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Aromatic amides can be used to construct light-harvesting materials with valuable optical properties. The amide bond is formed using well-known coupling agents in near quantitative yield, as illustrated here through the synthesis of two boron dipyrromethene derivatives bearing an amide linkage. The primary concern with acyl amides is rotation around the C-N bond, leading to cis and trans isomers. Using NMR spectroscopy, quantum chemical calculations and critical comparison to simpler benzamides, the stereochemistry of the target compounds has been addressed. The N-cyclohexyl derivative gave diffraction quality crystals that established a trans geometry for the amide bond. Quantum chemical calculations support the trans geometry as being the lowest-energy structure in solution but indicate that inversion of the aryl ring is an important structural feature. Indeed, rotation around the C(sp 2 )-C(aryl) bond has a strong influence on the solution-phase NMR spectra. The amide connection has minimal effect on the photophysical properties., (© 2023 Wiley-VCH GmbH.)

Ditetrelenes R 2 E=ER 2 (E=Si, Ge, Sn, Pb) substituted by multiple N/P/O/S-donor groups are extremely rare due to their propensity to disaggregate into their tetrylene monomers R 2 E. We report the synthesis of the first fully phosphanyl-substituted digermene {(Mes) 2 P} 2 Ge=Ge{P(Mes) 2 } 2 (3, Mes=2,4,6-Me 3 C 6 H 2 ), which adopts a highly unusual structure in the solid state, that is both strongly trans-bent and highly twisted. Variable-temperature 31 P{ 1 H} NMR spectroscopy suggests that 3 persists in solution, but is subject to a dynamic equilibrium between two conformations, which have different geometries about the Ge=Ge bond (twisted/non-twisted) due to a difference in the nature of their π-stacking interactions. Compound 3 undergoes unprecedented, spontaneous decomposition in solution to give a unique Ge I cluster {(Mes) 2 P} 4 Ge 4 ⋅5 CyMe (7)., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)