Charge-assisted hydrogen bonds (CAHBs) of N-H···Cl, N-H···Br, and P-H···Cl type were investigated using advanced computational approach (MP2/aug-cc-pVTZ level of theory). The properties of electron density function defined in the framework of Quantum Theory of Atoms in Molecules (QTAIM) were estimated as a function of distance in H-bridges. Additionally, the interaction energy decomposition was performed for H-bonded complexes with different H-bond lengths using the Symmetry-Adapted Perturbation Theory (SAPT). In this way both QTAIM parameters and SAPT energy components could be expressed as a function of the same variable, that is, the distance in H-bridge. A detailed analysis of the changes in QTAIM and SAPT parameters due to the changes in H···A distance revealed that, over some ranges of H···A distances, electrostatic, inductive and dispersive components of the SAPT interaction energy show a linear correlation with the value of the electron density at H-BCP ρ(BCP). The linear relation between the induction component, E(ind), and ρ(BCP) confirms numerically the intuitive expectation that the ρ(BCP) reflects directly the effects connected with the sharing of electron density between interacting centers. These conclusions are important in view of charge density studies performed for crystals in which the distance between atoms results not only from effects connected with the interaction between atomic centers directly involved in bonding, but also from packing effects which may strongly influence the length of the H-bond.

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Controlling the crystallization of perovskite in a thin film is essential in making solar cells. Processing tin-based perovskite films from solution is challenging because of the uncontrollable faster crystallization of tin than the most used lead perovskite. The best performing devices are prepared by depositing perovskite from dimethyl sulfoxide because it slows down the assembly of the tin–iodine network that forms perovskite. However, while dimethyl sulfoxide seems the best solution to control the crystallization, it oxidizes tin during processing. This work demonstrates that 4-( tert -butyl) pyridine can replace dimethyl sulfoxide to control the crystallization without oxidizing tin. We show that tin perovskite films deposited from pyridine have a 1 order of magnitude lower defect density, which promotes charge mobility and photovoltaic performance.

The N → Sn coordination occurring in the (Me 3 SnCN) 2 dimer has been investigated using various computational methods and several theoretical tools possessing great interpretative potential. The dimer is formed by moving the C≡N fragment of the first Me 3 SnCN molecule close to the Sn atom of the second molecule and the resulting N → Sn coordination corresponds to that observed in the crystal structure of trimethyltin cyanide. The geometry of (Me 3 SnCN) 2 is optimized using the MP2 method and its 11 variants, and then it is compared with the reference geometry obtained at the CCSD level of theory. SCS-MP2 reproduces best the reference geometry of (Me 3 SnCN) 2 and its accuracy is close to that of the MP4 (SDQ) method. Two families of basis sets, namely the correlation-consistent basis sets proposed by Dunning and co-workers and the 'def2' basis sets developed by Ahlrichs and co-workers, are taken into account and their effect on the geometry of the dimer is examined in detail. The intermolecular interaction in (Me 3 SnCN) 2 has been analyzed using SAPT, NBO, QTAIM, and ELF. The results indicate that the (Me 3 SnCN) 2 dimer possesses a weak N → Sn coordination bond whose character is predominantly ionic. A value of −7.64 kcal/mol is proposed to be the best estimate of the interaction energy between the Me 3 SnCN molecules in the dimer.

Abstract:The effective use of partial atomic charge models is essential for such purposes in molecular computations as a simplified representation of global charge distribution in a molecule and predicting its conformational behavior. In this work, ten of the most popular models of partial atomic charge are taken into consideration, and these models operate on the molecular wave functions/electron densities of five diheteroaryl ketones and their thiocarbonyl analogs. The ten models are tested in order to assess their usefulness in achieving the aforementioned purposes for the compounds in title. Therefore, the following criteria are used in the test: (1) how accurately these models reproduce the molecular dipole moments of the conformers of the investigated compounds; (2) whether these models are able to correctly determine the preferred conformer as well as the ordering of higher-energy conformers for each compound. The results of the test indicate that the Merz-Kollman-Singh (MKS) and Hu-Lu-Yang (HLY) models approximate the magnitude of the molecular dipole moments with the greatest accuracy. The natural partial atomic charges perform best in determining the conformational behavior of the investigated compounds. These findings may constitute important support for the effective computations of electrostatic effects occurring within and between the molecules of the compounds in question as well as similar compounds.