COMPOUNDS HAVING PHOTOCHEMICALLY REMOVABLE PROTECTING GROUPS BASED ON AN ELECTROCYCLIC REACTION BETWEEN A CHROMOPHORE ATTACHED VIA AN ANILIDE GROUP TO A BENZOTHIOPHENE RING
Photochemical and Thermal Isomerization Processes of a Chiral Auxiliary Based Donor–Acceptor Substituted Chiroptical Molecular Switch: Convergent Synthesis, Improved Resolution and Switching Properties
作者:Richard A. van Delden、Johannes H. Hurenkamp、Ben L. Feringa
DOI:10.1002/chem.200204660
日期:2003.6.16
of chiroptical molecular switch is presented where irradiation employing different wavelengths of light induces a reversible helix inversion of a sterically overcrowded alkene bearing a second chiral entity in the form of a stereogenic center present in a pyrrolidine unit. The additional stereogenic center in the chiral auxiliary group has a distinct influence on the switching selectivity of this system
Evaluation of intermolecular interactions in thioxanthone derivatives: substituent effect on crystal diversity
作者:C. Jacob、Fátima M. da Piedade、M. Paula Robalo、M. Teresa Duarte
DOI:10.1039/c0ce00783h
日期:——
A family of 9H-thioxanthen-9-one derivatives and two precursors, 2-[(4-bromophenyl)sulfanyl]-5-nitrobenzoic acid and 2-[(4-aminophenyl)sulfanyl]-5-nitrobenzoic acid, were synthesized and studied in order to assess the role of the different substituent groups in determining the supramolecular motifs. From our results we can conclude that Etter's rules are obeyed: whenever present the –COOH head to head strong hydrogen bonding dimer, R22(8) synthon, prevails as the dominant interaction. As for –NH2, the best donor when present also follows the expected hierarchy, an NH⋯O(COOH) was formed in the acid precursor (2) and an NH⋯O(CO) in the thioxanthone (4). The main role played by weaker hydrogen bonds such as CH⋯O, and other intermolecular interactions, π–π and Br⋯O, as well as the geometric restraints of packing patterns shows the energetic interplay governing crystal packing. A common feature is the relation between the π–π stacking and the unit cell dimensions. A new synthon notation, RR′, introduced in this paper, refers to the possibility of accounting for intra- and intermolecular interactions into recognizable and recurring aggregate patterns.