title: Crystal structure and Hirshfeld surface analysis of 1-carb-oxy-2-(3,4-di-hydroxy-phen-yl)ethan-1-aminium bromide 2-ammonio-3-(3,4-di-hydroxy-phen-yl)propano-ate.
abstract: In the title mol-ecular salt, C9H12NO4+·Br-·C9H11NO4, one of the dopa mol-ecules is in the cationic form in which the α-amino group is protonated and the α-carb-oxy-lic acid group is uncharged, while the second dopa mol-ecule is in the zwitterion form. The Br-anion occupies a special position and is located on a twofold rotation axis. The two dopa mol-ecules are inter-connected by short O-H⋯O hydrogen bonds. In the crystal, the various units are linked by O-H⋯O, N-H⋯Br and N-H⋯O hydrogen bonds, forming a three-dimensional framework. The title compound was refined as an inversion twin with an absolute structure parameter of 0.023 (8).
authors.affiliation: Crystal Growth Laboratory, PG and Research Department of Physics, Periyar EVR Government College (Autonomous), Tiruchirappalli 620 023, India.
authors.forename: Perumal
authors.initials: P
authors.lastname: Kathiravan
authors.affiliation: Crystal Growth Laboratory, PG and Research Department of Physics, Periyar EVR Government College (Autonomous), Tiruchirappalli 620 023, India.
authors.forename: Thangavelu
authors.initials: T
authors.lastname: Balakrishnan
authors.affiliation: Laboratorio de Polímeros, Centro de Química Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla (BUAP), Complejo de Ciencias, ICUAP, Edif. 103H, 22 Sur y San Claudio, C.P. 72570 Puebla, Puebla, Mexico.
authors.forename: Perumal
authors.initials: P
authors.lastname: Venkatesan
authors.affiliation: Crystal Growth and Thin Film Laboratory, Department of Physics and Nanotechnology, SRM University, Kattankulathur 603 203, India.
authors.forename: Kandasamy
authors.initials: K
authors.lastname: Ramamurthi
authors.affiliation: Laboratorio de Polímeros, Centro de Química Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla (BUAP), Complejo de Ciencias, ICUAP, Edif. 103H, 22 Sur y San Claudio, C.P. 72570 Puebla, Puebla, Mexico.
authors.forename: María Judith
authors.initials: MJ
authors.lastname: Percino
authors.affiliation: Biomolecular Crystallography Laboratory, Department of Bioinformatics, School of Chemical and Biotechnology, SASTRA University, Thanjavur 613 401, India.
authors.forename: Subbiah
authors.initials: S
authors.lastname: Thamotharan
keywords: Hirshfeld surfaces; crystal structure; cyclic N—H⋯Br hydrogen bonds; dopa; hydrogen bonding