Tert-butylphenyl Groups Research Articles

Controlled Self-assembly of Nanographdiynes Mediated by Molecular Dipoles Induced by Rotatory Asymmetric Substituents.

The discrete π- stacks of specific lengths and orientation is crucial for understanding the impact of intermolecular interactions on optical or electronic properties of nanographdiynes. We designed and synthesized nanographdiynes modified with bulky rotatable asymmetric substituents. The peripheral substituents with different push-pull electronic properties can induce molecular dipoles perpendicular to nanoGDY π surface with different orientation. Mediated by directional dipole-dipole interactions, o-TBGDY substituted with electron-donating tert-butylphenyl groups cofacially dimerized with a twist angle, involving intermolecular interlocking of ortho-substituted tert-butylphenyl groups. In contrast, OTFGDY substituted with electron-withdrawing trifluorophenyl groups formed dimeric H-aggregates with an in-plane shift along one diyne linkage, in which the ortho-substituted trifluorophenyl groups point toward the outside of the interacting π-plane. o-TBGDY can only exist as isolated H-dimer in the solid state, while OTFGDY can form a hybrid tetramer of H- and J-aggregates. Our researches reveal a new method for preparing discrete π-stacked dye assemblies with well-defined optoelectronic properties.

Helically chiral multiresonant thermally activated delayed fluorescent emitters and their use in hyperfluorescent organic light-emitting diodes.

Chiral multiresonant thermally activated delayed fluorescence (MR-TADF) materials show great potential as emitters in circularly polarized (CP) organic light-emitting diodes (CP-OLEDs) owing to their bright and narrowband CP emission. Here, two new chiral MR-TADF emitters tBuPh-BN and DPA-tBuPh-BN possessing intrinsically helical chirality have been synthesized and studied. The large steric interactions between the tert-butylphenyl groups not only induce the helical chirality but also provide a notable configurational stability to the enantiomers. Racemic mixtures of tBuPh-BN and DPA-tBuPh-BN show narrowband emission at 490 and 477 nm with full-width at half maximum (FWHM) of 25 and 28 nm and photoluminescence quantum yields, Φ PL, of 85 and 54% in toluene. The separated enantiomers of tBuPh-BN and DPA-tBuPh-BN show symmetric circularly polarized luminescence (CPL) with respective dissymmetry factors |g PL| values of 1.5 × 10-3 and 0.9 × 10-3. The hyperfluorescence organic light-emitting diodes (HF-OLEDs) with tBuPh-BN and DPA-tBuPh-BN acting as terminal emitters and 2,3,4,5,6-penta-(9H-carbazol-9-yl)benzonitrile (5CzBN) as their assistant dopant exhibited, respectively, maximum external quantum efficiencies (EQEmax) of 20.9 and 15.9% at 492 and 480 nm with FWHM of 34 and 38 nm. This work demonstrates a strategy for developing intrinsically helically chiral MR-TADF emitters possessing significant configurational stability, which can be used in HF-OLEDs.

Concomitant Polymorphism in an Organic Solid: Molecular and Crystal Structure and Intra- and Intermolecular Potential Contributions to tert-Butyl and Methyl Group Rotation.

We investigate the relationship between structure (crystal and molecular) and tert-butyl and methyl group dynamics in 2-(tert-butyl)-9-(4-(tert-butyl)phenyl)anthracene. Powder and single-crystal X-ray diffraction, taken together, show that different polycrystalline samples recrystallized from different solvents have different amounts of at least four polymorphs (crystallites having different crystal structures), of which we have identified three by single crystal X-ray diffraction. The molecules in the asymmetric units of the different crystal structures differ by the dihedral angle the tert-butylphenyl group makes with the anthracene moiety. Ab initio electronic structure calculations on the isolated molecule show that very little intramolecular energy is required to change this angle over a range of about 60° which is probably the origin of the concomitant polymorphism (crystals of more than one polymorph in a polycrystalline sample). Solid state 1 H nuclear magnetic resonance (NMR) spin-lattice relaxation experiments support the powder and single-crystal X-ray results and provide average NMR activation energies (closely related to rotational barriers) for the rotation of the tert-butyl groups and their constituent methyl groups. These barriers have both an intramolecular and an intermolecular component. The latter is sensitive to the crystal structure. The intramolecular components of the rotational barriers of the two tert-butyl groups in the isolated molecule are investigated with ab initio electronic structure calculations.

Building from Ga‐Porphyrins: Synthesis of Ga‐Acetylide Complexes Using Acetylenes and Polyynes

Multidimensional, conjugated building blocks have been formed through the axial coordination of polyynes to the central Ga atom of tetraarylporphyrins. Electron deficient pentafluorophenyl substituents in the meso-positions provide more stable σ-acetylide complexes to Ga than analogous structures with tert-butylphenyl groups. Mono-, di-, and triynes have been used, including a pyridyl endcapped diyne that allows for formation of porphyrin triads through coordination of the pyridyl ligand to a Ru porphyrin.

Distinguishing Two Ammonium and Triazolium Sites of Interaction in a Three-Station [2]Rotaxane Molecular Shuttle.

This paper reports on the synthesis of a tri-stable [2]rotaxane molecular shuttle, in which the motion of the macrocycle is triggered by either selective protonation/deprotonation or specific carbamoylation/decarbamoylation of an alkylbenzylamine. The threaded axle is surrounded by a dibenzo[24]crown[8] (DB24C8) macrocycle and contains three sites of different binding affinities towards the macrocycle. An N-methyltriazolium moiety acts as a molecular station that has weak affinity for the DB24C8 macrocycle and is located in the centre of the molecular axle. Two other molecular stations, arylammonium and alkylbenzylammonium moieties, sit on either side of the triazolium moiety along the molecular axle and have stronger affinities for the DB24C8 macrocycle. These two ammonium moieties are covalently linked to two different stopper groups at each extremity of the thread: a tert-butylphenyl group and a substituted DB24C8 unit. Owing to steric hindrance, the former does not allow any π-π stacking interactions with the encircling DB24C8 macrocycle, whereas the latter residue does; therefore, this allows the discrimination of the two ammonium stations by the surrounding DB24C8 macrocycle in the fully protonated state. In the deprotonated state, the contrasting reactivity of the amine functional groups, as either a base or a nucleophile, allows for selective reactions that trigger the controlled shuttling of the macrocycle around the three molecular stations.

Molecularly Engineered Azobenzene Derivatives for High Energy Density Solid-State Solar Thermal Fuels.

Solar thermal fuels (STFs) harvest and store solar energy in a closed cycle system through conformational change of molecules and can release the energy in the form of heat on demand. With the aim of developing tunable and optimized STFs for solid-state applications, we designed three azobenzene derivatives functionalized with bulky aromatic groups (phenyl, biphenyl, and tert-butyl phenyl groups). In contrast to pristine azobenzene, which crystallizes and makes nonuniform films, the bulky azobenzene derivatives formed uniform amorphous films that can be charged and discharged with light and heat for many cycles. Thermal stability of the films, a critical metric for thermally triggerable STFs, was greatly increased by the bulky functionalization (up to 180 °C), and we were able to achieve record high energy density of 135 J/g for solid-state STFs, over a 30% improvement compared to previous solid-state reports. Furthermore, the chargeability in the solid state was improved, up to 80% charged from 40% charged in previous solid-state reports. Our results point toward molecular engineering as an effective method to increase energy storage in STFs, improve chargeability, and improve the thermal stability of the thin film.

Access to Multiblock Copolymers via Supramolecular Host-Guest Chemistry and Photochemical Ligation.

We combine supramolecular host-guest interactions of β-cyclodextrin (CD) with light-induced Diels-Alder reactions of 2-methoxy-6-methylbenzaldehyde (photoenol, PE) for the formation of multiblock copolymers. Via the synthesis of a new bifunctional chain transfer agent (CTA) and subsequent reversible addition-fragmentation chain transfer (RAFT) polymerization, we introduce a supramolecular recognition unit (tert-butyl phenyl) and a photoactive unit (photoenol) to a polymer chain in order to obtain an α,ω-functionalized polymeric center block, having orthogonal recognition units at each chain end. Multiblock copolymers are formed via the light-induced reaction of the photoenol with a maleimide-functionalized polymer chain and the supramolecular self-assembly of the tert-butyl phenyl group with the β-CD end group of a third polymer chain. By employing the fast and efficient photoinduced Diels-Alder reaction in combination with supramolecular host-guest interactions, a novel method for macromolecular modular ligation is introduced.

A Structure-Activity Relationship Study for 2′-Deoxyadenosine Analogs at A9 Position in the Catalytic Core of 10-23 DNAzyme for Rate Enhancement

Modification on the catalytic core of 10-23 DNAzyme with protein-like functional groups is a potential approach to obtain its more efficient analogs. In our efforts for this purpose, a lead structure (DZ-2-9) with 8-aza-7-deaza-2'-deoxyadenosine at the A9 position in its catalytic core was obtained. Here we report our structure-activity relationship studies on this lead structure. Various functional groups of different chemical properties were introduced through the 7-substituents of 8-aza-7-deaza-2'-deoxyadenosine to DZ-2-9. The functional groups capable of forming hydrogen bonds, like amino and hydroxyl groups, are more favorable for catalytic rate enhancement than the large groups with spacial occupation, like phenyl and tert-butylphenyl groups, and the flexible alkyl linkage was the more preferred choice for optimizing their positive effect. Furthermore, they exerted positive effect cooperatively with the N8 atom. These results give us a clear hint in the design of compounds for A9 substitution of 10-23 DNAzyme for more efficient DNAzymes.

Structural and Molecular Characterization of meso-Substituted Zinc Porphyrins: A DFT Supported Study

Structural parameters of a range of over 100 meso-substituted zinc porphyrins were reviewed and compared to show how far the nature of the functional group may affect the interatomic distances and bond angles within the porphyrin core. It was proved that even despite evident deformations of the molecular structure, involving twisting of the porphyrin's central plane, the coupled π-bonding system remains flexible and stable. DFT calculations were applied to a number of selected porphyrins representative for the reviewed compounds to emphasize the relevance of theoretical methods in structural investigations of complex macrocyclic molecular systems. Experimental and DFT-simulated IR spectral data were reported and analyzed in context of the individual molecular features introduced by the meso substituents into the porphyrin moiety base. Raw experimental spectral data, including 1H- and 13C-NMR, UV-Vis, FTIR, XRD, and other relevant physicochemical details have been provided for a specially chosen reference zinc porphyrin functionalized by tert-butylphenyl groups.

Synthesis and Characterization of Organoboron Quinolate Polymers with Tunable Luminescence Properties

A modular one-pot approach for the synthesis of well-defined organoboron quinolate polymers and the tuning of their photoluminescence is reported. Highly selective borylation of poly(4-trimethylsilylstyrene) (PSSiMe3) followed by replacement of one of the bromine substituents in the resulting reactive polymer PSBBr2 with tert-butylphenyl groups led to the common intermediate PSBPhBr. A series of organoboron quinolate polymers PSBPhQ were then obtained in high isolated yields (65−85%) by in situ treatment of PSBPhBr with differently substituted 8-hydroxyquinoline derivatives. All the quinolate polymers were fully characterized by multinuclear NMR spectroscopy, elemental analysis, gel permeation chromatography in-line with multiangle laser light scattering (GPC-MALLS), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). Luminescence measurements revealed distinct emission bands, ranging from the blue to the red region (486−615 nm), depending on the substitution pattern on the qu...

The 4- tert-butylphenyl group as a simple tag for solution phase synthesis

A solution phase synthesis strategy was investigated using 4- tert-butylphenyl group as the tag and a beta-cyclodextrin column as the affinity chromatographic support for the isolation of compounds containing the tag. It was found that compounds containing the tag have significantly longer retention times on the beta-cyclodextrin column than those compounds that do not have such a tag. The tag is chemically inert and can be introduced onto and removed from target compounds readily. This solution phase synthesis method was applied to the synthesis of some simple amino acid derivatives.

Mechanisms of Thermal Oxidation of Poly(bisphenol A carbonate)

In the attempt to find evidence on the structure of the species produced in the thermal oxidative degradation of bisphenol A−polycarbonate (PC), two polycarbonate samples, one capped (incompletely) with phenyl groups at both ends (PC1) and the other one capped (incompletely) with tert-butyl phenyl groups at both ends (PC2), were used. The two PC samples were heated at 300 and 350 °C under atmospheric air for up to 180 min, producing a THF-insoluble gel at the longer heating times. The oxidative process was followed as a function of the exposure time by SEC, 1H NMR, MALDI-TOF, and SEC/MALDI-TOF techniques. The SEC curves showed extensive degradation, up to the formation of very low molar mass oligomers. Highly valuable structural information on the thermally oxidized PC species was obtained by using MALDI-TOF mass spectrometry. The MALDI-TOF spectra of the thermally oxidized PC1 and PC2 samples showed the presence of polymer chains containing acetophenone, phenyl-substituted acetone, phenols, benzyl alcoho...

Preparation and X-ray analysis of 2,2′,3,3′-tetraphosphinidene-1,1′-bicyclobutyl

A sterically protected diphosphinidenecyclobutene with the 2,4,6-tri- tert-butylphenyl group was allowed to react with tert-butyllithium and iodine, successively, to give 2,2′,3,3′-tetraphosphinidene-1,1′-bicyclobutyl derivative, and the structure was confirmed by X-ray analysis, showing unusual short contact between the CP moieties at the 2 and 2′ positions. A strong through-space interaction between them appears to play an important role in rationalization of the 31P NMR and UV/Vis.

An artificial cytochrome P450 that hydroxylates unactivated carbons with regio- and stereoselectivity and useful catalytic turnovers.

A catalyst has been synthesized comprising a manganese porphyrin carrying four beta-cyclodextrin groups. It catalyzes the hydroxylation of substrates of appropriate size carrying tert-butylphenyl groups that can hydrophobically bind into the cyclodextrin cavities. In one example as many as 650 catalytic turnovers are seen before the catalyst is oxidatively destroyed, and with a rate comparable to that of typical cytochrome P450 enzymes. In another example, a steroid derivative is regio- and stereoselectively hydroxylated at a single unactivated carbon atom, but more slowly and with fewer turnovers. The carbon attacked is not the most chemically reactive, and the selectivity is determined by the geometry of the catalyst-substrate complex. Nonbinding substrates are not reactive under the conditions used, and substrates with more flexible binding geometries give more than a single product.

Quantitative effects of antihydrophobic agents on binding constants and solubilities in water.

The effects of urea and of guanidinium chloride on binding constants in water for 6-(4-tert-butylanilino)-naphthalene-2-sulfonate and of bis(p-tert-butylphenyl) phosphate binding to beta-cyclodextrin and to N,N'-bis(6-beta-cyclo-dextrinyl)imidazolium ion have been determined. Their effects on the water solubility of p-tert-butylbenzyl alcohol and p-methylbenzyl alcohol have also been examined. Quantitative correlations show that the effects of these additives, which diminish hydrophobic effects, are similar for release of a tert-butylphenyl group from a cyclodextrin cavity into water or for solubilizing such a group from a second phase. The effects of these agents on the binding constants for double-ended substrates binding to the bis(cyclodextrin) host are much larger than for a simple substrate binding to monomeric cyclodextrin, consistent with additivity of free-energy perturbations. Ethanol also decreases binding in these systems, and increases solubilities, but the quantitative correlations are less straightforward.