Two-dimensional carbon materials and their derivatives are widely applied as promising electrocatalysts and supports of single-atom sites. Theoretical investigations of 2D carbon materials are usually based on planar models, yet ignore local curvature brought on by possible surface distortion, which can be significant to the exact catalytic performance as has been realized in latest research. In this work, the curvature-influenced electrocatalytic nitrogen reduction reaction (NRR) reactivity of heme-like FeN₄ single-atom site was predicted by a first-principle study, with FeN₄-CNT(m,m) (m = 5~10) models adopted as local curvature models. The results showed that a larger local curvature is favored for NRR, with a lower limiting potential and higher N₂ adsorption affinity, while a smaller local curvature shows lower NH₃ desorption energy and is beneficial for catalyst recovery. Using electronic structures and logarithm fitting, we also found that FeN₄-CNT(5,5) shows an intermediate-spin state, which is different from the high-spin state exhibited by other FeN₄-CNT(m,m) (m = 6~10) models with a smaller local curvature.

Organic long-persistent luminescence (OLPL) systems have long been experimentally investigated. First reported by Ifor D. W. Samuel et al., OLPL can be observed upon doping thermally activated delayed fluorescence (TADF) molecules in host materials of PPT, TPBi and PMMA and is proposed to proceed via a two-photon mechanism. In this work, OLPL that occurs upon doping CzPhAP in PPT/TPBi systems with charge-separation features was theoretically investigated to understand the essence of transformation from TADF to OLPL and to provide insights for further research. Theoretical results of this study revealed that OLPL emission from CzPhAP:PPT/TPBi systems proceeded via a double-luminescence mechanism. The main S₃ state emission peak (observed at 608 nm) was a mixture of TADF and OLPL. Moreover, large reorganization energy associated with converting S₁ into a low-lying charge-separation S₃ state enabled S₃ fluorescence with a larger emission rate (7.92 × 10⁷ s⁻¹) compared to that of S₁ fluorescence (3.94 × 10⁷ s⁻¹, shoulder peak observed at 584 nm). Thermodynamic equilibria between S₁ and low-lying charge-separation states of S₃ and T₃ were constructed, which stimulated fast conversion among the S₁, S₃ and T₃ states. Furthermore, our investigations indicated that when the reorganization energy of the ISC process is smaller than that of rISC, a larger ΔE_ST value is required to obtain k_rISC > k_ISC. Although a larger ΔE_ST value will make the ISC process deeply rooted in the Marcus inverted region, the ISC process will be strongly hindered and TADF emission could not be observed. Meanwhile, OLPL emission was enhanced with a larger ΔE_ST owing to frustrated charge recombination to the neutral T₁ state and electron–hole dissociation could occur. More importantly, our study indicated that the essence of conversion of TADF into OLPL in CzPhAP:PPT/TPBi systems is due to a low-lying neutral T₁ state.

Detailed structure–activity relationships and molecular design criteria for nonconventional and nonconjugated luminescent polymers are still ambiguous. This work reports n–π electron hybrid polyurethane derivatives (PUs) with varying separation of benzene rings in the backbone. Experimental and computational results show that although through-bond conjugation is not the main source of luminescence, the separated benzene rings still modulate the photophysical properties by affecting the molecular conformation and electron transport. Meanwhile, hydrogen bonds and p–π* interactions exert a significant influence on the emission wavelengths by regulating the aggregated-state structures. In PU1, the excited state is predominantly charge transfer. With an increase in the number of benzene rings along the chain, the energy gap between the acceptor π and π* orbitals is reduced; alongside these effects, the modulation from hydrogen bonds and p–π* interactions promotes a transition to LE-dominated states in PU3, which incorporates terphenyl units. Proof-of-concept applications are demonstrated in information transmission and colorful displays. This work enhances the understanding of the mechanisms underlying the excitation-dependent properties of nonconventional polymers and provides a strategy for tuning and exploiting their intrinsic luminescence.

A Fe/Zn metal–organic framework (MOF) that mimics the Fe^II/2-oxoglutarate-dependent complex (Fe^II/2-OGDC) was reported previously, but its oxygen-activation mechanism remains unclear. In the present research, density functional theory (DFT) calculations were used to study this Fe-based system and its Mn- and Co-substituted analogues. We found that all three systems follow the general oxygen-activation chemistry of Fe^II/2-OGDC but show clear metal-dependent differences. The Fe and Co systems generate high-spin TM^IV–oxo complexes, whereas the Mn system forms high-spin Mn^III-oxyl complexes. The energy profiles further show that the formation of the key oxidizing intermediate is more favorable in the Fe and Mn systems than in the Co system. Overall, this work explains how changing the metal center affects oxygen activation in MOF-based enzyme mimics and highlights Mn as a more promising substitute for Fe than Co.

The P450-catalyzed arene oxidation reaction (e.g., arene hydroxylation) is considered to have an arene oxide (or epoxide) intermediate. The two-electron transfer in the formation of arene oxide has two pathways. The electrophilic addition mechanism is initiated by substrate-to-porphyrin electron transfer, followed by electrophilic addition led by an FeIV-oxo complex on the arene carbon atom, resulting in an FeIV-alkoxyl complex and a substrate in the radical state. On the other hand, the radical addition by an FeIV-oxo complex transfers one electron from the substrate to the FeIV center, resulting in an FeIII-alkoxyl complex, while both the substrate and porphyrin ligand are in the radical state. This article investigated the P450-catalyzed oxygen-insertion reaction into cycloparaphenylenes, where computational results suggested a two-electron-transfer pathway that had not been reported in other P450-catalyzed arene oxidation reactions. The two-electron transfer pathway yields an FeIII-product complex and recovers the porphyrin ligand to a closed-shell state, directly from the FeIV-oxo complex and within one asynchronous transition state. This can be summarized as radical addition coupled with two-electron transfer (RAC2ET). Selectivity to the electron transfer pathways is controlled by the substrate curvature effect.