Raman spectroscopic study of complex formation between major calixarene derivatives and three pharmaceutical substances

Complex formation of six calix[n]arene derivatives – tert-butyl-calix[4]arene (C4), tert-butyl-calix[6]arene (C6), tert-butyl-calix[8]arene (C8) and their ethyl-acetic-ester derivatives (C4Es4, C6Es6, C8Es8) – has been the subject for our Raman spectroscopic study. Substances taken in study for complexation were the two widely used anticoagulants – warfarin and its 5-nitro- derivative, acenocoumarol – and their antidote, phytomenadione (also known as phylloquinone or vitamin K1).
For each standard substance, Raman spectra were studied between 3620 and 90 cm-1. In order to obtain the complexes, a mixture of solutions of each calixarene and each analyte was prepared, in a stoichiometric ratio of 1:1 and then the solvents were evaporated. Spectra of solid residues obtained were compared with those of initial molecules.
In all cases, there was observed a Raman band shifting or even the disappearance of some bands, indicating that calixarene derivatives interact with the studied molecules.
In conclusion, the six calixarene derivatives taken in study seem to be able to form complexes with the molecules of warfarin, acenocoumarol and phylloquinone.