Organic crystal engineering with piperazine-2,5-diones. 1. Crystal packing of piperazinediones derived from substituted 2-aminoindan-2-carboxylic acids

Organic Crystal Engineering with Piperazine-2,5-diones. 4. Crystal Packing of Piperazinediones Derived from 2-Amino-7-cyano-4-methoxyindan-2-carboxylic Acid

“…Control of order in the second and third dimensions for tapes of 2 depends on harnessing van der Waals interactions, arene−arene interactions, Coulombic interactions, and possibly additional hydrogen bonding interactions. van der Waals attractive interactions almost always contribute significantly to stabilization of the lattice as evidenced by the tendency of organic compounds to achieve closest packing in the solid state. ,− Arene “face-to-face” and “edge-to-face” interaction types have been recognized as important, from the packing of small molecules to the stabilization of protein tertiary structures. − Both the nature and magnitude of arene edge-to-face interactions have been called into question, but there is agreement that such interactions are stabilizing. − Arene edge-to-face association of neighboring tapes occurs for 3 , meso- 4 , rac - 4 , and ( S , S )- 4 , , and might be anticipated for 2 if the groups D and A are comparable in volume to bromine and methoxy substituents. The importance of dipolar interactions in determining crystal packing is less clear. − In crystals of ( S , S )- 4 , dipoles due to the p -bromoanisole moieties of edge-to-face associated neighboring tapes are opposed.…”

Organic Crystal Engineering with 1,4-Piperazine-2,5-diones. 6. Studies of the Hydrogen-Bond Association of Cyclo[(2-methylamino-4,7-dimethoxyindan-2-carboxylic acid)(2-amino-4,7-dimethoxyindan-2-carboxylic acid)]

“…c The dihedral angles α and β were previously defined (ref ) and are measures of the degree of nonplanarity of the piperazinedione ring (for flat rings α = β = 180°). d The dihedral χ was previously defined (ref ) and is a measure of the degree of nonplanarity of the cyclopentene ring component of the Indane moiety (for flat rings χ = 180°). e The C 4 −C 7 −O 3 −C 11 torsion angle, δ, measures the twist of the methoxy substituent relative to the plane of the benzene ring.…”

Crystal engineering with 1,4-piperazine-2,5-diones

“…In addition to piperazinedione 9, we studied the crystal packing of arene-substituted analogs 10-14. 82 Like 2-8, molecules 9, 10, and 13 are achiral and have no molecular dipole moment, at least in solution. Molecules 11, 12, and 14 are also achiral but are weakly dipolar.…”