A comparative theoretical study on the optoelectronic and nonlinear optical properties of [Pt(bpy)(qdt)] derivatives with electron-donating and -withdrawing anchors

Abstract

A series of [Pt(bpy)(qdt)] {bpy = 2,2′-bipyridine; qdt = quinoxaline-2,3-dithiolate} derivatives was chosen to study the effect of structural modifications on the optoelectronic and nonlinear optical (NLO) properties of the molecules. Here, this study examined eight bipyridine derivatives with different electron-donating and electron-withdrawing anchoring groups using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The results indicated that the electronic character of the [Pt(bpy)(qdt)] complex is sensitive to the type of anchoring groups connected to the bpy ligand. The considered electron-withdrawing anchors notably narrow the energy gap of the [Pt(bpy)(qdt)] complex in comparison to the electron-donating anchors. Interestingly, replacement of a hydrogen atom by electron-donating anchors in the [Pt(bpy)(qdt)] complex leads to high molar absorption coefficients, whilst complexes with electron-withdrawing anchors can be redshifted significantly. The values of light-harvesting efficiency (LHE) were also calculated and compared in both gas and solvent phases. Moreover, the results reveal that substituting H atoms of bpy ligand by electron-withdrawing anchors dramatically increases the static first hyperpolarizability (β₀) value. We expect that the present study would deepen the understanding of electron-donating and -withdrawing anchoring groups in diimine–dithiolate complexes and may contribute to the development of potentially high performance NLO materials.