An update to the combined vibrational-diffraction experimental and theoretical studies of small biologically important cyclic imides: Reference to saccharin

The small-sized cyclic imides and amides have been for a long time known as convenient models for study of numerous biochemical processes. In addition, owing to the structural resemblance with their naturally occurring analogues, biological activity has been documented for a number of these compounds. Recent development of the experimental and especially high-level theoretical structural methods has provided new evidences for their structure and properties. The present review aims to summarize the vibrational, structural and combined data published during the last decade on selected five- and six-membered ring imides and derivatives thereof, in the attempt to update the existing knowledge for this class of compounds. As an exceptionally suitable and thoroughly studied model system that has also been a subject for research to the authors for quite some time, the vibrational-structural results for sulfobenzimide (saccharin) and its compounds are also reviewed. The inferences are designed to be applied to other, less-studied imide systems. In spite of the recent vast progress of the analytical methods, simultaneous use of vibrational and diffraction experimental/theoretical results has proven to be far more reliable for better structural interpretation than any of these alone.