What's in a structure? The story of biguanides

Biguanides are a very interesting class of molecules which have been extensively studied for their medicinal applications. The structural and electronic structural aspects of biguanides have been explored in detail; however, even today, scientific literature continues to represent biguanides incorrectly as la. The X-ray crystal structure analysis and various spectroscopic studies such as UV, H-1 and N-15 NMR have confirmed that biguanide exists as tautomer lb. Electronic structure analysis also supports the existence of lb. This review focuses on the structure and electronic structure of biguanides and aims to emphasize the importance of the correct representation of a structure. There is a need to commence the use of lb for the general representation of biguanides in textbooks and research articles which will ensure a correct perspective for further studies on these molecules. (c) 2017 Elsevier B.V. All rights reserved.