Phosphonates have shown promising specificity and remarkable extractability towards actinide elements. Among all the organophosphorous compounds, phosphonates have the dual advantage of simplicity in preparation coupled with the flexibility to tailor-make their carbon chain structure. In the present work the relationship between structure and metal binding affinity of phosphonates has been examined both experimentally and quantum mechanically. Symmetrical Diisobutylisobutyl, Diisoamylisoamyl and unsymmetrical Diisoamylhexyl and Diisoamylbutyl branched phosphonates were synthesised and characterised by NMR and GC-MS. These ligands were used to bind Th(IV), U(VI), Pu(IV) and Am(III) at the liquidliquid interface. The ligands also were examined for their physicochemical properties of density, viscosity, aqueous solubility and dielectric constant which are significantly affected by changes in the alkyl chain structure. A combination of physico-chemical parameters, as well as the structure modulated chemical nature of the extractants, cause variations in the distribution ratios towards metal ions. These effects have been probed in detail using Th(IV), U(VI), Pu(IV) and Am(III) ion extractions and found to correlate with the carbon chain length of the organic groups on the phosphoryl centre. Further,density functional theory was employed to understand the electronic structure of the extractants and metal complexes.The computed complexation energies in the formation of metal-ligand complexes compared well with the trends observed in the experiments. Both experiment and quantum chemistry emphasizes the importance of the carbon chain structure on the actinide binding ability of phosphonate ligands.