A study of charge transfer interactions of some nitrogen heterocyclic compounds

Investigations on the significance of charge transfer interactions between some important biomolecules has been carried out and an attempt has been made to correlate the data with reported biochemical data. Interactions between catechol and l-epinephrine with nucleosides and nucleotides were investigated by UV and NMR methods. The association constants obtained were low but there were significant differences in the ability of catechol to associate with the nucleosides and nucleotides. The order of the association constants being Guanosine>adenosine>cytidine=thymidine>uridine. The studies carried out on I-epinephrine were discontinued since it was found that I-epinephrine was photosensitive. Charge transfer interaction between diazines and aromatic hydrocarbons was investigated using NMR and it was found that only 1:1 complexes were formed in these systems. The equilibrium constant, K[sub]c, for complex formation was measured for each system and the low values obtained indicated that only weak complexes occurred between donor and acceptor. There was no significant change in K[sub]c values with temperature change indicating that the enthalpy of complex formation is close to zero in the system studied. [increment]o values were measured for protons in the acceptor moiety of the diazine-aromatic hydrocarbon complexes and the results rationalised in terms of the relative positions of donor and acceptor molecules in the complex. The values of [increment]o for the pyrimidine-benzene and pyrazine-benzene systems were found to decrease as the temperature increased. This indicated that the separation between donor and acceptor in the complex increased as the temperature was increased. Attempts to study charge transfer interactions of nucleotides with polycyclic aromatic amines and some intercalating dyes in aqueous solutions were unsuccessful