Tuning Reactivity of Platinum(II) Complexes

The DFT calculations also reveal that the major influence of the para-substituent (Y), i.e.
pyridyl 4-position, is on the HOMO energy level-“ground-state effect” and not the LUMO
(Figure 6.2). The electron density of the HOMO orbitals are localized between the
pyridyl π-acceptor bridging ligand and the spacer S atom(s) in Pt1 and Pt2, whereas in
Pt3 the HOMO orbitals lie entirely on the Pt(II) centres and very sparsely on the
bridging moiety. In case of the LUMO orbitals, these comprise of contributions from the
metal centres and the donor atoms of the am(m)ine ligands in all the three complexes.
The effect of increasing the number of S-atoms results in decreasing the HOMO–LUMO
energy gap while replacing the S-atoms with –CH2–CH2– group raises the energy level as
the data in Table 6.2 shows.
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