Conformation of 1,4-dineopentyl-2,5-cis-diphenylpiperazine and its diammonium salts: remarkable change in conformation depending upon the counter anion.

@article{Takasu2001ConformationO1,
  title={Conformation of 1,4-dineopentyl-2,5-cis-diphenylpiperazine and its diammonium salts: remarkable change in conformation depending upon the counter anion.},
  author={Keiji Takasu and Ken-ichi Tanaka and Kaoru Fuji},
  journal={Chemical & pharmaceutical bulletin},
  year={2001},
  volume={49 5},
  pages={655-6}
}
The free base of 1,4-dineopentyl-2,5-diphenylpiperazine takes a chair conformation in CDCl3, while the conformation of its diammonium salts changes depending upon the counter anion.