Tert-butyl Units Research Articles

Insights into the Structural Modification of Selenium-Doped Derivatives with Narrowband Emissions: A Theory Study.

The research on boron/nitrogen (B/N)-based multiresonance thermally activated delayed fluorescence (MR-TADF) emitters has been a prominent topic due to their narrowband emission and high luminous efficiency. However, devices derived from the common types of narrowband TADF materials often experience an efficiency roll-off, which could be ascribed to their relatively slow triplet-singlet exciton interconversion. Since inserting the heavy Se atom into the B/N scheme has been a proven strategy to address the abovementioned issues, herein, extensive density functional theory (DFT) and time-dependent DFT (TD-DFT) simulations have been employed to explore the effects of the structural modification on a series of structurally modified selenium-doped derivatives. Furthermore, the two-layered ONIOM (QM/MM) model has been employed to study the pressure effects on the crystal structure and photophysical properties of the pristine CzBSe. The theoretical results found that the introduced tert-butyl units in Cz-BSeN could result in a shorter charge transfer distance and smaller reorganization energy than the parent CzBSe. In contrast to directly incorporating the o-carborane (Cb) unit to CzBSe, incorporating the bridged phenyl units is important in order to achieve narrowband emissions and high luminous efficiency. The lowest three triplet excited states of CzBSe, Cz-BSeN and PhCb-BSeN all contribute to their triplet-singlet exciton conversions, resulting in a high utilization of triplet excitons. The pressure has an evident influence on the photophysical properties of the aggregated CzBSe and is favored for obtaining narrowband emissions. Our work is promised to provide a feasible strategy for designing selenium-doped derivatives with narrowband emissions and rapid triplet-singlet exciton interconversions.

Effective donor and acceptor modifications of carbazole-benzonitrile thermally activated delayed fluorescence molecules enabling high-performance OLEDs

Carbazole-benzonitrile derivatives (CzBNs) have great potential to enable thermally activated delayed fluorescence (TADF) molecules with both high efficiency and good stability simultaneously. However, the device performances of most CzBN-based organic light-emitting diodes (OLEDs) still lag behind other types of TADF molecules. In this work, we proposed a design strategy to construct efficient CzBN-TADF molecules through acceptor and donor modifications. The cyano-modified acceptor enables the extension of the lowest unoccupied molecular orbital while mostly preserving the overlapped area with the highest occupied molecular orbital. The optimized distributions of frontier molecular orbitals contribute to tiny singlet-triplet energy gaps while maintaining a high radiative decay rate. The incorporation of tert-butyl units in the donor groups further enhances the TADF property of resulted tPCNBN molecule due to suppressed non-radiative decay and reduced exciton self-quenching. Accordingly, OLEDs based on tPCNBN present the best device performances, such as a maximum external quantum efficiency of 33.1 % at 400 cd m−2, which is still as high as 26.3 % at a high luminance of 4000 cd m−2, demonstrating relatively low efficiency roll-off. These results confirm the effectiveness of the proposed design strategy in developing efficient and stable CzBN-TADF materials and devices.

Synthesis of Low Molecular Weight Butadiene Polymers Using Cationic Catalytic Systems Based on Diethylaluminium Chloride

Сationic polymerization of butadiene with the catalytic systems based on diethylaluminium chloride (AlEt2Cl) in combination with tertiary alkyl halides (AH), such as tert-butyl chloride, tert-butyl bromide and 2-chloro-2-methylbutane, is an effective method for obtaining fully soluble butadiene polymers at a industrially relevant temperature of 20°C. It is shown that, regardless of the nature of AH in the catalytic system, with an increase in the duration of the polymerization process of butadiene, the values of the weight-average molecular weight and polydispersity of the polymers significantly increase with the simultaneous decrease of polybutadiene unsaturation, which is associated with the transfer reaction of the growing chain to the polymer double bond during polymerization. Using the 13C NMR spectroscopy method, it was found that polybutadiene macromolecules synthesized on the AlEt2Cl–tert-butyl chloride catalytic system consist mainly of 1,4-trans units, contain two types of initial tert-butyl units and two types of end chlorine-containing units formed as a result of the transfer reaction of the growing chain to tert-butyl chloride. Based on the data of 13C NMR spectra of polybutadiene, a method for calculating the conversion of butadiene during polymerization has been developed, and a mechanism of the process of cationic butadiene polymerization has been proposed. It is shown that the synthesized “cationic” polybutadiene is characterized by high film-forming properties and can be a promising component in the production of paint and varnish materials.

The role of the bulky blocking unit of the fluorescent emitter in efficient green hyper-fluorescent organic light-emitting diodes

The efficiency loss process of hyper-fluorescent organic light-emitting diodes (OLEDs) was analyzed with different fluorescent emitters. Two blocking units of tert-butyl and 2-phenylpropan-2-yl in fluorescent emitters suppressed the Dexter energy transfer from the host and thermally activated delayed fluorescent (TADF) sensitizer to the fluorescent emitter and concentration quenching caused by intermolecular interaction. The performance of the green hyper-fluorescent OLEDs showed that the device of the fluorescent emitter with the 2-phenylpropan-2-yl unit achieved a high external quantum efficiency of 18.1% with a low efficiency roll-off, compared to the device of the fluorescent emitter with the tert-butyl unit. This study demonstrated the usefulness of the 2-phenylpropan-2-yl blocking unit of the fluorescent emitter for hyper-fluorescent OLEDs, and exhibited the directionality of the development of hyper-fluorescent OLEDs.

Tunable Redox Potential, Optical Properties, and Enhanced Stability of Modified Ferrocene-Based Complexes.

We report a series of ferrocene-based derivatives and their corresponding oxidized forms in which the introduction of simple electron donating groups like methyl or tert-butyl units on cyclopentadienyl-rings afford great tunability of Fe+III/Fe+II redox potentials from +0.403 V down to −0.096 V versus saturated calomel electrode. The spin forbidden d–d transitions of ferrocene derivatives shift slightly toward the blue region with an increasing number of electron-donating groups on the cyclopentadienyl-rings with very little change in absorptivity values, whereas the ligand-to-metal transitions of the corresponding ferricinium salts move significantly to the near-IR region. The electron-donating groups also contribute in the strengthening of electron density of Fe+III d-orbitals, which therefore improves the chemical stability against the oxygen reaction. Further, density functional theory calculations show a reducing trend in outer shell reorganization energy with an increasing number of the electron donating units.

Exciplex System with Increased Donor-Acceptor Distance as the Sensitizing Host for Conventional Fluorescent OLEDs with High Efficiency and Extremely Low Roll-Off.

Exciplex systems with efficient thermally activated delayed fluorescence as the sensitizing hosts for fluorescent organic light-emitting diodes (OLEDs) have been flourished recently, while the device performances are still lagging behind. Here, a donor molecule sterically encapsulated with tert-butyl units is designed and synthesized to increase the donor-acceptor separation in an exciplex system, leading to reduced singlet-triplet energy gap (Δ ESTs) and improved reverse intersystem crossing (RISC) efficiency. OLEDs utilizing exciplexes with increased donor-acceptor distance ( rDA) as the hosts for conventional fluorescent dopants exhibit a maximum external quantum efficiency (EQEmax) as high as 16.5%, benefiting from the enhanced RISC process and suppressed exciton loss by the Dexter interaction. Furthermore, extremely low efficiency roll-off is obtained with EQEs of 16.2% at 5000 cd/m2 and 15.2% at 10 000 cd/m2. The results here represent the state-of-the-art performances for devices based on exciplexes as the hosts for conventional fluorescent dopants, manifesting the superiority of exciplexes with increased rDA as the sensitizing hosts for fluorescent dopants.

Role of tert-butyl in the linear and nonlinear optical property of push-pull chromophores

Through comparing the linear and nonlinear optical property of two pull-push chromophores, which are composed of difluoroboron β-diketonate functionalized with carbazole and tert-butyl carbazole, the role of tert-butyl in chromosphere has been discussed in detail. The tert-butyl unit would lead to the absorption and fluorescence peak red shift and accelerate the fluorescence relaxation rate of chromophores. Moreover, the tert-butyl unit would affect obviously the two-photon optical property of chromophore according to the Z-scan test. The transient absorption (TA) data shows that these two pull-push chromopphores both own intramolecular charge transfer (ICT) characteristics and the tert-butyl unit accelerate the dynamic rate of ICT generation and relaxation process, which may be responsible for the variance of fluorescence property.

Synthesis, characterization and electrochemical properties of poly(phenoxy-imine)s containing peril and tert-butyl units

Schiff bases were obtained by condensation reactions of 2-aminophenol and 4-aminophenol with 4-isopropenylcyclohex-1-ene-1-carbaldehyde (peril aldehyde) and 3,5-di-tert-butyl-2-hydroxy benzaldehyde. Then, polymers of these compounds were prepared via oxidative polymerization method in THF in the presence of NaOCl as an oxidant. The structures of compounds were confirmed by some techniques such as FT-IR, 1H NMR, 13C NMR and UV–vis. Moreover, cyclic voltammetry (CV) was used to calculate the HOMO−LUMO energy levels and electrochemical band gaps (Eg′) of compounds. Electrochemical band gaps (Eg′) values of P1, P2, P3 and P4 polymers were found as 2.61, 2.65, 2.89 and 2.28eV, respectively. Furthermore, TGA and DSC were employed to determine thermal properties of the Schiff bases and polymers. The photoluminescence (PL) properties of polymers were also determined in DMSO. Then, we found that their number-average molecular weight (Mn), weight average molecular weight (Mw) as well as polydispersity index (PDI) values by the size exclusion chromatography (SEC). Finally, we carried out their solubility tests in acetone, THF, chloroform, acetonitrile, methanol, ethyl acetate, n-hexane and DMSO.

Exploring the Photodeactivation Pathways of Pt[O^N^C^N] Complexes: A Theoretical Perspective.

In this article, the influence of the tert-butyl unit on the photodeactivation pathways of Pt[O^N^C^N] (O^N^C^N=2-(4-(3,5-di-tert-butylphenyl)-6-(3-(pyridin-2-l)phenyl) pyridin-2-yl)phenolate) is investigated by DFT/TDDFT calculations. To further explore the factors that determine the radiative processes, the transition dipole moments of the singlet excited states, spin-orbit coupling (SOC) matrix elements, and energy gaps between the lowest triplet excited states and singlet excited states are calculated. As demonstrated by the results, compared with Pt-3, Pt-1 and Pt-2 have larger SOC matrix elements between the lowest triplet excited states and singlet excited states, an indicator that they have faster radiative decay processes. In addition, the SOC matrix elements between the lowest triplet excited states and ground states are also computed to elucidate the temperature-independent non-radiative decay processes. Moreover, the temperature-dependent non-radiative decay mechanisms are also explored via the potential energy profiles.

Tunable Hydrophilic or Amphiphilic Coatings: A "Reactive Layer Stack" Approach.

Thin films with tunable properties are very interesting for potential applications as functional coatings with, for example, anti-icing or improved easy-to-clean properties. A novel "reactive layer stack" approach was developed to create covalently grafted mono- and multilayers of poly(glycidyl methacrylate)/poly(tert-butyl acrylate) diblock copolymers. Because these copolymers contain poly(glycidyl methacrylate) blocks they behave as self-cross-linking materials after creation of acrylic acid functionalities by splitting off the tert-butyl units. The ellipsometrically determined coating thickness of the resulting hydrophilic multilayers depended linearly on the number of applied layers. Amphiphilic films with tunable wettability were prepared using triblock terpolymers with an additional poly(methyl methacrylate) block. The mechanism of the formation of the (multi)layers was investigated in detail by studying the acidolysis of the surface-linked tert-butyl acrylate blocks by infrared reflection absorbance spectroscopy, accompanied by surface analysis using atomic force microscopy and contact angle measurements. In the case of the amphiphilic and switchable terpolymer layers this reaction was very sensitive to the used acidic reagent.

1-(3-tert-Butyl-4-hydroxyphenyl)ethanone

The title compound, C12H16O2, is approximately planar (r.m.s. deviation = 0.030 Å), apart from two methyl groups of the tert-butyl unit [deviations of the C atoms = 1.140 (2) and −1.367 (1) Å]. In the crystal, inter­molecular O—H⋯O hydrogen bonds link the mol­ecules into hexa­meric rings with R 6 6(48) graph-set motifs.

(4-tert-Butylphenyl)acetic acid

In the title compound, C12H16O2, the plane of the carboxylic acid group is almost perpendicular to the benzene ring [dihedral angle 80.9 (3)°] and the tert-butyl unit is disordered over two sets of sites in a 0.503 (6):0.497 (6) ratio. In the crystal structure, centrosymmetric dimers arise from pairs of O—H⋯O hydrogen bonds involving the carboxylic acid groups.

Natural neo acids and neo alkanes: Their analogs and derivatives

This review presents more than 260 naturally occurring (as well as 47 synthesized) neo fatty (carboxylic) acids, neo alkanes, and their analogs and derivatives, isolated and identified from plants, algae, fungi, marine invertebrates, and microorganisms, that demonstrate different biological activities. These natural metabolites are good prospects for future chemical preparations as antioxidants, and also as anticancer, antimicrobial, and antibacterial agents. Described also are some synthetic bioactive compounds containing a tertiary butyl group(s) that have shown high anticancer, antifungal, and other activities. Applications of some neo fatty (carboxylic) acid derivatives in cosmetic, agronomic, and pharmaceutical industries also are considered. This is the first review to consider naturally occurring neo fatty (carboxylic) acids, neo alkanes, and other metabolites containing a tertiary butyl group(s) [or tert-butyl unit(s)].

Synthesis and Viscoelastic Behavior of Multiarm Star Polyelectrolytes

Star-shaped poly(tert-butyl acrylate)s were synthesized by the atom transfer radical polymerization (ATRP) method. Subsequently, star-shaped poly(acrylic acid)s were induced by hydrolysis of tert-butyl units. The structural ordering of these stars was investigated through small-angle X-ray scattering (SAXS) in aqueous solution. Star with f = 30 and f = 97 formed a bcc structure above the overlap threshold (C*). The viscoelastic behavior of the stars was also investigated. This system showed the transition from a Maxwellian fluid of a weak liquid ordering to a solid of macrolattice structure with increasing the polymer concentration. This result reflected the stronger interaction among star polyelectrolytes at higher polymer concentration.