Gabapentin-lactum-chloranilic acid (1/1)

Area of Science:

• Crystallography
• Organic Chemistry
• Solid-State Chemistry

Background:

• Understanding the solid-state structure of pharmaceutical compounds is crucial for predicting their physical properties and stability.
• Gabapentin is a widely used anticonvulsant and analgesic, but its lactam form's structural characteristics in complex with other molecules are less explored.
• Chloranilic acid is a common organic acid used in co-crystallization studies due to its hydrogen bonding capabilities.

Purpose of the Study:

• To elucidate the crystal structure of the 1:1 co-crystal formed between 2-aza-spiro-[4.5]decan-3-one (a gabapentin lactam) and chloranilic acid.
• To analyze the conformational aspects of the lactam and cyclohexane rings within the co-crystal.
• To investigate the intermolecular interactions, particularly hydrogen bonding, governing the crystal packing.

Main Methods:

• Single-crystal X-ray diffraction was employed to determine the three-dimensional structure of the co-crystal.
• Analysis of bond lengths, bond angles, and dihedral angles to describe molecular conformations.
• Hydrogen bond analysis to identify and quantify intermolecular interactions and their role in crystal assembly.

Main Results:

• The crystal structure of 2-aza-spiro-[4.5]decan-3-one chloranilic acid (1:1) was successfully determined.
• The cyclohexane ring of the lactam exhibited a slightly distorted chair conformation, and the 3-azaspiro ring adopted a slightly distorted chair conformation.
• A significant dihedral angle of 84.0° was observed between the least-squares planes of the cyclohexane and 3-azaspiro rings.
• Extensive intermolecular N-H···O and O-H···O hydrogen bonds were identified, linking the chloranilic acid and lactam molecules.
• The hydrogen bonding network resulted in the formation of molecular chains propagating along the b axis.

Conclusions:

• The co-crystallization of 2-aza-spiro-[4.5]decan-3-one with chloranilic acid leads to a well-defined crystal structure with specific conformational preferences.
• Intermolecular hydrogen bonding plays a critical role in stabilizing the crystal lattice and dictating the observed molecular arrangement.
• The findings provide valuable insights into the solid-state behavior of gabapentin lactam derivatives, relevant for pharmaceutical formulation and development.