Formation of hydrogen-bonded chains between strong N-base and N-H acids - a FTIR study

Mixtures of imidazole derivatives with the strong base 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) were studied by FTIR spectroscopy as a function of the imidazole derivative:MTBD ratio. In the case of complexes of MTBD with the lowest acidic imidazole only molecular complexes are found. This is true in the chloroform solutions as well as in the acetonitrile solutions. With increasing acidity of the imidazoles in both solvents more and more polar structure of the complexes is found. In chloroform the polar structure predominates and the proton polarizability in the chains remains weak. In the acetonitrile solution the complexes dissociate. If more imidazole molecules are present one observes large proton polarizability of the negatively charged structurally symmetrical imidazole chains. (C) 1998 Elsevier Science B.V.