Theoretical study on the molecular stacking interactions and charge transport properties of triazasumanene crystals - from explanation to prediction

Fluorescence-quenching mechanisms of novel isomorphic Zn/Cd coordination polymers for selective nitrobenzene detection

Nitroaromatic compounds in aqueous undermine environmental sustainability and affect human health. The development of a fluorescent sensor capable of efficiently and selectively detecting trace amounts of nitroaromatic compounds presents a considerable challenge. This study introduced Zn/Cd isomeric coordination polymers (Zn-H2CIA-1/Cd-H2CIA-2), which are synthesized using 5-((4-carboxybenzyl)oxy)isophthalic acid (5-H3CIA) and 1,10-phenanthroline (Phen). The polymers have zero-dimensional discrete crystal structure with a six-coordinated scissor-like shape. The two coordination polymers can be used as fluorescent sensors for detecting nitrobenzene (NB) and demonstrated favorable sensitivity, with detection limits of 1.95 × 10-8 and 4.66 × 10-7 mol/L, respectively. Zn-H2CIA-1 exhibited stronger fluorescence and a more sensitive response to NB compared with Cd-H2CIA-2. To elucidate their fluorescence-quenching mechanisms, we analyzed Zn-H2CIA-1 by performing DFT and TD-DFT calculations. The pore structure, density of states, excitation energy, hole-electron distribution, and orbital composition were analyzed. The suitable size of pores in Zn-H2CIA-1 is the main reason for its high NB selectivity. Moreover, intermolecular π-π stacking interactions result in an orbital overlap between Zn-H2CIA-1 and NB, enabling the transfer of electrons from Zn-H2CIA-1 to NB. This electron transfer is identified as the fundamental cause of fluorescence quenching in Zn-H2CIA-1.

DFT Exploration of Metal Ion-Ligand Binding: Toward Rational Design of Chelating Agent in Semiconductor Manufacturing

Chelating agents are commonly employed in microelectronic processes to prevent metal ion contamination. The ligand fragments of a chelating agent largely determine its binding strength to metal ions. Identification of ligands with suitable characteristics will facilitate the design of chelating agents to enhance the capture and removal of metal ions from the substrate in microelectronic processes. This study employed quantum chemical calculations to simulate the binding process between eleven ligands and the hydrated forms of Ni2+, Cu2+, Al3+, and Fe3+ ions. The binding strength between the metal ions and ligands was quantified using binding energy and binding enthalpy. Additionally, we explored the binding interaction mechanisms and explained the differences in binding abilities of the eleven ligands using frontier molecular orbitals, nucleophilic indexes, electrostatic potentials, and energy decomposition calculations based on molecular force fields. Based on our computational results, promising chelating agent structures are proposed, aiming to guide the design of new chelating agents to address metal ion contamination issues in integrated circuit processes.

Catalytic Effect of Ferrocenyl Energetic Catalysts for N-Guanylurea Dinitramide (GUDN or FOX-12) Decomposition

Four N,N-dimethylaminomethylferrocene polynitrogen catalysts were applied to the thermal decomposition of FOX-12, and their catalytic effect on FOX-12 was investigated by TG-DSC. The kinetic parameters and kinetic model of the mixed system were revealed by the Kissinger method, Freidman method, and combined kinetic analysis. The results showed that MAFcTAZ is the catalyst with the strongest effect on FOX-12, the decomposition peak temperature of FOX-12 is reduced, and the decomposition weight loss is higher than those for other catalysts, which prove that the decomposition of FOX-12 is more thorough under the catalysis of MAFcTAZ. The introduction of the four catalysts reduced the thermal decomposition peak temperature of FOX-12. MAFcTAZ was the most active catalyst for the decomposition of FOX-12, and the maximum heat release of catalyzing the decomposition of FOX-12 can reach 1236.76 J·g^-1. The activation energy (E _a) of FOX-12 decomposition decreased from 217.91 to 128.19, 137.85, 157.65, and 151.91 kJ·mol^-1 under the effect of MAFcNO₃, MAFcPA, MAFcNTO, and MAFcTAZ. The Freidman analysis illustrated that MAFcTAZ reduced the activation energy during the entire decomposition process of FOX-12. The physical model of the decomposition reaction of FOX-12 transformed from the random nucleation and two-dimensional growth of nuclei model (A2) to the random scission model (L2) in the presence of MAFcNO₃ and two-dimensional diffusion (D2) under the effect of MAFcPA, MAFcNTO, and MAFcTAZ. By analyzing the molecular structures, MAFcTAZ has a higher iron content and nitrogen content, which are the essence of its excellent catalytic performance. From the perspective of interaction energy, the strong catalytic effect of MAFcTAZ is attributed to its large interaction energy with FOX-12 by energy decomposition analysis.

Exploration of conjugated π-bridge units in N,N-bis(4-methoxyphenyl)naphthalen-2-amine derivative-based hole transporting materials for perovskite solar cell applications: a DFT and experimental investigation

Organic small molecules as hole-transporting materials (HTMs) are an important part of perovskite solar cells (PSCs). On basis of the arylamine-based HTM (e.g. H101), two N,N-bis(4-methoxyphenyl)naphthalen-2-amine derivative-based HTMs (CP1 and CP2) with different conjugated π-bridge cores of fused aromatic ring are designed. The CP1 and CP2 were investigated by DFT and TD-DFT in combination with Marcus theory. The calculated results indicate that the designed CP1 and CP2 have better properties with good stability and high hole mobility compared with the parent H101. To validate the computational model for the screening of N,N-bis(4-methoxyphenyl)naphthalen-2-amine derivative-based HTMs, the promising CP1 and CP2 were synthesized and applied to PSC devices. The results show that the experimental data used in this paper can reproduce the theoretical results, such as frontier molecular orbital energies, optical properties and hole mobility, very well. Among them, the results show that the power conversion efficiency (PCE) of the H101-based PSC device is 14.78%, while the CP1-based PSC shows a better PCE of 15.91%, due to its high hole mobility and uniform smooth film morphology, which ultimately promoted a higher fill factor. Finally, this work shows that the computational model is a feasible way to obtain potential N,N-bis(4-methoxyphenyl)naphthalen-2-amine derivative-based HTMs.

Accurate Analysis of Anisotropic Carrier Mobility and Structure-property Relationships in Organic BOXD Crystalline Materials

Charge mobility is an essential factor of organic crystalline materials. Although many investigators have made important progress, the exact relationship between the crystal structure and carrier mobility remains to be clarified. Fortunately, a series of bis-1,3,4-oxadiazole derivatives have been successfully prepared and reported. They have similar main molecular fragments but different crystal packing modes, which provide an ideal research objective for studying the effect of molecular packing on charge mobility in organic photoelectric conversion systems. In this work, the charge mobilities of these molecules are systematically evaluated from the perspective of first-principles calculation, and the effect of a molecular overlap on orbital overlap integral and final charge carrier mobility is fully discussed. It can be seen that the small intermolecular distance (less than 6 Å) is the decisive factor to achieve high electron mobility in π stacking, and better mobility can be obtained by increasing the hole migration distance appropriately. A larger dihedral angle of anisotropy is an important point limiting the charge mobility in the herringbone arrangement. It is hoped that the correlation results between the crystal structure and mobility can assist the experimental study and provide an effective way to improve the photoelectric conversion efficiency of the organic semiconductor devices and multiple basis for multiscale material system characterization and material information.