This thesis presents investigations related to interactions of chelating ligands (macrocyclic and acyclic) with neutral and ionic species in solution. Following a brief introduction on coordination chemistry, each topic is presented separately in three chapters. In Chapter I, thermodynamic studies on drug cyclodextrin interactions in water and in chloroform at 298.15 K are discussed in relation to the effect of the macrocycle on the transfer of N1-substituted sulphonamides from water to chloroform. It is concluded that the transfer of the drug in this solvent system is thermodynamically more favoured in the absence than in the presence of cyclodextrin. Chapter II concerns thermodynamic aspects on calixarenes and their ester derivatives. As far as calixarenes are concerned, thermodynamic parameters of complexation of tert-butylamine and p-tert-butylcalix[4]arene in benzonitrile suggest that two processes are involved; the formation of the adduct followed by that of an endo-calix complex. The interaction of alkyl-p-tert-butylcalix[4]arene tetraethanoates with alkali-metal cations in acetonitrile and in benzonitrile at 298.15 K was studied by titration calorimetry. The limitation of this technique to derive stability constant data for highly stable complexes led to the development of a double competitive potentiometric method. Thermodynamic data are discussed in terms of the solvation of host, guest and resulting complex in these solvents. Chapter III discusses synthesis, characterisation and acid-base properties of ethylenedinitrilo-N,N1-diacetic-N,N1-bis(1-phenylethylacetamido) acid (edtamba) and ethylenedinitrilo-N,N1-diacetic-N,N'bis(pyridylacetamidoacetamioe)acid (edtapa) This is followed by the thermodynamics of complexation of these ligands with metal cations (Pb(II), Cd(II), Cu(II), Ni(II), Zn(II) and Co(II) in water at 298.15 K. These results show that unlike EDTA, edtamba and edtapa do not interact selectively with these cations as a result of a remarkable enthalpy-entropy compensation effect. Computer programs written during the course of these investigations are appended.