The DFT Study On Second-order Nonlinear Optical Property Of The Terpyridyl Complexes

Recently, with the rapid development of optoelectronic devices of telecommunications, information storage, seeking an excellent nonlinear optical material has become the hotspot of the scientist's researching. Especially, the materials exhibit that switchable NLO properties can be expected to novel application for optoelectronic technologies. The switchable NLO responses of molecules can be altered by oxidation, reduction, protonation, deprotonation or chemical modification and so on. The most attractive procedures involve the redox manipulation and the complexes contain the electron donor which is via aÏ€-conjugated bridge connected to an electron acceptor. Compared with inorganic materials and organic materials, metal complexes with nonlinear optical (NLO) properties have both their features. Therefore the metal complexes become an important area of the nonlinear optical materials research areas.The NLO properties of terpyridyl metal complexes have been studied by using quantum chemical calculations, the relationship between molecular structure and NLO properties have been analyzed. The research results suggest:(1) Quantum chemisty DFT BHandHLYP/6-311g**( SDD basis set for metal ions) was employed to calculate the second-order nonlinear optical properties of C^N^NPt(II) and N^C^NPt(II) complexes. The calculation absorption spectra of the C^N^NPt(II) complexes are well in agreement with the experiment value. The conjugation of ancillary ligands greatly affect the polarizability, the substituents of main ligands hardly affect the polarizability. This study also has revealed that theβvalues with the C^N^N of the complexes superior than the N^C^N ones. The first hyperpolarizability is greatly enhanced by the conjugation of ancillary ligands and the ability of substituents as the electron acceptor. Besides, the polarizability hardly influences byθ, but the first hyperpolarizability gradually reduce when with theθincreasingly.(2) Quantum chemisty DFT PBE1PBE/B3PW91/BhandHLYP/6-31g*were employed to calculate the second-order nonlinear optical properties of ruthenium carboxylate complexes by the process of the electron transfer, the proton transfer and the hydrogen atom transfer. The Ru(III)PhCOO- complex has the largestβvalue of 4972×10-30 esu. All absorption bands of Ru(II)PhCOO- are attributed to MLCT. It is most important that Ru(III) acts as an acceptor and the–COO- group acts as a donor which lead to the great increase of the NLO responses, as shown theβvalues of the Ru(III)PhCOO- and Ru(III)COO- complexes. The redox switching of NLO responses of four states (n=1) has been studied. Theβvalue of Ru(III)PhCOO- is ~36 times and ~48 times larger than those of Ru(II)PhCOO- and Ru(II)PhCOOH, respectively. The deprotonated anion Ru(III)PhCOO- has shown significantlyβtot value which is ~215 times larger than that of the protonated Ru(III)PhCOOH. (3) Quantum chemisty DFT PBE1PBE/CAM-B3LYP/B3P86/6-31g*were employed to calculate the second-order nonlinear optical properties of ruthenium complexes with redox-active noninnocent ligands by the sequential one-electron reduction processes. The complex 4 has largestβvalue of 186×10-30 esu calculated by B3P86, and the complexes with iminoquinonoid ligands have a better NLO response. Calculations indicated that the low energy absorption bands with decrease gradually in intensty through sequential one-electron reduction (2â†'3â†'4). Complex 4 has an intensity absorption band due to the L3 act as a strong donor through the two step sequential one-electron reduction. The redox switching of NLO responses of complexes show that 1and 2 of center metal redox can not be the outstanding redox NLO switching. However, it is worth noting thatβtot value calculated by functional B3P86 of complex 4 is ~7.7 times, ~10.6 times, and ~11.0 times larger than those of complexes 3, 2, and 1, respectively. This is due to that the redox processes change the charger transfer pattern and enhance the second-order NLO response. These switching values may be effectively used as excellent'off / on'NLO molecular switches materials.