Electronic Structures and Second-Order Nonlinear Optical Properties of a Series of Pt-Pt Bond-Containing Metal Complexes

The electronic structures and second-order nonlinear optical (NLO) properties of a series of Pt-Pt bond-containing metal complexes were calculated using density factional theory (DFT) combined with the finite field (FF) method. The results show that the replacement of a conjugated ligand does not substantially affect the Pt-Pt bond. Additionally, the strength of charge transfer (CT) from the ligand to the metal group increases as the length of the conjugated ligand becomes longer. The first-order hyperpolarizabilities of these metal complexes increase as the length of the conjugated ligand becomes longer but this is not sensitive to the change in charge of these metal complexes. Complex IId containing a relevant long p-conjugated ligand possesses the largest first-order hyperpolarizability according to our DFT-FF calculations. Time-dependent (TD)-DFT calculations show that the pi.pi* intraligand mixing metal to ligand charge transfer transitions directly contribute to the second-order NLO response of the Pt-Pt bond-containing metal complex IId.