The Li+ affinities of a series of substituted acetophenones in their low-lying excited triplet state: A DFT study

A detailed study of Li+ affinities of a series of para-substituted acetophenones and their O-Li+ counterparts was performed using density functional theory (Becke, Lee, yang and parr [B3LYP]) method using 6-311G(d,p) basis sets with complete geometry optimization in the relevant excited state. The gas phase O-Li+ complex formation turns out to be exothermic case and the local stereochemical disposition of the Li+ is found to be almost the same in each case. The presence of para-substituent is seen to cause very little change of the Li+ affinity relative to the unsubstituted acetophenones. Electron releasing p-substituents increase it by 0.028 hartree and electron withdrawing p-substituents decrease it by 0.006 hartree. Computed Li+ affinities are sought to be correlated with a number of computed system parameters such as the net charge on the Li+ and the carbonyl oxygen of the Li+ complexes and the net charge on the carbonyl oxygen of the free bases and also the computed hardness of the free bases. The Li+ ion-induced shifts are in general red shifts for the low-lying excited triplet state. The energetics, structural and electronic properties of the complexes indicate that in the lowest excited triplet state the interaction between the Li+ ion and a carbonyl base is predominantly an ion-dipole attraction and the ion-induced dipole interaction as well rather than a covalent interaction.