Direct evidence for hula twist and single-bond rotation photoproducts

Abstract

Photoisomerization reactions are quintessential processes driving molecular machines and motors, govern smart materials, catalytic processes, and photopharmacology, and lie at the heart of vision, phototaxis, or vitamin production. Despite this plethora of applications fundamental photoisomerization mechanisms are not well understood at present. The famous hula-twist motion—a coupled single and double-bond rotation—was proposed to explain proficient photoswitching in restricted environments but fast thermal follow-up reactions hamper identification of primary photo products. Herein we describe an asymmetric chromophore possessing four geometrically distinct diastereomeric states that do not interconvert thermally and can be crystallized separately. Employing this molecular setup direct and unequivocal evidence for the hula-twist photoreaction and for photoinduced single-bond rotation is obtained. The influences of the surrounding medium and temperature are quantified and used to favor unusual photoreactions. Based on our findings molecular engineers will be able to implement photo control of complex molecular motions more consciously.

Previtamin D:Z–Ephotoisomerizationviaa Hula-twist conical intersection

“…Perhaps the criterion, when to expect a CI of either HT-or DBT-type, should be the energetic gap, not the polarity. This would also be consistent with the results for the relatively polar hemithioindigos, 40 where the product spectrum seems typical of an HT CI.…”

“…It should, however, be emphasized that a medium effect is not required for HT (contrary to Liu's assumption [20][21][22][23][24][25][26][27] ), as shown by experiments in the gas phase and in solution (see the compilation in ref. 30 and the recent results for substituted hemithioindigos 40 ) and confirmed also for Pre by calculations of dynamics in the gas phase. 41,43 More recently it was pointed out that the direction of leaving from the lower cone of the CI can be predetermined: 30,42 there can be some memory of a momentum acquired before the CI, for example via a predistortion of the molecule.…”

“…with stilbene in the gas phase or in solution. 31 An impressive example of free molecules showing all reactions expected from an HT CI is the recent work on substituted hemithioindigos in solution: 40 both conformers of each, the Z and E isomer, could be isolated and individually investigated by NMR spectroscopy; they showed DBT, HT and SBR in various ratios. (Most recently, a similar system was used to demonstrate a photon-only driven molecular motor, exploiting SBR, DBT and HT.…”

Nickel(II) complexes based on L-amino-acid-derived ligands: synthesis, characterization and study of the role of the supramolecular structure in carbon dioxide capture

“…In this sense, this becomes the first report of magnetic behaviour of this type for an Ni 3 -3 -CO 3 system. From studies of related Cu complexes, it has been stated that this bridging mode favours ferromagnetic Cu II Á Á ÁCu II interactions (Dussart et al, 2002;Newell et al, 2005;Martínez-Prieto et al, 2013;Yoo & Lee, 2016;Jonasson et al, 2018;Gerwien et al, 2018). However, the existence of an additional magnetic orbital in Ni II ions, together with low-symmetry environments, makes a direct comparison unreliable.…”

Analisis Molekular dan Transpor Ion Amonium Clorida

“…Banyak senyawa yang paling penting pada bidang industry, seperti amonia (42)(43)(44)(45)(46) , asam nitrat (47) , nitrat organik (propelan dan bahan peledak), serta sianida, mengandung nitrogen. Nitrogen banyak ditemukan dalam bentuk ikatan rangkap dua dan tiga, namun ada juga yang membentuk ikatan tunggal(single bond) (48)(49)(50)(51)(52)(53) . Ikatan rangkap tiga pada atom nitrogen sangat kuat jika dibandingkan dengan ikatan tunggal dan ikatan rangkap dua.…”