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Importance of the Anchor Group Position (Para versus Meta) in Tetraphenylmethane Tripods: Synthesis and Self‐Assembly Features 下载免费PDF全文
Marcin Lindner Dr. Michal Valášek Jan Homberg Kevin Edelmann Dr. Lukas Gerhard Prof. Dr. Wulf Wulfhekel Dr. Olaf Fuhr Tobias Wächter Prof. Dr. Michael Zharnikov Dr. Viliam Kolivoška Dr. Lubomír Pospíšil Dr. Gábor Mészáros Dr. Magdaléna Hromadová Prof. Dr. Marcel Mayor 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(37):13218-13235
The efficient synthesis of tripodal platforms based on tetraphenylmethane with three acetyl‐protected thiol groups in either meta or para positions relative to the central sp3 carbon for deposition on Au (111) surfaces is reported. These platforms are intended to provide a vertical arrangement of the substituent in position 4 of the perpendicular phenyl ring and an electronic coupling to the gold substrate. The self‐assembly features of both derivatives are analyzed on Au (111) surfaces by low‐temperature ultra‐high‐vacuum STM, high‐resolution X‐ray photoelectron spectroscopy, near‐edge X‐ray absorption fine structure spectroscopy, and reductive voltammetric desorption studies. These experiments indicated that the meta derivative forms a well‐ordered monolayer, with most of the anchoring groups bound to the surface, whereas the para derivative forms a multilayer film with physically adsorbed adlayers on the chemisorbed para monolayer. Single‐molecule conductance values for both tripodal platforms are obtained through an STM break junction experiment. 相似文献
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Synthesis and X-ray diffraction studies on the first examples of ‘double chiral’ calixsalens are presented. In these molecules, one can clearly distinguish two chiral zones. The first one is made by the macrocycle base, whereas the second chiral zone is set up of the additional chirality elements in the tail of the molecule. The ‘double chiral’ calixsalens are formed through cyclocondensation between chiral vicinal diamine of trans-1,2-diaminocyclohexane type and chiral C-5 substituted 2-hydroxyisophthalaldehyde derivatives. The absolute configuration of the dialdehyde did not affect the yield of the macrocyclization reaction. The presence of secondary amides in the tail part of the macrocycle leads to formation of hydrogen bonding network in the solid state, while sterical hindrance preserve interdigitation, thus, ‘double chiral’ calixsalens do not form aggregates typical for other calixsalens. 相似文献
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The distinguishing index of a graph is the least cardinal number such that has an edge-coloring with colors, which is preserved only by the trivial automorphism. We prove a general upper bound for any connected infinite graph with finite maximum degree . This is in contrast with finite graphs since for every there exist infinitely many connected, finite graphs with . We also give examples showing that this bound is sharp for any maximum degree . 相似文献
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