Abstract A series of novel bisphosphonates (BPs) were designed and synthesised as longer- chain analogues of the clinically widely used BP–zoledronate (ZL). They were characterised by mass spectrometry, infrared spectroscopy, NMR spectroscopy, and single-crystal X-ray diffraction. All the crystals are zwitterions with one of the phosphonate oxygen atoms deprotonated and the hydrogen atom transferred to the nitrogen of the imidazole ring. A lot ...