Das Franck‐Condon‐Prinzip

The quantum mechanical model is fully recognized and used for rotational and vibronic transitions in molecules, where according to the model, transitions occur between discrete, the resonance condition matching states, only. It is also accepted that selection rules are implied for rotational and vibronic transitions. Why is it so hard to recognize that this established quantum mechanical model is also valid for vibronic transitions, where the Franck‐Condon principle instead of a selection rule applies to the population of vibronic states in the electronic excitation state? In any case, supposed illustrative and comfortable but wrong explanations, also if they are widely used, must not replace more sophisticated, correct quantum mechanical models. In scientific publications as well as in teaching only the quantum mechanical version of the Franck‐Condon principle should be used. Terms like “Franck‐Condon point” or ”Franck‐Condon region of the photochemical reaction" should be avoided in the future.     

Ring Opening of Bicyclo[3.1.0]hexan‐2‐ones: A Versatile Synthetic Platform for the Construction of Substituted Benzoates

Described is the development of a highly efficient 2π disrotatory ring‐opening aromatization sequence using bicyclo[3.1.0]hexan‐2‐ones. This unprecedented transformation efficiently proceeds under thermal conditions and allows facile construction of uniquely substituted and polyfunctionalized benzoates. In the presence of either amines or alcohols formation of substituted anilines or ethers, respectively, is achieved. Additionally, the utility of this method was demonstrated in a short synthesis of sekikaic acid methyl ester.     

Pyridine‐Fused Bis(Norcorrole) through Hantzsch‐Type Cyclization: Enhancement of Antiaromaticity by an Aromatic Bridge

A non‐catalytic condensation of Ni^II β‐aminonorcorrole with aryl aldehydes is shown to produce a family of pyrromethane dimers that undergo deaminative cyclization to yield pyridine‐fused bis(norcorrole)s comprising two antiaromatic macrocycles communicating by an aromatic moiety. The new compounds were characterized by spectroscopic, structural, and electrochemical methods supported by DFT calculations, all of which revealed unexpected antiaromaticity enhancement in the fused system.