title: U-shaped building blocks
title: formation of discrete assemblies through molecular recognition
titleType: Subtitle
Creators: name: Hartwick, Christopher J.
Publisher: name: University of Iowa
Year: 2023
Subjects: Boronic Ester
Crystal engineering
Dative Bond
Host-guest chemistry
Supramolecular Chemistry
Molecular Recognition

description: Functionalization of the 1,8- positions on naphthalene using cross coupling reactions to form pyridyl substituted naphthalene derivatives have produced unique molecular recognition U-shaped molecules. Having been synthesized in the last two decades, these have been used in the formation of cocrystals and assemblies through hydrogen or halogen, and metal coordination. Extending upon the 4-pyridyl derivative through elongation via vinyl and ethynyl groups has resulted in derivatives which have been explored to a lesser degree. Formation of dative bond coordinated boronic esters formed from catechol and boronic acids via a condensation reaction result in a strong, reversible noncovalent interaction. This reaction formed unique assemblies with complimentary geometries involving U-shaped bipyridines and both mono- and diboronic ester catecholates. Regarding the plug-in assemblies, two species form crystals containing inclusions of small molecules, with one assembly forming inclusions with small molecules like dichloromethane and the other with the aromatic m-xylenes. Reactions with monoboronic acids yield chiral space groups for the 4-pyridyl derivative which are promising materials for applications where dipoles within the crystal lattice are useful, such as nonlinear optics or piezoelectricity, while the 4-ethenylpyridyl derivative shows selectivity for aromatics like benzene, toluene, and ethylbenzene over similar aromatic molecules (i.e xylenes, styrene, thiophene), presenting a method for an important industrial petrochemical separation. Throughout the series the electrostatic calculations performed on all examples reinforce how the electron poor and electron rich areas interact strongly which correlates strongly with data from single crystal measurements. Overall, these represent the first instances of interactions between the U-shaped naphthalene derivatives where both N atoms are involved with noncovalent interactions. Continuation of this phenomenon has extended into exploration of single and double boroxines of the 4-ethenylpyridyl derivative which result in a photodimerized Z- shaped molecule. Exploration of the halogen bonding of with diiodotetrafluorobenzene isomers and hydrogen bonding of dihydroxybenzene isomers has furthered the understanding of molecular recognition work through comparative crystal packing studies.
description: In addition to this work, development of an apparatus allowing for increased scale of mechanochemical reactions through use of a combination of UV LEDs and glass jars containing ball bearings tumbled by a rock tumbler as a cheap, effective ball milling method. This has allowed for greater, scalable production of pyridyl substituted cyclobutanes through already established template methods featuring silver and dihydroxybenzene molecules. With this apparatus, the exploration into the use of catalytic amounts of template have been undertaken in order to have these molecules produced with greener methodology.