The product of proton transfer reactions between donors and acceptors in which the proton from one species is transferred to the basic center has been designated by different names such as “proton transfer compound” (PTC), “charge transfer complex” (CT-complex) and “H-bonded complex”. These are equivalent and merely emphasize different aspects of the same phenomenon. In recent years, the design and development of new active pharmaceutical ingredients (APIs) based on the proton transfer reactions have been widely developed (1).
N,N-dimethylbiguanide (known as metformin), is the first line drug of choice to treat non-insulin dependent mellitus, which contains the guanidine moiety that can easily forms strong hydrogen bonds with the acidic functionalities like acids and phenols (2). Metformin can be administered in the form of one of its pharmaceutically acceptable salts of various organic and inorganic acids. As part of our studies on proton transfer compounds and their metal complexes of biological interest, here-in, we report new proton transfer compound, [(MetH2)(HO-dipicH)2·H2O], metformin with 4-hydroxy-2,6-pyridinedicarboxylic acid. The proton transfer compound was synthesized and characterized by FTIR, 1H and 13C NMR, and single crystal X-ray studies (Fig 1). The solution potentiometric studies provided additional evidences of interaction between HO-dipicH2 and metformin, supporting the results obtained from the solid state studies.
We gratefully acknowledge the support of this work by the Sistan and Baluchestan University. Financial support from Spanish Ministerio de Economía y Competitividad (MAT2013-40950-R and MAT2016-78155-C2-1-R), Factoría de Cristalización—Consolider Ingenio 2010).