A combination of excited-state intramolecular proton transfer (ESIPT) and aggregation-induced emission (AIE) has opened new opportunities to develop color-tunable luminescent materials with high ...quantum yield. Understanding the emission mechanism of these luminophores is essential for the molecular design and construction of a functional system. Herein, we report QM (MS-CASPT2//TD-DFT, MS-CASPT2//CASSCF) and ONIOM (QM/MM) studies on the fluorescence quenching and AIE mechanisms of 2-(2-hydroxy-phenyl)-4(3H)-quinazolinone with typical characteristics of AIE and ESIPT as an example. The computational results indicate that in the tetrahydrofuran solution, once being excited to the S1 state, the molecule tends to undergo an ultrafast, barrierless ESIPT from enol to keto tautomer and then accesses a S1/S0 conical intersection in the vicinity of a CC bond twisted intramolecular charge-transfer (TICT) intermediate, leading to a nonradiative decay from the excited to ground state. Hence, the TICT-induced nonadiabatic transition, which has been further confirmed by the on-the-fly trajectory surface hopping dynamics simulations, accounts for the fluorescence quenching in solution. In contrast, in the solid state, the nonradiative relaxation pathway via the CC bond rotation is suppressed due to environmental hindrance, leaving the ESIPT-induced enol–keto tautomerization as the only excited-decay channel, thus the fluorescence is observably enhanced in the crystal.
Natural biomolecules have been used extensively as chiral scaffolds that bind/surround metal complexes to achieve stereoselectivity in catalytic reactions. ATP is ubiquitously found in nature as an ...energy-storing molecule and can complex diverse metal cations. However, in biotic reactions ATP-metal complexes are thought to function mostly as co-substrates undergoing phosphoanhydride bond cleavage reactions rather than participating in catalytic mechanisms. Here, we report that a specific Cu(II)-ATP complex (Cu
·ATP) efficiently catalyses Diels-Alder reactions with high reactivity and enantioselectivity. We investigate the substrates and stereoselectivity of the reaction, characterise the catalyst by a range of physicochemical experiments and propose the reaction mechanism based on density functional theory (DFT) calculations. It is found that three key residues (N7, β-phosphate and γ-phosphate) in ATP are important for the efficient catalytic activity and stereocontrol via complexation of the Cu(II) ion. In addition to the potential technological uses, these findings could have general implications for the chemical selection of complex mixtures in prebiotic scenarios.
Reconfigurable micro–nanostructures have been largely used in the development of modern photocontrol technology. In this work, a dynamically adjustable hydrogel of supramolecule structures is ...realized by molecule self-assembly and cross-link in microscale. Calculations based on the molecule modeling systematically illuminate the assembly process and the mechanism of the dynamically adjustable micro–nanostructure. The transmittance changes of the hydrogel, which are measured in the visible-light range before and after electric heating, show outstanding light-control function. Thus, the one-step fabrication, bio-compatibility (no initiator, cross linker, or monomer residual), and agile photocontrol application demonstrate the potential of the adjustable physically bonded hydrogel in development of low-loss and integrated dynamical light-control devices.
Synthesis of buckybowls have stayed highly challenging due to the large structural strain caused by curved π surface. In this paper, we report the synthesis and properties of two ...trichalcogenasupersumanenes which three chalcogen (sulfur or selenium) atoms and three methylene groups bridge at the bay regions of hexa-peri-hexabenzocoronene. These trichalcogenasupersumanenes are synthesized quickly in three steps using an Aldol cyclotrimerization, a Scholl oxidative cyclization, and a Stille type reaction. X-ray crystallography analysis reveals that they encompass bowl diameters of 11.06 Å and 11.35 Å and bowl depths of 2.29 Å and 2.16 Å for the trithiasupersumanene and triselenosupersumanene, respectively. Furthermore, trithiasupersumanene derivative with methyl chains can form host-guest complexes with C
or C
, which are driven by concave-convex π ⋯ π interactions and multiple C-H ⋯ π interactions between bowl and fullerenes.
The theoretical methods behaving as important as experimental methods play crucial rules in fullerene chemistry, including the optimal geometries, electronic structures, reaction mechanism, and ...fullerene-formation mechanisms.
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•Foreknowledge of theoretical study on fullerene chemistry and the existence of C60.•Elucidation of geometries of fullerenes by experimental and theoretical methods.•Clear reaction mechanisms on fullerenes based on density functional theory.•Theoretical evidence on fullerene-formation mechanisms beyond experiment.•Systematic comprehensive overview of theoretical progress on fullerene chemistry.
The elucidation of geometries is the fundamental to further investigate and develop fullerene chemistry, an epoch-making discipline since 1985. Although the geometries of fullerenes, including their derivatives, could be characterized by various experimental methods, single-crystal X-ray diffraction is the only precise one. Notably, the electronic structures and reaction mechanisms cannot be clearly studied in experiment. Theoretical study is a valid and credible choice with foresight.
In this account, we highlight the advanced theoretical contributions to the structures, reaction mechanisms, and formation mechanisms of fullerenes, including endohedral fullerenes (EFs). Several rules previously proposed were highlighted to screen the stabilities of (endohedral) fullerenes. In addition, the semi-empirical molecular orbital methods (SEMOMs), molecular dynamics, and Hartree-Fock (HF) method are also performed to characterize the relative stability of EFs. Subsequently, with the developments of theoretical level and computational efficiency, density functional theory (DFT) computation combined with statistic thermodynamically analysis (STA) is successful for predicting the stable isomers of EFs, on which the first non-IPR EF, Ce@C70, was revealed. In addition, the results of the single-crystal X-ray diffraction results confirm many of theoretical predictions. The long-range corrections in DFT play a key role in the study of Sc2C2n system. Additionally, the electronic structures of EFs have also been studied in theory, and there is no choice but to the theoretical study on reaction mechanism of EFs. The experimental method is languorous on the fullerene-formation mechanism, including endohedral fullerenes, which is still ambiguous up to now, due to the ultra-formation conditions. There is much theoretical evidence for the fullerene-formation process based on top-down and bottom-up models. At the end, the machine learning is expected to be used in fullerene chemistry in the future.
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► Non-IPR isomers have been taken into account in the study of La3N@C92 system. ► 126 359:C2 isomer is suggested as the most suitable host cage of La3N cluster. ► The electron ...transfer is mainly attributed to the 6s orbital of La atoms.
Systemic investigations on lanthanum nitride endohedral metallofullerene La3N@C92 are carried out by a hybrid density functional theory technique combined with statistical mechanics treatment. A novel isolated-pentagon-rule (IPR) isomer with C2 symmetry is determined as the most suitable host cage for the encapsulation of La3N with the lowest energy and predominant thermodynamic stability related to fullerene formation. Natural electron configuration analyses reveal that electron transfer between the La3N cluster and C92 cage is mainly contributed by the 6s orbital of lanthanum atoms. The present work may supply some information reliable for synthesis and experimental characterization of large trimetallic nitride endohedral fullerenes.
The determination of active sites of materials is essential for the molecular design of high-performance catalysts. In this study, the first-principles method is applied to investigate the active ...sites of low-cost Ni metal-based electrocatalysts for hydrogen evolution reactions (HER), which is a promising alternative to expensive Pt metal-based catalysts. The adsorption of hydrogen on different sites of pristine and partially oxidized Ni(111) surface is investigated. All of the possible configurations have been systematically investigated here with the consideration of their Boltzmann distribution. Using the Gibbs free energy of intermediate H atoms (ΔG H*) as a descriptor, it is found that the ΔG H* increases with the increase of the coverage of oxygen atoms. The slightly oxidized surface Ni atoms are theoretically identified to be the best catalytic centers for the electrocatalytic HERs when the coverage of oxygen is considerably low. On the basis of the analyses of Bader charge distribution and density of states, our results reveal that the superior performance of the slightly oxidized surface Ni atoms can be ascribed to the optimal electronic properties.
With the massive consumption of traditional fossil resources, environmental issues such as air pollution and greenhouse gas emissions have motivated a transition towards clean and sustainable energy ...sources capable of meeting the increasing energy demands of our modern society ...
Diels–Alder (DA) cycloaddition is one important method to generate new derivatives of fullerenes, which is important to accelerating their application. In this study, the DA reaction of 1,3-butadiene ...and M3N@I h -C800/1+ (M = Sc and Y) has been investigated by density functional theory calculations to further uncover the effects of different metallic clusters and oxidation states on the reactivity and regioselectivity. 5,6-adduct 2 is thermodynamically most favored for M3N@I h -C80 (M = Sc and Y) but is less favorable in Y3N@I h -C80 than in Sc3N@I h -C80, which arises from the large distortion energy of Y3N@I h -C80 in 5,6-adduct 2. Further analyses reveal a correlation between the geometrical change of Y3N and the distortion energy of Y3N@I h -C80. Furthermore, the oxidized endohedral metallofullerenes M3N@I h -C80+ (M = Sc or Y) showing electron-withdrawing characteristics showed higher reactivity, lower regioselectivity, and quite a different reaction mechanism as compared with the neutral one. The theoretical results suggest that strain plays a significant role in the reactivity of Y3N@I h -C80+. The spin density distribution of the 5,6-bond has a considerable influence on the 5,6-addition but little influence on the 6,6-addition.
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