Polymeric architectures of bismuth citrate based on dimeric building blocks

Four bismuth complexes, (H₂En)[Bi₂(cit)₂(H₂O)_4/3]·(H₂O) _x (1), (H₂En)₃[Bi₂(cit)₂Cl₄]·(H₂O) _x (2), (HPy)₂[Bi₂(cit)₂(H₂O)_8/5]·(H₂O) _x (3) and (H₂En)[Bi₂(cit)₂](H₂O) _x (4) [cit = citrate^4-; En = ethylenediamine; Py = pyridine] have been synthesized and crystallized. The crystal structures reveal that the basic building blocks in all of these complexes are bismuth citrate dimeric units which combine to form polymeric architectures. The embedded protonated ethylenediamine and pyridine moieties in the polymeric frameworks have been identified by X-ray crystallography and solid-state cross polarization/magic angle spinning (CP/MAS) ¹³C NMR. Based on the framework of complex 1, a structural model of a clinically used antiulcer drug, ranitidine bismuth citrate (RBC) was generated. The behavior of the protonated amine-bismuth citrate complexes in acidic aqueous solution has been studied by electrospray ionization-mass spectrometry (ESI-MS).

Electronic supplementary material: Supplementary material is available for this article at 10.1007/s11426-010-4113-x and is accessible for authorized users.