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The activation of dinitrogen (N2) is a crucial step in synthesizing nitrogen-based compounds and remains a significant challenge due to its strong triple bond. Currently, industrial N2 conversion relies on the Haber–Bosch process, a highly energy-intensive method that utilizes transition metal-based catalysts. Frustrated Lewis pairs (FLPs) have emerged as a promising alternative for N2 activation without the need for transition metals. In this work, we employ density functional theory (DFT) to investigate the activation of N2 by transition metal-free Lewis acids (LAs) and bases (LBs). Our study demonstrates that LAs play a crucial role in capturing N2 and determining the thermodynamics of activation, while LBs play a complementary role by reducing the bond order of the N2 molecule, thereby promoting activation. The efficiency of N2 capture is directly linked to the electroaccepting characteristics of the LAs. A principal component analysis (PCA) reveals that the key factors influencing the electroaccepting power of LAs are the degree of pyramidalization and orbital occupation at the acidic site, as well as the local electrophilicity index. The LA-N2 interaction is found to be electrostatic with partially covalent character. Among the 21 LAs analyzed, triptycene-based systems exhibit the highest stability in forming LA-N2 complexes, highlighting their potential as effective N2-capturing agents. However, the N2 triple bond remains largely intact, necessitating the involvement of LBs in LA-N2-LB complexes for full activation, in a "push–pull" mechanism. Six LBs are analyzed in complexes with the most promising LAs. Bonding analysis indicates that the LB-N2 interaction can be regarded as a covalent bond, which may explain the main role of the LB in the reduction of the N2 bond order. Furthermore, the bond activation is significantly enhanced by increasing the nucleophilicity of the LB. Among all the LA–LB pair combinations, only three exhibit the defining characteristics of frustrated Lewis pairs (FLPs), with moderate interaction energies and substantial LA–LB distances. Our findings suggest that FLPs composed of triptycene-based LAs and tris-tert-butylphosphine represent the most promising candidates for N2 activation. [ABSTRACT FROM AUTHOR]

We report an investigation of a series of auropolyynes, Au—(C≡C)n—Au− (n = 1–3), using high-resolution photoelectron imaging and ab initio calculations. Vibrationally resolved photoelectron spectra are obtained, allowing the electron affinities of Au—(C≡C)n—Au to be accurately measured as 1.651(1), 1.715(1), and 1.873(1) eV for n = 1–3, respectively. Both the Au—C symmetric stretching and a bending vibrational frequency are observed for each neutral auropolyyne. Theoretical calculations find that the ground state of Au2C2− has a linear acetylenic Au—C≡C—Au− structure, whereas the asymmetric Au—Au—C≡C− structure is a low-lying isomer. However, for Au2C4− and Au2C6−, our calculations show that the asymmetric Au—Au—(C≡C)n− isomers are the global minima and the Au—(C≡C)n—Au− symmetric structures become low-lying isomers. All the asymmetric Au—Au—(C≡C)n− isomers are found computationally to have much higher electron binding energies and are not accessible at the detachment photon energies used in the current study. For neutral Au2C2n, the Au—(C≡C)n—Au auropolyyne structures are found to be the global minima for n = 1–3. The electronic structures and bonding for Au—(C≡C)n—Au (n = 1–3) are compared with the corresponding Au—(C≡C)n and Au—(C≡C)n—H species. [ABSTRACT FROM AUTHOR]

There is a constant need for versatile technologies to reduce the continuously increasing concentration of CO2 in the atmosphere, able to provide effective solutions under different conditions (temperature, pressure) and composition of the flue gas. In this work, a combination of graphene oxide (GO) and functionalized waterborne polymer particles was investigated, as versatile and promising candidates for CO2 capture application, with the aim to develop an easily scalable, inexpensive, and environmentally friendly CO2 capture technology. There are huge possibilities of different functional monomers that can be selected to functionalize the polymer particles and to provide CO2-philicity to the composite nanostructures. Density functional theory (DFT) was employed to gain a deeper understanding of the interactions of these complex composite materials with CO2 and N2 molecules, and to build a basis for efficient screening for functional monomers. Estimation of the binding energy between CO2 and a set of GO/polymer composites, comprising copolymers of methyl methacrylate, n-butyl acrylate, and different functional monomers, shows that it depends strongly on the polymer functionalities. In some cases, there is a lack of cooperative effect of GO. It is explained by a remarkably strong GO-polymer binding, which induced less effective CO2-polymer interactions. When compared with experimental results, in the cases when the nanocomposite structures presented similar textural properties, the same trends for selective CO2 capture over N2 were attained. Besides novel functional materials for CO2 capture and a deeper understanding of the interactions between CO2 molecules with various materials, this study additionally demonstrates that DFT calculations can be a shorter route toward the efficient selection of the best functionalization of the composite materials for selective CO2 capture. [ABSTRACT FROM AUTHOR]

We report a joint photoelectron spectroscopy and theoretical study on AuC4-, AuC6-, and AuCnH- (n = 2, 4, and 6) using high-resolution photoelectron imaging and ab initio calculations. The ground state of AuC2H-, AuC4H-, and AuC6H- is found to be linear, while that of AuC4- and AuC6- is bent. All the species are found to be linear in their neutral ground states. The electron affinities EAs) are measured to be 3.366(1) and 3.593(1) eV for AuC4 and AuC6, respectively. Both bending and stretching frequencies are resolved in the spectra of AuC4- and AuC6-. High-resolution data of AuCnH- reveal major vibrational progressions in the Au--C stretching and bending modes. AuC2H- has a ground state stretching frequency of 445(10) cm-1 and a bending frequency of 260(10) cm-1; AuC4H- has a ground state stretching frequency of 340(10) cm-1; AuC6H- has a ground state stretching frequency of 260(10) cm-1 and a bending frequency of 55(10) cm-1. The EAs are measured to be 1.475(1), 1.778(1), and 1.962(1) eV for AuC2H, AuC4H, and AuC6H, respectively. The strength of the Au--C bond decreases as the number of carbon atoms increases. The current study provides a wealth of electronic structure information about AuC4 -, AuC6-, and AuCnH- (n = 2, 4, and 6) and their corresponding neutrals. [ABSTRACT FROM AUTHOR]

The optical spectrum of diatomic IrSi has been investigated for the first time, with transitions observed in the range from 17 178 to 23 858 cm-1 (582-419 nm). A rich spectrum has been recorded, consisting of 14 electronic band systems and a number of unclassified bands. Thirty-one bands have been investigated with rotational resolution, allowing the ground state to be identified as X2Δ5/2 arising from the 1σ21π42σ21δ33σ2 configuration. The ground X2Δ5/2 state is characterized by ΔG1/2 = 533 cm-1 and r0 = 2.0899(1) Å for the more abundant isotopic form, 193Ir28Si (57.8%). The measured excited electronic states have equilibrium bond lengths ranging from 2.17 to 2.25 Å and vibrational frequencies ranging from 365 to 452 cm-1. Ab initio calculations were also carried out on the molecule using the complete active space self-consistent field and multistate complete active space second-order perturbation theory methods, with relativistic and spin-orbit effects included through the restricted active space state-interaction with spin-orbit coupling method. The calculated ground state agrees with experiment, and a large number of excited states lying within 20 000 cm-1 of the ground state are reported. [ABSTRACT FROM AUTHOR]