Nuclear Quadrupolar Resonance Structural Characterization of Halide Perovskites and Perovskitoids: A Roadmap from Electronic Structure Calculations for Lead-Iodide-Based Compounds.

Metal halide perovskites, including some of their related perovskitoid structures, form a semiconductor class of their own, which is arousing ever-growing interest from the scientific community. With halides being involved in the various structural arrangements, namely, pure corner-sharing MX (M is metal and X is halide) octahedra, for perovskite networks, or alternatively a combination of corner-, edge-, and/or face-sharing for related perovskitoids, they represent the ideal probe for characterizing the way octahedra are linked together. Well known for their inherently large quadrupolar constants, which is detrimental to the resolution of nuclear magnetic resonance spectroscopy, most abundant halide isotopes (Cl, Br, I) are in turn attractive for magnetic field-free nuclear quadrupolar resonance (NQR) spectroscopy.

Photoisomerization of Arylidene Heterocycles: Toward the Formation of Fused Heterocyclic Quinolines.

We report herein the photoinduced isomerization of a series of arylidene heterocycles . The photoreaction mechanism was investigated by a combined UV-vis/photo-NMR spectroscopic study, and we showed that Ar-TZDs exhibit a positive P-type photochromism, which limits their isomerization efficiency. By exploring the solvatochromism in a series of solvents, the conditions favoring the conversion toward one or the other stereoisomer have been studied, in particular by choosing the appropriate wavelengths.

Solid-State Photo-NMR Study on Light-Induced Nitrosyl Linkage Isomers Uncovers Their Structural, Electronic, and Diamagnetic Nature.

A light-induced linkage NO isomer (MS1) in -[Ru(NO)(py)F](ClO) is detected and measured for the first time by solid-state MAS NMR. Chemical shift tensors of N and F, along with (N-F) spin-spin couplings and relaxation times of MS1, are compared with the ground state (GS) at temperatures < 250 K. Isotropic chemical shifts (N and F) are well resolved for two crystallographically independent cations (A and B) [Ru(NO)(py)F], allowing to define separately both populations of MS1 isomers and thermal decay rates for two structural sites.

Photoinduced linkage isomers in a model ruthenium nitrosyl complex: Identification and assignment of vibrational modes.

Photoinduced NO-linkage isomers were investigated in the solid state of labelled trans-[Ru(NO)(py)F](ClO) complex by combined IR-spectroscopy and DFT calculations. Based on the experimental data and the DFT calculations of this isotopically labelled NO nitrosyl compound, we present a complete assignment of the vibrational bands of three nitrosyl linkage isomers in a range from 4000 to 200 cm. The calculated IR-spectra match well with the experimental data allowing reliable assignment of the vibrational bands.