Electronic Structures of Anti-Ferromagnetic Tetraradicals: <i>Ab Initio</i> and Semi-Empirical Studies

The energy relationships and electronic structures of the lowest-lying spin states in several anti-ferromagnetic tetraradical model systems are studied with high-level <i>ab initio</i> and semi-empirical methods. The Full-CI method (FCI), the complete active space second-order perturbation theory (CASPT2), and the <i>n</i>-electron valence state perturbation theory (NEVPT2) are employed to obtain reference results. By comparing the energy relationships predicted from the Heisenberg and Hubbard models with <i>ab initio</i> benchmarks, the accuracy of the widely used Heisenberg model for anti-ferromagnetic spin-coupling in low-spin polyradicals is cautiously tested in this work. It is found that the strength of electron correlation (|<i>U</i>/<i>t</i>|) concerning anti-ferromagnetically coupled radical centers could range widely from strong to moderate correlation regimes and could become another degree of freedom besides the spin multiplicity. Accordingly, the Heisenberg-type model works well in the regime of strong correlation, which reproduces well the energy relationships along with the wave functions of all the spin states. In moderately spin-correlated tetraradicals, the results of the prototype Heisenberg model deviate severely from those of multi-reference electron correlation <i>ab initio</i> methods, while the extended Heisenberg model, containing four-body terms, can introduce reasonable corrections and maintains its accuracy in this condition. In the weak correlation regime, both the prototype Heisenberg model and its extended forms containing higher-order correction terms will encounter difficulties. Meanwhile, the Hubbard model shows balanced accuracy from strong to weak correlation cases and can reproduce qualitatively correct electronic structures, which makes it more suitable for the study of anti-ferromagnetic coupling in polyradical systems

A Versatile Synthesis of 3-Substituted Indolines and Indoles

A Versatile Synthesis of 3-Substituted Indolines and Indole

Ambient Temperature, Ullmann-like Reductive Coupling of Aryl, Heteroaryl, and Alkenyl Halides

Ambient Temperature, Ullmann-like Reductive Coupling of Aryl, Heteroaryl, and Alkenyl Halide

Versatile Synthesis of Dihydroquinolines and Quinoline Quinones Using Cyclobutenediones. Construction of the Pyridoacridine Ring System

1-BOC-2-lithio-1,4-dihydropyridines were condensed with 3,4-disubstituted cyclobutenediones to produce 1,2-adducts. Neat thermolysis under oxygen-free conditions produced substituted 1,4-dihydroquinoline hydroquinones in which the tert-butoxy residue of the BOC group was displaced by a phenolic residue, generating an oxazolone ring that functioned to protect both rings of the dihydroquinoline hydroquinone from untimely oxidation. Oxidative aromatization with concomitant loss of the oxazolone ring was achieved using 2 equiv of o-chloranil in acetic acid and provided substituted quinoline quinones in good yields. By use of this strategy, a concise synthesis of the pyridoacridine ring system was achieved

Inorganic–Organic Shape Memory Polymer (SMP) Foams with Highly Tunable Properties

Thermoresponsive shape memory polymers (SMPs) are a class of smart materials that can return from a temporary to a permanent shape with the application of heat. Porous SMP foams exhibit unique properties versus solid, nonporous SMPs, enabling their utility in different applications, including some in the biomedical field. Reports on SMP foams have focused on those based on organic polymer systems. In this study, we have prepared inorganic–organic SMP foams comprising inorganic polydimethylsiloxane (PDMS) segments and organic poly­(ε-caprolactone) PCL segments. The PCL segments served as switching segments to induce shape changing behavior whereas the length of the PDMS soft segment was systematically tuned. SMP foams were formed via the photochemical cure of acrylated (AcO) macromers AcO-PCL40-block-PDMSm-block-PCL40-OAc (m = 0, 20, 37, 66 and 130) using a revised solvent casting/particulate leaching (SCPL) method. By varying the PDMS segment length, PDMS-PCL foams having excellent shape memory behavior were obtained that exhibited highly tunable properties, including pore size, % porosity, compressive modulus, and degradation rate

Development of a Coke Oven Gas Assisted Coal to Ethylene Glycol Process for High Techno-Economic Performance and Low Emission

Developing a coal to ethylene glycol (CtEG) process is of great interest to many countries, especially China. However, because the hydrogen to carbon ratio of the coal-gasified gas is far less than the desired value, the CtEG process suffers from high CO₂ emission and wastes precious carbon resources. At the same, most coke oven gas (COG) is discharged directly or used as fuel, resulting in a waste of resources, serious environmental pollution, and economic loss. To develop efficient and clean utilization of coal and COG resources, we propose a novel coke oven gas assisted coal to ethylene glycol (CaCtEG) process. The proposed process introduces the hydrogen-rich COG to adjust the hydrogen to carbon ratio and reduce CO₂ emission by integrating a dry methane reforming unit. Key operational parameters are investigated and optimized based on the established mathematical model. The advantages of the process are studied by a detailed techno-economic analysis. Results show that, compared with the conventional CtEG process, the CaCtEG process is promising since it increases the carbon element and exergy efficiency by 18.35% and 10.59%. The CO₂ emission ratio of the proposed process is reduced from 2.58 t/t-EG to 0.44 t/t-EG. From an economic point of view, the CaCtEG process can save production costs by 5.11% and increase the internal rate of return by 3.41%. The capital investment, however, is slightly increased because of the two additional units

Open-Shell Ground State of Polyacenes: A Valence Bond Study

Applying the density matrix renormalization group (DRMG) method to a nonempirical valence bond (VB) model Hamiltonian, we studied polyacene oligomers of different lengths in the strong electron correlation limit. Geometrical optimizations were performed for the lowest singlet and triplet states of oligomers up to [40]-acene, and a convergence of the bond lengths toward the polymer limit is observed in the interior of the oligomer. For large oligomers, as well as for the polymer, the ground state can be reasonably determined to be a singlet. Furthermore, a high similarity between the singlet geometries and triplet geometries suggests an open-shell character for the singlet ground state. A reasonable speculation of the soliton−antisoliton pair character of the singlet ground state was supported by a spin distribution analysis of the triplet state wave function of large oligomers, with each of the two solitons being broadly delocalized over the upper or bottom edge of the oligomers, respectively

Laser-Induced Graphene Electrodes on Poly(ether–ether–ketone)/PDMS Composite Films for Flexible Strain and Humidity Sensors

Laser-induced graphene prepared on polymer substrates with a high modulus is a widely applied method to fabricate varied flexible electronics; however, the resulting relatively poor stretchability considerably limits its applicability. In this paper, an elastic composite consisting of poly(ether–ether–ketone) powder and poly(dimethylsiloxane) (PDMS) is reported to fabricate stretchable electrodes using direct laser-induced graphitization without transferring. The liquid composites before curing can be cast into various shapes for different applications. To balance the conductivity and stretchability of stretchable electrodes, we optimized the composite mass ratios and laser parameters and performed a series of morphological and performance characterizations on the composites; furthermore, we analyzed the elemental composition and functional groups of the laser-induced products. With the proper encapsulating method, strain sensors were prepared, exhibiting high sensitivity (a gauge factor of 78) and a stable resistance response over 50% operating range with the ability to monitor both fine pulse beats and larger strains such as human joint movement. Furthermore, a humidity sensor composited with laser-patterned interdigital electrode and graphene oxide on the elastic composite substrate had characteristics of high sensitivity (14.18 pF/%RH) and fast recovery time (9 s), which could be used for breathing monitoring and noncontact sensing. In conclusion, laser-induced graphene prepared in one step on a stretchable composite film of polymers with a high modulus and low modulus is a promising method to fabricate wearable electronics

Docking accuracy enhanced by QM-derived protein charges

<p>Effects of protein polari sation on docking accuracy were investigated using molecular docking programme AutoDock 4 in which topology-specific empirical Gasteiger charges were replaced with Polarised protein-specific charges (PPC) to represent quantum mechanics- polarised protein. Docking was successfully conducted for 50 diverse protein–ligand complexes. The docking with PPC charges shows a decrease in the root-mean-square deviation (RMSD) values of ligands compared to those from the docking with Gasteiger charges. Ligand binding orientations and their key interactions such as hydrogen bonding interactions in X-ray structures were substantially reproduced in complexes docked using PPC scheme with 98% of the RMSDs of the best docking poses less than 2 Å compared to 74% in the docking with Gasteiger charges. Considerable improvements in docking accuracy were observed by simply altering the atomic partial charges in the scoring function, which reflects the importance of protein polarisation in molecular docking. Further research can be carried out to (1) include polarisation of both ligands and proteins to account for polarisation effects within protein and between protein and ligand, and (2) develop a PPC-based scoring function to increase the docking accuracies for protein–ligand complexes from a larger variety of protein families.</p

Bioinspired Compound Eyes for Diffused Light-Harvesting Application

Natural compound eyes endow arthropods with wide-field high-performance light-harvesting capability that enables them to capture prey and avoid natural enemies in dim light. Inspired by natural compound eyes, a curved artificial-compound-eye (cACE) photodetector for diffused light harvesting is proposed and fabricated, and its light-harvesting capability is systematically investigated. The cACE photodetector is fabricated by introducing a cACE as a light-harvesting layer on the surface of a silicon-based photodetector, with the cACE being prepared via planar artificial-compound-eye (pACE) template deformation. The distinctive geometric morphology of the as-prepared cACE effectively reduces its surface reflection and the dependence of the projected area on the incident light direction, thereby significantly improving the light-harvesting ability and output photocurrent of the silicon-based photodetector. Furthermore, the performances of cACE, pACE, and bare polydimethylsiloxane (PDMS)-attached photodetectors as diffused light detectors are investigated under different luminances. The cACE-photodetector output photocurrent is 1.395 and 1.29 times those of the bare PDMS-attached and pACE photodetectors, respectively. Moreover, this photodetector has a desirable geometric shape. Thus, the proposed cACE photodetector will facilitate development of high-performance photodetectors for luminance sensing