of ECL proved to depend largely on the nature of the substituent, with triarylamine and bromo groups imparting constant ECL intensity over more than 60 cycles.

ON-OFF luminescence signaling of hybrid organic-inorganic switches.

The dyads 1OFF and 2OFF were prepared by combining the inorganic luminophores [Ru(phen)2(2-[imidazol-2-yl]pyridine)](2+) and [Re(CO)3Cl(2-[imidazol-2-yl]pyridine)] with 2-(anthracen-9-yl)-4-methylphenol as a second photoactive moiety. In both cases, the inorganic unit operates as the emitter, whereas the organic part acts as a controller. Emission of the inorganic luminophore can be reversibly switched ON and OFF by adjusting the energetic level of the (3)π-π* state of the appended anthracene unit through either dearomatization using a photohydration or aromatization applying a thermal dehydration. Emission of both switches is reversibly recorded and erased multiple times without significant degradation.

9,10-Diarylanthracenes as stable electrochemiluminescent emitters in water.

Two hydrophilic diarylanthracenes, explicitly 9,10-bis(N-methylimidazolium-3-propoxyphenyl)anthracene (DAA1) and 9,10-bis(N-methylimidazolium-3-propoxy-2,6-dimethylphenyl)anthracene (DAA2), are synthesized and fully characterized. Both are found to be soluble in aqueous medium and to exhibit optical properties similar to those of the parent 9,10-diphenylanthracene, whose solubility is virtually negligible in water. The detailed analysis of their photochemical stability as well as electrochemical and electrochemiluminescent properties reveals that the sterically highly shielded anthracene DAA2 shows inertness toward reactions with singlet oxygen and OH(-) ions during photo- and electrochemical initiation and stable ECL emission in aqueous medium.

Crystal engineering: lattice inclusion based on O-H···O hydrogen-bonded self-assembly and guest-induced structural mimicry.

Pyrene-tetraphenol TP2 constitutes a molecular system with inherent features for inclusion of two or more guest molecules that are complementary in terms of size and shape. Hydrogen-bonded self-assembly of TP2 in the solid state is shown to lead to voids within which the guest molecules are incorporated. A large aromatic expanse extant to the pyrene core in TP2 permits inclusion of two different types of guest species interchangeably. The robust association manifests in packing equivalence in all of the inclusion compounds of TP2 with the exception of the compound formed with pyridine and o-dichlorobenzene guests; in the latter, pyridine terminates the otherwise 3-dimensional hydrogen-bonded organization. The half-component of TP2, i.e., 4,6-bis(4-hydroxyphenyl)-m-xylene (BX), deduced by simple structural reduction, is shown to exhibit guest inclusion, but with considerably less guest accessible volume. The limited yet meaningful set of guests allows mimicry of the two expected patterns of molecular organization based on hydrogen bonding for both TP2 and BX in the solid state.

Electrochemistry and electrogenerated chemiluminescence of twisted anthracene-functionalized bimesitylenes.

The electrochemistry, spectroscopy, and electrogenerated chemiluminescence (ECL) of a variety of 2- and 4-fold anthracene-functionalized tetraarylbimesityls, AB1-4, were investigated. AB1-4 compounds contain a bimesityl core with 2- and 4-fold anthracene functionalities, which generate a rigid D(2d)-symmetric structure. Cyclic voltammetry of AB1 and AB2 showed two reversible, closely spaced one-electron transfers for both oxidation and reduction, and that of AB3 and AB4 showed four reversible, closely spaced one-electron transfers for oxidation and reduction in a benzene/acetonitrile solution. The multielectron transfer properties of all four compounds were confirmed by chronoamperometric experiments with an ultramicroelectrode and digital simulations. These serve as models to probe how interacting groups on a molecule affect the energies of successive electron transfers. AB1-4 compounds are highly fluorescent in nonaqueous solvents and display blue-green emission. They produce very strong ECL with emission at 480 nm, near that of the photoluminescence spectra that can be assigned to emission by direct formation of the singlet via the S-route.

Guest subset guest subset host multicomponent molecular crystals: entrapment of guest subset guest in honeycomb networks formed by self-assembly of 1,3,5-tri(4-hydroxyaryl)benzenes.

Sterically-engineered rigid trigonal molecular modules based on 1,3,5-tri(4-hydroxyphenyl)benzenes H1 and H2 undergo O-H...O hydrogen-bonded self-assembly into eight-fold catenated hexagonal (6,3) and two-fold interpenetrated undulated square (4,4) networks, respectively. In the presence of [18]crown-6 as a guest, the triphenol H1 is found to self-assemble into a honeycomb network with hexagonal voids created between three triphenol building blocks. The guest [18]crown-6 molecules are found to be nicely nested in hexagonal enclosures. The empty spaces within the crowns can be further filled with neutral (MeOH/water, MeOH/MeNO(2)) or ionic guest species such as KI/KAcAc to furnish novel multicomponent assemblies, that is, guest subset guest subset host, that typify Russian dolls. In contrast, triphenol H2 is found to yield analogous multicomponent molecular crystals in which the guest crown-K(+) acts as a spacers in the hydrogen-bonded self-assembly that leads to distorted chicken wire networks.

Engineering of ternary co-crystals based on differential binding of guest molecules by a tetraarylpyrene inclusion host.

Tetraarylpyrene host TP exhibits remarkable differential binding of guest molecules in the solid state to include aromatic and aliphatic guests in different domains to permit synthesis of ternary co-crystals in a predictable manner.

Nondoped pure-blue OLEDs based on amorphous phenylenevinylene-functionalized twisted bimesitylenes.

The twisted bimesitylene scaffold hinders crystallization and imparts amorphous nature to the oligophenylenevinylenes (OPVs) generated by 2- and/or 4-fold functionalization. The resultant phenylenevinylenes 1-5 with unique molecular topology exhibit excellent thermal and solid-state luminescence properties. The amorphous nature permits their application as pure-blue emissive materials in OLEDs. Under nondoped conditions, the device performances observed surpass those for analogous and simple oligophenylenevinylenes known so far; for example, the device based on OPV 2 as an emitting material and structurally analogous Bim-DPAB as a hole-transporting material yields pure-blue electroluminescence with an external quantum efficiency of ca. 4.70% at 20 mA/cm(2), which is higher than those reported for nondoped pure-blue OPV emitters.

Abundant lattice inclusion phenomenon with sterically hindered and inherently shape-selective tetraarylpyrenes.

Tetraarylpyrenes H1-H4 that typify molecular systems with orthogonal planes and lack hydrogen bonding functional groups were designed as new host systems with three distinct domains for guest inclusion. In particular, H2 and H4 hosts are found to include a variety of guest molecules. We have determined 42 crystal structures overall (i) to establish the importance of skeletal features of the hosts, (ii) to determine their adaptability in binding diverse guest molecules, and (iii) to delineate favored domains for location of guest molecules and preferred modes of association of the host systems. The unique features of H1-H4 are found to permit binding of aliphatic and aromatic guest species differently: the small-sized guest molecules such as CHCl(3), (CH(3))(2)S, etc. are found to be bound in the basin domain, whereas aliphatic and aromatic guests are found to be included in the channel/concave and trough regions, respectively. The crystal structure analyses reveal that as many as 20 out of 28 inclusion compounds of H2 are isostructural with one or more; we have identified 8 different crystal packing types with which each inclusion compound may be associated. The guest-binding potential of host H2 has been exploited to demonstrate the utility of these host systems in (i) the separation of regioisomeric methyl-substituted benzenes and mixtures of cis-trans isomers of decalin, perhydroisoquinoline, and cinnamonitrile, (ii) the stabilization of the keto-enol form of 1,3-diketones, and (iii) the conformational locking of flexible cycloalkanes.

De novo design for functional amorphous materials: synthesis and thermal and light-emitting properties of twisted anthracene-functionalized bimesitylenes.

The unique structural attributes inherent to D(2d)-symmetric rigid tetraarylbimesityls render their close packing in the solid state difficult. We have exploited the indisposed tendency of such modules based on the bimesityl scaffold toward crystallization to design a novel class of amorphous functional materials with high glass transition temperatures and thermal stability (T(d) > 400 degrees C). It is shown that a variety of 2- and 4-fold anthracene-functionalized bimesityls, 1-7, that exhibit excellent amorphous properties (T(g) = ca. 190-330 degrees C) can be readily prepared via facile Pd(0)-mediated cross-coupling strategies. As the communication between the bimesityl core and the anchored anthracenes is negligible or only marginal, the trends observed for luminescence of model constituent anthracenes are reproduced in the condensed-phase photoluminescence and electroluminescence of 1-7. In other words, the emission characteristics, i.e., lambda(max) and quantum yields, are readily modulated via appropriate modification of the fluorophores. The functional behavior of this unique class of amorphous materials based on the bimesityl scaffold is demonstrated by fabrication of OLED devices. The 2-fold functionalized derivatives 1 and 2 lend themselves to sublimation techniques, so that the electroluminescence is captured with high efficiencies at low turn-on voltages (3.5-6.5 V). The device ITO/NPB (400 A)/1% 2:MADN (400 A)/TPBI (400 A)/LiF (10 A)/Al (1500 A) for 2 yields the highest luminance of approximately 13,900 cd/m(2) at 17.5 V, a maximum luminance efficiency of approximately 7.4 cd/A at 4.5 V, and a power efficiency of approximately 5.3 lm/W at 4.0 V. Further, at a brightness of 800 cd/m(2) and a current density of 13.8 mA/cm(2), the device is found to exhibit excellent luminance efficiency of 5.8 cd/A, external quantum efficiency of 4.3% with a power efficiency of 2.2 lm/W, and pure blue light with a CIE(x,y) (x = 0.13, y = 0.18). The performance characteristics of the devices fabricated for 1 and 2 are remarkable. Although the 4-fold functionalized systems did not permit sublimation leading to spin-coating as a means for device fabrication, the observed electroluminescence for 4 and 5 attests to a broader scope and applicability of this new category of amorphous molecules for application in OLEDs.