Theoretical study on the stability of the complexes A···BX3 [A = CH3NH3+, NH2CHNH2+, NH2CHOH+; B = Sn2+, Pb2+; X = F-, Cl-, Br-, I-]

The interaction of corresponding molecular building blocks of the complexes A···BX₃ would provide valuable information to quickly estimate the properties of the solar cell. In this work, the H···X hydrogen bond between the organic cations A⁺ (CH₃NH₃⁺, NH₂CHNH₂⁺, NH₂CHOH⁺) and the inorganic anions BX₃^- (B = Sn²⁺, Pb²⁺, X = F^-, Cl^-, Br^-, I^-) were studied by theoretical calculation at the B3LYP-D3/ma-def2-TZVP level to investigate the stability of the complexes A···BX₃. The strength of H···X hydrogen bond is enhanced in the order of NH₂CHNH₂⁺ < CH₃NH₃⁺ < NH₂CHOH⁺, Sn²⁺ < Pb²⁺, and weakened in the order of F^- > Cl^- > Br^- > I^-, indicating that the complexes A···BX₃ enhances with the increase of electron donating ability of B and the decrease of electron donating ability of X, and application of the substituent A = NH₂CHOH⁺ may be effective to enhance the stability of perovskite and replace the toxic metal Pb by Sn. Graphical abstract.

The mechanism of ring-opening polymerization of L-lactide by ICl3 catalysts: Halogen bond catalysis or participating in reactions?

The mechanism of ring-opening polymerization of L-lactide by iodine trichloride (ICl₃ ) catalyst has been explored by using density functional theory (DFT) calculations and three catalytic pathways were proposed. The first and second pathways belong to the halogen bond catalysis, and the third pathway involves the ICl₃ catalysts participating in reactions. When the carbonyl group was maintained involved in the reaction and activated catalytically by the halogen bond, there are two possible pathways. The first pathway involves only one transition state, and the second pathway requires two transition states. There is another pathway in which ICl₃ directly participates in the reaction, it is named the third pathway. Two different transition states of the four-membered rings are generated successively, the transfer of I─O bonds determined the progress of the reaction. Theoretical calculations in this work provide the most basic understanding of ring-opening polymerization of L-lactide by ICl₃ catalysts. © 2019 Wiley Periodicals, Inc.

Phenylacetylene as a gas phase sliding balance for solvating alcohols

Phenylacetylene offers two similarly attractive π binding sites to OH containing solvent molecules, the phenyl ring and the acetylenic triple bond. By systematically varying the solvent molecule and by methylating aromatic or acetylenic CH groups, the docking preference can be controlled. It ranges from almost exclusive acetylene docking to predominant phenyl docking, depending on how electron density is deposited into the conjugated system and how large the London dispersion interaction is. FTIR spectroscopy of supersonic jet expansions is used to observe the competitive docking preferences in phenylacetylene and some of its methylated derivatives. A new data evaluation procedure that estimates band strength uncertainties based on a Monte Carlo approach is introduced. We test how well two density functionals (B3LYP-D3 and M06-2X) in combination with a def2-TZVP basis set are able to describe the docking switch. B3LYP-D3 is slightly biased towards acetylenic hydrogen bond docking and M06-2X is strongly biased towards phenyl hydrogen bond docking. More accurate theoretical predictions are invited and some previous experimental assignments are questioned.

Comparison of pnicogen and tetrel bonds in complexes containing CX2 carbenes (X = F, Cl, Br, OH, OMe, NH2, and NMe2)

The similarities and differences of pnicogen and tetrel bonds formed by carbenes CX₂ with H₃AsO and H₃SiCN were investigated by carrying out ab initio calculations in association with topological analysis of electron density.