Michal Rouchal

Determination of Intrinsic Binding Modes by Mass Spectrometry: Gas-Phase Behavior of Adamantylated Bisimidazolium Guests Complexed to Cucurbiturils

Adamantylated bisimidazolium cations exhibit a distinct fragmentation pathway in contrast to their cucurbit[7]uril (CB7) complexes. The observed alternative fragmentation of the guest molecule in a complex clearly correlates to the supposed sterically hindered or allowed slippage of the macrocycle over the axel molecule.

Novel adamantane-bearing anilines and properties of their supramolecular complexes with β-cyclodextrin

Several novel anilines bearing 1-adamantyl substituents that are useful for drug modification were synthesised from the corresponding 1-adamantyl (nitrophenyl) ketones. The host–guest systems of these prepared ligands with β-cyclodextrin (β-CD) were studied using electrospray ionisation mass spectrometry, NMR spectroscopy, titration calorimetry and semi-empirical calculations. The complexes with 1:1 stoichiometry were found to predominantly exist as pseudorotaxane-like threaded structures with the adamantane cage sitting deep in the cavity of β-CD close to the wider rim. Such geometry was observed for all examined amines and is independent of their structure and/or presence of protic substituents.

Rotaxanes Capped with Host Molecules: Supramolecular Behavior of Adamantylated Bisimidazolium Salts Containing a Biphenyl Centerpiece

Bisimidazolium salts with one central biphenyl binding site and two terminal adamantyl binding sites form water-soluble binary or ternary aggregates with cucurbit[7]uril (CB7) and β-cyclodextrin (β-CD) with rotaxane and pseudorotaxane architectures. The observed arrangements result from cooperation of the supramolecular stopper binding strength and steric barriers against free slippage of the CB7 and β-CD host molecules over the bisimidazolium guest axle.

2-(1-Adamant­yl)-1-{4-[(2-chloro-9-isopropyl-9H-purin-6-yl)amino­meth­yl]phen­yl}ethanone

The structure of the title compound, C27H32ClN5O, consists of two crystallographically independent conformers differing slightly in all geometric parameters. Both contain nearly planar purine and benzene ring systems [maximum deviations of 0.046 (3) and 0.005 (2) Å, respectively], the dihedral angles between them being 76.44 (6) and 82.39 (6)°, and an adamantane cage consisting of three fused cyclohexane rings in almost ideal chair conformations, with C—C—C angles in the range 108.7 (2)–110.6 (2)°. The carbonyl plane and the benzene ring are almost coplanar [dihedral angles of 6.43 (9) and 0.64 (8)° in the two conformers]. The crystal structure is stabilized by intermolecular N—H⋯N interactions that link adjacent molecules into dimers and by some non-bonding contacts of the C—H⋯Cl type.

(1-Adamant-yl){4-[(2-chloro-9-isopropyl-9H-purin-6-yl)aminometh-yl]phen-yl}methanone trichloro-methane solvate.

In the title compound, C26H30ClN5O·CHCl3, the purine molecule consists of essentially planar benzene and purine ring systems [maximum deviation 0.010 (4) Å for both ring systems] forming a dihedral angle of 85.52 (9)°. Intermolecular N—H⋯N hydrogen bonds link adjacent molecules into centrosymmetric dimers. The structure also contains intermolecular C—H⋯O and C—H⋯N interactions. The benzene rings form offset face-to-face π–π stacking interactions with an interplanar distance of 3.541 (4) Å and a centroid-to-centroid distance of 4.022 (4) Å.

1-(2-Phenyl­eth­yl)adamantane

In the title compound, C18H24, the adamantane cage consists of three fused cyclohexane rings in almost ideal chair conformations, with C—C—C angles in the range 108.0 (14)–111.1 (15)°. The phenyl and 1-adamantyl substituents adopt anti orientations with a C—C—C—C torsion angle of 177.10 (16)°. In the crystal packing, the molecules are linked by weak C—H⋯π interactions into chains along the a axis.

(1-Adamant­yl)(4-amino­phen­yl)methanol

In the racemic crystal of the title compound, C17H23NO, enantiomers of the two crystallographically independent molecules are linked into face-to-face RSdimers via intermolecular O—H⋯N hydrogen bonds and π–π interactions with centroid–centroid distances of 3.7610 (2) Å. The molecules adopt slightly different conformations and contain an adamantane cage consisting of three fused cyclohexane rings in almost ideal chair conformations, with C—C—C angles varying within the range 107.2 (4)–111.4 (4)°. In the hydrogen-bonded pair, the benzene rings are almost coplanar, the dihedral angle between them being 1.29 (13)°. The molecular packing in the crystal is stabilized by additional intermolecular N—H⋯O hydrogen bonds.

Cubane Arrives on the Cucurbituril Scene

Cubane, an intriguing chemical curiosity first studied in the early 1960s, has become a valuable structural motif and has recently been involved in the structures of a great number of prospective compounds. The first dicationic supramolecular guest 5 is prepared and derived from a 1,4-disubstituted cubane moiety, and its binding behavior toward cucurbit[n]urils (CBn) and cyclodextrins (CD) is studied. The bisimidazolium salt 5 forms 1:1 inclusion complexes with CB7, CB8, and β-CD with the respective association constants (6.7 ± 0.5) × 1011 M-1, (1.5 ± 0.2) × 109 M-1, and <102 M-1 in water. The solid-state structures of the 5@CB7 and 5@CB8 complexes are also reported.

Adamantane-bearing benzylamines and benzylamides: novel building blocks for supramolecular systems with finely tuned binding properties towards β-cyclodextrin

Novel building blocks for the synthesis of supramolecular components based on adamantane-bearing benzylamines were prepared. The binding properties of these amines and the corresponding acetamides towards β-cyclodextrin (β-CD) were studied using mass spectrometry, NMR spectrometry, isothermal titration calorimetry and semi-empirical calculations. It was found that all of the examined guests predominantly formed 1:1 inclusion complexes in an enthalpy-driven manner with association constants of the order of 102–103 M− 1. Stronger binding to the β-CD cavity was observed for guests with a longer spacer between the adamantane and benzene moieties and/or a 1,4-disubstituted benzene ring.

2-(1-Adamant-yl)-1-(3-amino-phen-yl)ethanol.

In the crystal structure of the title compound, C18H25NO, molecules are linked via O—H⋯N hydrogen bonds, forming chains parallel to the c axis. Additional weak N—H⋯O interactions stabilize the crystal packing. The adamantane cage consists of three fused cyclohexane rings in almost ideal chair conformations, with C—C—C angles in the range 107.9 (10)–111.3 (11)°.