Investigation of second-order nonlinear optical responses in a series of V-shaped binuclear platinum(ii) complexes.

A series of four D-(π-Pt-π-A)2 new V-shaped binuclear platinum(ii) complexes bearing a diphenylpyranylidene ligand as a pro-aromatic donor group (D) and various electron-attracting groups (A) separated by platinum bis-acetylide fragments have been synthesized, characterized and studied for their electrochemical, photophysical and second-order nonlinear optical (NLO) properties. The nonlinear optical properties of these complexes have been determined by using the Electric-Field-Induced Second Harmonic (EFISH) generation technique, and their optical properties have been rationalized by Time-Dependent Density Functional Theory (TD-DFT) calculations relying on a range-separated hybrid. All complexes display positive µß0 values. In addition, the second-order NLO responses of the complexes could be easily modulated by incorporating various end-capped electron-attracting groups, namely malononitrile, indane-1,3-dione, pyrimidine and pyrimidinium. Remarkably, complex 7 bearing a pyrimidinium fragment displays the highest µß0 value among all the complexes of this series. Its NLO response is twice as high as that of the mononuclear analogue complex RD2, which has been confirmed both experimentally and theoretically.

First principles investigation of the spectral properties of neutral, zwitterionic, and bis-cationic azaacenes.

An in-depth investigation of the optical properties of recently-synthesized linear azaacene derivatives of various electronic nature (neutral, dicationic, and zwitterionic) is presented. Our simulations include not only the determination of the vertical transitions, but also of the adiabatic energies and vibrationally-resolved spectra using the adiabatic Hessian approach in connection with the Time-Dependent Density Functional Theory (TD-DFT) and second-order Coupled-Cluster (CC2) methods. We show that the theoretical results are in excellent agreement with experiment for both the λmax and the band topologies, a statement holding in the full visible domain. We also analyse the nature of the key vibrations explaining the specific band shapes of these compounds. In addition, we investigate a series of yet-unknown substituted systems in an effort to design new compounds with improved (redshifted) properties for optoelectronics applications.