Binuclear Coordination Assemblies of Metal Tetraphenylporphyrins (M = Mn, Fe, and In) with Anionic Thioindigo Bridges as Promising Magnetic Systems with Tunable Properties.

A series of hybrids comprising two metal (Mn, Fe, and In) tetraphenylporphyrins axially substituted with anionic bidentate -thioindigo ligands (TI) were obtained. Substitution of the axial chloride anion by an oxygen atom of the dye forms short M-O bonds. Crystalline binuclear assemblies (TI)·{[MnTPP]·[MnTPP]}·CHCl ( = 2 for or 1 for ) and (TI){[MTPP]}·CHCl (M = Fe and = 2 for , M = In and = 1 for ) were synthesized.

Enhanced Performance and Stability of Perovskite Solar Cells Through Surface Modification with Benzocaine Hydrochloride.

Current development of inverted p-i-n perovskite solar cells (PSCs), with nickel oxide as the hole transport layer, is progressing toward lower net costs, higher efficiencies, and superior stabilities. Unfortunately, the high density of defect-based traps on the surface of perovskite films significantly limits the photoelectric conversion efficiency and operational stability of perovskite solar cells. Finding cost-effective interface modifiers is crucial for the further commercial development of p-i-n PSCs.

Nitrogen Reduction to Ammonia on a Fe Nanocluster: A Computational Study of Catalysis.

The sequence of elementary steps leading to reductive ammonia formation from N and H catalyzed by a Fe cluster is studied using generalized gradient approximation density functional theory and an all-electron basis set of triple-ζ quality. The computational methods are validated by comparison to experimental data such as binding energies where possible. First, the associative and dissociative attachment of N to Fe is considered, followed by exploration of the pathways leading to distal (Fe-N-NH) and enzymatic (NFe-NH) formation of an amino group.

Molecular Structure-Intrinsic Photostability Relationships for a Series of Conjugated Polymers: Backbone Substitution Matters!

Herein, we present an efficient approach for screening the intrinsic photostability of organic absorber materials used in photovoltaic applications. Using a series of structurally related conjugated polymers and a set of complementary techniques, we established important "material structure-photostability" relationships. In particular, we have revealed that the introduction of alkoxy, thioalkyl, and fluorine substituents adversely affects the material photostability.

Redox Chemistry of the Subphases of α-CsPbIBr and β-CsPbIBr: Theory Reveals New Potential for Photostability.

The logic in the design of a halide-mixed APb(I1−xBrx)3 perovskite is quite straightforward: to combine the superior photovoltaic qualities of iodine-based perovskites with the increased stability of bromine-based perovskites. However, even small amounts of Br doped into the iodine-based materials leads to some instability. In the present report, using first-principles computations, we analyzed a wide variety of α-CsPbI2Br and β-CsPbI2Br phases, compared their mixing enthalpies, explored their oxidative properties, and calculated their hole-coupled and hole-free charged Frenkel defect (CFD) formations by considering all possible channels of oxidation.

Mechanisms of Complete Dissociation of CO on Iron Clusters.

Dissociation of CO on iron clusters was studied by using semilocal density functional theory and basis sets of triple-zeta quality. Fe , Fe , and Fe clusters were selected as the representative host clusters. When searching for isomers of Fe CO , n=2, 4 and 16 corresponding to carbon dioxide attachment to the host clusters, its reduction to O and CO, and to the complete dissociation, it was found that the total spin magnetic moments of the lowest energy states of the isomers are often quenched with respect to those of initial reagents Fe +CO .

Ultrafast Dynamics of Nitro-Nitrite Rearrangement and Dissociation in Nitromethane Cation.

We report new insights into the ultrafast rearrangement and dissociation dynamics of nitromethane cation (NM) using pump-probe measurements, electronic structure calculations, and ab initio molecular dynamics simulations. The "roaming" nitro-nitrite rearrangement (NNR) pathway involving large-amplitude atomic motion, which has been previously described for neutral nitromethane, is demonstrated for NM. Excess energy resulting from initial population of the electronically excited D state of NM upon strong-field ionization provides the necessary energy to initiate NNR and subsequent dissociation into NO.

Evolution of Ferromagnetic and Antiferromagnetic States in Iron Nitride Clusters FeN and FeN ( = 1-10).

First-principles density functional theory calculations on neutral and singly negatively and positively charged iron clusters Fe and iron nitride clusters FeN and FeN ( = 1-10) in the range of 1 ≤ ≤ 10 revealed that there is a strong competition between ferromagnetic and antiferromagnetic states especially in the FeN cluster series. This phenomenon was related to superexchange via a bridging N atom between two iron atoms in the FeN cluster series and to a double superexchange effect via a Fe atom shared by two N atoms in the FeN series. A thorough examination of the structure-energy-spin state relationships in these clusters is conducted, leading to new insights and confirmation of available experimental results on structural parameters and dissociation energetics.

Superhalogens Among 3-Metal Compounds: F, F, F, and F ( = Sc-Zn).

The ground states of the neutral and anionic tetrafluoride and hexafluoride series of 3-metal atoms from Sc to Zn were assigned by using a double-check approach in which the pure and hybrid density functional methods were interchangeably used. It was confirmed that all these neutral fluorides are superhalogens except for TiF. The electron affinities of the hexafluorides were shown to be consistently higher than those of the tetrafluorides in accordance with the superhalogen conception of the extra electron delocalization over a larger number of the electronegative ligands.

Dissociation of dinitrogen on iron clusters: a detailed study of the Fe + N case.

The coalescence of two Fe8N as well as the structure of the Fe16N2 cluster were studied using density functional theory with the generalized gradient approximation and a basis set of triple-zeta quality. It was found that the coalescence may proceed without an energy barrier and that the geometrical structures of the resulting clusters depend strongly on the mutual orientations of the initial moieties. The dissociation of N2 is energetically favorable on Fe16, and the nitrogen atoms share the same Fe atom in the lowest energy state of the Fe16N2 species.

Influence of back donation effects on the structure of ZnO nanoclusters.

The structure and properties of ZnO quantum dots is a very popular and rapidly growing field of research for which accurate quantum calculations are challenging to perform. Since the dependence between system size and wall time scales nonlinearly, certain compromises have to be made. A particularly important limiting factor is the size of the basis used, this is especially the case if accurate large calculations are to be carried out.

Dissociation of Singly and Multiply Charged Nitromethane Cations: Femtosecond Laser Mass Spectrometry and Theoretical Modeling.

Dissociation pathways of singly- and multiply charged gas-phase nitromethane cations were investigated with strong-field laser photoionization mass spectrometry and density functional theory computations. There are multiple isomers of the singly charged nitromethane radical cation, several of which can be accessed by rearrangement of the parent CH-NO structure with low energy barriers. While direct cleavage of the C-N bond from the parent nitromethane cation produces NO and CH, rearrangement prior to dissociation accounts for fragmentation products including NO, CHOH, and CHNO.

Unravelling the Material Composition Effects on the Gamma Ray Stability of Lead Halide Perovskite Solar Cells: MAPbI Breaks the Records.

In this work, we report a comparative study of the gamma ray stability of perovskite solar cells based on a series of perovskite absorbers including MAPbI (MA = methylammonium), MAPbBr, CsFAPbI (FA = formamidinim), CsMAFAPbI, CsPbI, and CsPbBr We reveal that the composition of the perovskite material strongly affects the radiation stability of the solar cells. In particular, solar cells based on the MAPbI were found to be the most resistant to gamma rays since this perovskite undergoes rapid self-healing due to the special gas-phase chemistry analyzed with calculations. The fact that the solar cells based on MAPbI can withstand a 1000 kRad gamma ray dose without any noticeable degradation of the photovoltaic properties is particularly exciting and shifts the paradigm of research in this field toward designing more dynamic rather than intrinsically robust (e.

Homocoupling and Heterocoupling of Grignard Perfluorobenzene Reagents via Aryne Intermediates: A DFT Study.

Perfluorobenzenes are reactive species with the lowest magnesium metalation barriers among all hexahalobenzenes. This fact makes them good candidates for the study of heterocoupling reactions of the Grignard type. In this work, we investigated a number of pathways for both heterocoupling and homocoupling reactions and estimated the solvated energy barrier heights.

Conserved Vibrational Coherence in the Ultrafast Rearrangement of 2-Nitrotoluene Radical Cation.

2-Nitrotoluene (2-NT) is a good model for both photolabile protecting groups for organic synthesis and the military explosive 2,4,6-trinitrotoluene (TNT). In addition to the direct C-NO bond-cleavage reaction that initiates detonation in TNT, 2-NT undergoes an H atom attack reaction common to the photolabile 2-nitrobenzyl group, which forms the aci-nitro tautomer. In this work, femtosecond pump-probe measurements with mass spectrometric detection and density functional theory (DFT) calculations demonstrate that the initially prepared vibrational coherence in the 2-NT radical cation (2-NT) is preserved following H atom attack.

Structure and properties of iron oxide clusters: From Fe6 to Fe6 O20 and from Fe7 to Fe7 O24.

Geometrical and electronic structures of the neutral and singly negatively charged Fe6 On and Fe7 Om clusters in the range of 1 ≤ n ≤ 20 and 1 ≤ m ≤ 24, respectively, are computed using density functional theory with the generalized gradient approximation. The largest clusters in the two series, Fe6 O20 and Fe7 O24 , can be described as Fe(FeO4 )5 and Fe(FeO4 )6 or alternatively as [FeO5 ](FeO3 )5 and [FeO6 ](FeO3 )6 , respectively. The Fe6 O20 and Fe7 O24 clusters possess adiabatic electron affinities (EAad ) of 5.