The relative free energies of the isomers formed upon N-chlorination of each nitrogen atom within the DNA nucleobases (adenine, guanine, and thymine) have been obtained using the high-level G4(MP2) composite ab initio method (the free energies of the N-chlorinated isomers of cytosine have been reported at the same level of theory previously). Having identified the lowest energy N-chlorinated derivatives for each nucleobase, we have computed the free energies associated with chlorine transfer from N-chlorinated nucleobases to other unsubstituted bases. Our results provide quantitative support pertaining to the results of previous experimental studies, which demonstrated that rapid chlorine transfer occurs from N-chlorothymidine to cytidine or adenosine. The results of our calculations in the gas-phase reveal that chlorine transfer from N-chlorothymine to either cytosine, adenine, or guanine proceed via exergonic processes with ∆G^o values of −50.3 (cytosine), −28.0 (guanine), and −6.7 (adenine) kJ mol^–1. Additionally, we consider the effect of aqueous solvation by augmenting our gas-phase G4(MP2) energies with solvation corrections obtained using the conductor-like polarizable continuum model. In aqueous solution, we obtain the following G4(MP2) free energies associated with chlorine transfer from N-chlorothymine to the three other nucleobases: −58.4 (cytosine), −26.4 (adenine), and −18.7 (guanine) kJ mol^–1. Therefore, our calculations, whether in the gas phase or in aqueous solution, clearly indicate that chlorine transfer from any of the N-chlorinated nucleobases to cytosine provides a thermodynamic sink for the active chlorine. This thermodynamic preference for chlorine transfer to cytidine may be particularly deleterious since previous experimental studies have shown that nitrogen-centered radical formation (via N–Cl bond homolysis) is more easily achieved in N-chlorinated cytidine than in other N-chlorinated nucleosides.

Carbazole-based molecules play a significant role in dye-sensitized solar cells (DSSCs) due to their advantageous properties. Carbazole derivatives are known for their thermal stability, high hole-transport capability, electron-rich (p-type) characteristics, elevated photoconductivity, excellent chemical stability, and commercial availability. This review focuses on DSSCs, including their structures, working principles, device characterization, and the photovoltaic performance of carbazole-based derivatives. Specifically, it covers compounds such as 2,7-carbazole and indolo[3,2-b]carbazole, which are combined with various acceptors like benzothiadiazole, thiazolothiazole, diketopyrrolopyrrole, and quinoxaline, as reported over the past decade. The review will also outline the relationship between molecular structure and power-conversion efficiencies. Its goal is to summarize recent research and advancements in carbazole-based dyes featuring a D-π-A architecture for DSSCs. Additionally, this review addresses the evolution of carbazole-based hole-transport materials (HTMs), which present a promising alternative to the costly spiro-OMeTAD. We explore the development of novel HTMs that leverage the unique properties of carbazole derivatives to enhance charge transport, stability, and overall device performance. By examining recent innovations and emerging trends in carbazole-based HTMs, we provide insights into their potential to reduce costs and improve the efficiency of DSSCs.

This article investigates the environmentally friendly synthesis and characterization of carbon dots (CDs) derived from soybean biomass, in conjunction with their composites containing potassium chloride (KCl) or zeolite. By using an environmentally sustainable synthetic approach, this study sought to unlock the potential of these materials for various applications. The physicochemical properties of the CDs and composites were comprehensively analyzed using various techniques including scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analysis. In addition, various optical properties such as UV–Vis absorption, band gap, and excitation–emission behavior were investigated. A key finding to arise from this study was that the inclusion of a doping agent such as KCl or zeolite significantly reduced the size of the resulting CDs. In this light, whereas the undoped species are associated with average sizes of 8.86 ± 0.10 nm, those doped with either zeolite or KCl were associated with average sizes of 3.09 ± 0.05 and 2.07 ± 0.05 nm, respectively. In addition, it was shown that doping with either zeolite or KCl resulted in an alteration of the elemental composition of the CDs and influenced their optical properties, especially their excitation-dependent emission. These promising results point to potential applications in environmental sensing and energy-related fields.

We obtain gas-phase homolytic Al–H bond dissociation enthalpies (BDEs) at the CCSD(T)/CBS level for a set of neutral aluminium hydrides (which we refer to as the AlHBDE dataset). The Al–H BDEs in this dataset differ by as much as 79.2 kJ mol⁻¹, with (H₂B)₂Al–H having the lowest BDE (288.1 kJ mol⁻¹) and (H₂N)₂Al–H having the largest (367.3 kJ mol⁻¹). These results show that substitution with at least one –AlH₂ or –BH₂ substituent exerts by far the greatest effect in modifying the Al–H BDEs compared with the BDE of monomeric H₂Al–H (354.3 kJ mol⁻¹). To facilitate quantum chemical investigations of large aluminium hydrides, for which the use of rigorous methods such as W2w may not be computationally feasible, we assess the performance of 53 density functional theory (DFT) functionals. We find that the performance of the DFT methods does not strictly improve along the rungs of Jacob's Ladder. The bestperforming methods from each rung of Jacob's Ladder are (mean absolute deviations are given in parentheses): the GGA B97-D (6.9), the meta-GGA M06-L (2.3), the global hybrid-GGA SOGGA11-X (3.3), the range-separated hybrid-GGA CAM-B3LYP (2.1), the hybrid-meta-GGA ωB97M-V (2.5) and the double-hybrid methods mPW2-PLYP and B2GP-PLYP (4.1 kJ mol⁻¹).

Fluoroborane-type molecules (R¹R²B–F) are of interest in synthetic chemistry, but to date, apart from a handful of small species (such as H₂BF, HBF₂, and BF₃ ), little is known concerning the effect of substituents in governing the strength of the B–F bonds of such species toward homolytic dissociation in the gas phase. In this study, we have calculated the bond dissociation enthalpies (BDEs) of thirty unique B–F bonds at the CCSD(T)/CBS level using the high-level W1w thermochemical protocol. The B–F bonds in all species considered are very strong, ranging from 545.9 kJ mol⁻¹ in (H₂B)₂B–F to 729.2 kJ mol⁻¹ HBF². Nevertheless, these BDEs still vary over a wide range of 183.3 kJ mol⁻¹ . The structural properties that affect the BDEs are examined in detail, and the homolytic BDEs are rationalized based on molecule stabilization enthalpies and radical stabilization enthalpies. Since polar B–F bonds may represent a challenging test case for density functional theory (DFT) methods, we proceed to examine the performance of a wide range of DFT methods across the rungs of Jacob’s Ladder for their ability to compute B–F BDEs. We find that only a handful of DFT methods can reproduce the CCSD(T)/CBS BDEs with mean absolute deviations (MADs) below the threshold of chemical accuracy (i.e., with average deviations below 4.2 kJ mol⁻¹ ). The only functionals capable of achieving this feat were (MADs given in parentheses): ωB97M-V (4.0), BMK (3.5), DSD-BLYP (3.8), and DSD-PBEB95 (1.8 kJ mol⁻¹ ).

This study reports the gas-phase homolytic P–H BDEs of a set of 30 phosphine-type oxides (i.e., R¹R²P(=O)H) obtained using the W1w thermochemical protocol. We note that the P–H BDEs (at 298 K) of the species in this dataset differ by as much as 157.2 kJ mol^–1, with (H₂B)₂P(=O)H having the lowest BDE (249.3 kJ mol^–1) and F₂P(=O)H having the highest (406.5 kJ mol^–1). Furthermore, using the full set of 30 all-electron, non-relativistic, vibrationless bottom-of-the-well W1w P–H BDEs as reference values, we have identified several well-performing DFT methods that could be applied to the computation of the P–H BDEs of phosphine-type oxides. The best-performing DFTs (in conjunction with the A'VTZ basis set) were shown to be MN12-SX (MAD = 1.7 kJ mol^–1) and MN12-L (MAD = 2.7 kJ mol^–1).

We report that bifunctional molecules containing hydroxyl and carbonyl functional groups can undergo an effective transfer hydrogenation via an intramolecular proton-coupled hydride transfer (PCHT) mechanism. In this reaction mechanism, a hydride transfer between two carbon atoms is coupled with a proton transfer between two oxygen atoms via a cyclic bond rearrangement transition structure. The coupled transfer of the two hydrogens as H^δ+ and H^δ− is supported by atomic polar tensor charges. The activation energy for the PCHT reaction is strongly dependent on the length of the alkyl chain between the hydroxyl and carbonyl functional groups but relatively weakly dependent on the functional groups attached to the hydroxyl and carbonyl carbons. We investigate the PCHT reaction mechanism using the Gaussian-4 thermochemical protocol and obtain high activation energy barriers (ΔH^‡₂₉₈) of 210.5–228.3 kJ mol^–1 for chain lengths of one carbon atom and 160.2–163.9 kJ mol^–1 for chain lengths of two carbon atoms. However, for longer chain lengths containing 3–4 carbon atoms, we obtain ΔH^‡₂₉₈ values as low as 101.9 kJ mol^–1. Importantly, the hydride transfer between two carbon atoms proceeds without the need for a catalyst or hydride transfer activating agent. These results indicate that the intramolecular PCHT reaction provides an effective avenue for uncatalyzed, metal-free hydride transfers at ambient temperatures.

Fluoroborane-type molecules (R¹R²B–F) are of interest in synthetic chemistry, but to date, apart from a handful of small species (such as H₂BF, HBF₂ , and BF₃), little is known concerning the effect of substituents in governing the strength of the B–F bonds of such species toward homolytic dissociation in the gas phase. In this study, we have calculated the bond dissociation enthalpies (BDEs) of thirty unique B–F bonds at the CCSD(T)/CBS level using the high-level W1w thermochemical protocol. The B–F bonds in all species considered are very strong, ranging from 545.9 kJ mol⁻¹ in (H₂B)₂B–F to 729.2 kJ mol⁻¹ HBF₂. Nevertheless, these BDEs still vary over a wide range of 183.3 kJ mol⁻¹. The structural properties that affect the BDEs are examined in detail, and the homolytic BDEs are rationalized based on molecule stabilization enthalpies and radical stabilization enthalpies. Since polar B–F bonds may represent a challenging test case for density functional theory (DFT) methods, we proceed to examine the performance of a wide range of DFT methods across the rungs of Jacob's Ladder for their ability to compute B–F BDEs. We find that only a handful of DFT methods can reproduce the CCSD(T)/CBS BDEs with mean absolute deviations (MADs) below the threshold of chemical accuracy (i.e., with average deviations below 4.2 kJ mol⁻¹). The only functionals capable of achieving this feat were (MADs given in parentheses): ωB97M-V (4.0), BMK (3.5), DSD-BLYP (3.8), and DSD-PBEB95 (1.8 kJ mol⁻¹).

This study reports accurate gas-phase homolytic B–Cl bond dissociation energies, obtained using the benchmark-quality W1w thermochemical protocol, for a set of 25 chloroborane-type molecules (known herein as the BCl25BDE dataset). The BDEs of these species differ by as much as 136.6 kJ mol^–1 at 298 K, with (BH₂)₂ BCl having the lowest BDE (388.5 kJ mol^–1 at 298 K) and (CH₃ )HBCl having the highest (525.1 kJ mol^–1). Using the W1w BDEs as reference values, the accuracy of a diverse set of more economical DFT procedures (which may be applied to the study of molecules sufficiently large that the use of benchmark-quality methods such as W1w is rendered computationally prohibitive) have been investigated. As a result of this analysis, the most accurate methods for the computation of B–Cl BDEs are ωB97/A'VQZ (MAD = 3.0 kJ mol^–1) and M06/A'VTZ (MAD = 3.2 kJ mol^–1). The double-hybrid functional DSD-PBEP86 in conjunction with the A'VQZ basis set (MAD = 4.0 kJ mol^–1) was found to give the lowest largest deviation (LD = 6.4 kJ mol^–1) of any of methods considered in this assessment study.