Pierre Baillargeon

Rational Design and Gas-Phase Characterization of Molecular Capsules by Self-Assembly of a Symmetric Hexasubstituted Benzene with Seven-Membered Lactams

A novel very simple C3-symmetric lactam has been rationally designed to self-assemble as dimers or larger platonic solid capsules. Its core flat benzene ring bears three seven-membered lactams, resulting in tripod molecules that aggregate into robust tetrameric capsules. The self-assembly process was templated by tetraethylammonium cations and proven to be reversible by ESI spectroscopy in various solvents.

Hydrogen Bonds between Acidic Protons from Alkynes (C–H···O) and Amides (N–H···O) and Carbonyl Oxygen Atoms as Acceptor Partners

Crystals of tert-butyl (2S)-2-(prop-2-yn-1-ylcarbamoyl)pyrrolidine-1-carboxylate (Boc-L-Pro-NHCH2CCH) have been obtained. The title compound crystallizes easily as sharp needles in orthorhombic system, space group P 21 21 21 with a = 9.2890(2), b = 9.7292(2), c = 15.7918(4) A, V = 1427.18(6) A3, and Z = 4. The main feature of the structure is the orientation of the carbamate and amide. Their dipoles add up and the molecule displays an electric dipole moment of 5.61 D from B3LYP/6-31G(d) calculations. The antiparallel H bonding of amides and the alignment of dipoles induce columnar stacking (the dipole moment along the columnar a axis is 4.46 D for each molecule). The other components across the other axes are, therefore weaker, (3.17 D and 1.23 D along the b and c axes, resp.). The resulting anisotropic columns pack side by side, in an antiparallel fashion mostly by (alkyne) CH···O=C (carbamate) interactions.