Substantial second-order nonlinear optical properties of novel hexamolybdate-julolidine hybrids: A density functional theory (DFT) study

Series of new inorganic-organic hybrid hexamolybdate-julolidine materials are theoretically designed and studied via density functional theory (DFT) and time-dependent density functional theory (TD-DFT). Their geometric and electronic structures, linear optical and second-order nonlinear properties have also been evaluated. By the introduction of julolidine into the organoimido-hexamolybdate, the studied systems show substantial second-order nonlinear (NLO) responses of up to 1048 x 10(-30) esu for compound 3. Upon enlarging the pi-conjugated linker, the calculated beta-responses are enhanced by a factor of 2.1. In addition, TD-DFT calculations indicate that the strong low-energy transition can mainly be attributed to charge transfer (CT) from julolidine-arylimido to the hexamolybdate cluster, indicating strong communication between the POM and julolidine components, which is responsible for the linear and non-linear optical behavior of these compounds. Ortho-methylation to the imido-bond has a significant effect on the stability and hence the length and linearity of the bond, although it slightly reduces the first hyperpolarizability. The whole set of results demonstrates the excellent NLO activity for julolidine-POMs chromophores while keeping relatively good transparency window compared to similar purely organic systems.

Automated summary

A series of new inorganic-organic hybrid hexamolybdate-julolidine materials were designed and studied using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The systems showed substantial second-order nonlinear (NLO) responses, with a maximum value of 1048 x 10(-30) esu for compound 3. The introduction of julolidine and enlarging the pi-conjugated linker enhanced the NLO responses. TD-DFT calculations confirmed the strong communication between the POM and julolidine components, which is responsible for the optical behavior of these compounds.